Hello All,

I have some questions regarding sizing of a geothermal pump that I had installed 18 months ago. I did see the previous thread on geothermal pump sizing:

Geothermal – Sizing Issues – 4 Ton or 5 Ton?

Background:

I have a 1780 sq ft older home ( I believe built in 1930s but with a more recent addition in the 1990s) in Cleveland; it was previously heated using a 3 ton electric heat pump which I believe did the job fine.  I had a geothermal system put in about 18 months ago by a HVAC contractor that exclusively installs geothermal pumps. He installed a 4 ton, 2-stage Hydron Module pump, basing sizing on “experience” rather than performing a Manual J. He didn’t recommend any changes prior to the install to reduce load like air sealing, additional insulation, etc. as mentioned in earlier posts.

I’ve had several contractors that eyeballed it say they thought it should be more like a 2.5 or 3 ton for this house. I recently had another contractor do a Manual J (summary image attached), although I think it is a stripped-down version. He felt that the house needed a 2.5 ton unit based on his result (he also said the sizing should be based on the the cooling load). The contractor that installed the system says he sizes his systems based on heating load. As an aside, I found it quite difficult to find an HVAC contractor willing to perform a Manual J as a standalone service..

I pulled the data log from the thermostat, and I’m hoping this can help shed some light on whether my unit is oversized (readout attached). I’m not sure if just having the monthly cycle count and run times provides enough information for that; the thermostat seems to only save detailed hourly data from the past week. (I didn’t know about the data log function until recently, so I don’t have earlier detailed hourly or daily logs).

My main questions are: Is this unit oversized? Do the cycling rate and run times suggest it is oversized? Is there a certain proportion of time a dual stage heat pump should run in stage 1 versus 2?

Besides opinions of other contractors, one reason I’m afraid it may be oversized is that I have also noticed that humidity in the house was very high in the summers since it was installed, often in the high 70s. The basement doesn’t have water issues, but does have a communicating dirt crawlspace. The basement was waterproofed a couple months before installing the geothermal Unit.  Putting a dehumidifier in the basement hasn’t help at all with house humidity level. We did have the ducting supply and return size increased to accommodate the larger pump per recommendation of the geo installer, but this also didn’t help the humidity issue. As of yet I haven’t done any additional air sealing or insulation.

My other question is, assuming the heat pump is appropriately sized, is there anything that can be done to make the geothermal unit perform a better job dehumidifying in the summer?

Thanks everyone,

Salim