How to shut off a circuit automatically only when generator is running?

[reader2580]

I have several battery chargers in my motorhome that are in use when the RV is parked with power, like at home.

I have a diesel generator with automatic transfer switch in the motorhome. I do not want the circuit the battery chargers are plugged into to be energized when the generator is running. I don't want both the battery chargers and the engine alternators to be charging the batteries. Does anything like this exist that is automatic?

 

[The Cobbler]

maybe a normally closed relay on the circuit with the coil powered from the generator feed. when the generator is running, the coil is pulled to open the contacts

 

[CoogarXR]

Wouldn't that just be a circuit that isn't on the transfer switch? It's on when you have shore power, but is not connected to the generator?

 

[Gozo]

I was in the process of saying exactly that when the ‘a response has been posted’ message came up. A relay is probably the simplest way to cobble something up, but I’ve had varying results with NC contacts getting flaky after a while with higher current loads. Maybe something like an optoisolator solid state relay. No physical contacts to get wonky.

 

[wyliesdiesels]

maybe a normally closed relay on the circuit with the coil powered from the generator feed. when the generator is running, the coil is pulled to open the contacts

this. you beat me to it

run the battery charger circuit thru a contactor.

connect contactor coil thru a relay that is normally closed. connect relay coil to power feed from genny. when genny provides power, relay opens removing power from contactor relay which then shuts off charger circuit.

not difficult

 

[dcg9381]

One of these.. Pretty easy. You can "lock out" the entire circuit.

Generac Help Center

support.generac.com

I have two of them. Apparently there is a "lock out" mode that drops the circuit while on generator power.

 

[reader2580]

Wouldn't that just be a circuit that isn't on the transfer switch? It's on when you have shore power, but is not connected to the generator?

All of the circuits are in a main load center that is connected after the transfer switch.

 

[ToolsRCool]

Put the battery charger circuit on the utility side of the transfer switch. I don't know all the correct RV terminology, but whatever the side is where the connectivity plug is on the outside wall of the RV, that plugs into the power pole at the campground, that would normally be using utility power.

 

[reader2580]

I am thinking I would need to install another small load center if I connected a circuit before the transfer switch. I am trying to avoid that if I can due to lack of room. I can’t just install a junction box with no circuit protection for the charging circuit.

This might be the best option if I can find the the space.

 

[dave*99]

I have several battery chargers in my motorhome that are in use when the RV is parked with power, like at home.

How many individual RV circuits are used to power the several chargers?
Could they all be put on one circuit?

 

[larry_g]

If you have an on/off/start for the generator and the engine then have the power line to each activate a relay that breaks the power to the chargers if either of the engines have ignition power. You could also activate the relay with a oil pressure switch. If the engine has oil pressure then the power to the charger is cut off. Either one is a simple OR logic function.

lg
no neat sig line

 

[dave*99]

I have several battery chargers in my motorhome that are in use when the RV is parked with power, like at home.

I have a diesel generator with automatic transfer switch in the motorhome. I do not want the circuit the battery chargers are plugged into to be energized when the generator is running. I don't want both the battery chargers and the engine alternators to be charging the batteries. Does anything like this exist that is automatic?

What drives your concern? You mention "both the battery chargers and the engine alternators to be charging the batteries"

For example, are you worried about overcharging the batteries? I have a smart charger on my truck battery. If I leave the smart charger energized and I start the engine, the smart charger will see the alternator voltage and it will automatically stop supplying power to the batteries.

Is there a different concern?

 

[Chuckster in NJ]

Shunt Trip breaker on the main panel? I know Square D makes a 2 pole 60 amp.

 

[mm08822]

One of these.. Pretty easy. You can "lock out" the entire circuit.

Generac Help Center

support.generac.com

I have two of them. Apparently there is a "lock out" mode that drops the circuit while on generator power.

It would drop it on utility power to. I assume OP only wants an automated l/o vs. something he has manually do each time.

 

[mm08822]

Check if the transfer switch has an aux contact or provisions for one.

 

[dcg9381]

It would drop it on utility power to. I assume OP only wants an automated l/o vs. something he has manually do each time.

That doesn't make a lot of sense to me.

"A priority dial on the Load Managers allows users to set a load priority from 1 to 8 or can be set to “lock out only” mode for loads that do not need to run during a power outage. If the Lockout Switch is set to "Lockout Load on Generator", the connected appliance will not get power from the generator. This setting is used as a permanent lockout that customers can control."

 

[Chuckster in NJ]

Check if the transfer switch has an aux contact or provisions for one.

"IF" the transfer switch has an aux contact you can control a shunt trip breaker with it.