American Standard indoor coil problem ?

[2elaines]

I had an A/S Allegiance 15 R410 complete system installed in Jan. 2008. The hot weather just hit in Houston (Mid 90's) and it is obvious 2 rooms in my house are not cooling well. The return air temp is 77 degrees and most of the outputs are around 57 degrees. The output in the 2 problem rooms is 62degrees and the supply duct comes off the top of the plenum for both rooms. Installer claims everything appears to be working fine and the R410 freon charge & pressures are fine. He called the A/S rep and he advised to open the indoor coil and check the tubes for even cooling. Installer found the upper tubes of the coil were not cooling or sweating as much as the rest of the coil . A/S Rep recommended TXV valve replacement first, complete coil replacement if TXV didn"t take care of problem.

Have any of you heard of this problem ? Are they really tackling the correct problem ?

[beenthere]

Could be a TXV feed problem that the coil isn't getting as cold on the top. Or it could be it low on charge.

[BaldLoonie]

Could happen. More likely the coil than TXV though.

Had a fairly new coil another dealer put in, every time it got hot so was the house. Found only 1/2 the coil getting cold due to a plugged distributor. From the condensate staining on the front of the coil it was clear it was bad from day 1.

Seems if it is getting a 20° drop, might not have a problem with the unit. Could be duct heat gain on those runs too. In the one I found last year, we had 11° temp difference on the runs to 1 side of the house and 1° temp drop on the other side!

[2elaines]

Baldloonie ,
The installer mentioned heat gain as a possible culprit as his infrared thermometer indicated the flex & hardpipe were 107 degrees on the outside . Both rooms supply off the top of the plenum and both are new flex duct, the rest of my ducting is mostly hardpipe. One of the problem rooms has a new return installed (my 30 year old system had trouble cooling this room) and is farthest from the unit (approx 50') only about 10 " more than other ducts that are cooling fine.

Beenthere, Installer claims unit is not low on freon. The A/S rep actually had him overfill it (from 370 to 410psi) temporarilly to see if the coil would fill and cool properly.

Installer has ordered a new TXV valve, just didn't want them tearing into my unit if it wasn't necesarry.

Thanks

[2elaines]

Baldloonie,
What did you do to resolve the duct heat gain problem ?

Thanks

[accutrol]

this problem will occur more and more as piston metering devices are replaced with txv's. The bulbs are located near the stub out of the coil and if not wrapped or some type of heat sink not used there is a very real danger of damage to the txv valve.

[accutrol]

there could possibly be some duct heat gain. You said the supply temp in those 2 rooms was about 62 degrees. If the thermostat is set on say 72, when the sytem satisfies, are those 2 rooms warmer thatn the rest of the house???

Just because the air temp is slightly different, if those 2 rooms are staying warmer than the rest of the house, and you've got a 50' flex run, it just makes sense that the air flow is dying in the flexduct, therefore you are not dumping enough air in those 2 rooms to overcome the heat gain of the room.

[Mr Bill]

Maybe a booster fan in the 50' flex run "could" help some but most importantly is the 50' run
of flex at least R-8 value flex?

[Mr Bill]

there could possibly be some duct heat gain.

No, in Houston were 99% of the duct and systems are in the attics, you can bet no doubt there is some heat gain in a 50' run, it has really not even got hot here yet and we were in an attic the other day looking at replacing a job and it was 129*, and this attic had a ridge vent and two turbines and soffit vents.

[accutrol]

i have never been a supporter of the booster fan idea. something need to be done with the ductwork.

Is this a spider system?

Are there any rooms that are cooler than the t-stat is set at?? Maybe dampering and balancing the system out will provide some extra air to the 2 rooms.

Might want to consider upsizing the runs. Are they 6"? 8"?

[accutrol]

5 degrees in temp difference is a difference, but not going to make a whole lot of difference in cooling an area. Need to know how much air is coming out of the registers and is it enough to cool the 2 rooms

[Mr Bill]

i have never been a supporter of the booster fan idea.

And to be completely honest with you neither have I, but in my 30 years I have done a couple of them that did resolve the problems the customer was having with a long duct run, but may not in all cases.

[2elaines]

Thanks for your replies, I will look up info. and post replies to your questions.

Got home from work and wanted to post these specs real quick.
88 degree outside. Intake at wall filter is 64 degrees. Output in 2 problem rooms is 56 & 60 degrees. Other outputs in house 50 to 54 degrees. Not near the 20 degree drop from the other day. Temperature in farthest problem room is 77 degree the other 76 degree. Thermostat set @ 74 degrees