A/C Not holding set temp?

[MIXMAN812]

Hello,

This is my first post and all replys and help is VERY much apperciated. Ok heres my issue, basically my a/c wont hold the temp i have it set at (78). The equipment i have is a TempStar 10 Condenser (outside unit) with the matching airhandler/furance (attic unit). I bought the house brand new in 2001 and havent had any problems with it since new. So far i have cleaned both the indoor & outdoor coils, replaced filters, etc, so everything is as clean as a virgins honeypot. The typical DIY stuff i can do. Before i call a tech and spend money, i was hoping to get some good advice before i spend money on something i overlooked or can possibly check myself. The only info i cant help with is the specs on the unit, those manuels are long gone. Any advice?

Extra info: Insulation is decent, not great, windows and blinds always closed during the day. Air temp in is 78*, air temp out is 67* from the registers. Its also been between 105*-110* here these past couple of weeks.

[NY2GA01]

Hello,

So far i have cleaned both the indoor & outdoor coils, replaced filters, etc, so everything is as clean as a virgins honeypot. The typical DIY stuff i can do.

I learned something new today, I did not know cleaning coils was a DIY project.

The are lots of things to list that you over looked. The best thing to do at this point is to call in a service.

[MIXMAN812]

Lol, well as DIY as it can be i guess. Both were cleaned with foaming cleaners that I purchased at an HVAC supply (friend owns it). He said its what the techs use when they clean coils. Anywho, thanks for the advice.

[udarrell]

Extra info: Insulation is decent, not great, windows and blinds always closed during the day.
Air temp in is 78*, air temp out is 67* from the registers.
It's also been between 105*-110* here these past couple of weeks.
The indoor air-temp-split is only 11F; at around 50% indoor relative humidity it should be around 20F.

Let us know what the SEER Rating (just noticed it looks like a 10-seer R-22 condenser; I'll look up the pres/temps) is of the outdoor condenser &, get the air-temp entering & leaving the condenser; that will help us determine what the cause may be for the low indoor temp-split.

If possible, use a digital thermometer so you get the tenth's readings; also buy a low cost humidity gage for indoor use; everyone needs one in their home.

How hot is it in the attic where the equipment & ducts are located.
Could be insufficient insulation, plus various air leaks.

Approximately what are the outdoor humidity levels?

If the condenser discharge-air-temp is way too high for that SEER Rated condenser, I'd look for a Return Air leak coming from the hot attic area.

Unless you have very high indoor humidity, something is causing the indoor air-temp-split to be way too low!

The Outdoor humidity could be 50% but will hold a lot of grains of moisture at 105 to 110-F.

Therefore, it wouldn't take much of a RA leak to have a dominate latent/high humidity overloaded indoor coil, that would drop the indoor-split & raise the outdoor condenser split.

[ar_hvac_man]

Air temp in is 78*, air temp out is 67* from the registers. Its also been between 105*-110* here these past couple of weeks.

This says alot to me. You have a very slight non-fixable for DIY'ers problem that is just now showing up due to the intense heat.

[second opinion]

The indoor air-temp-split is only 11F; at around 50% indoor relative humidity it should be around 20F.

Let us know what the SEER Rating (just noticed it looks like a 10-seer R-22 condenser; I'll look up the pres/temps) is of the outdoor condenser &, get the air-temp entering & leaving the condenser; that will help us determine what the cause may be for the low indoor temp-split.

If possible, use a digital thermometer so you get the tenth's readings; also buy a low cost humidity gage for indoor use; everyone needs one in their home.

How hot is it in the attic where the equipment & ducts are located.
Could be insufficient insulation, plus various air leaks.

Approximately what are the outdoor humidity levels?

If the condenser discharge-air-temp is way too high for that SEER Rated condenser, I'd look for a Return Air leak coming from the hot attic area.

Unless you have very high indoor humidity, something is causing the indoor air-temp-split to be way too low!

The Outdoor humidity could be 50% but will hold a lot of grains of moisture at 105 to 110-F.

Therefore, it wouldn't take much of a RA leak to have a dominate latent/high humidity overloaded indoor coil, that would drop the indoor-split & raise the outdoor condenser split.

And where is here that is 105, you may be well above design temperature?

[udarrell]

And where is here, that is 105, you may be well above design temperature?

They should always tell use the state & what major city they are near or, the relative location in that state. (Should be a requirement)

However, even if the condenser were undersized relative to the summer design the unit will still perform within the same specification parameters relative to the data factors.

The smaller unit would just have less airflow volume (perhaps more efficient airflow) &, less total Btuh output, its indoor & outdoor performance specifications would, of course, be relatively the same even though undersized.

[tipsrfine]

The indoor air-temp-split is only 11F; at around 50% indoor relative humidity it should be around 20F.

Let us know what the SEER Rating (just noticed it looks like a 10-seer R-22 condenser; I'll look up the pres/temps) is of the outdoor condenser &, get the air-temp entering & leaving the condenser; that will help us determine what the cause may be for the low indoor temp-split.

If possible, use a digital thermometer so you get the tenth's readings; also buy a low cost humidity gage for indoor use; everyone needs one in their home.

How hot is it in the attic where the equipment & ducts are located.
Could be insufficient insulation, plus various air leaks.

Approximately what are the outdoor humidity levels?

If the condenser discharge-air-temp is way too high for that SEER Rated condenser, I'd look for a Return Air leak coming from the hot attic area.

Unless you have very high indoor humidity, something is causing the indoor air-temp-split to be way too low!

The Outdoor humidity could be 50% but will hold a lot of grains of moisture at 105 to 110-F.

Therefore, it wouldn't take much of a RA leak to have a dominate latent/high humidity overloaded indoor coil, that would drop the indoor-split & raise the outdoor condenser split.

Liking the thinking in blue, but of course the others could be on the right track, or more likely a combination of both; too bad there are too few pros' that know how to address both.

[MIXMAN812]

"Let us know what the SEER Rating (just noticed it looks like a 10-seer R-22 condenser; I'll look up the pres/temps) is of the outdoor condenser &, get the air-temp entering & leaving the condenser; that will help us determine what the cause may be for the low indoor temp-split."

Ok entering the condenser as of right this second the air temp is-98*.
Coming out of the top its-108*
"How hot is it in the attic where the equipment & ducts are located."

As of right now its 135*

"Approximately what are the outdoor humidity levels?"

Outdoor humidity right now is 9%, in my house its 12%

[MIXMAN812]

I live in LAS VEGAS NV btw sorry, forgot to put that.

[MIXMAN812]

That is true....the problem is that this is the first year i have had this problem...even when it hit 114* a few years back it at least held the 78* temp...this year it seems not to want to do that for some reason

[second opinion]

That is true....the problem is that this is the first year i have had this problem...even when it hit 114* a few years back it at least held the 78* temp...this year it seems not to want to do that for some reason

Have the system serviced if it's performance has changed

[MIXMAN812]

thank you. i am, i was just answering everybodys questions thats all.

[udarrell]

"Let us know what the SEER Rating (just noticed it looks like a 10-seer R-22 condenser; I'll look up the pres/temps) is of the outdoor condenser &, get the air-temp entering & leaving the condenser; that will help us determine what the cause may be for the low indoor temp-split."

Ok entering the condenser as of right this second the air temp is-98*.
Coming out of the top its-108*
"How hot is it in the attic where the equipment & ducts are located."

As of right now its 135*

"Approximately what are the outdoor humidity levels?"

Outdoor humidity right now is 9%, in my house its 12%
Just now, saw your post.

Well, the condenser split is only 10-F, which is extremely low, however, that indoor 12% Relative Humidity (RH) is extremely low, which greatly lowers the condenser split.

We now need the indoor Return Air & Supply Air temp-split, which should be very high at a mere 12% RH; however, we will have to start over to get all the readings including the new % of RH.

At 12% RH indoors &, @ 400-CFM per ton of cooling; at 88-F Return Air temp, & at the closest SA diffuser to the evaporator it should show close to 59-F Supply Air temp. That's a 29-F Temp-Split.


Air temp in is 78*, air temp out is 67* from the registers.
The indoor air-temp-split is only 11F; at around 12% indoor relative humidity it should be around 29F. An 11-F indoor temp-split would be WAY OFF...

This will be more difficult to pinpoint a problem using this method because, the indoor humidity is, so low, it's way off the normal "Expanded Cooling Data" charts, therefore, it will be more difficult to figure what the condenser discharge air temp should be with those unusual conditions...

So that is the original condenser in that 2001 new home. Do you know what SEER Rating the condenser is?

[MIXMAN812]

Just now, saw your post.

Well, the condenser split is only 10-F, which is extremely low, however, that indoor 12% Relative Humidity (RH) is extremely low, which greatly lowers the condenser split.

We now need the indoor Return Air & Supply Air temp-split, which should be very high at a mere 12% RH; however, we will have to start over to get all the readings including the new % of RH.

At 12% RH indoors &, @ 400-CFM per ton of cooling; at 88-F Return Air temp, & at the closest SA diffuser to the evaporator it should show close to 59-F Supply Air temp. That's a 29-F Temp-Split.


The indoor air-temp-split is only 11F; at around 12% indoor relative humidity it should be around 29F. An 11-F indoor temp-split would be WAY OFF...

This will be more difficult to pinpoint a problem using this method because, the indoor humidity is, so low, it's way off the normal "Expanded Cooling Data" charts, therefore, it will be more difficult to figure what the condenser discharge air temp should be with those unusual conditions...

So that is the original condenser in that 2001 new home. Do you know what SEER Rating the condenser is?

udarrell,


Thank you so much fro helpling me on this btw........


OK as far as i can tell from looking it up online....its a 10 SEER.....and yes its VERY low humidity here in vegas. As for the return temps and register temps i just did them again and they are the same as before. This unit only is shutting off at night so the temps that you are asking are usually the same through the day. Also its about 110* today id that helps with anything.

[udarrell]

udarrell,Thank you so much for helping me on this btw........

OK as far as i can tell from looking it up online....its a 10 SEER.....and yes its VERY low humidity here in Vegas. As for the return temps and register temps i just did them again and they are the same as before.
This unit only is shutting off at night so the temps that you are asking are usually the same through the day. Also its about 110* today if that helps with anything.
Well, at those ultra high outdoor temps the condenser split is also reduced, therefore it may not be far out of line.

However, the indoor temp-split of only 11-F is unacceptable & should be above 20-F; therefore, there appears to be a problem with the system that needs addressing.

[B]The ultra high outdoor temps 110 to 115-F considerably reduce the Btuh capacity of the Rated tonnage by around 20 to 30%.

You really need to know what CFM volume of airflow is going through the indoor evaporator coil.

Also, the charge needs to be checked, some refrigerant may need to be added; or, someone could have way overcharged it simply trying to get the suction line beer can cold.

Find a good service tech somewhere that knows how to run all the right diagnostic checks.

[MIXMAN812]

[QUOTE=udarrell;13597971]Well, at those ultra high outdoor temps the condenser split is also reduced, therefore it may not be far out of line.

However, the indoor temp-split of only 11-F is unacceptable & should be above 20-F; therefore, there appears to be a problem with the system that needs addressing.

[B]The ultra high outdoor temps 110 to 115-F considerably reduce the Btuh capacity of the Rated tonnage by around 20 to 30%.

You really need to know what CFM volume of airflow is going through the indoor evaporator coil.

Also, the charge needs to be checked, some refrigerant may need to be added; or, someone could have way overcharged it simply trying to get the suction line beer can cold.

Find a good service tech somewhere that knows how to run all the right diagnostic checks.[/QU

Awsome!!! Thank you udarrell for all your help....i dont have a cfm meter or i would tell you what the measurement is. However i will do what you say and report what the issue is. Just an FYI The charge hasant been checked since i purchased the house so that is the first thing i will have checked. Also, just curious....what should the cfm's be so i know the tech is doing his job?

[udarrell]

[QUOTE=udarrell;13597971]Well, at those ultra high outdoor temps the condenser split is also reduced, therefore it may not be far out of line.

However, the indoor temp-split of only 11-F is unacceptable & should be above 20-F; therefore, there appears to be a problem with the system that needs addressing.

[B]The ultra high outdoor temps 110 to 115-F considerably reduce the Btuh capacity of the Rated tonnage by around 20 to 30%.

You really need to know what CFM volume of airflow is going through the indoor evaporator coil.

Also, the charge needs to be checked, some refrigerant may need to be added; or, someone could have way overcharged it simply trying to get the suction line beer can cold.

Find a good service tech somewhere that knows how to run all the right diagnostic checks.[/QU

Awsome!!! Thank you udarrell for all your help....i dont have a cfm meter or i would tell you what the measurement is. However i will do what you say and report what the issue is. Just an FYI The charge hasant been checked since i purchased the house so that is the first thing i will have checked. Also, just curious....what should the cfm's be so i know the tech is doing his job?
We need to know the Tonnage Rating of the condenser.
In your extremely low humidity climate, I'd want at least 450-CFM per Ton of cooling.

I.E., a 4-Ton condenser @ 450 per ton would need 1800-CFM.

I doubt the duct system is sized large enough with enough supply-side runs & Returns for it to use 450-CFM per Ton; but that's what I would want in order to get as much a sensible load through the evaporator as possible.

Tell the contractor on the phone that you want an accurate as possible CFM test performed on the duct system's airflow; the contractor may not have an anemometer or anything to do an actual CFM test.
Before the CFM test is performed check the blower wheel blades & the evaporator coil for lint & other debris.

Static pressure tests of various sectors of the duct system should also be performed, along with as much of a Manual D that can be performed; that tells the Tech what the blower is able to deliver through that duct system sizing & configuration.

Don't forget the proper enlarged sizing of the Return Air filtering system areas...that can make a lot of difference in delivered airflow to & from the rooms.

[marvin]

you should be getting a better split than you are. sounds like you need to get hold of your friend at the parts house for a recomendation for
a good tech. while your looking for a tech dont shop from the right hand side of the menu.

[Special Ed]

[QUOTE=MIXMAN812;13601991]
We need to know the Tonnage Rating of the condenser.
In your extremely low humidity climate, I'd want at least 450-CFM per Ton of cooling.

I.E., a 4-Ton condenser @ 450 per ton would need 1800-CFM.

I doubt the duct system is sized large enough with enough supply-side runs & Returns for it to use 450-CFM per Ton; but that's what I would want in order to get as much a sensible load through the evaporator as possible.

Tell the contractor on the phone that you want an accurate as possible CFM test performed on the duct system's airflow; the contractor may not have an anemometer or anything to do an actual CFM test.
Before the CFM test is performed check the blower wheel blades & the evaporator coil for lint & other debris.

Static pressure tests of various sectors of the duct system should also be performed, along with as much of a Manual D that can be performed; that tells the Tech what the blower is able to deliver through that duct system sizing & configuration.

Don't forget the proper enlarged sizing of the Return Air filtering system areas...that can make a lot of difference in delivered airflow to & from the rooms.

Also be prepared to spend quite a bit more than just the diagnostic fee if you want all of that done - good to have it done, but I probably wouldn't do all those time-consuming tests for less than $250....

BTW, it's probably just low on Freon - may need to have it topped-off & leak-checked.

[MIXMAN812]

[QUOTE=MIXMAN812;13601991]
We need to know the Tonnage Rating of the condenser.
In your extremely low humidity climate, I'd want at least 450-CFM per Ton of cooling.

I.E., a 4-Ton condenser @ 450 per ton would need 1800-CFM.

I doubt the duct system is sized large enough with enough supply-side runs & Returns for it to use 450-CFM per Ton; but that's what I would want in order to get as much a sensible load through the evaporator as possible.

Tell the contractor on the phone that you want an accurate as possible CFM test performed on the duct system's airflow; the contractor may not have an anemometer or anything to do an actual CFM test.
Before the CFM test is performed check the blower wheel blades & the evaporator coil for lint & other debris.

Static pressure tests of various sectors of the duct system should also be performed, along with as much of a Manual D that can be performed; that tells the Tech what the blower is able to deliver through that duct system sizing & configuration.

Don't forget the proper enlarged sizing of the Return Air filtering system areas...that can make a lot of difference in delivered airflow to & from the rooms.

Ok i will ask him to do it all. I have seen cheap cfm meters at the home depot, maybe i will just pick one up. But i did clean the evap coil this past week and it was filthy!! But after i was done the air coming out of the registers was litterly almost double! So at least i can rule that issue out and tackle everything else you suggested. So just so im understanding what your saying, it is possible that the duct sizing isnt enough? I have a register in every room, including the bathrooms. but i will tell him everything you said and post what he finds here.

[MIXMAN812]

you should be getting a better split than you are. sounds like you need to get hold of your friend at the parts house for a recomendation for
a good tech. while your looking for a tech dont shop from the right hand side of the menu.

lol thank you for the advice!

[MIXMAN812]

[QUOTE=udarrell;13603081]

Also be prepared to spend quite a bit more than just the diagnostic fee if you want all of that done - good to have it done, but I probably wouldn't do all those time-consuming tests for less than $250....

BTW, it's probably just low on Freon - may need to have it topped-off & leak-checked.

Since you mentioned it just curious about something......if its low on freon it has to be from a leak correct? if i understand it, the system is closed and should never need freon if there isnt a leak? or does some freon leak out over time? always wondered this lol

[jpsmith1cm]

Since you mentioned it just curious about something......if its low on freon it has to be from a leak correct? if i understand it, the system is closed and should never need freon if there isnt a leak? or does some freon leak out over time? always wondered this lol

That is correct, to a point.

We must first assume that the system was properly charged.

If a system that was properly charged requires refrigerant, then there is a leak.

[udarrell]

[QUOTE=udarrell;13603081]The quotes are wrong; This is Special Ed's QUOTE not mine! Not originally posted by me!

Also be prepared to spend quite a bit more than just the diagnostic fee if you want all of that done - good to have it done, but I probably wouldn't do all those time-consuming tests for less than $250....

BTW, it's probably just low on Freon - may need to have it topped-off & leak-checked.
First, I am not saying that you are at all wrong in your statement...

However, if the Tech has the proper test instruments & does those tests rather routinely; as they should be doing them when there are similar problems; it doesn't take long to do them, thus the charges to the customer ought to be kept as low as possible, for such critically required diagnostic testing.

I will agree that if someone is doing those tests rarely or for the first time, it will take considerably longer.

The airflow has to be within the required perimeters before checking the charge. Also, the required CFM will be determined by whether the evaporator has the desired heatload passing through it &, that it is absorbing enough of it.

Air conditioning users can do a lot of easy & totally safe testing with just a digital thermometer & an indoor humidity gauge. Then we can help them, with possible clues to problems, with just that simple recorded data.

[smoke]

But after all of this he still needs to call a technician. Sounds like too much homeowner diagnostic to me, wasting time and not finding the answers because you need test equipment.

Checking an air filter is one thing, making this guy run around his house gathering data that he doesn't fully understand doesn't make much sense.

[smoke]

It's been working fine since 2001, I'm sure it's not a design issue.

[udarrell]

But after all of this he still needs to call a technician. Sounds like too much homeowner diagnostic to me, wasting time and not finding the answers because you need test equipment.

Checking an air filter is one thing, making this guy run around his house gathering data that he doesn't fully understand doesn't make much sense.
Those are very simple things that anyone can do & when the result is that it's not in its performance ballpark, - they will call a contractor & get a Tech to further diagnose the problem.

If they want an efficient performing A/C they will jump at the opportunity to log a little simple temperature data & note the indoor humidity percentage.

The methodology is easy to explain &, is easily understood by most of them.
They don't have to do it...it's their choice...you'll get a lot more calls if they do it...

Many go for many years with a system that is not functioning near its Nominal Performance Ratings; largely because someone tells them it's doing all it can; or, that there is nothing more we can do.

I know, even my late brother has been one of them. Those situations need to be exposed & the problems addressed.

[MIXMAN812]

That is correct, to a point.

We must first assume that the system was properly charged.

If a system that was properly charged requires refrigerant, then there is a leak.

i can only guess it was. i hope lol. as far as i can remember at least......the tech has vever added freon to the system, just riutine maint and cleaning as needed. i hope there is no leak.

[MIXMAN812]

Those are very simple things that anyone can do & when the result is that it's not in its performance ballpark, - they will call a contractor & get a Tech to further diagnose the problem.

If they want an efficient performing A/C they will jump at the opportunity to log a little simple temperature data & note the indoor humidity percentage.

The methodology is easy to explain &, is easily understood by most of them.
They don't have to do it...it's their choice...you'll get a lot more calls if they do it...

Many go for many years with a system that is not functioning near its Nominal Performance Ratings; largely because someone tells them it's doing all it can; or, that there is nothing more we can do.

I know, even my late brother has been one of them. Those situations need to be exposed & the problems addressed.

Again UDARREL thank you and everyone else for all your help!!

to be honest i am enjoying learning and doing all you have told me so far. I know that some of the stuff is beyond me because i would have to go to school and learn it but at least what your showing me will help me make sure that the tech is doing his job correctly so i know hes not just going to say something like " yeah the system is old, you should purchase a new one for $XXXX.00 from me to make it work." When it could be something as simple as a low freon charge.
@udarrell.......i am going to pick up a cfm meter this week and post the answer to your questions. also i might have found the specs for this model but bear with me while i make sure its correct before i post it here.

[MIXMAN812]

Ok so i finally got someone to come out and check out my issue......here is the answer i got.....

1. Ac is not meant to run at these temps and is working as best as it can to keep up. (outside temp was 111, when hes tested it.)

2. @ udarrel.. when i asked him to run those tests he said they would cost close to $$$$ to run them so i told him no thank you.

3. Said it did not need FREON, ac was working fine.

Ok so am i crazy? Or do i need a new ac guy?

[MIXMAN812]

Sorry i didnt mean to put the price on there, i will edit it out.

[MIXMAN812]

ok had a new person come out and here are the readings....

Temp out side is 113 degrees..

low pressure is 65
high is 300
any ideas what would be causing such a high pressure? they all keep trying to sell me a new system and not telling me anything else. any help would be apperciated.

Also, if it does need a new system, cant i just purchase a new compressor or have it rebuilt?

[udarrell]

ok had a new person come out and here are the readings....

Temp out side is 113 degrees..

low pressure is 65
high is 300
any ideas what would be causing such a high pressure? they all keep trying to sell me a new system and not telling me anything else. any help would be appreciated.

Also, if it does need a new system, cant i just purchase a new compressor or have it rebuilt?
At 113-F outdoors a 300-psig R-22 head pressure is not much out of line; 65-psig suction is a cold 37.5-F evap-coil.

What is the Superheat & Subcooling at? He should have taken those readings.

An older 10-SEER unit with a larger capacity compressor to the coil sizes & amount of R-22 might get the suction that low.

If it is a piston orifice metering device; at near 115-F & a low indoor humidity it would be flooding the evaporator coil with little or no superheat.

Unless there is a restriction somewhere, that pressure differential indicates that the compressor is pumping okay! Ten SEER units do well in high load situations as they can get the indoor coil colder...

[MIXMAN812]

like an idiot i didnt even think to ask about those readings.....from either guy...ok thats it....im going to hvac school because i cant find a decent tech who will actually try to fix this unit and not keep trying to sell me a new one!! At this rate im going to fly UDARRELL out here to fix this damn thing. It will be cheaper than the quotes im getting GUARANTEED!!!!!
:censored::censored:

Just curious...but what type of restriction are you referring to? The outside is free of any debri.

[udarrell]

like an idiot i didnt even think to ask about those readings.....from either guy...ok thats it....im going to hvac school because i cant find a decent tech who will actually try to fix this unit and not keep trying to sell me a new one!! At this rate im going to fly UDARRELL out here to fix this damn thing. It will be cheaper than the quotes im getting GUARANTEED!!!!!
:censored::censored:

Just curious...but what type of restriction are you referring to? The outside is free of any debris
A restriction in the refrigerant system could cause the suction pressure to pull down to a lower pressure reading however, this would cause the Superheat to rise well above where it should be.

Therefore, the low reading of the suction pressure would not result in a cold functioning full capacity evaporator coil.
That would also reduce the heat removal capacity of the indoor evaporator coil, thus causing it to not be able to pull indoor temps down enough.

You can take all those temperature readings yourself, &, you'll find a Tech that will have a digital manifold gauge that checks everything including Superheat, Subcooling &, even the Btuh working capacity of your system.

Click my image & go to my website for Videos of those modern system analyzers...every tech ought to have one.

[MIXMAN812]

275981
ok im going to browse your site for the info and get better info for you, btw i got all the info on my system that you asked for, hope this helps...

forgot to add that he said the RLA on the compressor was reading at 16 whatever that means...which is why he said its best to replace the whole unit.