New Heat Pump Undersized

(Sam Morris, LC #341 CMI) #1

Inspecting a 1400 sq ft house today with a** 2 ton heat pump**. Heat pump had a difficult time heating the house. I jumped the thermostat to 73* not getting a 100* surface temp from register vent after 35 min. of trying (I usually set temp at 70* and get 100* surface temp from register to call it good. I know what the size tonnage should be (2.5) but, in TN we don’t inspect the size as part of our inspection. How do state something in report without getting out of my inspector lane. ??

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(Randy Mayo, P.E.) #2

State your concerns and recommend a qualified HVAC company check it out. Then move on to your next inspection. If they take your advice fine, if not that’s fine too.

(Charley L. Bottger) #3

Are you sure its a 2 ton I see a 42 in the model # it also has 12.8 RLA on the compressor. Just asking did you look it up. I also saw the 24 in the model #. What was the temp in the house when you started the HP was the house vacant and the temp turned down

(David A. Andersen, TN HI# 40) #4

To start with, the most important thing is, what was the outdoor air temperature? It’s been cold here for the last few days.

Next, your method of testing for temperature differential is not an accepted industry standard. Temperature measurements should be taken about four air duct diameters from the equipment.

How did you measure the surface temperature of the register? I’m assuming IR. This would not be appropriate for “system capacity diagnosis” of a fluid. A thermocouple is more appropriate. IR just validates the temperature differential is happening.

What was the discharge temperature you are recording? You make no mention of that.

You do realize that there are two heaters in a heat pump system. Raising the temperature two degrees will call in the auxiliary heat. You made no mention of verifying that that was coming on. The auxiliary heat (if installed) has the capability of raising the register temperature to one hundred degrees. The heat pump does not, if there isn’t sufficient heat in the outdoor air.

What are you going to call out in your report? It could be the HVAC equipment, the HVAC air duct system, or the building construction.

There are very simple procedures that you don’t even need any test equipment for to determine if the HVAC is operating correctly. Way more accurate than that newfangled IR thermometer contraption.

Also, a 2 ton should be more than sufficient for that size house in this region.

(Sam Morris, LC #341 CMI) #5

Not for a 1464 sq ft home in Northeast Tennessee, should be a minimum of 2.5 tonnage. Maybe in Nashville but not here

(Stephen W. Stanczyk, WA License #221) #6

All that is based on average per square footage. Did you measure the size and number of windows and doors? Insulation? Air leakage? A large 60 year old home used to have a 100K btu furnace. Nowadays, a new construction, same size home can get away with 40K. The information you supplied is not truly enough to ascertain if the heat pump is large enough.

(Sam Morris, LC #341 CMI) #7

Yes, I totally agree with you, I leave the sizing to the HVAC professionals. All that still didn’t heat the house like it should, so I called out a licensed HVAC contractor to evaluate and estimate any repairs needed. Im not paying for an upgrade so I called out a licensed HVAC contractor and feel OK with that, Im a generalist not an expert in the HVAC field.