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. :eek:

[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

[Mr Bill]

Just FYI in case no one has told you yet the TD "temperature differential" is not measured from return air grille to supply grilles, it's measured across the coil from the return air can on the furnace to the plenum were all the ducts take off, if you getting a 16 to 20 degree differential there you are good to go, you will automatically have "some" heat gain in all ducts unless it's maybe a two foot run.

[2elaines]

Thanks mrbill, I do understand where the temperature differential should be measured.
I am going by the fact that when the installer measured at the coil the temps were almost the same at the return ( unit sits directly above the wall return) and the supply register in the closest room ( about 4 ft from plenum).

Thanks again, Your input is appreciated. I had talked to you on the phone when I had this unit installed ( You worked too far from Pasadena to do the job ).

[2elaines]

Thanks to all especially accutrol & mr. bill

I have spent all afternoon checking temps and looking in the attic.
when the thermostat shuts off I have 3 rooms that are hotter than the set point & they are all the new flex which is all R8. The 2 hotter rooms actually come off the same line from the top of the plenum which is about 25' of 9" flex then a triangular box with about 5' of 7" and about 25' of 7" going to the rooms. I also have another room with about 8' of 7" that is kind of crumpled up looking. All 3 of these rooms are getting less air flow from the registers than the other rooms. The other rooms have a lot of airflow. Installer told me the blower was set up for 400cfm per ton x 4 ton. I will have my installer come out with his hood and check air flow before installin a txv valve.
About what should my cfm ratings be on return and supply registers ??

Thanks again to all.

[accutrol]

It is my opinion, just my opinion, that the 9" flex into the triangular box is not a standard practice. At least not here in kentucky. Each room should have it's own flex run from the plenum. I have never used this method of supplying air to romms, nor will I ever use it. Maybe if they had put 1 8" run to each room, that might help the problem.

I still say there is too much flex there. There should have been some duct run towards the area where the 2 rooms are located.

[beenthere]

Running a larger flex to a pie is common in some areas. Nothing wrong with it if its sized right.

[accutrol]

Might be, but to me it is just a cheap way for an installer to try to get air to a far away area when properly sized ductwork would achieve such better results.

[beenthere]

If the flex to the pie, and the flex to the registers are sized properly, then it is a properly sized duct system.

Key phrase is properly sized.

You can run a metal duct that is undersized and it won't work.

[kevinmac]

Just a thought, could an additonal return at his far side of the house where he is having his cooling issues fix this problem?

[beenthere]

If lack of return is the problem, yes.

[Mr Bill]

I don't like or ever use triangle boxes "period" we use wyes "sometimes" when we are going to a bedroom and a short run to a small bath only, but as another poster said it's really better to run dedicated runs to all rooms with dampers on each collar of each run, that way trust me you won't be having these issues, or if you do you have the ability to close or open dampers to every room to get what air you need were you want it.

[2elaines]

accutrol,
these 2 rooms were a problem for my old system to cool. the old hardpipe supplied these 2 rooms and the kitchen. these 2 rooms were taken off the hard pipe and the flex ran to them. the old hardpipe now supplies the kitchen only and keeps it cool.

kevinmac,
the farthest room has a new 14" flex return with a 14" x 25" grill mounted in the ceiling.

thanks

[Mr Bill]

the farthest room has a new 14" flex return with a 14" x 25" grill mounted in the ceiling.

thanks
What you need to do is measure all your duct take offs at the plenum and post it along with the cfm's of your system and we can tell you if it's even in the park. You can have to large of duct runs and IMO it does give you volume, but it kills your pressure and it sounds like you need more pressure to these furtherest rooms. If all your duct is oversized to all rooms good luck getting air to the needed rooms.

[2elaines]

ok, so you need diameter of each line and length ??

Does the position on the plenum matter as most all are on one side and the top.

[beenthere]

Yes, and yes.

[johncavh]

HO stated return air temp. at wall grille 64 that seems a bit low if stat is set to main 74 :confused:

[beenthere]

In the first post, it was 77, so I took th 67 as a typo.

[2elaines]

beenthere, post stating 64* at intake is not a typo. I am using a refrigeration
thermometer with about a 5" stem on it and pushing it thru the cheap fiberglass filter. The ubit does have a 5" media filter upstairs, I do not rely on cheap fiberglass filter alone.

I will post size, length of ducts in a little while.

Here are some specs from today.

thermostat left at 74* all day.
82* outside - intake 64* - rm1 76* in room w/58* at register,
rm 2 73* in room w/56* at register, rm3 74* in room w/58* at register

95* outside - intake 65* - rm 1 76* in room w/51* at register,
rm 2 73* in room w/58* at register, rm 3 77* in room w/62* at register.

Room 2 seamed to get better ??

Thanks

[beenthere]

Sounds like some supply air is traveling across teh ceiling and into the return.

Remove your 1" filter and try it that way for the weekend.
2 air filters in series can slow the air down more then you think.

[2elaines]

Thanks beenthere, I will remove fiberglass filters.

Here are the approx. duct sizes. I don't envy you guys crawling around in an attic ! When the new unit was installed the hard pipe was cut back and hooked to plenum with flex. Approx lengths include the flex.

36' of 12" hardpipe serving 1 register to kitchen
36' of 16" hardpipe serving 3 registers to den & dining room
25' of 12" hardpipe serving 2 resisters to bedroom & bath
12' of 12" hardpipe serving 1 register to bedroom with Y of 7' of 8" to bath
45' of 5" flex serving 1 register to washroom
6' of 7" flex serving 1 register to bedroom
20' of 9" flex with the triangle box then 5' of 7" to bedroom & 25' of 7" to office

1 20 x 30 hall return & 1 14 x 25 ceiling return

All I know about cfm is installer told me 400cfm per ton x 4 ton = 1600cfm
Home is 1950 sq ft

[beenthere]

The air extra filters out will help alittle. Maybe enough.
With the majority of your system being hard piped. The flex runs are alittle too restrictive for the air flow you need.

[2elaines]

The air extra filters out will help alittle. Maybe enough.
With the majority of your system being hard piped. The flex runs are alittle too restrictive for the air flow you need.


Does this mean the flex is undersized ?

I took the filters out for now. Will see if that helps.

Thanks

[beenthere]

Not so much undersized for the amount of air needed. As much as for the size of the existing hard ducts. With dampers installed and the hard pipe runs balanced, the flex runs would work fine.

See how it does for you this weekend.

[Mr Bill]

Well according to my air duct calculator @.1 static you have enough duct sizes to provide for over 4000 cfm's of air, the air velocity must be terrible especially with those long runs, but at least your volume is good. :D

36' of 12" hardpipe serving 1 register to kitchen = 700 cfm's
36' of 16" hardpipe serving 3 registers to den & dining room =1500 cfm's
25' of 12" hardpipe serving 2 resisters to bedroom & bath =700 cfm's
12' of 12" hardpipe serving 1 register to bedroom with Y of 7' of 8" to bath = 700 cfm's
45' of 5" flex serving 1 register to washroom = 70 cfm's
6' of 7" flex serving 1 register to bedroom = 150 cfm's
20' of 9" flex =300 cfm's

[2elaines]

Does all this mean my hardpipe is hogging all the air and not letting the flex get what it needs ?

[beenthere]

Air takes the path of least resistance. So without balancing dampers, yes.

[accutrol]

It means that you have very little static pressure in your duct system. If you put 1600 cfm's into a duct system that will carry 4000 cfm's, by the time that the air gets to the registers, there is no air. I would really like to see the numbers that are produced if the system is tested with a hood at the registers.

[beenthere]

How about pulling a 5 ton unit from duct work that if you used .1 FR was sized for 6.5 tons. And Installing a 3 ton VS system.

Its quiet and all registers still have good throw. CFM was at 1275 when measured.
Balancing dampers in all supplies.

[2elaines]

I will get my installer to show me the cfm at each register with his hood and have him balance the ducts before he installs the new txv valve he ordered.

Not that it would make a big difference, I failed to mention the hard pipe diameters I posted are actually outside diameters of the pipe.

Thanks again, I have been been watching this site since my unit was installed and the posters to my question are the ones I have come to trust !


Mr. Bill, If my installer can't get my flow issues fixed. I might need you !

[beenthere]

The dimensions being inside or out, does make a big difference. The pipe could be 2" smaller on the inside.

Have you noticed any difference with the 1" filters removed.

[Mr Bill]

Mr. Bill, If my installer can't get my flow issues fixed. I might need you !


Probably going to need someone with a flow hood for your job, I only own a CFM/Velocity
meter, as big as those ducts are I don't know if my Velocity meter would pick anything up,
and my CFM's starts at 25 cfm's I wonder if the 16 " is putting out 25 CFM's. :eek:

[2elaines]

beenthere, did not see any difference with the 1" filters removed.

My house cools ok , just not as evenly as I would like for the money I spent and compared to to 30 yr old BDP system that was replaced. Most of my register have a lot of flow (velocity)

I just took the following temperatures @ 85* outside temp.
Thermostat set @ 74*
Temp AT coil (I used the holes the installer punched in plenum)
68* in - 51* out , temp @ wall return below unit is 64* , temp @ ceiling return in problem room at other end of house is 72*.

I am confused at this point and would like guidance on how to proceed with my installer. Should I let him replace the TXV per A/S recomendation or should I insist on balancing of supply air before considering any mechanical work.

mr. bill, you know how to make a fella feel good, but I always liked a straight shooter !!

[beenthere]

Although I think you have more air balance trouble then TXV problem, if the labor is under warranty. Let him change it out.
Then if the coil still doesn't get cold at the top. Have him balance the system.
it may be that too much air is going through the coil and thats why its not the same temp on teh top as it is on the bottom.

[2elaines]

Although I think you have more air balance trouble then TXV problem, if the labor is under warranty. Let him change it out.
Then if the coil still doesn't get cold at the top. Have him balance the system.
it may be that too much air is going through the coil and thats why its not the same temp on teh top as it is on the bottom.

I have the 10 year parts & labor warranty with a 1 year comfort satisfaction garantee or my money back. I will follow your suggestion. Was wondering if too much air through coil would be because of balancing or fan speed set too high.

[catmanacman]

the txv could very well be bad have been finding some faulty on start up on trane coils same coil as am std but it will not fix airflow problem

[beenthere]

A combination of duct size and fan speed setting.
To know if the fan speed is too high, total CFM has to be measured.

[2elaines]

One last question and I will leave ya'll alone. I do appreciate all the input from everyone.
I will let my installer proceed with the txv change out and have him check all my registers and intakes with his hood and post the numbers and his remedy next week. Again many thanks to all !!

What is the proper procedure to change the TXV ? I assume the system must be opened.

[beenthere]

Pump refrigerant back to condense and close service valves, remove old valve put new one in. Remove old filter frier install new one. Check for leaks. Pull Vacuum on system.
Open service valves and run system.

[accutrol]

The installer needs to be extremely careful that he does not overheat the valve. Wrapping it with pieces of wet rag work very well. I always have a cup of water and rags and immediately after brazing pour a little water on the rags to help disipate the heat from the valve. Make sure the bulb is well insulated.

Will be looking for those airflow numbers next week.

Happy memorial day. We need to show our support for our troops over in Iraq. My 20 year old son is one of them.

[2elaines]

Happy memorial day. We need to show our support for our troops over in Iraq. My 20 year old son is one of them.[/QUOTE]


Accutrol, My wife does volunteer work for Houston Marine Moms.
If you would like to send me your sons address, I will have my wife put him on the mailing list for care packages. They send the boys & girls all kind of good stuff. They just got through sending a bunch of girl scout cookies and are about to send some more out.

My email is listed on my profile, so is the Houston Marine Moms website

[dash]

Ductolators show the cfms at a given FR (friction rate),not static.

You can't guess what the FR is,and determine the cfms.

If the returns are ducted and flex is used with tri-boxes,the Fr could be as low as .04 Fr,or less so the cfms could easily be half when compared to .1 FR on the ductolator.

[2elaines]

Installer was out this afternoon and changed the TXV. Today was not as hot as it's been, so I couldn't tell if it helped any (I don't think it did) I had him take CFM readings before he adjusted a few of the dampners. He is going to talk to his boss about re-doing the flex to the triangle box and come back to do more balancing as it was getting late and he still had 2 calls to make.

36' of 12" OD ! hardpipe serving 1 register to kitchen 12' x 11' *210cfm*

36' of 16" OD ! hardpipe serving 2 registers to den 18' x 18' *195cfm* & *180cfm* and 1 register to dining room 11'x10' *100cfm*

25' of 12" OD ! hardpipe serving 1 resister to bedroom 16' x 13' *250CFM* & 1 register to bath 10' x 10' *115CFM*

12' of 12" OD ! hardpipe serving 1 register to bedroom 10' x 14' *175CFM* with Y of 7' of 8" OD ! hardpipe to bath (forgot to get this one)

45' of 5" flex serving 1 register to washroom (vent above refrig-couldn't get hood to ceiling)

6' of 7" flex serving 1 register to bedroom 12' x 12' *110CFM*

20' of 9" flex with the triangle box then 5' of 7" to bedroom 10' x 10' *150CFM* & 25' of 7" to office 14'x11' *120CFM*

1 20 x 30 hall return *950CFM*
1 14 x 25 ceiling return *500CFM*

[mark beiser]

Those triangle boxes should be illegal. Depending on the air velocity through them, it is like having an extra 50-75 feet of duct on the run. :rolleyes:

[beenthere]

Totaling the CFMs you posted for the supplies, it comes out to 1605 CFM. You don't have CFMs for 2 supplies. And it still comes out to more then what he measured at the return.

1605 CFM measured supplies, and 1450 measured return.

Either you got a big return air leak, or he blotched his readings.

[jrbenny]

Might be some return duct leakage.

However, there's is most likely supply boot induction. When the boots aren't sealed to the floor or ceiling, supply air rushing through the boot causes a low pressure area. Air is sucked into the boot.

It causes your supply readings to be high.

It's also a big cause for inadequate cooling with a ceiling supply system.

[beenthere]

True.

But either way. Its a problem that needs addressed.

[beenthere]

True.

But either way. Its a problem that needs addressed.

[2elaines]

All the supply registers (except 2 that are too difficult to get to in the attic) are pookied in the attic and caulked from inside at the ceiling. The main wall return is totally caulked insine and the metal transition to heater is pookied at all seams .The 2nd ceiling return is totally caulked inside and pookied in the attic.

The cfm readings are an average as the meter on the hood did fluctuate (is this normal or poor equipment) I did question the difference between supply & return CFM. He said his hood was smaller than the 20 x 30 return and he had to block the top 6 or so inches at the grille, and that when he checked a return the hood causes a slight restriction and causes the other return to pull more.

He did adjust some dampners and I noticed last night that a couple of registers have a choppy air flow sound and they used to be smooth & quiet,

[jrbenny]

Your home is one of the few to be sealed in that manner.

[2elaines]

Your home is one of the few to be sealed in that manner.

Thats