Temperature Rise and Airflow

[tact]

http://www.goodmanmfg.com/Portals/0/pdf/SS-GAEPF.pdf
Goodman 5-ton Heat Pump with Variable Speed Air handler
2500 sq ft home located in NC.

I purchased the heat pump online in 2004 and installed it myself then managed to have a pro take care of the refrigerant end of the install. A bad move that I know. So no warranty exists. However the system has adequately heated and cooled the house for five years.

After doing research recently, I have discovered that my return plenum box and system filter, 16"x 20", is undersized for the 5-ton heat pump. This probably accounts for excessive noise at the air handler and condenser at the highest setting (1960 CFM). I have recently set blower to the lowest setting (1530CFM) and the the system is noticeably quieter and heats the home comfortably. I am concerned about the temperature rise. Here are my readings:

Outdoor Temperature = 47°
Supply Temperature = 100°
Return Temperature = 70°
--------------------------
Temperature Rise = 30°

I realize that the return plenum needs to be enlarged. Is this temperature rise OK or a detriment to the life of the system until which time I can make return plenum size corrections?

[Robert]

Hi,


Ok, here is my best advice IF you can find one. Try to locate a reputable hvac tech with better than average heat pump experience and allow him/her to come out and inspect unit.


Then maybe he/she can start at beginning and get everything as it should have been.


There is not a set in stone cfm rating for a Goodman heat pump in 5 tons.

So, the return and filter size is also not set in stone.


It's going to take some testing and calculating to get that as close to what it should be.


Also would be good to get an ACCA Manual J Load Calc done to see if you have correct size unit.


The "pro" that did the charging 5 years ago should have known all this and took care of it then.


Although you may feel it has performed adequately for 5 years, I can almost gaurantee that it hasn't and has been straining at best.


Get that puppy up to par as it should be and allow it to run as designed.


Without the proper tests results, I cannot answer your questions and neither can anyone else honestly.


Best wishes on getting it running smoothly, be picky on anyone you allow to work on it, heat pumps are very finicky.



Thanks,
Robert

[tact]

I increased the cross-flow opening under the air filter rack to a true 20"x20". What a difference. The ECM blower and the condenser have quieted down considerably and appear to run more efficiently. Most important of all is that the temperature rise (delta temperature) falls within specifications at all temperature ratings, as per manufacturer. I wish I would have done this years ago. The bottom line is that air requirements, whether its cross-flow opening in the return plenum and return/supply ducting, for any size heat pump should not be ignored.

[Robert]

Hi,

Shouldn't be ignored, but should only be done after testing to know you have correct airflow sizing.




Take care and best wishes,
Robert