Is this new HVAC system performance acceptable?

[ejohnson10]

I just had a new HVAC system installed in a new house and it has been running for about two months. I haver not fully paid for the system yet as the contractor still has some work left to do (load balance & cosmetic stuff).

Today the temperature is 100 outside. I have my thermostat set to 77 and the actual temperature is 81. (This is upstairs, downstairs a separate system is maintaining the selected temperature.)

I am getting about a 20 degree drop. The contractor tells me that this is normal performance and I should not expect more than a 20 degree drop.

Is that acceptable as an industry standard for residential systems, or should the system be doing better? Should I accept the system as-is or demand better performance?

In my location 95-102 degree days occur every summer but it is rare to have more than 10-15 of them per year. I would rather have a slightly undersized system than an oversized one.

Thanks for any help!

[SubCooled]

Your contractor is lying to you. You need a 45 degree drop. You probably have one of those digital thermostats installed, those things are notorious for only having a 20 degree drop when they are installed in upstairs applications. I'd call them and tell them you want a 45 degree drop and you are going to withold the balance do until they fix it.

[udarrell]

If it has low airflow or a very low latent heat load (humidity) the temp drop can be rather meaningless. The evaporator may not have enough airflow through it, which throws charging the refrigerant system off, which compromises performance.

That temp drop can vary from 14 to 26-F & still be within tolerances. What is the % of Relative Humidity in your home. (Get a Humidity gauge at a good hardware store!)

Take the air discharge temp split of the outdoor condenser & list the SEER Rating & tonnage of the condenser. Provide all that data here, which will only provide us some clues & not a bullseye diagnosis.

- udarrell

[ejohnson10]

Thanks. I will do what you suggest, however in one sense the SEER and tonnage rating do not matter to me as far as determining if the contractor did an acceptable job. Part of his job was to design the system. We agreed on a SEER rating and he selected the tonnages he felt would do the job. He was to design a system that would properly heat & cool the house and he chose all of the equipment, designed the ducts (vent & return), selected the thermostats, etc.

I will say that the air flow seems quite high out of the vents so there must be a lot of air going through the evaporator. The compressors are in the sun. (Would it help to provide share for them?)

(Note: I accidentally started this thread us> [e-mail] wrote:

[Zephyr]

People are funny.

What's the chance that this O.P. 's contractor [actually] performed a Manual J and/or Manual D?

ejohnson10:

Did you receive as part of the job the Manual J calc's, and a drawing illustrating the completed duct installation?

Zyp