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Old 05-27-2016, 12:13 PM   #1
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Can't keep the upstairs cool


Hello,

I've been reading this forum for awhile and now I have some specific questions. I recently purchased a foreclosure which was vacant for 4-5 years (differing timelines from neighbors). The house is 5333 square feet, and has two Trane 5 ton heat pumps.

I had a family member who has worked in HVAC come and check out the units to make sure they were in working order. The downstairs unit was found to be working fine, with a decent amount of 410a. The upstairs unit, however was found to have no 410a whatsoever, so it was charged. It seemed to be working fine with heat, though I hardly used it at all in the past 3 weeks since moving in.

Now that I am living there, the air conditioning downstairs seems to work well. I placed a meat thermometer in the vent (high tech, I know) and it read about 62 degrees with an outside air temperature of approximately 75 degrees. Upstairs, however, didn't seem to cool down at all. The thermostat is located in the master bedroom and read 82. Putting my hand under the vent seemed to blow relatively cool air, but not super cold. The meat thermometer read about 79-80 degrees in one of the master bedroom vents. I ran the A/C for a few hours and it barely cooled down (to about 78 degrees) the master bedroom. The upstairs hallway seemed to be about 5 degrees cooler than the bedroom and was tolerable. However, the master bedroom is very large (17x29) and only has vents on one side, opposite the thermostat. The Trane 2.5 ton unit I had installed in my old house would push air so cold at these ambient temperatures that you could nearly see your breath.

I asked the family member to come back and check things out as I was worried the coolant leaked out again due to whatever caused it to leak in the first place. He came out and said that the coil was reading 40 degrees so there is definitely 410a in it. He suggested to change the air filters because they were old and dirty (I had not changed them yet). I went in the attic and removed the filter entirely and ran the system from 7:30 p.m. to about 10:30 pm. The master bedroom cooled from about 82 degrees to 77 degrees in this time. It was about 75 degrees outside. Feeling the copper lines going into the condenser they felt cool, but not "cold."

This morning the sun was beating on the roof and the thermostat was set to 76 degrees. It kicked on to cool when it hit 78 degrees. After about 20-30 minutes of running, the thermostat then read 79 degrees, so it had not cooled at all, it had actually increased in temperature. The upstairs hallway again seemed about 5 degrees cooler than the master.

I have a very crude drawing of the master bedroom and the locations of the vents (here: https://drive.google.com/open?id=0B8...FlGZ2JXU1JCMG8). I have a few theories here:

1. The coolant is low and the family member did not check it well. He is kind of a "parts changer" and not really what I would call an expert. He has a good amount of experience though, certainly more than I do.

2. There are not enough vents in the master bedroom. Some should be added on the opposite wall, perhaps tapped off of the master bathroom vents?

3. The attic is way too hot and I need to add fans. There is a window in attic on the front of the house that probably lets a lot of sunlight in.

4. All of these?

Any help would be greatly appreciated. I've found in this area that most HVAC vendors are just parts changers and either charge me $300 to add coolant, or tell me the whole thing needs to be replaced. I cringe at the cost of a 5 ton heat pump. Thanks.

Last edited by CaptainHook; 05-27-2016 at 12:28 PM.
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Old 05-27-2016, 12:22 PM   #2
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Re: Can't keep the upstairs cool


I can't seem to post a link to the drawing. It keeps telling me I need at least one post.
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Old 05-27-2016, 12:23 PM   #3
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Re: Can't keep the upstairs cool


Here is my attempt at a drawing:

https://drive.google.com/open?id=0B8...FlGZ2JXU1JCMG8
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Old 05-27-2016, 01:02 PM   #4
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Re: Can't keep the upstairs cool


If the upstairs unit had no refrigerant then there is a leak some where.
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Old 05-27-2016, 01:02 PM   #5
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Re: Can't keep the upstairs cool


Before you go cutting vents and adding insulation, have the system professionally serviced and diagnosed. It will be money well spent.
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Old 05-27-2016, 02:14 PM   #6
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Re: Can't keep the upstairs cool


Quote:
1. The coolant is low and the family member did not check it well. He is kind of a "parts changer" and not really what I would call an expert. He has a good amount of experience though, certainly more than I do.
based on your description, don't use this guy.

experience means nothing. i have less hands on experience than this guy but know just on your description - relying on saturation temp alone to check the charge, guessing -> he doesn't know the theory, isn't a diagnostician/troubleshooter.







---------------------
The temperature drop should be checked across the air handler and airflow verified. (there are charts that tell u what it should be based on what's called wetbulb return air temp - takes humidity into account)

temperature at vents is not reliable at all.

the charge isn't only based on pressure, u can have a 40 degree coil and have too much or too little refrigerant -> depends on many factors, u need superheat/subcool readings taken, airflow verified.

On a 5 ton the airflow may be too low, won't be too high and u can't check the or adjust charge properly if the airflow is way off.

You should be able to hang meat with a 10 tons cooling just over 5000 sq ft even with crappy insulation, ducts in attic, etc, etc.
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Last edited by user_12345a; 05-27-2016 at 02:24 PM.
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Old 05-27-2016, 02:22 PM   #7
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Re: Can't keep the upstairs cool


Quote:
Any help would be greatly appreciated. I've found in this area that most HVAC vendors are just parts changers and either charge me $300 to add coolant, or tell me the whole thing needs to be replaced. I cringe at the cost of a 5 ton heat pump. Thanks.
U don't need replacement unless the compressor has failed or there's a leak that's too much money to repair.

If there's a leak in the evap coil a new coil may cost u almost half as much as a new heatpump.
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Old 05-27-2016, 02:26 PM   #8
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Re: Can't keep the upstairs cool


Quote:
Originally Posted by Bitters View Post
If the upstairs unit had no refrigerant then there is a leak some where.
Right, I'm not sure how bad the leak is.

Quote:
Originally Posted by ZTMAN View Post
Before you go cutting vents and adding insulation, have the system professionally serviced and diagnosed. It will be money well spent.
I am leaning towards this at this point.

Quote:
Originally Posted by user_12345a View Post

You should be able to hang meat with a 10 tons cooling just over 5000 sq ft even with crappy insulation, ducts in attic, etc, etc.
Thank you, this statement speaks volumes. The insulation in the house is good. I don't see that any corners were cut during construction (unlike my old house which had terrible insulation and it was apparent).
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Old 05-27-2016, 06:52 PM   #9
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Re: Can't keep the upstairs cool


New development. I noticed that the problem condenser unit's fan is ramping up and down repeatedly nonstop. Also my electric meter is showing I am ripping through electricity (1 kWh or so per ten minutes). That's about as much electricity as I would expect to use in one day per hour. This is getting really fun.
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Old 06-01-2016, 09:52 AM   #10
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Re: Can't keep the upstairs cool


Quote:
Originally Posted by CaptainHook View Post
New development. I noticed that the problem condenser unit's fan is ramping up and down repeatedly nonstop. Also my electric meter is showing I am ripping through electricity (1 kWh or so per ten minutes). That's about as much electricity as I would expect to use in one day per hour. This is getting really fun.
It honestly sounds like some backup heat may be stuck on.

granted the 5 ton will draw a lot of current.

what are the model numbers of the indoor and outdoor units? condenser may have an ecm fan motor.

this is going to be tricky to solve.
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Old 06-01-2016, 10:26 AM   #11
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Re: Can't keep the upstairs cool


I don't think the emergency heat is on but who knows. It has a 15kW heat strip unit. The air in the vents upstairs is blowing about 69-70 degrees, which is 5 degrees less than the return air. Downstairs is working better, blowing in the low 60s and it actually does shut off but I still don't feel it is working optimally downstairs either. The upstairs essentially runs all the time when on except at night and it still never gets really what I would call "comfortable" as it stays in the 50ish percentile in terms of humidity according to the thermostat. I am basing my comparison on my old house, in which I had a very similar Trane XL16 system installed downstairs--weather in the 70s would allow that thing to work so efficiently that you could nearly see your breath in the vent exhaust. I never measured the temperature coming out, but it was COLD. I still own that house so I should go and check it, perhaps I am remembering incorrectly. In addition, I could go downstairs and touch the copper refrigerant line coming inside from the outdoor unit and it was FREEZING cold. In the new house I would call the downstairs copper line temperature to the touch "cold" and the upstairs "moderately cool." It just feels like these units are not running properly.

I've also come to the realization that the Trane XL624 thermostats I had installed (original tstats were stolen during foreclosure) run hot and seem to read a little high. I'm not sure if it's the ZWave functionality making it run hotter but I believe they have some sort of calibration and modifier that I haven't played with yet.

The model numbers of both the upstairs and downstairs units are the same, indoor units are 4TEE3F65A1000AB. Outdoor units are 4TWX6060B1000AA (and 4TWX6060A1000AA but I don't think that makes any difference, probably just a date or location code or something).

The ramping up and down of the fan motor in the outdoor unit stopped, it only did that after I hosed it off hoping it was dirty and that was part of the problem.

On Saturday I had the family member come back one more time just to check things out even though I had an appointment lined up with a real Trane dealer and he found that one of the vents/ducts in the master bedroom was disconnected. I went up there and fixed it but it made a negligible difference in temperature in the room. He also said that the insulation in the attic "wasn't the greatest" but it looks to be about 13" of blown insulation to me. Not to mention my ceiling really isn't that warm (80 degrees when it's 120+ in the attic) so I am not sure he was correct.

The Trane dealer bailed on me yesterday and was supposed to show up this morning by 9, and of course called me 20 minutes before appointment time saying they couldn't come until somewhere between 11 and 2, which was very convenient considering I took half the day off of work to meet them. Hopefully I can convey all of this over the phone with my wife home when they finally do show up.
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Old 06-01-2016, 01:00 PM   #12
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Re: Can't keep the upstairs cool


Quote:
I don't think the emergency heat is on but who knows.
Turn the disconnect off with the cooling and see if the vent temp exceeds ambient.

Taking temperature at the vents isn't accurate, yet with a 5 degree split something's rotten.

It's gotta be a refrigerant issue (wrong charge or restriction, txv issue, check valve issue), disconnected return in the attic, or heat strip coming on, unit only running on low

Needs further diagnostics by a tech.

I would want the following readings/info if it was my unit:

1. Air temp going into return and coming out of vents
2. Air temp at air handler inlet and outlet, wetbulb return air temp
3. Charge numbers - pressures, refrigerant line temperatures
4. Mode of operation to rule of miswiring of controls -> correct low voltage terminals energized at the condenser.

The condenser is a two speed, specs say multi-stage fan so it could be an ecm motor or two speed.

You need a really good tech, perhaps a manufacturer's rep if the machine is still in warranty.

There could be multiple issues with this system, like running on low only with a one of the heat strips coming on at the same time along with a refrigerant leak or failing txv.
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Old 06-01-2016, 01:08 PM   #13
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Re: Can't keep the upstairs cool


With the comment you made on the outdoor fan, it sounds like the compressor is trying to start but is cycling right back off.
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Old 06-01-2016, 02:47 PM   #14
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Re: Can't keep the upstairs cool


Thanks for the comments.

A Trane-certified company came out today and diagnosed it with low refrigerant. I ran through my list of findings and problems with him over the phone and it seemed a bit like it was going in one ear and right out the other. He didn't seem overly enthusiastic about finding the source of the problem, just that it was low on coolant. I was emailed an invoice when they left and it said "QTY 2 Refrigerant" which I am assuming is 2lbs. I know from the manual my unit requires 13lbs, 3ozs. He did tell me it could be a bad TXV valve, or just low on refrigerant. He went through a few methods of them testing for leaks and indicated it would be two hours minimum, but I didn't gather that he had any inclination of doing that today--it seemed like he just wanted to fill it up again and come back if it leaked some more. My issue is there is obviously a leak, or else the refrigerant wouldn't be low so why not fix the source of the problem, not just continue the revenue cycle. Perhaps I am jaded and this is the proper procedure.

No one is home at my house right now but I can remotely connect to my thermostats through their ZWave functionality over the internet. The upstairs thermostat is currently set to 77, and it is 78 degrees in the room. This is an improvement from last week thus far when it would likely have been 81 degrees or more on an 86 degree day like today. Unfortunately I cannot see if the units are running remotely, just what the thermostat is set to and the room temperature. I also have the thermostats set to a 2 degree split, so it must reach two degrees above the setting temperature before it turns on, and then it runs until it lowers the temp to an even temperature (for example, 77.0 degrees). These are defaults in the thermostat, but I am still experimenting with the settings. I'm not sure if it makes sense to allow the temperature to build up that high and run for longer intervals, but less frequently, or run more frequently for shorter periods. The house may just be too big to allow for much fluctuation in temperature.

I know the air handler is operating at multiple speeds because of the sound of air flowing through the vents and the thermostat does indicate when the second stage of cooling engages. I have two stages of cooling enabled for the outdoor compressor in the thermostat.
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Old 06-01-2016, 02:49 PM   #15
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Re: Can't keep the upstairs cool


If it needed refrigerant and no leak was found, then it will continue to leak and go down again.
Refrigerant is not a consumable material.
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