I'd be curious how much horsepower your well and septic pumps require. The most I've seen is 15hp @ 11kW, but that is pretty massive for an average home, even an off-grid one. Typical requirements would be in 0.75kW - 5kW range, which is a wide range.
Do you know how much power the heat pump requires?
I'd struggle to see how a 20kW generator struggles to to run a home, unless you've also got heated floors, saunas, steam baths, water and space heaters, electric stoves and ovens all running at the same time :-).
Once upon a time, Mark Tinka <mark@tinka.africa> said:
I'd struggle to see how a 20kW generator struggles to to run a home,
unless you've also got heated floors, saunas, steam baths, water and
space heaters, electric stoves and ovens all running at the same
time :-).
My house isn't very big, and I live alone (so less demand for hot water
for example), and I hit a peak demand of 15kW a couple of months ago
during a cold snap (I've seen it higher, maybe 16kW IIRC, just didn't
dig any deeper). I probably took a hot shower while the heat was
running, but I didn't cook anything that day, which could easily pulled
another 1-2kW (oven, microwave, etc.). And that's without any
water/septic pumps.
Electric heat pumps are great for power efficiency until the temperature
drops and they switch over to pure electric heat.
My all electric house is in a rural area. The generator that came with the place is a 20KW Onan, The bad news is in can't handle the house. I think it is the Aux Heat on the heat pump that is the problem. I have to also power the well pump and the septic pump.
Is your house single or 3-phase?
Single phase. The house is 200A service and the barn is another 200A service
I'd be curious how much horsepower your well and septic pumps require. The most I've seen is 15hp @ 11kW, but that is pretty massive for an average home, even an off-grid one. Typical requirements would be in 0.75kW - 5kW range, which is a wide range.
Do you know how much power the heat pump requires?
I don't know how much the pumps require. The water well is about 100 feet from the house and the pressure tank.
The septic pump has to pump uphill to the drainage field. Distance is about 250 feet and elevation gain of 100 feet or so.
The heat pump doesn't seem to be a problem but the aux heat is on two 20amp 220v circuits. There is a switch on the fan enclosure to disable the aux heat.
Another biggie is the electric hot water heater.
On 1/30 it never broke 32 degrees and the house used 145KWHR (average was 6KWH). Thank goodness I am not far from the Columbia River and the BPA has a major substation about 5 miles away so I pay less than 10 cents per KWH
Over 2022, I lost power about 8 times. The longest outage was 15 hours.
At -30c external, with +20c internal the units produce heat at
approximately 2x of the electric input.
But many other units do not perform that well even at -20c external.
And these units are premium priced. Modern R32 units consistently
outperform old R410A units.
20 KW should easily cover the 9KW you could max draw with your strip heat. It is super uncommon to have even peak loads over 20 KW in a house. Even your peak day was only an average of 6 KW.
You might need some load shedding just to keep the big stuff from coming on all at once but that is pretty easy. If you have instant hot water that also could be a problem those are huge, typically 15-20 KW by themselves.
My guess is that your 20kw Onan isn't up to stably producing 20kw any
more. Or perhaps the older transfer switch with its mechanical timer
relays has gotten dodgy. The modern consumer gear is very reliable but
the pre-2010s commercial/industrial gear (such as Onan) takes a lot of
TLC to keep it working right.
Another thing that can happen is uneven load. The utility won't care
that 80% of your draw is on one side of the circuit but that'll stop a
generator in its tracks.
If you want to know for sure, get yourself an inductive clamp meter
and start checking the amperages at the breakers. You can get a cheap
one under 50 bucks. You just set it for AC amps, take the cover off
your breaker panel and clamp the jaws around the "hot" wires coming
from each breaker, one at a time.
As John mentioned, unless you have a really large house or a tankless
electric water heater, it's really odd to overwhelm a 20kw generator.
Even with the auxiliary resistive heat.
