Does anyone make low voltage cutout for power from generator?

belfert · August 04, 2014, 05:27:16 PM

I have a problem with my generator where sometimes while running all three A/C units the voltage will drop really low to like 50 volts. Is there a device that can disconnect the voltage from the generator when this happens?

The last time this happened the A/C units were running fine for several hours and then they just all stopped due to the voltage drop. As soon as I turned one off the voltage went back up to about 117 volts. I don't think there is anything wrong with the generator as it will run all three units for a number of hours. The regulator went out previously and I couldn't even run one A/C unit before the voltage dropped too low.

dukegrad98 · August 04, 2014, 05:50:17 PM

When the drop happened, did your generator engine bog way down? That's important. You need to figure out whether there was a mechanical overload (for whatever reason) that bogged the engine, or whether something electrical is wrong with the generator head itself that caused output to drop. If it's spinning the right RPM, it should be putting out the right voltage. A drop to half-voltage should have been very obvious on the primary mover. On my Kubota diesel genset, I could hear a 50rpm change easily just by the tone of the engine. A good governor should bump it right back up to speed after a start-up load or similar event.

Maybe your fridge tried to kick on while all three ACs were maxing out the genset? I would think that would trip a breaker somewhere in the system, though.

Cheers, John

belfert · August 04, 2014, 06:07:48 PM

No changes in engine speed I could detect by ear. I was outside near the generator while this was happening. Everything in the bus except the A/C units was off. I believe the inverter was off and not charging. I had been using a handheld grinder and when I used it a second time the grinder was running really slow with no power. That is when I went inside to find the A/C units not running. I figured the voltage was low and my multimeter showed I was right.

It was only in the low 80s when this happened and not super hot. No breakers tripped like they did in the desert when it was 107 degrees with no shade.

oldmansax · August 05, 2014, 05:05:13 AM

Brian,

If your transfer switch is electrically controlled, then there are a number of units that can be installed to monitor and disconnect either power source upon various conditions. Here is one I have used a lot:

http://www.icmcontrols.com/Digital-singlephase-line-voltage-monitor-fully-programmble-with-5fault-memory-protects-against-underover-voltage-rapid-short-cycling-80300-VAC-24240-control-VAC-Prodview.html

I used this on on my home made transfer switch.

TOM

belfert · August 05, 2014, 04:35:31 PM

Quote from: oldmansax on August 05, 2014, 05:05:13 AM
If your transfer switch is electrically controlled, then there are a number of units that can be installed to monitor and disconnect either power source upon various conditions. Here is one I have used a lot:

What exactly is an electrically controlled transfer switch. My transfer switch is a fairly standard IOTA 50 amp transfer switch (no longer made).

The default position for the transfer switch is shore power. I am surprised the transfer switch didn't kick back to shore power when the voltage dropped to under 60 volts. When I had regulator issues with the generator the transfer switch would go back to shore power when the voltage dropping too low.

oldmansax · August 05, 2014, 05:33:58 PM

Quote from: belfert on August 05, 2014, 04:35:31 PM
What exactly is an electrically controlled transfer switch. My transfer switch is a fairly standard IOTA 50 amp transfer switch (no longer made).

One that is actuated using electricity instead of manually. The manual ones have to be changed by hand using a big knob. The electric ones are changed by an electric switch. Some will switch back and forth automatically when they sense where the power is coming from (shore or generator). I don't like those. I like to choose what I am using myself.

TOM

belfert · August 05, 2014, 07:55:24 PM

Quote from: oldmansax on August 05, 2014, 05:33:58 PM
One that is actuated using electricity instead of manually. The manual ones have to be changed by hand using a big knob. The electric ones are changed by an electric switch. Some will switch back and forth automatically when they sense where the power is coming from (shore or generator). I don't like those. I like to choose what I am using myself.

I wasn't sure what you meant here. Mine is fully automatic. I could get by without a transfer switch considering I never stay any place with power on the road. Heck, I leave the power cable at home most of the time. I will look closer at the device you mentioned.

TomC · August 06, 2014, 05:17:19 PM

My 10kw Powertech Generator is wired straight 120vac. Hence, no balancing of loads. When hooked up to power pole, I just use one leg of 50amps. Just have to be a bit careful about overloading. I like it so much, I'm wiring my truck the same way using a Wrico 12kw that is also wired straight 120vac. Just have to run two sets of 3 wire from the generator to the breaker box and use jumper wires between all mains to keep the loads equal. Good Luck, TomC

belfert · August 06, 2014, 05:27:09 PM

Quote from: TomC on August 06, 2014, 05:17:19 PM
My 10kw Powertech Generator is wired straight 120vac. Hence, no balancing of loads. When hooked up to power pole, I just use one leg of 50amps. Just have to be a bit careful about overloading. I like it so much, I'm wiring my truck the same way using a Wrico 12kw that is also wired straight 120vac. Just have to run two sets of 3 wire from the generator to the breaker box and use jumper wires between all mains to keep the loads equal. Good Luck, TomC

I am running straight 120 volt too from my generator. I was originally running 240 volt which is why I have a 50 amp transfer switch. The transfer switch still works as I still have two hot leads coming off the generator joined by a jumper inside the generator junction box.