20DL4 and creative wiring questions?

[Isaac-1]

As some of you know I have been looking for a backup generator for my mother's house, she lives on a farm and the house is all electric single phase with a water well. The well is located in a separate building from the house with a separate electrical connection with its own cutoff switch. sharing one post mounted meter. Now for the creative and 20DL4 question part, I have found a running surplus 20DL4 available, the catch is it is a 15R voltage code unit, I therefore assume if hooked up single phase it would would have an output of about 13KW which is a bit light for her needs (most likely cause of major outage would be hurricane, so central air, etc would be needed). The well is set up with a pair of 1 HP 115/230 motors one for the well pump and one for the pressurizing pump, currently these are wired for 230v, would it be possible to connect the spare 3 phase leg up 120V and reconnect the well motors for 115V on a separate small transfer switch/switch panel from the main house load to get better use of the 20DL4? Also any thoughts or comments on this particular model generator, I have read there were issues with the water temp switch, anything else?

thanks Ike

[Jim Davis]

All electric? What kind of heat does she have?

[Isaac-1]

Traditional resistive electric heat (also 2 forced air heat fireplaces which can provide for the majority of the heating needs in a winter out of power situation)

Ike

[Jim Rankin]

I think you could realistically expect to get more than 15 kW/kVA out of it instead of 13

20kW usually equates to 25kVA (0.8 pf)
25kVa x 2/3 = 16.6kVA which is less than the engine capability of 20 kW so pf=1.0
so 16.6kW/kVA Not sure what the nameplate will say, probably most likely 13!

I believe I would simply use a single phase connection and one full sized transfer switch ahead of the well supply disconnect. You would spend the money for the transfer switch and its installation and not have to do that over even if the generator wasn't entirely satisfactory. In that case, you could probably get your money out of it quite easily. That size seems to always sell well compared to larger machines.

I think you could do what you suggest with the well pumps and the 3rd phase, but I would do it with a single 3 phase transfer switch for simplicity. To use only the one leg (120 volts) You would have to use 120/208 3 phase (or perhaps jack it up to 127/220 for motor starting if you want) because the other low voltage 3phase connnection (120/240 3ph 4 wire) has only two 120 volt legs which would go to the house, the other is 200-208 to neutral. You could use the 120/240 3phase and leave the pumps on a 240V circuit using the high voltage leg as one of the hots for the pump circuit and the most lightly loaded 120 volt leg as the other.

[Isaac-1]

A single transfer switch is not an an easy option as there is no central service entrance point. The well and the building it is in was built before the house, and as a result it has a separate feed and weatherhead from the transformer even though it is only a few feet from the service entrance fro the house (the meter is a post mounted remote meter, not a standard pass through residential meterbase so no cutoff switch there)

Ike

[Jim Davis]

It is difficult in a backup situation to list all the items and combinations of items that cannot be operated, especially when there is already stress due to the cause of the outage. I read about people struggling to make small generators work for them after going through all the expense of buying them and setting them up. Diesel consumption is linear to load for the most part so why not get a larger generator that would be worry free. Electric heat generally is 15 to 20 kw alone here in southeast Texas, why not be able to operate it in an ice storm? The larger generator is easier to find and costs less.

[Jim Rankin]

Originally Posted by Isaac-1

A single transfer switch is not an an easy option as there is no central service entrance point. The well and the building it is in was built before the house, and as a result it has a separate feed and weatherhead from the transformer even though it is only a few feet from the service entrance fro the house (the meter is a post mounted remote meter, not a standard pass through residential meterbase so no cutoff switch there)

Ike

With such a short distance involved, I would seriously consider swapping the expense of another transfer switch for rewiring the pump house feeder line to come out of a panel after the main transfer switch or connect it's feeders to the load connection of the transfer switch and keep using the existing disconnect to protect the feeder conductors.

I have a rewiring project at the dairy that involves a similar setup. Original panel had only 2 spaces for 3 phase breakers so when additional equipment was added, a couple of fused disconnects were tapped onto the load side of the transfer switch and feed a sub panel in one case and a single condensing unit in the other. I have a larger 3 phase panel, some 6x6" wiring chase to extend what is there and it will all work out, just take a lot of work and there isn't much time to get it completed between milkings.

The reason for all this is that the old wiring between the generator breaker and the transfer switch (welding cable taped along a conduit to keep it off the ground, but otherwise exposed) failed while the generator was being exercised. A couple of phase conductors arced between and for some reason the 225 amp generator breaker never tripped. The arc finally blew out enough wire to extinguish itself. The amperage must not have ever gotten high enough to trip the breaker, but it was quite a show none the less.