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Old 08-08-2017, 01:08 PM   #1
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Generator distribution - single phase 30A panel

We have replaced all of the AC appliances on board. Old equipment, it was possible to run the refrigerator + water heater + battery charger off the generator.

New equipment, generator main breaker trips after approx 10 minutes. The overall load has increased slightly.

Main AC panel is supplied from a 30A 120v shore power (single conductor).

The generator is 3.6 kw, single phase. One conductor feeds to the AC selector switch. The second conductor is unused. Genset main breakers are 15A 120v per conductor (two breakers)

Is there a safe and approved procedure to wire as follows? Install a secondary selector switch to feed the AC water heater. Primary selector "shore / genset" TO secondary water heater "shore / genset?" The secondary selector switch would pull from the second conductor on the genset.

This change should make the genset run smoother, less vibration from a balanced load of approx 7.5A per conductor vs single conductor @ 15A.
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Old 08-08-2017, 01:29 PM   #2
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Im not an electrician but it looks like you have 30 amps available from the generator no matter how you divide it up. You need to provide us with the load of your battery charger and your refrigerator to calculate the loads. Your water heater will be 1500, likely. Do you have any lighting, toaster, stereo or tv on those circuits too? Cell phone chargers? With the generator running and the loads applied, what is your system voltage before the breaker blows? How is the 120 wiring? Is there any resistance in the old wiring? Is the breaker used as a switch and if so, often? They wear out...

I also fail to see how the wiring of the load will "smooth out" the operation of the genset but I await the input of smarter people.
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Old 08-08-2017, 02:57 PM   #3
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From what I understand of his description he has 2 x 15 amp feeds available from the genset, one unused. So he has currently only 15 amps available even if the genset is capable of delivering 30 amps.

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Old 08-08-2017, 03:17 PM   #4
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Correct, the genset is single phase. 15amps available per side x 2 conductors. The points on the generator are opposed 180 degrees. If a 15a load on one side, the unit rotates like a out of ballance wheel, all the magnetic pull is on one side.

Vs pulling a even load of say 7.5 amps off each conductor. At least that is how I understand the science.

The sinewave from the two 15a sides are 180 degrees opposite and when combined create 240 volts. My water heater is single conductor 120v. So not possible to use both to feed water heater.

Load for the fridge + battery charger + water heater is approx 15amps.

I'll draw up a schematic and post it. Hopefully less confusing.
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Old 08-08-2017, 03:53 PM   #5
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A schematic would be interesting, I can't fathom a single phase with a system that you describe. I'm boggled with researching generator wiring and maybe you can clarify?
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Old 08-08-2017, 04:04 PM   #6
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How about this? I have to get my head around where the coils are located. Also, both sides of the generator are producing power, one side is not connected. I will have to do more reading to understamd the assymetry. I'm working on it.
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Old 08-08-2017, 04:31 PM   #7
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I forgot the shop manual, with wiring schematics, was left behind at the repair shop. Here is a photo of the unit.
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Old 08-08-2017, 04:57 PM   #8
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Should have two windings. Put them in parallel if you only need 120v. Put in series with center tap for 120/240v. There should be a reconnection diagram for the gennie. If you connect them wrong, they will be out of phase and form a short. Once paralleled, you can use a single pole 30A breaker.
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Old 08-08-2017, 05:14 PM   #9
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Quote:
Originally Posted by Ski in NC View Post
Should have two windings. Put them in parallel if you only need 120v. Put in series with center tap for 120/240v. There should be a reconnection diagram for the gennie. If you connect them wrong, they will be out of phase and form a short. Once paralleled, you can use a single pole 30A breaker.
Done! Figured it out based on described above. I'm metering 115v across two taps which are on an internal terminal block. Need to order a 30A single breaker.

Thank you all for the assistance.
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