Carrier Infinity - poor performance high stage

[rogressem]

Just an update on this, or lack of update. (Carrier Infinity supply air temp goes up from low to high stage, suction pressure goes up - good performance at low stage) Original thread:
http://hvac-talk.com/vbb/showthread.php?t=1113821

My original installer (from 2007) is waiting on a response from the local Carrier technical representative. In the meantime, I've been taking careful return/supply air temps at the air handler (return duct at air handler and a few feet downstream of evaporator). I've taken them almost every day, early morning and middle of these hot afternoons and the numbers are pretty consistent. BTU performance from low to high stage is essentially constant. This morning:

LOW STAGE:
Return Dry Bulb: 71.8
Return Wet Bulb: 58.7
Supply Dry Bulb: 48.7
Supply Wet Bulb:47.4
Following 3 readings from Infinity Controller
CFM: 882
Blower RPM: 599
Static Pressure: .24


HIGH STAGE:
Return Dry Bulb: 71.5
Return Web Bulb: 59
Supply Dry Bulb: 55.4
Supply Wet Bulb: 52.7
Following 3 readings from Infinity Controller
CFM: 1400
Blower RPM: 960
Static Pressure: .61

[hvacrmedic]

The compressor isn't switching to second stage. Have your contractor correct the fault.

[rogressem]

Yea - long thread on that topic, and I guess that is what has prevented them from being able to quickly fix this. (and going to local Carrier for help). They've already noted that compressor amp draw goes from 5A to 10A (rough numbers) and head pressure goes up a few (<5) psig, suction pressure goes up about 10pisg. High stage contactor engages. So it seems to be switching, but just not performing as designed.

I may have to ping on them again - haven't heard anything since Tuesday, but I'm sure they've been swamped with more critical repairs during this heat wave. At least it "sort of" works. Wish I could figure out how to make it stay in low stage, because I'm wasting money letting it run high stage.


The compressor isn't switching to second stage. Have your contractor correct the fault.

[tinknocker service tech]

have they tried to slow the blower down to 1200 cfms and lower the sat temp in high stage

sounds like an air flo problem more then a compressor problem IMO

[rogressem]

have they tried to slow the blower down to 1200 cfms and lower the sat temp in high stage

sounds like an air flo problem more then a compressor problem IMO

I think on the Infinity systems with Infinity controller, that 1400 is by design, and is not adjustable other than 350cfm/ton when set to efficiency, 400cfm/ton when set to maximum. (this is a 4 ton system).

[motoguy128]

I know on the newest version of Infinity controller there is a setting to force the unit to run only in low stage. You could then also set it to run at 400CFM (Maximum) with no dehumidification for a little more capacity for now.

[motoguy128]

have they tried to slow the blower down to 1200 cfms and lower the sat temp in high stage

sounds like an air flo problem more then a compressor problem IMO

Do you mean airflow at the condenser?

Airflow at he evaporator looks just fine. The blower isn't anywhere near maximum RPM. Static is probably <0.8".

THe lowest you could force the indoor blower is 1300CFM unless you remove the infinity controller and use a regular thermostat and dip switches. However, if it's a ANA1, I think it will only run with an Infinity controller.

[motoguy128]

I think on the Infinity systems with Infinity controller, that 1400 is by design, and is not adjustable other than 350cfm/ton when set to efficiency, 400cfm/ton when set to maximum. (this is a 4 ton system).

That CFM setting, on my system at least, can vary as well depending on outdoor temperature and humidity level. Mine runs an even lower CFM/ton on high stage over about 85F it seems.

[hvacrmedic]

I think on the Infinity systems with Infinity controller, that 1400 is by design, and is not adjustable other than 350cfm/ton when set to efficiency, 400cfm/ton when set to maximum. (this is a 4 ton system).

Efficiency is 400 cfm per ton. Maximum is 450 cfm per ton. Comfort s 350 cfm per ton. That's irrelevant since there's very little change in total capacity between those air flow settings. Your system is producing 2 tons in both first and second stage. If the high speed contactor is energized, then the compressor is broken, period. Another thread won't fix it.

The Bristol 2 speed runs one piston in low stage and two pistons in high. In high stage the compressor rotation reverses and picks up the second piston, doubling its pumping capacity. When the mechanism is broken you get low stage capacity in both modes.

[rogressem]

Interesting thought there - I knew that about the Bristol/reverse direction compressor, but never thought about the mechanism that picks up the 2nd cylinder - being broken. I wonder if the amp draw would still double?

At any rate, I will let them figure it out and I'll post the outcome here. Its been one of those where I've had a hard time convincing them something is wrong. (and no one took wet bulb temps until I did it and started doing comparisons between stages)

p.s., my Infinity controller documentation reads:
EFFICIENCY -- fixed airflow used to achieve specified ratings --
no dehumidification airflow reduction. This is nominally 350
CFM/ton, but will vary if a 2--stage outdoor unit is used.
MAXIMUM -- 400 CFM/ton. No dehumidification airflow
reduction

But as you said, thats irrelevant for this issue.

Will let everyone know what the outcome is.




Efficiency is 400 cfm per ton. Maximum is 450 cfm per ton. Comfort s 350 cfm per ton. That's irrelevant since there's very little change in total capacity between those air flow settings. Your system is producing 2 tons in both first and second stage. If the high speed contactor is energized, then the compressor is broken, period. Another thread won't fix it.

The Bristol 2 speed runs one piston in low stage and two pistons in high. In high stage the compressor rotation reverses and picks up the second piston, doubling its pumping capacity. When the mechanism is broken you get low stage capacity in both modes.

[hvacrmedic]

Interesting thought there - I knew that about the Bristol/reverse direction compressor, but never thought about the mechanism that picks up the 2nd cylinder - being broken. I wonder if the amp draw would still double?

At any rate, I will let them figure it out and I'll post the outcome here. Its been one of those where I've had a hard time convincing them something is wrong. (and no one took wet bulb temps until I did it and started doing comparisons between stages)

p.s., my Infinity controller documentation reads:
EFFICIENCY -- fixed airflow used to achieve specified ratings --
no dehumidification airflow reduction. This is nominally 350
CFM/ton, but will vary if a 2--stage outdoor unit is used.o
MAXIMUM -- 400 CFM/ton. No dehumidification airflow
reduction

But as you said, thats irrelevant for this issue.

Will let everyone know what the outcome is.

Yes, I forgot for a moment that the cfm settings depend upon the indoor model. It's been a very long week, heck, make that a very long couple of months.

Hope you get it worked out. I've only seen this fault twice, but I can just about guarantee that this is what has happened to yours, assuming that all of your data is accurate.

[tinknocker service tech]

Do you mean airflow at the condenser?

Airflow at he evaporator looks just fine. The blower isn't anywhere near maximum RPM. Static is probably <0.8".

THe lowest you could force the indoor blower is 1300CFM unless you remove the infinity controller and use a regular thermostat and dip switches. However, if it's a ANA1, I think it will only run with an Infinity controller.


didnt see the size of the unit so spoke to soon on cfm
i do tend to feel there is an airflo issue

[beshvac]

Interesting thought there - I knew that about the Bristol/reverse direction compressor, but never thought about the mechanism that picks up the 2nd cylinder - being broken. I wonder if the amp draw would still double?

At any rate, I will let them figure it out and I'll post the outcome here. Its been one of those where I've had a hard time convincing them something is wrong. (and no one took wet bulb temps until I did it and started doing comparisons between stages)

.

The bristol I found like that had the same amps in either stage.

[hvacrmedic]

The bristol I found like that had the same amps in either stage.

It could be that instead there's a busted discharge valve on the second cylinder. Either way the second piston doesn't seem to be providing any refrigeration effect.

If any of you pros don't have or have access to a psychrometric program or calculator, then you should think about locating one. It'll save a lot of head scratching. I have one posted in the educational forums, and there are several psychrometric apps available from itunes and the android market. You could also just use a wet bulb/enthalpy table and the total capacity formula

btuh total = 4.5 x cfm x ΔH

[motoguy128]

I don't see a airflow problem. Even if it was the condenser fan not going to high speed, you're still get a significant increase in capacity, but high head pressures and high amp draw.

IF inside airflow was a problem, you'd have low discharge air temps, not higher.

It seems clear to me that it's not generating capacity.

[mark beiser]

After all these service calls, if the intalling contractor hasn't figured out that the compressor is broken by now, Carrier should cut them off and not sell them anything more complicated than a single stage system until they get some remedial training for their technicians from an outside source...:rolleyes:

[udarrell]

Just an update on this, or lack of update. (Carrier Infinity supply air temp goes up from low to high stage, suction pressure goes up - good performance at low stage) Original thread:
http://hvac-talk.com/vbb/showthread.php?t=1113821

My original installer (from 2007) is waiting on a response from the local Carrier technical representative. In the meantime, I've been taking careful return/supply air temps at the air handler (return duct at air handler and a few feet downstream of evaporator). I've taken them almost every day, early morning and middle of these hot afternoons and the numbers are pretty consistent. BTU performance from low to high stage is essentially constant. This morning:

LOW STAGE:
Return Dry Bulb: 71.8
Return Wet Bulb: 58.7
Supply Dry Bulb: 48.7
Supply Wet Bulb:47.4
Following 3 readings from Infinity Controller
CFM: 882
Blower RPM: 599
Static Pressure: .24


HIGH STAGE:
Return Dry Bulb: 71.5
Return Web Bulb: 59
Supply Dry Bulb: 55.4
Supply Wet Bulb: 52.7
Following 3 readings from Infinity Controller
CFM: 1400
Blower RPM: 960
Static Pressure: .61
Using the wet bulb temps & enthalpy chart I get 42,071.4-Btuh Low Stage &, 39,690-Btuh High Stage.

Hope I didn't make an error...it's easy to do...4.5* CFM * enthalpy change. The Low Stage should not be higher than the High stage; maybe I made a mistake somewhere?

If not; you got a real problem!

[mark beiser]

Using the wet bulb temps & enthalpy chart I get 42,071.4-Btuh Low Stage &, 39,690-Btuh High Stage.

Hope I didn't make an error...it's easy to do...4.5* CFM * enthalpy change. The Low Stage should not be higher than the High stage; maybe I made a mistake somewhere?

If not; you got a real problem!

I think you got the enthalpy change to high.
With the conditions listed, the first stage enthalpy change is 6.7 btu/lb, and 2nd stage is 3.927 btu/lb.

Using that equation, 1st stage would be at 26,592 btu/hr, and 2nd stage would be at 24,740 btu/hr.

The psychrometrics app I use is corrected for my local conditions, but the variation from standard should only be slight.

The psychrometrics process calculator app I use, instead of that equation, gives slightly lower total capacity numbers, but they are within 1,500 btu/hr of the simplified equation.
I like using the process calculator because it breaks out sensible and latent capacity.

The way the system is operating now, it has higher total and latent capacity in 1st stage than in 2nd stage.
In 2nd stage the sensible capacity is slightly higher, but there is almost no latent cooling being done.

If there is a way to lock the system into only using 1st stage, I'd highly recommend doing so until the compressor is replaced.

[rogressem]

I got similar numbers (about 26,000 btu/hr) for both. I'm using that Psychometrics app for iphone/android (maybe the same one your using), which also seems to match the regular enthalpy charts that I see. I'm pretty much at sea level (+14 feet I think)

I've been trying to figure out how to lock it in 1st stage until its fixed...not seeing a way to do that.


I think you got the enthalpy change to high.
With the conditions listed, the first stage enthalpy change is 6.7 btu/lb, and 2nd stage is 3.927 btu/lb.

Using that equation, 1st stage would be at 26,592 btu/hr, and 2nd stage would be at 24,740 btu/hr.

The psychrometrics app I use is corrected for my local conditions, but the variation from standard should only be slight.

The psychrometrics process calculator app I use, instead of that equation, gives slightly lower total capacity numbers, but they are within 1,500 btu/hr of the simplified equation.
I like using the process calculator because it breaks out sensible and latent capacity.

The way the system is operating now, it has higher total and latent capacity in 1st stage than in 2nd stage.
In 2nd stage the sensible capacity is slightly higher, but there is almost no latent cooling being done.

If there is a way to lock the system into only using 1st stage, I'd highly recommend doing so until the compressor is replaced.

[rogressem]

Beginning to wonder that myself. I know this company has had some turnover lately, so I'm not sure how good their Carrier expertise is anymore (not a big company, so I know that must be a challenge).

I've already been looking at the other factory authorized Carrier dealers in my area, but I was hesitant with starting over with somebody new. I've also been giving them a break during this heat wave - at least I have some cooling!


After all these service calls, if the intalling contractor hasn't figured out that the compressor is broken by now, Carrier should cut them off and not sell them anything more complicated than a single stage system until they get some remedial training for their technicians from an outside source...:rolleyes:

[udarrell]

I think you got the enthalpy change to high.
With the conditions listed, the first stage enthalpy change is 6.7 btu/lb, and 2nd stage is 3.927 btu/lb.

Using that equation, 1st stage would be at 26,592 btu/hr, and 2nd stage would be at 24,740 btu/hr.

The psychrometrics app I use is corrected for my local conditions, but the variation from standard should only be slight.

The psychrometrics process calculator app I use, instead of that equation, gives slightly lower total capacity numbers, but they are within 1,500 btu/hr of the simplified equation.
I like using the process calculator because it breaks out sensible and latent capacity.

The way the system is operating now, it has higher total and latent capacity in 1st stage than in 2nd stage.
In 2nd stage the sensible capacity is slightly higher, but there is almost no latent cooling being done.

If there is a way to lock the system into only using 1st stage, I'd highly recommend doing so until the compressor is replaced.
Well, re-figuring the Low Stage I get enthalpy change of 6.69 which gets 26,553-Btuh; discovered switching back & forth to get WB #s; I ended up reading WB #s from the wrong stages.:grin2:

Now I get 1400-cfm * 4.5 is 6300*3.86 enthalpy change is 24,318-Btuh.

Well,I read the 47.4-F off the Low stage & then subtracted it from the High stage wet bulb of 59-F which gave me a false 6.69 enthalpy change on the chart which gave me the false high of 39,696 figure, looked okay for a sick 4-ton system.:whistle:

Well, I believe it's supposed to be a 4-Ton system.
Is it a heat pump or straight A/C system?

It is simple if you get the right WB numbers...I was switching back & forth & somehow ended up reading the wrong WB#'s from different stages, WOW.:whistle:
Had some distractions here too...:grin2:

[motoguy128]

I agree, that locking it into 1st stage would be best. I'd also set airflow to maximum. This way you'll get the most capacity. On my newer controller,you can select low stage only form the advanced menus. I think it's in the system staging in under the lockout settings.

[rogressem]

OK, here is the latest on this issue. Based on the info my local HVAC contractor passed to Carrier, Carrier concluded the TXV was bad. It was just in the 5 year parts warranty, so Carrier paid the cost of the TXV (I actually paid the difference and had the entire evaporator replaced with a newer aluminum Carrier N coil). No need going through all that and then have the evaporator leak in a year or so.

At any rate, made no difference at all, and I knew 10 minutes after they fired it back up. Same symptons:

1) Supply air temp goes up 5-10F from low to high stage

2) Delta T, measured at the evap is 10-14F in high stage, good 20 or so in low stage

3) Suction pressure always goes up about 10psig from low to high stage, head pressure essentially doesn't change. Local tech says Carrier told him this was OK, although the Carrier application and service guide for the 24ANA7 reads: "Suction pressure should be reduced by 5--10% when switching from low to high capacity. There should be a 10--20% increase in liquid pressure when switching from low to high capacity."

4) When I take careful and repeated wet bulb/dry bulb return/supply temps at the appropriate locations near the evaporator BTU calculations are essentially unchanged from low to high stage. (I've posted figures here before - no need to post them again - they didn't change)

Now, before Carrier agreed to replace the TXV, they did have the local tech come back out an check compressor amp draw (because he neglected to do that on the first visit). On a super hot day it was 6A low stage and just over 9A hi stage. Again, the Carrier service guide reads: "Compressor current should increase 100--250% when switching from low to high stage.", but this apparently didn't throw any red flags for the Carrier service rep, so they went with a TXV replacement

At this point, I'm waiting the local HVAC company to get a response from Carrier on the next step. I figure I probably have a good case. Carrier didn't agree to do an in-warranty TXV replacement if they didn't think something was wrong, and since the symptons have not changed, I wouldn't think that they could now say everything is OK. I still think its that Bristol TS compressor.

Here is my question: If I hit a dead end here, can I go directly to Carrier Mid Atlantic and start working this issue myself? Does Carrier have service reps that respond to things like this, rather than going through a local HVAC contractor?

No major complaints with the company I'm using - they are Carrier factory authorized, but I have the feeling they aren't the most experienced with these types of issues (they only have two techs). In most cases, I actually like dealing with a small company, but I think they may be in over their head on this one.

[mark beiser]

There is not one single thing about the readings you have passed on to us that would even hint that the problem was related to the TXV.:rolleyes:

The compressor is clearly not functioning properly in 2nd stage.

It is ridiculous that this fiasco has continued this long.

The preemptive move to the all aluminum coil was a good call though, so there is that.

[catmanacman]

I wonder what part about a bad compressor there not understanding ,also i would refuse to pay for the coil replacement .

[mark beiser]

This is sad.
I just realized that you posted about the poor performance of this system just over 2 years ago, and it still isn't fixed...

For the record, I said the compressor wasn't working at full capacity in 2nd stage 2 years ago when you first posted about it. :p

[rogressem]

Yea, I probably could have been a little more diligent about finding a company who does more thorough testing. Every time I complained, we attributed poor performance to flex duct temperature losses. Summer of 2010, the owner of the company responded: "I really don’t see any issues with your system and spoke in-depth with my technician and he said it was on the money."

Of course, the thing that was on the money was the subcooling and superheat values. This seems to be a good example of - don't rely on just those values to determine if everything is working ok.

I finally started taking a better readings at the appropriate locations before and after the evaporator, started doing BTU calculations, and was able to prove that something wasn't right. Funny thing, this company still hasn't taken their own detailed return/supply temperature measurements - they are taking my numbers and passing it on to Carrier.

And I can't blame just this company, I did call someone else to get another opinion (last summer I believe). This was the guy that punched a hole in the return flex duct, took a quick measurement, compared to supply temp at nearest register and said everything was fine. I realized at this point, that this larger, Carrier dealer was not going to be able to help either.

Will post another update when I have one.



This is sad.
I just realized that you posted about the poor performance of this system just over 2 years ago, and it still isn't fixed...

For the record, I said the compressor wasn't working at full capacity in 2nd stage 2 years ago when you first posted about it. :p

[rogressem]

Another update, and hopefully we are moving in the right direction. Finally got the Carrier service rep out here, and I was impressed - he definitely seemed to know his stuff.

He said that I need that 4" spacer between the furnace and the N coil. Even though the two are matched sizes, he said that Carrier now recommends that spacer, especially in larger systems (4 ton in my case). He said at hi stage, there really isn't enough room for air to exit the heat exchanger, and then flow into that right leg of the N coil. He said this was now in the CNPVP coil installation instructions (although I couldn't find anything in the instructions that specifically said that).

He acknowledged that I've really had this problem since day 1 (July 2007). I just could never prove it until I did my own BTU calculations.

Once the spacer is installed, hopefully I'll post my final update.

In case anyone is wondering:
Furnace: 58CVA110-20
Coil: CNPVP4821ALA
Installed July 2007



OK, here is the latest on this issue. Based on the info my local HVAC contractor passed to Carrier, Carrier concluded the TXV was bad. It was just in the 5 year parts warranty, so Carrier paid the cost of the TXV (I actually paid the difference and had the entire evaporator replaced with a newer aluminum Carrier N coil). No need going through all that and then have the evaporator leak in a year or so.

At any rate, made no difference at all, and I knew 10 minutes after they fired it back up. Same symptons:

1) Supply air temp goes up 5-10F from low to high stage

2) Delta T, measured at the evap is 10-14F in high stage, good 20 or so in low stage

3) Suction pressure always goes up about 10psig from low to high stage, head pressure essentially doesn't change. Local tech says Carrier told him this was OK, although the Carrier application and service guide for the 24ANA7 reads: "Suction pressure should be reduced by 5--10% when switching from low to high capacity. There should be a 10--20% increase in liquid pressure when switching from low to high capacity."

4) When I take careful and repeated wet bulb/dry bulb return/supply temps at the appropriate locations near the evaporator BTU calculations are essentially unchanged from low to high stage. (I've posted figures here before - no need to post them again - they didn't change)

Now, before Carrier agreed to replace the TXV, they did have the local tech come back out an check compressor amp draw (because he neglected to do that on the first visit). On a super hot day it was 6A low stage and just over 9A hi stage. Again, the Carrier service guide reads: "Compressor current should increase 100--250% when switching from low to high stage.", but this apparently didn't throw any red flags for the Carrier service rep, so they went with a TXV replacement

At this point, I'm waiting the local HVAC company to get a response from Carrier on the next step. I figure I probably have a good case. Carrier didn't agree to do an in-warranty TXV replacement if they didn't think something was wrong, and since the symptons have not changed, I wouldn't think that they could now say everything is OK. I still think its that Bristol TS compressor.

Here is my question: If I hit a dead end here, can I go directly to Carrier Mid Atlantic and start working this issue myself? Does Carrier have service reps that respond to things like this, rather than going through a local HVAC contractor?

No major complaints with the company I'm using - they are Carrier factory authorized, but I have the feeling they aren't the most experienced with these types of issues (they only have two techs). In most cases, I actually like dealing with a small company, but I think they may be in over their head on this one.

[mark beiser]

Tell them to bring a compressor with them when they come out to install the spacer.
Until you get a new compressor in there, nothing else they do will make a lick of difference.

[beshvac]

I just looked at the current installation instructions....no mention of spacer...... and that coil is still listed as offset-able..??

[chuckcrj]

Another update, and hopefully we are moving in the right direction. Finally got the Carrier service rep out here, and I was impressed - he definitely seemed to know his stuff.

He said that I need that 4" spacer between the furnace and the N coil. Even though the two are matched sizes, he said that Carrier now recommends that spacer, especially in larger systems (4 ton in my case). He said at hi stage, there really isn't enough room for air to exit the heat exchanger, and then flow into that right leg of the N coil. He said this was now in the CNPVP coil installation instructions (although I couldn't find anything in the instructions that specifically said that).

He acknowledged that I've really had this problem since day 1 (July 2007). I just could never prove it until I did my own BTU calculations.

Once the spacer is installed, hopefully I'll post my final update.

In case anyone is wondering:
Furnace: 58CVA110-20
Coil: CNPVP4821ALA
Installed July 2007
Out of curiosity, what all kinds of measurements did he take and how long was he there?

I believe, like Mark and others, after reading all your posts that he came to the wrong conclusion.

[second opinion]

Was your reps initials T H ?

[rogressem]

Out of curiosity, what all kinds of measurements did he take and how long was he there?

I believe, like Mark and others, after reading all your posts that he came to the wrong conclusion.

First he looked at the furnace and coil, and had pretty much concluded that spacer was the problem, but he also talked about moving the txv sensing bulb outside the coil case.

Went outside to check superheat, and although it was < 20 (I think it was about 14F), he said he expects that to be lower - lets put that spacer in. He also verified subcooling was +/- 3 of the required 15F.

He worked out a deal with the HVAC company and agreed to pay for 4 hours of his labor and the cost of the spacer. He did no checks of the compressor and is relying on info passed to him during previous checks.

No his initials were not T H, he's a Carrier Midatlantic rep. Really seemed to know his stuff, gave me his card and email address, so in general he seemed very cooperative and helpful. I won't be too upset if he's wrong. They've gone down a path they can't back out of now (admitting that something is wrong) - they have to keep going until its fixed.

We did talk about that compressor, and the problem with Bristol TS's. He said the real problem with those has been that mechanism that engages the 2nd piston, and since amp draw is going up (although only about 50%), he says that isn't the problem.

I can't wait for the next chapter in this story.

[rogressem]

OK, another update. 4" spacer installed between the air handler and the N coil evaporator. No difference. And unfortunately, they didn't bring a new compressor.

I'm standing by for round 3.



Tell them to bring a compressor with them when they come out to install the spacer.
Until you get a new compressor in there, nothing else they do will make a lick of difference.

[Krzyd]

I've just read this thread, I can't believe you've been this patient. I also can't beleive your original contractor hasn't condemned the compressor and fixed your problem.

[Krzyd]

Just realized I'm not supposed to post here, sorry mods. Damn! That's twice!

[motoguy128]

OK, another update. 4" spacer installed between the air handler and the N coil evaporator. No difference. And unfortunately, they didn't bring a new compressor.

I'm standing by for round 3.

That was predicitble. Almost pathetic that a mfg rep would even recommend that as a possible solution. Clearly their goal and objective is to admit that the comressor is the problem at all cost.

Funny, we're having the same problem with a large industrial air compressor with motor. issues We're on our 3rd attempt to repair it and finally convinced them to order a different brand motor (the one we should ahve had all along for this application). Some of the fixes probably made hte problem worse. The finger pointing is truely impressive.

[mark beiser]

OK, another update. 4" spacer installed between the air handler and the N coil evaporator. No difference. And unfortunately, they didn't bring a new compressor.

I'm standing by for round 3.

Did they finally decide to replace the compressor, or are they still scratching their heads?

[mark beiser]

rogressem, anything new to report?

[catmanacman]

Im betting it is a crappy bristol ts compressor and they are a huge peice of junk have replaced many .

[rogressem]

Nothing yet, but I'll have an update next Wed. I'm working with the same Carrier rep, and have been able to communicate directly with him. But I decided to go with another HVAC contractor. I decided that the company I was with, even though they originally installed it, didn't have the expertise to help Carrier and I troubleshoot. Carrier apparently agreed, because Carrier is paying to have a new company (that I picked from his list) come out next Wed. and essentially start over with the diagnosis.

He (Carrier) wants to have them check CFM, to make sure its actually what the Infinity controller is calling for (1400), and then do a more thorough compressor check - something that has yet to happen.

Even though this is taking a long time to fix, I take comfort in the fact that Carrier is paying for all the troubleshooting. I assume that is because I had to pay for initial troubleshooting and installation of a TXV, which didn't work. Carrier paid all costs to install that 4" spacer between the furnace and the evaporator. Not sure what will happen when we finally decide its the compressor.

I have a compressor pump down question, but I'll post that as a new thread



rogressem, anything new to report?

[mark beiser]

Thanks for the update.

[rogressem]

The latest on this - a new company (paid for by Carrier) came out a couple of weeks ago, and measured CFM by measuring gas flow at the gas meter outside and return/supply air temps. They were getting about 1700CFM. They spent about 2-3 hours.
After a few days, Carrier decided to have them replace the blower motor. I guess Carrier thinks the CFM is too high. Doesn't seem to be any concern over the compressor.
So, I'm waiting for the new blower motor to be installed.

If they don't hurry, its going to get too cold to troubleshoot this problem any more this season.

[54regcab]

Any chance of a large return leak in the attic causing the problem? When the blower switches to high it would pull more hot attic air in. Other than that I agree with others, do the compressor.

[motoguy128]

Seems like they want to try absolutely every other remote possibility before replacing the compressor. Maybe they think that's too obvious. It's amazing with warranty issues, that rather than spend say $1000 repalcing a compressor, they will spend $200-300 increments 10X for twice the total amount to avoid it. Don;t feel bad, Ingersoll Rand (parent company to Trane) on the industrial side doesn't handle things any better.

[mark beiser]

The latest on this - a new company (paid for by Carrier) came out a couple of weeks ago, and measured CFM by measuring gas flow at the gas meter outside and return/supply air temps. They were getting about 1700CFM. They spent about 2-3 hours.
After a few days, Carrier decided to have them replace the blower motor. I guess Carrier thinks the CFM is too high. Doesn't seem to be any concern over the compressor.
So, I'm waiting for the new blower motor to be installed.

More lunacy!
If the indoor airflow were to high, with a correctly operating compressor 2nd stage, the system would have no problem cooling the house down in 2nd stage.
It would actually do a better job of lowering the actual air temperature in the house than with normal airflow, but would have poor humidity control.

Also, I'd love to hear an explanation of how checking the airflow in the HEATING mode, with a method that is subject to a rather broad range of error, translates in any way to what the airflow is in the COOLING mode on a system that uses different airflows for every stage of heating and cooling.

The problem is the COMPRESSOR!

[mark beiser]

I know, raising a zombie thread, but I'm still wondering if this ever got fixed, so hoping this generates an email notification to the OP. :)

[beshvac]

I am curious too.

- there is now a bulletin about replacing bristol compressors and offering a replacement credit for a scroll outdoor unit.

[Trehak01]

I hate to ask this, but... could someone break it down and explain to me how there getting the btu/hr based off the figures listed at the beginning of this thread. I attempted inputting figures into a psychometric calculate but Im not getting far with it. thank you.

[Trehak01]

double post

[udarrell]

Just an update on this, or lack of update. (Carrier Infinity supply air temp goes up from low to high stage, suction pressure goes up - good performance at low stage) Original thread:
http://hvac-talk.com/vbb/showthread.php?t=1113821

My original installer (from 2007) is waiting on a response from the local Carrier technical representative. In the meantime, I've been taking careful return/supply air temps at the air handler (return duct at air handler and a few feet downstream of evaporator). I've taken them almost every day, early morning and middle of these hot afternoons and the numbers are pretty consistent. BTU performance from low to high stage is essentially constant. This morning:

LOW STAGE:
Return Dry Bulb: 71.8
Return Wet Bulb: 58.7
Supply Dry Bulb: 48.7
Supply Wet Bulb:47.4
Following 3 readings from Infinity Controller
CFM: 882
Blower RPM: 599
Static Pressure: .24


HIGH STAGE:
Return Dry Bulb: 71.5
Return Web Bulb: 59
Supply Dry Bulb: 55.4
Supply Wet Bulb: 52.7
Following 3 readings from Infinity Controller
CFM: 1400
Blower RPM: 960
Static Pressure: .61
Using only the bold-ed data & running the enthalpy numbers; I compared those enthalpy results to the "Expanded Performance Data" of a 4-Ton Goodman 2-stage unit.

1st stage I got 26,553-Btuh; 2nd stage only 28,476-Btuh; Goodman 2nd stage - Expanded Performance Data, using 85-F OAT it shows 40,700-Btuh or under 3.5-Ton, but way above that 28,476. Always state the Outdoor Air Temp for comparative purposes. Seems as though Carrier's 2nd stage ought to be similar.

On 1st stage the Goodman has a higher CFM airflow, but 2nd stage performance is what we are concerned with here, using 1400-CFM for both.

2nd stage, at 80F-RA & 59F Wet bulb, Goodman shows a 24-F indoor airflow temp drop; Carrier's was way less; in 2nd stage the enthalpy change number is way below what it ought to be.

Trehak01 look up wet bulb temps on chart, subtract for enthalpy change difference - follow multiplying directions at bottom: http://www.udarrell.com/wet_bulb_enthalpy_chart.pdf

[Trehak01]

So, let me get this straight. I am going to find my supply wet bulb, return wet bulb and my static pressure.. that will give me the the BTU per pound of dry air. subtract the two, to get the difference. Use the difference in equation(total heat=CFMx4.5xEnthalpyChange)

I did so and got 27,657.. not what I was thinking.. I would assume I did something wrong here...

[udarrell]

So, let me get this straight. I am going to find my supply wet bulb, return wet bulb and my static pressure..(NO!) that will give me the the BTU per pound of dry air. subtract the two, to get the difference. Use the (enthalpy change) difference in equation(total heat removed=CFMx4.5xEnthalpyChange)

I did so and got 27,657.. not what I was thinking.. I would assume I did something wrong here...

The SA RA wet bulb temps have to be looked up on the enthalpy chart; then subtract the lower enthalpy number from the higher enthalpy number.
Then multiply the CFM airflow * 4.5 if at sea level & that result times the enthalpy difference. That's supposed to give you the Btu.

You don't use the static pressure number.

[Trehak01]

my bad, I was looking at it all wrong.

[mark beiser]

@ Trehak01

I really recommend you take the time to learn how to do the calculations by hand, using a psychrometrics chart, and what it all means.

Once you gain a good understanding of it, retire the charts, and get a good psychrometrics app for your smart phone, preferably one that will calculate cooling and mixed air processes, and use it in the course of service calls.

You will be amazed at how it demystifies some problem systems, the system that is the subject of this thread is a prime example.
Unfortunately for the OP, there has been a 2.5 year parade of techs , including a manufacturers tech rep, that have utterly failed to diagnose the problem, even done thousands of dollars worth of useless repairs under warranty, because they either didn't take the air side readings necessary to see what the system was really doing, or they utterly failed to understand what the readings were telling them.

Sadly, even the most basic training in air side diagnostics is hard to come by in most areas.

[Trehak01]

Mark,

Thank you very much for the words of wisdom. This is something I was never taught in school, so it rather overwhelming to comprehend at the moment. I talked to my service manager about using psychometric charts and calculations, he gave me a lot of good information on it, and showed me a few things. I am also signed up for a few classes next month paid by the company. Not to say I will be a pro at in the next month or two but I'm sure I will be better off.



@ Trehak01

I really recommend you take the time to learn how to do the calculations by hand, using a psychrometrics chart, and what it all means.

Once you gain a good understanding of it, retire the charts, and get a good psychrometrics app for your smart phone, preferably one that will calculate cooling and mixed air processes, and use it in the course of service calls.

You will be amazed at how it demystifies some problem systems, the system that is the subject of this thread is a prime example.
Unfortunately for the OP, there has been a 2.5 year parade of techs , including a manufacturers tech rep, that have utterly failed to diagnose the problem, even done thousands of dollars worth of useless repairs under warranty, because they either didn't take the air side readings necessary to see what the system was really doing, or they utterly failed to understand what the readings were telling them.

Sadly, even the most basic training in air side diagnostics is hard to come by in most areas.

[mark beiser]

This is something I was never taught in school, so it rather overwhelming to comprehend at the moment.

The college program I went to had a 1 semester "Psychrometrics and Duct Sizing", class, but it didn't really cover psychrrometrics much, it was mainly about Manual J load calks, and Manual D duct design. Other than that, there was absolutely nothing taught about how to use psychrometrics, or air side diagnostics in general.

It always struck me as strange that most 2 year college and tech school HVAC programs teach almost nothing about AIR...:confused:


One thing that you will find immediately helpful in understanding things, and how to apply it on service calls in the field, is the Testo AC & Refrigeration Application Guide.

Good stuff for anyone doing HVAC service, regardless of experience level.
http://markbeiser.com/HVAC/documents/testo/TestoGuide_2007.pdf

A smart dude named Jim Bergman wrote it while he was working for Testo.

[udarrell]

Mark, from what I have witnessed, we need a total retraining of service techs; few pay much if any attention to 'first & foremost' getting airflow right. I also believe they need to be certified as to, at the least, their knowledge. These horrible shortcomings need to be eliminated if we are to begin to reduce the wasteful use of energy...

I've seen some unbelievable A/C add-ons, on older belt-drive blower oil furnaces that will literally blow your mind when it comes to extreme low airflow; that should never happen to an HVAC consumer. Plus, most of them are left that way until a furnace change-out many, many long years later!

Few homes are energy efficiency rater/audited, & then after retro-work is done, have a room by room heat-gain heat-loss performed for proper equipment sizing & airflow to each room. Only the proper sequenced Best Practices will yield total optimal efficiency & optimally reduced energy utility bills.

[Trehak01]

I attended a trade school that mainly tough the basics of electricity and refrigeration.. I had to learn everything from there in the field. I spend most nights reading on this site and reading articles on subjects that trouble me most. If i had a call that I didn't get or didn't understand why something happen, more than likely you'll find me reading what I can when I get home. My education started when I started my first day of work.

[bmathews]

I may or may not have read this. If it's a reciprocating 2 speed compressor. Bristol brand I believe had a problem shifting to high. I put about the same year model on this house and it worked great for a while, then would crap out and run again then crap out. Never not cooling, just not very well. It's a flaw with the compressors, I think there was some bulletin on them. I got a brand new unit for my customer with a scroll compressor. I had another one which was about a 2009 recip. They could get a brand new scroll for cost basically, they got a much better unit for a small amount more. When the crankshaft reverses positions in the compressor, it doesn't shift all the way as I recall. I think getting a little blow by in the 1st cylinder or not enough. I don't remember all the details, but was a problem.

[rogressem]

Checking in for the new cooling season. This never got fixed (mediocre performance 2nd stage, supply air temp goes up about 5F from low to hi stage). Last season, TXV was replaced, 4" spacer inserted between blower and evap, and finally a new blower motor. Carrier footed the bill for most of that.

Unfortunately, the local Carrier rep has moved on, and I'm somewhat starting over trying to get Carrier re-engaged this season. Still think its that Bristol 2 stage compressor. I figure that Carrier can't now say everything is "within specs", otherwise they would not have spent the money doing those things last season.

Will keep you updated.

[motoguy128]

I guess Carrier wants to save face, but it seems like they'd almost be money ahead just sending a whole new Infinity 16 or 17 2 stage scroll unit any time they have significant issues where a Bristol is involved. Carrier discontined this product for a reason. I think contractor didn't want to touch them anymore.

[Shophound]

Checking in for the new cooling season. This never got fixed (mediocre performance 2nd stage, supply air temp goes up about 5F from low to hi stage). Last season, TXV was replaced, 4" spacer inserted between blower and evap, and finally a new blower motor. Carrier footed the bill for most of that.

Unfortunately, the local Carrier rep has moved on, and I'm somewhat starting over trying to get Carrier re-engaged this season. Still think its that Bristol 2 stage compressor. I figure that Carrier can't now say everything is "within specs", otherwise they would not have spent the money doing those things last season.

Will keep you updated.

I just read through this thread for the first time and there's no stifling a gut reaction to shake my head in disbelief until my neck is sore. :gah:

Bottom line is you need someone who knows refrigeration and airflow theory with experience and confidence. You have them here on this site but you don't have someone you know personally - yet - that you can pick up the phone, tell him to come over, and replace that damn compressor, even if you have to pay out of pocket for it.

If I were in your shoes I'd yank that Bristol out of there and install a Copeland Ultratech scroll in its place. Of course that might freak out the Infinity control, but it might not, given what it has been dealing with so far. :grin2:

Something I noticed while reading earlier in the thread as to why capacity seemed worse in 2nd Stage vs. first...chalk it up to coil bypass factor. If the compressor is doing little to no more real work in 2nd stage, the only thing that changed was the indoor blower speed. That means you're moving more air across the evaporator with no increase in refrigeration capacity. The coil warms up, which would explain the modest increase in suction pressure with little change in head pressure. The 50% increase in amp draw can be attributed to perhaps a partial loading of the second stage cylinder. I'm inclined to agree with others who have stated the second stage valves are weak. I've seen weak valves on single stage compressors where the comp will still move refrigerant but the loss of capacity is just enough to bring comfort complaints. No reason why this can't be a similar situation with your Bristol TS.

[motoguy128]

I don't think retofit will work sicne it's a communicating unit and the condenser control board has logic specific for that 2 step recip. I'm not sure if the piping would even be sized right. You have ot gut the whole unit.

Better to just work hard with the distributor, contractor and Carrier to have mercy and swap out the whole condenser with a new Infinity 17 or 16 (can't remember if this was a heat pump) 2 stage scroll.

[Shophound]

I don't think retofit will work sicne it's a communicating unit and the condenser control board has logic specific for that 2 step recip. I'm not sure if the piping would even be sized right. You have ot gut the whole unit.

Better to just work hard with the distributor, contractor and Carrier to have mercy and swap out the whole condenser with a new Infinity 17 or 16 (can't remember if this was a heat pump) 2 stage scroll.

You're probably right...my remark was made out of frustration for the OP's ongoing tragic saga of getting this resolved.

Funny how folks who design and sell stuff can't find anybody smart enough to fix it when something goes wrong.

[mark beiser]

You're probably right...my remark was made out of frustration for the OP's ongoing tragic saga of getting this resolved.

Funny how folks who design and sell stuff can't find anybody smart enough to fix it when something goes wrong.

The funny/sad thing is, I diagnosed his problem 2 or 3 years ago in one of his first threads about it, before the Carrier "tech rep" suggested the first of several rounds of repairing things that were blatantly obviously(to anyone who understood what the measurements were all but screaming at them) NOT the problem, to the tune of several thousand dollars worth of work.

[Shophound]

The funny/sad thing is, I diagnosed his problem 2 or 3 years ago in one of his first threads about it, before the Carrier "tech rep" suggested the first of several rounds of repairing things that were blatantly obviously(to anyone who understood what the measurements were all but screaming at them) NOT the problem, to the tune of several thousand dollars worth of work.

It's tragic, when you think about it. They keep dancing around the problem while remaining in obstinate denial about what the problem truly is! I mean here we are, supposedly low food chain service techs, and rather than try umpteen million things, a form of "poke and hope" diagnostics, we actually analyze the system's behavior and make an informed decision on a remedy. I mean come on...for the OP's system, what CAN'T twenty minutes of time with your SMAN3 and digital duct probe psychrometer tell you about what's going on here? The OEM rep should have a tool chest of resources at his disposal, such as a way to talk with the engineers who designed the thing! Or is everything so compartmentalized these days that the left hand has no idea what the right hand does? Where engineers only understand how it should work, but not know what can go wrong, and how to correct it? To me, if you design and build something, you should know the various ways it could barf all over the end user before you let it out the door.

[bmathews]

I replied to this post sometime in the past. Not sure when. I just replaced another one of these Bristol recip 2 speeds last week that took a crap. Carrier still has the program where they subsidize the changing of unit. It's a time based scale. They will credit $450 to new compressor. 1-3 years is free new unit. 3.1 -6 years $995 and 6.1-10 years $1995. The customer has to pay whatever labor is involved to their contractor. It's all in the bulletin to give to the customer.