POLAR FOAM and rusty leaking EVAPORATOR COILS

[Delnan]

We built our home in 2005 and had Polar Foam insulation put on all exterior walls, attics and between 1st and 2nd floor.

Is anyone aware of the effects of polar foam on air handlers in attics? Two of three Trane units have had thus far in 7 years, each 2 new evaporator coils. Coils completely rusted out and leaking all refrigerant within 24 hrs. The 2.5 ton has required 2 new fan motors as well. The latest replacement on the 2.5 ton is an aluminum evaporator coil, but very pricey! The other unit, 2 ton for upstairs, had a burned up fan motor and completely rusted evaporator coil. Fan also completely covered in mold. It was recommended to replace the air handler and condenser. Thought it would be more cost effective. We did, but with a Broan. Now we can't get the air cool and humidity down unless we drop the thermostat to 72 degrees. Can't wait for my next electric bill.
The upstairs is 1108 sq ft with a 2 ton 14 seer rating (cooling), and cooling capacity (Btuh) 24000. No clue if this means anything.
Our third unit is in a closet on the main floor with no coil or fan issues whatsoever.
All three Trane units have always been set at 77 degrees for cooling in the past, with cooling and humidity control excellent. Pretty good for Florida during the hottest time of year.

It was also recommended to have two attic vents placed in the roof where the new Broan is located. Other than cutting into the foam and creating a hotter attic, this has not improved our situation. So far they have no other recommendations for us, other than slowing down the fan speed for better humidity control? I don't even feel the blower as it is, at the speed it is set at.

Today we told the rep and installer that this unit is unacceptable as it is and to come up with a solution or removal and refund.
Any ideas what the problem could be with the Broan?
Any thoughts on foam insulation and air handlers in attics?

Thanks,
Delnan

[Stamas]

Some more info on the equipment, new and old, model #'s would help.
Any other equipment installed when house was built to ventilate?

[beenthere]

You had a hole put in a foamed roof? Defeats the purpose of having it foamed.

[mark beiser]

The foam isn't "the" problem, but it is common for builders and HVAC contractors to completely fail at designing and installing appropriate HVAC systems for homes that are insulated with foam.
Distressingly common...

More than likely, you have a combination of issues, including over sized equipment, restrictive duct systems, off gassing of VOC's from all of the materials used to build, finish, and furnish the home, and not enough fresh air changes to purge it all.

Also, whoever recommended ventilating the attic is clueless. You need to have the holes repaired, and seal the attic back up.

[Delnan]

Old unit Trane 2 ton model #4TEE3F31A1000AB serial # 4455MOCIV

New unit Broan 2 ton model #B6UMAX24K-B serial #B6D120203989

Unfortunately no other equipment installed to ventilate.

[motoguy128]

An 1100 sqft all foam insualted upstairs likely doesn't even need 1.5 tons. Believe it or not, Florida is very humid, but not nearly as hito as people think it is in terms of designing equipment. It just stays hot year round and has no winter. But the design temperatures are no different than many parts of the midwest. Very common to have oversized equipment in the south.

The old equipment probably had a smaller coil surface. THh newer higher effciency equipment has larger coils that don't dehumidify as well, but in lab testing (where they are only trying to move totla heat energy (latent & sensible), not control humidity).

What can you do now? Have the airflow evaluated. You may be able to reduce the airflwo for better dehumidification. Make sure ductwork is sealed well. Foamed attics, especially if open cell foam was used and depending on how well sealed it is, can still allow a lot of humidity in there even if it doesn't get that hot. The indoor space being cooler, and hte wood roof deck being hot, will cause moisture ot migrate indoor in the afternoon. The process can reverse itself at night. It's still normal for a foamed attic to get to 90F in the later afternoon. But an unfoamed attic would be an unbearable 130F. Also, did they remove the insulation form the attic floor when they foamed the roof deck? You need ot have that insulaiton removed so the space can communicate with the conditioned space. Also, if it's cellulose, that material holds a lot of moisture.

[beenthere]

Old unit Trane 2 ton model #4TEE3F31A1000AB serial # 4455MOCIV

New unit Broan 2 ton model #B6UMAX24K-B serial #B6D120203989

Unfortunately no other equipment installed to ventilate.

I believe those are the air handler model numbers, post the outdoor units model number also.

[Delnan]

model # 4TWR2018A1000AB serial # 5161KT02F Trane

model #NT4BD-024K Broan

[jtrammel]

My guess is the Unit is oversized thus creating high humidity in your house and air handler, due to short cycling

[jtrammel]

Also need to ventilate the house because it's choking!

[catmanacman]

What was the reason for the larger unit other then more profit for the installer .

[beenthere]

What was the reason for the larger unit other then more profit for the installer .

Cause the house is the same size as the last house they put that size A/C in.

[Delnan]

Both units are 2 ton. The previous Trane unit was 2 ton as is this one so he says. The unit says 2 ton.

[Delnan]

Does short cycling cause a higher electric bill?

[mark beiser]

Both units are 2 ton. The previous Trane unit was 2 ton as is this one so he says. The unit says 2 ton.

If the old unit was a 4TWR2018A1000AB, it was a 12 SEER 1.5 ton unit.

[Stamas]

He can't read.

[Delnan]

Thank you all. As one stated, the previous unit was 1.5 ton. I verified with the original installer. So here we are with a 2 ton...having huge difficulty with
the installer of this one.

[beenthere]

4TWR2018A1000AB

Thats a 1.5 ton unit model number.

[energy_rater_La]

short cycling does add to utility costs.
start up of compressor uses more amps than
running of compressor.
if the unit comes on and stays on for a long period
of time it costs less than one that starts and stops
several times in the same length of time.

short cycling adds to high humidity in that the
unit doesn't run long enough to remove humidity.

not familiar with the polar foam. open cell, closed cell?
new home with foam as only insulation, is how I read the
original post. is this correct?
were any load calcs or correction of rule of thumb sizing
used in a foam sealed house with foam sealed unvented attic?
this seems to be the big disconnect with foam insulation companies
and hvac companies.

best of luck.

[Delnan]

Our installer has agreed to change the outside unit to a 1.5 ton. However, he tells me the inside unit that is 2 ton is no different than a 1.5 ton, and he can leave that inside unit there to work with the outside 1.5. This makes no sense to me. To anyone else? Other than he is trying to save money.