Converting an RV 12V Light Circuit to 120V for a Ceiling Fan

[RJTampa]

I am looking for some technical advice regarding a lighting and fan installation in my RV.

Currently, I have a bank of switches controlling several LED lights on a 12v DC circuit. One specific switch controls two LED lights. I would like to replace one of those lights with a DC motor ceiling fan I have selected. However, the fan's controller requires AC power.

In my RV, the outlets run on AC power, while the lighting remains on a 12v DC circuit. Is it possible to convert this specific switch from DC to AC power? My goal is to replace one 12v LED with the fan and the other 12v LED with a new AC-powered LED light.

Please let me know if this conversion is feasible and what steps would be required.

 

[bigbAZ]

You'll either have to run 120 volt wire to the switch location and to the fan location, or just to the fan location and use a 12/120 volt relay to switch the 120 volt circuit. If you run 120V to the switch you'll probably need a different switch as well, and most certainly a box to contain the 120 volt wiring.

What you cannot do is run AC line voltage through the existing 12 volt wiring. Not only is the 12 volt wire itself not rated for it, but most RV lighting uses the metal framework of the RV for negative current or at least has it's negative bonded to the metal framework which would be very dangerous for AC line voltage.

Also all AC line voltage requires a separate grounding wire which does not exist in 12 VDC wiring.

 

[RJTampa]

You'll either have to run 120 volt wire to the switch location and to the fan location, or just to the fan location and use a 12/120 volt relay to switch the 120 volt circuit. If you run 120V to the switch you'll probably need a different switch as well, and most certainly a box to contain the 120 volt wiring.

What you cannot do is run AC line voltage through the existing 12 volt wiring. Not only is the 12 volt wire itself not rated for it, but most RV lighting uses the metal framework of the RV for negative current or at least has it's negative bonded to the metal framework which would be very dangerous for AC line voltage.

Also all AC line voltage requires a separate grounding wire which does not exist in 12 VDC wiring.

Thanks for responding, I assumed that I would be able to use the same wiring. I'll see if it's feasible to run new wiring to that location.

 

[Gary RV_Wizard]

I would like to replace one of those lights with a DC motor ceiling fan I have selected. However, the fan's controller requires AC power.

That seems bizarre! Why would anyone design a 12vdc fan that also requires 120vac to operate? What does this controller do? Is it physically part of the fan or a separate unit? Maybe we could help more if you posted the name of that fan and its install instructions.

But to answer your question, No you cannot simply re-use the 12v switch & wiring for 120v. For one thing, 120v requires two wires to/from the device (hot & neutral), whereas 12v RV wiring uses only one (a hot) and gets its ground through the RV body/chassis. And the wire itself may not be adequate in either insulation or amp rating. Ditto for the switches. Led light circuits are very low power and typically use very slim wiring.

 

[bigbAZ]

That seems bizarre! Why would anyone design a 12vdc fan that also requires 120vac to operate? What does this controller do? Is it physically part of the fan or a separate unit? Maybe we could help more if you posted the name of that fan and its install instructions.

But to answer your question, No you cannot simply re-use the 12v switch & wiring for 120v. For one thing, 120v requires two wires to/from the device (hot & neutral), whereas 12v RV wiring uses only one (a hot) and gets its ground through the RV body/chassis. And the wire itself may not be adequate in either insulation or amp rating. Ditto for the switches. Led light circuits are very low power and typically use very slim wiring.

Gary,

There are DC fans that connect to AC power and have an integral converter, they have been around for close to 20 years. Installed a few in my career, and they continue to gain in popularity due to their many advantages. Many of the Big Ass fans you see are DC.

See this from Hunter Fans, scroll down to read the advantages, one of which is lighter weight which would be good in an RV:

DC Motor Ceiling Fans

DC fans are excellent for cooling a space and can work effectively in the winter to provide additional warmth. Shop DC motor ceiling fans!

www.hunterfan.com

 

[Gary RV_Wizard]

There are DC fans that connect to AC power and have an integral converter, they have been around for close to 20 years. Installed a few in my career, and they continue to gain in popularity due to their many advantages. Many of the Big Ass fans you see are DC.

Yeah, I get that, but that doesn't seem to be what he is describing. The OP seems to be saying a 12vdc fan circuit plus a 120vac light circuit. What you described is more likely, so I asked the OP for more details.

It's obvious the OP doesn't have much electrical knowledge, so he could be mistaken about the fan circuits needed.,

 

[Mark_K5LXP]

At least in my winnebago they use the same wire for all circuits. But as has been pointed out DC wiring methods are different and probably not practical to repurpose. Even with diagrams I'd be wondering if reality matched the print and there'd be a shock hazard or fireworks hooking it up. Running new wires is the only way to know for sure. To Gary's point about amp rating, running 120v vs 12v loads over a given wire will likely result in reduced current and way more power capacity over the same wire.

Mark B.
Albuquerque, NM

 

[RJTampa]

Yeah, I get that, but that doesn't seem to be what he is describing. The OP seems to be saying a 12vdc fan circuit plus a 120vac light circuit. What you described is more likely, so I asked the OP for more details.

It's obvious the OP doesn't have much electrical knowledge, so he could be mistaken about the fan circuits needed.,

That seems bizarre! Why would anyone design a 12vdc fan that also requires 120vac to operate? What does this controller do? Is it physically part of the fan or a separate unit? Maybe we could help more if you posted the name of that fan and its install instructions.

But to answer your question, No you cannot simply re-use the 12v switch & wiring for 120v. For one thing, 120v requires two wires to/from the device (hot & neutral), whereas 12v RV wiring uses only one (a hot) and gets its ground through the RV body/chassis. And the wire itself may not be adequate in either insulation or amp rating. Ditto for the switches. Led light circuits are very low power and typically use very slim wiring.

Here is a pic of the Controller that the AC line gets connected to. The fan is a Fanbulous 52 Inch Ceiling Fan. I've been looking on Amazon and Google for a DC Controller. However, I haven't found one yet. My assumption was that a fan with a DC motor should have no issues running on a 12v DC.

 

[Kirk]

My assumption was that a fan with a DC motor should have no issues running on a 12v DC.

Not a good assumption. Look at the label you posted. It reads "Input: AC 110-260V." There is no provision for a DC input and it also does not say what the DC output to the motor is. If we were to assume that output is 12V, you would still need to get into the internal wiring and disconnect the supply from that motor control driver and replace it with your power supply. Since you realize that you don't know much about electrical work, how do you propose to do that? Rather than trying to re-engineer the 120V fan, why don't you get one designed for a 12V RV like this one on Amazon?

 

[Gary RV_Wizard]

As Kirk says, that is a 120v fan that internally uses DC to power the motor. That's both quiet & efficient. However, you do not supply DC power to it - just 120vac. Note that means you could only use the fan when you had shore power or generator active (or an inverter with adequate batteries). If that's a problem for you, get a 12v only fan.

Another thing: RV ceilings are mostly low, so you want a "ceiling hugger" model. The Fanbulous fans all have a down-rod at least several inches long so will hang down a bit. And swing around some as you drive, too.