High Suction/Normal Discharge

[smurry]

Hello, all. I'm new to the forum, but have read a lot of useful information over the years. Now I've got a system that has me stumped.

Complaint: Poor cooling/poor efficiency. Unit runs all day (and night), but can't get temp down below 80 degrees on a warm day (in Houston).

Unit: York CZE04811 Condenser, G2FD060A24 Indoor Unit, both 3 years old.

R-410A system with TXV

Readings:
Outdoor dB: 95
Outdoor wB: 87
Indoor dB: 82
Indoor wB: 72
Suction Pressure: 164
Suction Temp: 61
Discharge Press: 350
Discharge temp: 96
Supply temperature: 66

So, I've got 11 degrees of Subcooling, which means the charge is about right (based on the chart on the unit), but only 2 degrees of Superheat.

I've already replaced the TXV, and verified that it is operating. I have also verified both compressor stages are operating (had to replace the rectifier for the 2nd stage, but it only brought the suction down a few PSI).

Also, I've checked the airflow (both evaporator and condensor). All looks good.

I'm thinking maybe the refrigerant is contaminated, but other than this I'm running out of ideas. Can anyone offer any suggestions?

Any suggestions on how I might verify whether the refrigerant is contaminated (besides discharging and replacing with new)?

[BaldLoonie]

We'd be glad to help but we need to get you promoted to a pro member. To do so, you have to get in 15 posts then click the link above to apply for professional membership. So find some topics to post in, get your pro membership and we'll move this thread to the pro tech section and you'll get all kinds of replies. Right & crazy!

[smurry]

Does responding to my own thread count as one?

[Sleuth]

It seems that it does. :p

[smurry]

Excellent. Then only 4 more to go...

[udarrell]

Look for whatever is causing the sensor bulb to be too cold & thus over feeding the coil - compared to a lesser heatload going through the coil.

Anything blocking airflow through some circuits? Check for variation of temps at the outlet of the circuits at the evap manifold. Can't say more w/o being too technical.

[smurry]

Just applied for Pro Membership. Assuming it get approved, anybody know how to move this thread over, or do I just repost it there?

[jpsmith1cm]

As I am reading this, the solution seems so obvious you are probably tripping over it.

Did you check amperage?

[jpsmith1cm]

Just applied for Pro Membership. Assuming it get approved, anybody know how to move this thread over, or do I just repost it there?

It may take a week or two to be approved.

[udarrell]

The moderators will move it for you.

The extremely low superheat with a replaced TXV indicates that something in the evap circuitry maybe causing some abnormal temps sensed by the TXV bulb.

Does TXV have a proper functioning External Equalizer? What's your response?

[smurry]

Hmmm. Hopefully I will have solved the problem before I get approved, then.

[smurry]

Yes, I did check amperage. 12 Amps on first stage, 18 amps with both stages running (Copeland Scroll).

If the compressor were out, I'd expect that the head pressure would be low, too, but it's normal, and I can get it to vary with charge.

[beenthere]

A mod can move it.

Don't make double post, or a mod will delete one of them.

I could move it now. Of course you wouldn't be able to read the answers though. :D

[smurry]

udarell, that's why I'm thinking it might be a bad mix of refrigerant. If the compressor and TXV are working properly, but somehow there is mixed refrigerant then the saturation temperature of whatever mix is in there might be higher than normal for R-410A, thus the high suction pressure.

With basically no superheat it's obviously flooding the evap, but the pressure is high so bad mix?

I'm thiking about disconnecting the compressor and running just the condensor fan and waiting for the pressure and temperature to equalize at whatever the outdoor drybulb is. Then, a pressure measurement ought to give me a quick check whether the refrigerant mix is off. If the pressure at the equilibrium temperature doesn't match the saturation for R-410A at that temp, then there has got to be something else in the mix.

Is there any test kit for refrigerant type? It would probably cost more to test than just to replace the refrigerant, but I would hate to replace the charge and then find out it's something else...

Sorry if this is supposed to be in the pro forum. If posting this in the "open" is against the rules, I'll stop...

[udarrell]

udarell, that's why I'm thinking it might be a bad mix of refrigerant. If the compressor and TXV are working properly, but somehow there is mixed refrigerant then the saturation temperature of whatever mix is in there might be higher than normal for R-410A, thus the high suction pressure.

With basically no superheat it's obviously flooding the evap, but the pressure is high so bad mix?

I'm thinking about disconnecting the compressor and running just the condensor fan and waiting for the pressure and temperature to equalize at whatever the outdoor drybulb is. Then, a pressure measurement ought to give me a quick check whether the refrigerant mix is off. If the pressure at the equilibrium temperature doesn't match the saturation for R-410A at that temp, then there has got to be something else in the mix.

That is a proper procedural check for correct refrigerant or non-condensibles.


Is there any test kit for refrigerant type? It would probably cost more to test than just to replace the refrigerant, but I would hate to replace the charge and then find out it's something else...

Sorry if this is supposed to be in the pro forum. If posting this in the "open" is against the rules, I'll stop...
Well, DIY's can't perform any part of what we are talking about or might do, so not much to be concerned about.

I can't get back to the indoor split, was it low or high?

[smurry]

Low split. Supply: 66, return: 82.

High indoor dewpoint, clearly not cooling properly.

[beenthere]

Well, DIY's can't perform any part of what we are talking about or might do, so not much to be concerned about.



More then one DIYer has thir own manifolds, and full set of tools.

So DIY is a concern.

[udarrell]

Low split. Supply: 66, return: 82.

High indoor dewpoint, clearly not cooling properly.

Agreed Beenthere, we need to take their gauges & tools away from them because they disable or kill themselves.

Of course, they will probably cause so much damage they'll have to call a PRO.

The high indoor dew point is because the coil is not cold enough, &/or there is also a lot of high humidity air infiltration...

The low 16-F split is normal with high indoor humidity conditions; if it were condensing a lot of moisture, - which it isn't doing!

An oil clogged interior insulated evap, or un-removed oil film on the exterior of coil & fins (causing lack of sensible & latent heat loading.

[beenthere]

Agreed Beenthere, we need to take their gauges & tools away from them because they disable or kill themselves.

Of course, they will probably cause so much damage they'll have to call a PRO.




Or, easier yet, just not post DIY advise.

[smurry]

udarrell, Right, the low split is due to coil not being cold enough. Also not condensing much water, which of course makes sense.

I don't think it's an infiltration problem. Attic appears to be well insulated (radiant barrier, not overly hot for this area). Plus, I checked the return (wall plenum) and it seems to be pretty well sealed.

Oil clogging/insulating the evap could be a problem. Certainly that would create a low (apparent) heat load. However, then the TXV should just throttle back the refrigerant, and I still should have SOME superheat.

[udarrell]

Or, easier yet, just not post DIY advise.

I made a living servicing calls where either so-called techs had caused the problems or some were DIY'ers claiming a tech had serviced their equipment.

That is why I say the more they think they know, & start messing with things, the more calls you PROs' will get.

They can really mess up equipment, big-time. It's money in the bank, a win/win for you & them when they finally get a pro.

[beenthere]

Site rules, no DIY.
Means not giving out the advice.

[smurry]

udarrell, I just noticed your earlier question about the external equalizer. Yes, it is externally equalized. I replaced the entire TXV, too, not just the power head, in case that's the next question that might come up.

[nick muniz]

Just have the whole system replaced by a qualified person and it will be fine then.

[udarrell]

Site rules, no DIY.
Means not giving out the advice.
This is just my opinion based on my experience since before the mid-1970's.

When someone takes it on themselves to try anything that requires a licensed & fully insured contractor, they assume all the liability & loss due to their mistakes.

We & our insurance company cover all facets of liabilities. Therefore, it is not a wise DIY'er to do something that is illegal, dangerous & could result in serious human & material loss, with no redeeming recourse or recovery.

Severe injuries or death are never recoverable.

Yes, I tell them on Twitter how they can check whether their A/C is performing properly, & how they can greatly reduce their utility bills.

I assure you, I know from experience this gets their focus on why it doesn't seem to be keeping them comfortable, & some will try to check their A/C in a totally safe way, but end up calling a contractor for help to make it cool better.

When the combination of a digital thermometer, a wet cotton cloth, &/or a low cost humidity gauge - shows something is not right, I tell them to call a HVAC contractor.

I would say the user's of over 95% of A/C systems operating well below their rated nominal Capacities - don't have a clue, concerning the reason it doesn't cool their home.

Many times the clueless so-called service person doesn't have a clue & convinces the user that their A/C is doing all it can, & their fix is a larger tonnage unit.

I can demonstrate to anyone whether their A/C is performing as it should with only a low cost digital thermometer that can be used on the lines to measure those temps, along with the condenser discharge temp, & indoor split, plus wet bulb or humidity. How many Techs know how that can be done?

If I were back in business & they read & tried my simple methods a huge percentage of them would call me. I know that because of the responses I get.

They end up calling contractors, they don't try to correct what they don't know for sure is wrong or how to remedy the problems without professional help.

If you lose one job out of 20 that you got you're way ahead. Plus, most that try to go it alone will call for help, my prayer is that they get a PRO & not someone that won't do right by them.

If we get too uptight about possible DIY'ers because we talked tech way above their heads, then we won't meet the interests' or needs of users', & lose service calls - whereby both would end-up winners. - Darrell

[davefr]

I read this thread a couple time. There is no request for "step by step DIY advice".

The forum should either:
1. Modify the rules to include "no technical info"
2. Lock up the site to pros only
3. Point the DIY'ers to the DIY HVAC forum

The reason every other post on this forum get's banned is because the rules aren't spelled out clearly. There's a huge difference between "step by step DIY" advice and threads like this where pros asking for "in depth questions" that typical homeowners wouldn't understand.

udarrelle is a breath of fresh air on this forum.

I could easily make the case that if homeowners understood some basic refrigeration concepts they could enhance the efficiency of pros doing diagnostics. However even basic refrigeration theory is a taboo subject here.

[catmanacman]

i went to a house monday that the home owner caught on fire installing a used condensor that he bought on craigslist

[beenthere]

I read this thread a couple time. There is no request for "step by step DIY advice".

And it hasn't been closed, yet

The forum should either:
1. Modify the rules to include "no technical info", No
2. Lock up the site to pros only. No
3. Point the DIY'ers to the DIY HVAC forum. No

The reason every other post on this forum get's banned is because the rules aren't spelled out clearly. There's a huge difference between "step by step DIY" advice and threads like this where pros asking for "in depth questions" that typical homeowners wouldn't understand.

udarrelle is a breath of fresh air on this forum.

I could easily make the case that if homeowners understood some basic refrigeration concepts they could enhance the efficiency of pros doing diagnostics. However even basic refrigeration theory is a taboo subject here.

You can always start your own forum, and make what ever rules you want. And run it the way you like.

[beenthere]

We have Pro only forums, for pro's to get the technical advise they need, or want.
No reason for that advise or info to be posted, and discussed in the open forms.

[beenthere]

[B]This is just my opinion based on my experience since before the mid-1970's.


If we get too uptight about possible DIY'ers because we talked tech way above their heads, then we won't meet the interests' or needs of users', & lose service calls - whereby both would end-up winners. - Darrell


Same NO DIY rules, as when BOSS started this forum back in 2000.

They're not open to debate.

[Airmechanical]

The reason every other post on this forum get's banned is because the rules aren't spelled out clearly.

i agree, if you speak SWAHEALY it's not clear!:rolleyes:

but in English, no DIY= no DIY

how can you do it yourself without step by step instructions?

and if step by step instructions were given, a lot of people will start getting hurt

believe it or not, this is a very dangerous trade

we don't want to see inexperienced people like yourself getting hurt

so basically, we are protecting you from yourself:eek:



.

[udarrell]

First, I am NOT telling anyone how to run their forum, it can be run anyway that any of them want to run it.

If we care about providing good service to the user, then because of what I've witnessed regarding very poor service, the user needs very simple & totally safe ways & means, without the use of a manifold gauge, to check their own systems operating condition.

I have witnessed three different service personnel, 3 different times checking a couple years old system that their company installed, & merely checking suction pressure on TXV metered systems & then telling the user that the charge is okay & it's doing all it can. (It also has sub-par indoor airflow.)

Since I know the users, without using a manifold gauge, using a low cost digital Thermometer bought at an HVAC/R Supply outlet, I checked the condenser air discharge temp, the liquid line subcooling even indoors in the basement where the bend goes into the plenum. (Not quite 1-F SC.)

I know these methods are accurate enough, because I have verified the pressure & temp test relationships many times in the field.

Now here is the scoop on that system, the airflow is horribly low, because of long experience, & with only five 6" branch runs, I estimated the airflow at well under 300-cfm per-ton. (Field testing has also verified that there are far too many operating with similar sub-par conditions.)

Now, the Subcooling was barely 1-F, - with & even without your ear on it, there was loud surging in the liquid-line going into the TXV.

The temp coming off the 1.5-Ton 12-SEER condenser was a mere 12-F, when under those outdoor & indoor conditions it should have been 20-F. I know because I have the performance data on that exact unit with a 2-ton TXV E-Coil. There are also CT temp variant perimeters regarding different SEER levels.

Now, because the user knows nothing concerning a simple & totally safe way to check the charge & relative performance of their A/C, the user believes the service company's techs & will put up with half the cooling performance they paid for! (That's Realty I have personally witnessed.)

Now, don't tell me I can't check an A/C with just a digital thermometer that lays flat on the tubing which I insulate, & a wet cotton cloth to take wet bulb temps. I had the best sensor bulb SH & SC instruments going, which I no longer have.

Now, the A/C check is safe to do, it violates no codes or regs, & it provides users' a way to keep unethical or unskilled characters from deluding them.

We should all want users' to be well served by our profession.
I consider what is happening to far too many users' as fraudulent conduct by some service companies & their service personnel.

All of us in this industry need to do our very best to turn this situation around in favor of those we are dedicated to serve.

If we're 'not doing the Works of the Word' then we are guilty of the 'Sin of Omission' by which we will be most harshly judged. - Darrell

[smurry]

Seems like I may have started something by posting this question in the "open" forum. Sorry for that. As I mentioned in some of my posts, I'm new to this forum and probably should have waited for my "PRO" membership t be approved. I did e-mail all the information over yesterday, but I understand it may take a couple of weeks to be approved.

All that being said, it would be nice if this forum had a "private message" function like some do. That way, if anyone wanted to send me some thoughts without endangering the lives of all the DIY'ers out there, they could do it over PM.

[davefr]

All that being said, it would be nice if this forum had a "private message" function like some do. That way, if anyone wanted to send me some thoughts without endangering the lives of all the DIY'ers out there, they could do it over PM.

A PM feature would be good. They're probably worried that all the DIY requests would then go to PM's. However most modern forum SW allows the PM feature to be turned on and off by the member.

[beenthere]

We have the PM feature restricted to Pro members only.

[smurry]

Sounds like the "Pro" version is really the way to go. Can't wait to try it out.

[just_opinion]

Readings:
Outdoor dB: 95
Outdoor wB: 87
Indoor dB: 82
Indoor wB: 72
Suction Pressure: 164
Suction Temp: 61
Discharge Press: 350
Discharge temp: 96
Supply temperature: 66

)?

With two more measurements (supplying WB, and CFM) then you can tell if the unit performs properly or not. Then you don't have to hear all these guys yapping for 2 days

[tinknocker service tech]

We have Pro only forums, for pro's to get the technical advise they need, or want.
No reason for that advise or info to be posted, and discussed in the open forms.


I agree


What some of us think is normal or second nature can be very dangerous if proper caution isn't used:confused:

[smurry]

CFM is 1820, didn't measure the supply wet bulb, but I'm going back tomorrow. I'll check and post again.

[udarrell]

CFM is 1820, didn't measure the supply wet bulb, but I'm going back tomorrow. I'll check and post again.
If all your data is quite accurate, we can ballpark the BTUH it's delivering.:)

[smurry]

For the CFM, I used a Fluke 922 and did a 5-point duct traverse. Not sure how accurate that is, but it's what Fluke recommends for airflow measurments. I guess it should be pretty close.

I'm not sure how to estimate the BTUH without the supply wet-bulb. How can we estimate the latent heat removal without the supply wet bulb (or measuring the volume of condensate draining out)?

[udarrell]

For the CFM, I used a Fluke 922 and did a 5-point duct traverse. Not sure how accurate that is, but it's what Fluke recommends for airflow measurments. I guess it should be pretty close.

I'm not sure how to estimate the BTUH without the supply wet-bulb. How can we estimate the latent heat removal without the supply wet bulb (or measuring the volume of condensate draining out)?
I'd stay with the wet bulb.
There are good instruments at reasonable prices to do the wet bulb checks.
Testo 605-H2 Humidity Stick (wet bulb) Do a search for it.

You'd have to time the collection of condensate & its easier for me to get the result with the wet bulb.