New Trane XR14 AC Not Cooling Properly
I have an 8 year old house with 2 Units (one on the main level and one upstairs). Each level has about 1750 sq. feet. The builder installed a 3 ton unit downstairs and a 2 1/2 ton unit upstairs (where the heat is, go figure).
After "fighting" with the upstairs unit pretty much since we bought the house (it leaked freon, never cooled properly, etc), we decided to have everything ripped out and replaced (new compressor, new coil, new line set). The original system was a 2.5 ton Lennox AC / Furnace system.
I had a new Trane 3 ton XR14 unit and 3 ton XTV Coil installed upstairs (retained the original Lennox furnace as we never had issues heating, just cooling). The contractor also identified issues with our plenum and ducts, so they replaced all of that as well (one of the reasons we chose the contractor we are working with is they asked if we had air flow issues which we did. They were the only ones to identify this issue out of 3 bids we had).
Unfortunately, the unit still is not able to achieve our desired temperature. As it gets very hot in Atlanta, I'm ok with (would like better, but can live with) the unit's performance during the daylight hours (recently, the outside temp hit 94 / 95 degrees, and the unit maintained 76 degrees indoors).
My issue: even 2 1/2 hours after the sun goes down and the outside temperature is in the low 80's, the inside temperature is still sitting at 76 degrees( basically, hasn't moved even though the heat load should've significantly decreased over 2 1/2 hours). Also, on a recent electricity bill, I've registered a 30% increase in the amount of electricity used by the new unit over the older less efficient Lennox unit (the old unit was 10SEER, but it leaked freon so I doubt that it ever got 10 SEER).
The contractor has "double sealed" and insulated all of the supplies and returns, yet, the air temp coming out of the supplies (as measured with a Raytek Infrared Thermometer is between 61 - 65 degrees during the day and the same 2 1/2 hours after the sun has gone down). The contractor says they've meased the temp at the coil at 53 degrees, yet, I'm losing 12 to 15 degrees in the supply lines.
The one exception is one of my children's bedrooms. The air temp coming out of the supply in this room is around 57 / 58 during the day, and this room is 2 - 3 degrees cooler than the rest of the upstairs (reads 74 when the other rooms read 76 / 77). There is a bathroom and another bedroom on the same side of the house (facing West) and they are both reading 76 degrees.
In the morning when I get up (around 5:00), the house is at 72 degrees (where the programmable thermostat is set), and the supplies are putting out air that reads anywhere from 53 - 57 degrees.
The unit is located in my attic with one attic forced exhaust fan set at 90 degrees. I measured the temp in the attic last night at 90 degrees when the sun had been down for 2 1/2 hours with the Raytek.
The contractor has been very pleasant to work with. They have added a supply in the upstairs hallway and added a return in one of the bedrooms that didn't have one. They have been out at least 6 times trying to get the system to perform as we all believe it should. They have looked at the system and claim it is functioning to manufacturer's specification, but even they agree that it should work better.
So, any ideas as to how to get my upstairs temperature down? Is it ?normal? to lose 12 to 15 degrees in air temperature between the coil and the supply vents? Am I asking too much to have the room temperature drop ( even a little!?!) 2 1/2 hours after the sun has gone down?
Any suggestions on things for the contractor or I to look at or advice would be greatly appreciated. I really don't mind investing in getting the home to be comfortable, I just want what I paid for to work.
Some Tranes units have had problems with the TXV.
They may want ot check it.
Beenthere, thanks for the reply! I certainly don't want to insult the contractor as they have been very nice to deal with. They are meeting me there yet again tomorrow morning to look things over. Is there something specific I should ask them to check or just mention that I read on the Internet that the TXV valve on someof the Trane's have been problematic?
Again, thanks for your suggestion.
Some TXVs have been found to have bad power heads.
So they don't open as far as they should.
They can also check to make sure the distributors of the evap coil to make sure its being fed evenly.
A restricted distributor tube can cause this, and will not always show up on the Sh, and SC readings.
Also, they should be checking SH, and SC, not just pressure.
If the coil isn't being fed evenly, its possible that where they check its temp is being fed right, and doesn't show the feed imbalance.
Cover the flex ducts all over the attic with more insulation. Whether it is blown over or cover them with batts, do something to keep the 150° attic heat out of the flex. That R4.2 insulation on the flex does little as you are finding. I have a 14" flex return that runs 20' and made quite a difference by wrapping it with R13 batts. Bury them in the existing insulation then lay batts on top or buy some bags and the home stores will let you use a machine to blow another 6" or more inches over them. Common problem and why I hate to see any ducts in the attic. Cooling the attic can help a bit too.
The OP said the contractor double sealed and insulated the supplies.
Beenthere / Baldloonie,
Thanks both for the replies. I will have the contractor check the TXV mesasurements you mentioned in the morning.
As to the isulation, the flex is suspended from the rafters and distributes out from the plenum. The insulation is just the ?normal? insulation that comes on the flex (I do not believe they added any additional insulation) but they did ?doubel wrap? the supplies and returns to make sure they were properly sealed. So, if I mislead you with what I said, my appologies (sorry, I'm a computer guy not a HVAC guy). I have a very high attic roof line above the top floor (say 20 - 30 feet at peak), so there is definitely a lot of heat trapped up there.
I can't bury the flex in the "blown-in" insulation the way it distributes off of the plenum, but adding batts might be an option. Would it just be a matter of cutting and taping the batts around the supplies and returns? Does anyone manufacture a product that might make it easier to add insulation?
Again, thanks to you both for taking the time to reply.
no matter what turn the PAV off
Don't beat me up, but why turn off the PAV? I thought the idea was to pull the outside air through the soffets to get the heat out of the attic? Again, not trying to disagree, just a homeowner trying to understand?
Careful with that
Originally Posted by BaldLoonie
I have experienced, that if you get your attic temp close to the dew point, and have flex ducts without an air gap around them, they will condensate on the outside and cause water damage to the ceiling.
We had a contractor that was building his own house that installed full length ridge vents, two large attic exhaust fans, R-30 batt insulation, then blew in 10" more of insulation on top of the batts. They covered our fiberglass trunks and flex ducts.
About 8 days after start-up they called saying that they had water streaming down the walls and it was coming from our ductwork. We moved the blown in insulation from around the ducts, set the stat higher on the attic fans, and all has been good since then.
That was the first time that I realized that you could actually over insulate and over ventilate an attic space.
It was over insulation or venting.
Originally Posted by forcryinoutloud
It was improper insulation of the ducts.
I'm just another novice, but somehow your problem does not sound like the system to me. You are in Hotlanta area (same here), and in the evening have:
(input air temp) 76 --> Furnace --> 61 (supply vent temp)
I seem to remember that 15-20 degree drop was all that you should expect, which by itself should cool the house down. Anyway, my experience in this area has been to reduce the load on the house and duct work, by any means possible. I replaced turbines with continous ridge vents, sealed the ducts in the attic, AND installed 2 Power Vents. The power vents are THE main reason I can keep my systems in the 75-76 range. Recently one died, and the upstairs went to 78, you can believe I replaced that motor quickly!
Two conclusions that I've come to:
1) Attic temps bake the ducts unmercifully, even if they are insulated.
2) South / West facing brick walls store massive amounts of heat from the sun, and keep pumping it into the house till late in the night.
I'll be anxious to see what you come up with, since I can only dream of waking up to 72.