Carrier Infinity - poor performance high stage

[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...


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...Guide_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.