Brand new AC does not seem all that cool


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Old 08-27-07, 04:18 PM
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Brand new AC does not seem all that cool

I have a brand new 2.5T Carrier 24ABA condenser and CNPHP Evaporator installed last week because my old system leaked freon. The tech had to recharge the old 2.5T Carrier system twice and found leaks in the evaporator. It seemed to cool fine for a couple of days after it was recharged, but gradually got worse. We ended up having the whole system replaced. Now it is 96 outside and the system won't cool below 79. It had been running most of the day when I took the following temperatures:

I used a thermocouple and DMM:
Intake temp: 80
Air duct Exhaust: 72
Condensor fan exhaust temp: 105
Outside ambient: 96
Small condensor line outside: 93
Large condensor line outside: 83

The AC company said that it is normal for a unit to cool about 20deg below the outside temp and they would charge me for the visit if nothing is wrong. The new unit is Puron. I have another unit upstairs which is a 3T Freon system and it works fine. It has a 15deg difference between the intake and exhaust and the outside fan exhaust is running 10deg hotter than the new one. (the thermostat upstairs is set at 82 right now and that unit cycles)

Does it sound like my new system has an issue? The AC company made it sound like this is all that I should expect from this system and I would end up paying for their return visit.

Can anyone tell if I have an issue given these temperatures?
 
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Old 08-27-07, 04:45 PM
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Originally Posted by steve-1
The AC company said that it is normal for a unit to cool about 20deg below the outside temp
Yes, but according to your figures, it take forever to get there. And your outside big line is hotter temp than the air coming out the register? (according to your figures). Were you using an infrared thermometer and 'missed' the copper line and picked up some ground temperature mixed with it?

We had temps in the mid 90's here and a/c's I checked on in condos were putting out about 60 degrees or less from the registers inside, depending on what the starting temp inside the condo was. If it was about 80 in the condo, the temp at the register was about 60.

I used a thermocouple and DMM:
I'm curious how that system works.
 

Last edited by ecman51; 08-27-07 at 04:54 PM. Reason: Added more
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Old 08-27-07, 06:50 PM
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If you are using a thermocouple on a multimeter they are known to be not that accurate and a digital thermometer would be a better tool to use.
Twenty bucks would not be too much to spend considering what the system cost.

A better gauge of cooling is the temperature drop between the supply and return ducts should be 15 degF or better.
Another thing you can do is compare the temp of the suction line on the new and old unit.
That 83 deg on the larger line I assume is the suction line and should be much lower if the unit is sized properly.

Get a better thermometer and measure the temp of the suction line at the furnace and compare the two readings.
Tape the sensor to the suction line securely.

Could be low on refrigerant but hard to tell without seeing the system.
 
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Old 08-27-07, 06:52 PM
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I measured the temp by contacting the thermocouple with the line. There may have been some error due to the location on the line, but it didn't feel very cold to the touch either. I used a K-Type thermocouple with a digital multimeter and an adapter to connect the thermocouple to the meter.
see: http://en.wikipedia.org/wiki/Thermocouple

If I call them back do you think they will say all is ok and charge me for the visit? I was hoping that with a new system downstairs that it would work as well as my upstairs unit.
 
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Old 08-27-07, 06:54 PM
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You got 8 degree drop across the coil with the readings you got now..

Get closer to the coil, and air filter for temps reading.

As Greg said, need about 15˚ temp drop...

Is the furnace in the basement?
 
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Old 08-27-07, 07:16 PM
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The furnace is in the attic. We had some thunderstorms a few minutes ago and it has cooled down to about 80 outside. The suction line is barely cool to the touch and the inside temp is now 78, and the unit is still running. This is not right. I'm calling them back tomorrow, and I hope they don't tell me that it is supposed to run like this.

Thanks for the advice everyone.
 
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Old 08-27-07, 07:27 PM
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Considering the cost of the system being charged for the call would be the least of your worries.
If the system replaced one of the same size then you should expect the same cooling effect.

I have not had much luck with thermocouple probes when used at the range you are measuring.
They are more suited to higher temps.
Thermistor type sensors are the preferred type.

To check yours you can crush some ice, put in a glass and add water to the top of the ice.
Stir the water/ice mixture with the probe and you should register close to 0 degC/32 degF.

It would be good to know the temp of the suction line at the indoor coil.
 
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Old 08-27-07, 08:03 PM
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I know very little about ac units, but I am an electrical engineer and use thermocouples at work all the time. Type K thermocouples are very precise over their temperature range.

I think the error we see when using adapters to connect them to a multimeter is the lack of temperature compensation in the adapter. As the adapter and meter connections heat up, an unwanted voltage (and error) is introduced into the circuit. It only takes a few mV. I searched the Fluke website and did not see any mention of temperature compensation issues with their 80AK adapters. I think the cheaper adapters like the no-name one I have at home is not very good, but I would trust the Fluke ones to be within 1% as long as the meter and adapter are between -10 and 50C.
 
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Old 09-01-07, 08:48 AM
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I had the service tech come out and he said it was low on refrigerant. He said it was reading 35 deg instead of 40 on at the evaporator when he had his pressure gauges hooked up outside at the condensor. He added refrigerant, then checked for leaks with a spray solution. He said there was a leak at the evaporator, which he then fixed by re-soldering the joint. He did not top up the refrigerant, but said it was ok.

It worked great for a couple of days and now it's not running that well again. I measured the temperature of the suction line at the evaporator coil and it was 75 deg while it was 80 deg inside the house (I taped it to the hose). I did an ice water check and found my meter can have up to 5deg of error depending on the temperature of the meter. I shoved my thermocouple down the drain line and it read 60deg. Does this make sense?
 
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Old 09-01-07, 09:13 AM
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Wink

He added refrigerant, then checked for leaks with a spray solution. He said there was a leak at the evaporator, which he then fixed by re-soldering the joint. He did not top up the refrigerant, but said it was ok.

Have to ask Did he recover the freon out of the unit???? Then fix the leak also put a new drier in the unit. Vac the whole unit down??? Then put all new freon in?????
The new unit is Puron. thats R410a If you had a leak it is best to put all new freon back in it as a liquid .Cause the R410 freon is a mix of 2 freons The big copper line should be cold and wet at the outdoor condenser.
 
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Old 09-01-07, 12:20 PM
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This sounds like a real circus!

If he soldered a joint he would have had to connect a reclaimer to remove the refrigerant to remove the pressure from the lines.

Did he do this?

As Ed said, this refrigerant is made up of a mixture of different gasses and when a system leaks the higher vapor pressure component only will leak, leaving you with a refrigerant that will be way out of spec.
I can't remember the percentage but after a certain amount of leakage you need to refill the system totally with brand new gas.

Also, this refrigerant requires the system to be very dry.
The tech should have pulled a deep vacuum and if he did the smallest of leaks would show up on his micron gauge right away.

My suggestion would be to talk to the owner, even direct him to this thread.
If you do not get satisfaction, especially on the point of replacing the charge and the micron reading the tech should have seen I would suggest you call Carrier directly.
I use Carrier almost exclusively and can say that they as a company are quite concerned about this sort of thing.
I am sure they will bend over backwards to help you.
 
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Old 09-01-07, 01:06 PM
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When he did the repair, he closed one of the valves outside at the condensor and ran the unit until it made a horrible groaning noise and shut itself off. He then closed the other valve and asked me to shut off the breaker. I think this captured all of the refrigerant in the condensor. He then bled the remaining gas out of the evaporator side of the system and went upstairs to do the solder repair.

Following this, he opened the valves again and turned power back on. He had is gauges connected still and they read 40 deg and 300PSI. It was about 78 inside the house. He did nothing else to the system. Before starting the repair, he did top it off with a canister of 410a. He did not install anything else, but when the system was installed a week ago, they did install a small canister in the high pressure line at the condensor (I assume this is the drier). The suction line outside at the condensor outside is barely cool to the touch (measured 81 with my TC and meter). My other ac unit (14years old) is cold and has condensation on it.

I am not sure what a micron reading is, but he had two pressure gauges hooked up outside at the condensor to do his diagnostics. Is that what you are referring to?

Sadly, the first thing I did when they replaced my system was to give them a great review for their service on the Carrier website.
 
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Old 09-01-07, 02:01 PM
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Exclamation Honestly, I think we have pretty much worn out this problem here.

Micron is the measurement of vacuum that should be pulled after installing or servicing a system.

From what you are describing he closed the liquid line and pumped the system down until it shut off on the low pressure control if it has one.
He then vented the remaining refrigerant to atmosphere, welded the line, opened the liquid line to release the refrigerant back into the system and topped up the system.

Firstly, venting R-401 refrigerant to atmosphere may be unlawful where you are but if not can be considered a very bad practice as is not pulling a vacuum after the repair and charging without replacing the charge.

Venting R-401 is unlawful here but maybe someone familiar with EPA can comment on that one.

It is quite obvious if your description of events is accurate the service you have been getting is not up to the standards that Carrier would expect.

My suggestion is first thing next week call Carrier to help with this problem.

I personally think their equipment is quite good and they would like to hear if one of their dealers is not performing the way they should.
Again, refer them to this thread.....it might help.

The least I would ask for is a thorough leak test and repair, full reclaim of the system refrigerant, vacuum pulled to 500 microns and for it to hold for at least five minutes and a proper recharge with new refrigerant.
I can say that if a system holds five hundred microns it ain't got no leaks!
(I would be curious to know if the tech had this equipment in his vehicle.)

Let us know what they say.
 
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Old 09-01-07, 03:50 PM
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I can't say that a machine that holds 500 microns has no leaks. A negative pressure test, while a good start is no substitute for a pressure test, before the vacuum is pulled. The system has been installed to very poor standards and you should call Carrier immediately. 410A is much to picky of a refrigerant to be treated in this manner. A warm suction line indicates an incorrect charge or a malfunctioning TXV. Call the tech back, with his supervisor, and have them correct the problem immediately.
 
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Old 09-01-07, 04:54 PM
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If no vacuum pump was used, that pretty much sums it up. Get a real technician.
 
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Old 09-02-07, 01:24 AM
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Steve, im having the same problem as you. My unit is a carrier to and it 2 years old. Guess what? I have had 3 tech out and no luck on fixing it. I got another schedulled to come out again in a week. Today my temp was outside was 85....the inside temp was 78. My line temp was 124. Yeah i have a problem with it. My first call for repair was before the 2 years mark. I currently trying to get them to replace the whole thing.
 
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Old 09-02-07, 09:38 AM
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I have followed Greg's advice and sent an email to Carrier with a link to this thread. I asked them to contact the installer of my unit and ensure that the installer understands the correct procedures to verify the system is functioning correctly, has no leaks and is recharged with puron correctly. I am sure that Carrier has a bulletproof procedure to fix this problem permanently.

Steve.
 
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Old 09-11-07, 07:43 PM
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I contacted Carrier by phone and by email and in both cases they referred me back to the dealer. Apparently, they do not provide technical information to consumers regarding the installation of their systems.

I ended up providing the information from this post to my installer and they came back out and did the job right. They recovered the puron, vacuumed the system down and checked for leaks then put new puron in. They found no leaks, but now my system works great.

Thanks for your help guys. I think I would still be battling the installer if it wasn't for this forum.
 
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Old 09-12-07, 04:20 AM
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From my own personal experience, I learned when calling or emailing customer service at Carrier for problems not solved by the installing dealer is that you should request the phone number of the Carrier regional manager of your location.

The people who originally take your call or email are office help and have no clue as to understand your problem and thats why they will refer you back to the installing dealer. But you should still send an email from their website, listing the model numbers of your equipment and tell them what is wrong and your observations of the equipment and what the technician did.
Now the email is supposed to be delivered to the regional manager but it may get bogged down and not be read right away. Follow up on your email with a phone call to the regional manager about two days after and ask if he has your complaint file at hand.
I suspect that your complaint never reached the manager's desk. Once he see's what the situation is all about, he will have a good idea of what is correct and what is not. He will call the installing dealer and have things corrected and if necessary, do an on site inspection of the system with the installing dealer to trouble shoot the system.
 
 

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