Controlling DC switch with AC current

[OldToby]

Here’s an odd question. I am installing a tankless propane water heater under my galley counter. The heater operates on AC, which will come either from shore or inverter current. All my clearances are good, but I want to make sure there’s sufficient air to support combustion. My plan is to install a couple of DC fans to draw cabin air into the space while the heater is operating. Is there a way to wire the DC fans so that they only run when the heater is operating?

 

[CEC]

Hopefully your using a propane water heater designed for a boat, if not your need for a fan sounds life threatening to me..


The propane only runs when there's water flow, so you have two options you could use a flow detector to kick on the DC fan, or if your using a DC pump to provide the water pressure you could put the fan on that circuit, so when the pump runs the fans turn on.

 

[Ski in NC]

Yep, you can get relays with AC coils controlling DC through the contacts.

Or why not just get AC fans? Or AC through a small transformer and bridge rectifier to make 12Vdc.

 

[diver dave]

I would not mix power sources for critical applications. Use ac for fans.

 

[diver dave]

Yes. Like ski said! Plus ac low power fans do not make sparks.