4 geo heat pumps added to an existing service

[Fred B]

This maybe a stupid question but never came across one like it and would like some guidance. Got a load calculation question. Have an environmental company adding 4 geo heat pumps to an existing service. Info on these 4 units from the enviro company they have listed at a total of 214 Amps. Existing loads calculations for a 6500sqft house come in at 139Amp on a 200 Amp service, and a 1200sqft apt. seperate building, comes in at 77A was seperate feed that owner wanted to combine with the house feed. I can reduce the geos loads calc by only counting concurrent loads and get down to 189A. The geos go with the main house. POCO is limiting to a max 400A 1ph meter. No 3ph available. How would I add these loads together for a new service calculation? Is it as simple as just adding the numbers or would there be additional reductions that can be applied that would allow all three loads to be supplied from the single 400A service?

 

[Eddie702]

I don't see how. Your at 139 +77+189=405

I can't imagine 4 geo units totaling 189 or 214 for that matter for a 6500 square ft house.

600 square feet/ton of cooling is pretty conservative. Modern construction is probably less than yhat. That comes out to only 11 tons

Where are all the amps for the geo load coming from?

Bunch of electric strip heaters?
I know you must have a couple of pumps in their

11 tons should be more like 50-60 amps of load


Are you counting electric strip heaters and compressors which probably won't run at the same time?? Maybe there is some relief their

 

[Fred B]

I don't see how. Your at 139 +77+189=405

I can't imagine 4 geo units totaling 189 or 214 for that matter for a 6500 square ft house.

600 square feet/ton of cooling is pretty conservative. Modern construction is probably less than yhat. That comes out to only 11 tons

Where are all the amps for the geo load coming from?

Bunch of electric strip heaters?
I know you must have a couple of pumps in their

11 tons should be more like 50-60 amps of load


Are you counting electric strip heaters and compressors which probably won't run at the same time?? Maybe there is some relief their

Nothing in spec sheets that indicates strip heaters but they have sized 4- 5 ton compressors, all 4 can run at same time but will have sequential startup. These units are supposed to provide for the domestic hot water as well in combination with 2 50 gal electric water heaters, and other pumps and controllers.The system has 4 1000ft geothermal wells. 2 large supply pumps, but only 1 runs at any given time.
I Wasn't involved in the original process, just brought in to get them the power needed to operate what they already installed. House dates to the 1800's no insulation. I think the HO would have been better served to spend the $100G on insulation than an oversized "Green" heating/cooling equipment, that cant get the POCO to provide the needed power. But too late for that discussion.

So my assumption to just add the individual loads together was correct?

 

[Eddie702]

I don't see any electrical relief on the loads unless you can take something off for the electric water heaters, there probably not used if the heat pumps are making hot water. That's probably 9000 watts or 37 amps

The equipment seems grossly over sized to me but you hit the nail on the head. They should have spent the money on insulation. 20 tons of heat pumps will do about 300,000 btu on heat and 240,000 on cooling. Crazy. Your hands are kind of tied at this point.

Like a guy told me once. "They tie your hands and feet together and expect you to swim"

maybe someone else will chime in

 

[Fred B]

I don't see any electrical relief on the loads unless you can take something off for the electric water heaters, there probably not used if the heat pumps are making hot water. That's probably 9000 watts or 37 amps

The equipment seems grossly over sized to me but you hit the nail on the head. They should have spent the money on insulation. 20 tons of heat pumps will do about 300,000 btu on heat and 240,000 on cooling. Crazy. Your hands are kind of tied at this point.

Like a guy told me once. "They tie your hands and feet together and expect you to swim"

maybe someone else will chime in

Talked to the engineer that set this up. He confirmed what I thought, they never did a load calculation for existing house prior to selling the system. He said they never do. He also volunteered that he was only a mechanical engineer and not familiar with sizing electrical loads. He said they've installed a lot of these systems even though only half this size and never had an issue with power on a 200 amp service and doesn't understand why there is an issue now. He said they hooked one heat pump up on a temp power source and had the guys there meter it and the heat pump was only drawing 24A, (spec sheet shows 30A) and the starting surge was only 30.8A (spec sheet shows 50.6A). Even using these numbers X4 along with the other loads won't get me into a 200A service from what I see.

 

[Eddie702]

Unfortunately what he thinks the load is doesn't count only the equipment nameplate does.

Don't let them stick you with the problem

 

[winnie]

The customer wants to convert the service to a separate building into a feeder from the main house, and add all the new heat pump loading.

The utility won't do more than a 400A meter.

The calculated loads will exceed 400A but we know that load calculations are conservative. Also the heat pump system is grossly oversized and will likely never use total nameplate.

I think you can offer your customer something along the lines of keeping the other building on the separate service, installing a 400A service on the main building, and providing demand metering for a year to actually measure if the two services could be combined.

328 < 400 so a 400A service for the main building is good, and the separate building is existing so that is good, and a _calculated_ combined 405A will likely come out well less than 400A when _measured_, but you have to actually make the measurement.

Jon

 

[junkhound]

Install a relay on the most used GSHP that locks out the least used GSHP, so now under 400A.

As other have said, that is one leaky house!

Own house is 5300 sq ft with single 5T GSHP, draws 16A running. I'd look at the nameplates of the GSHP vs using the sales co numbers!