Need advice about wiring DC water heater...

Mary W. · 11-22-2022, 06:55 PM

Hey. I need some electrical advice.... I have a 2004 Challenger by Keystone. It's our living quarters -- not moving anywhere. The hot water heater died -- sprung a leak. It was the original one and
it was exclusively AC powered. We bought a tankless water heater and I put it in (water, gas) and am stumped on the electrical..... This new unit is DC, yet the Romex wire that ran the old AC one is the center of the issue. Can anyone help me figure out how I'm supposed to wire this unit? I had an electrician out (a cousin) today and they're not familiar with RV electrical systems. (I'm wiped out right now so I'll have to check this tomorrow... been a long, busy day). Thanks in advance.

**chuckster57** · 11-22-2022, 07:10 PM

Welcome to the forum

DO NOT connect the Romex to the water heater, it is 120 VAC and your water heater is 12VDC. You need to either remove the Romex or at least cap the ends SEPARATELY.

Then you need to locate the power distribution panel, one side will have breakers (120VAC) and the other side will have fuses (12VDC). You need to run the appropriate gauge stranded wire from the fuse panel to the water heater.

That’s the quick start, but make sure you follow the instructions included for installation.

Mary W. · 11-23-2022, 04:29 AM

Thanks. Yeah, I know not to attach 120VAC to a 12VDC, but can I take the 120VAC off the breaker there on the 120VAC panel and connect it to the DC panel? Also, the DC panel has black and white areas.... I suppose I'll have to connect the romex black wire on the black block and the white onto the white block? I know there are 2 fuse locations open on one black block, but none open on the white blocks. Ideas?

wiredgeorge · 11-23-2022, 04:49 AM

AC can not be connected to the DC side of the power distribution panel. AC is converted to DC by your converter and the DC connects to the DC side. Direct connection would surely cause damage. You may have empty fuse sockets on the fuse panel on the DC side. Figure out which gauge 12V wire is needed (hopefully from install directions) and use the appropriately sized fuse and pull stranded wire from the fuse panel to pull to your water heater. Since 12V likely isn't being used to actually heat it is more than likely for the control and should not use heavy wire which means it should be easier to pull to where is needed. You might want to wait until Chuck gets back on the site (he is on the west coast) so it may be a couple hours before proceeding as I am not an expert or tech.

**chuckster57** · 11-23-2022, 05:31 AM

Quote:

Originally Posted by Mary W.

Thanks. Yeah, I know not to attach 120VAC to a 12VDC, but can I take the 120VAC off the breaker there on the 120VAC panel and connect it to the DC panel? Also, the DC panel has black and white areas.... I suppose I'll have to connect the romex black wire on the black block and the white onto the white block? I know there are 2 fuse locations open on one black block, but none open on the white blocks. Ideas?

I would run new wire as I stated in my first post. Could you use the Romex in place of stranded wire? I suppose you could, but why? Romex is 3 wire and you only need 2 wires.

The DC side will have a ground block with all the grounds ( commonly white) attached and individual fuses with the positive leads ( commonly white with a colored stripe) attached. Do yourself and anybody else in the future a favor and use the proper wire. You can get “duplex” stranded wire at the hardware store, it will have a pair of wires in a sheath and you can use the white for ground and the black for positive.

If any of this doesn’t make sense, then get a real electrician to do it for you.

**sourdough** · 11-23-2022, 05:41 AM

I would follow Chuck's suggestion to do this right. The Romex "could" be used but it could definitely be confusing to someone in the future.

In addition, have you given thought to the limitations of a tankless water heater. I know you're in TX but it can get pretty cold there....and if it does you probably won't have hot water. Also, what kind of battery power do you have, converter, age etc.? This will be a 12vdc draw that your trailer needs to be equipped for. Here is an excerpt from the RecPro website on the limitations of a tankless water heater;

If the temperature of the water flowing into the water heater is less than 43°F or higher than 90°, the water heater will not heat the water. If the water in the pipes is colder than 43°, it is recommended to use tank and tubing heater pads to heat the water before it reaches the water heater.

At higher altitudes, this unit will have two problems: the thermal efficiency will decrease and the power will be lost, and the insufficient combustion will lead to worse combustion conditions, substandard combustion emissions, or abnormal ignition. Above 4,000 ft elevation, this unit will lose 4% of its BTU for every 1,000 ft above this height.

The temperature of your water will come out cooler than the set temperature on the water heater due to heat dissipating as it travels through your water lines.

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