In Depth

Replacing an Atwood Propane Water Heater with a Propane/Electric

  • 8 October 2016

The leak from the belly pan seemed to def be the water heater. I chose to replace it, rather than disassemble it and try to find the exact source of the leak and see if I could fix just that part. It looked old, and I wanted to upgrade from propane only, to a propane/electric dual fuel.

Replacing the unit was relatively easy with no issues. I only had some questions with the wiring after the new unit was in. I did not add a bypass, as I plan on blowing out my water lines when I winterize, rather than using anti-freeze. However, I did put a ball-valve on the cold-water input line. I'm not sure why, but I guess I thought it would be easier if I ever had to replace it again or take it off-line for some reason.

Adding a Circuit

Since the new water heater had an electric heating element as well, I had to add a 120V AC circuit.

With a four-space panel box with all slots full, I thought I had to add a main lug or replace the whole box with perhaps a six-space unit. After finding out about thin breakers, I researched Tandem vs. Double-Pole breakers. I needed a GE tandem breaker (two individual circuits in the width of one normal breaker.) But could only find a GE double-pole breaker. I tried to convert it to a tandem breaker by cutting the pin that linked the two handles. But it didn't work.

Tandem vs. Double-Pole Breakers (hint: the answer was neither!)

With a four-space panel box with all slots full, I thought I had to add a main lug or replace the whole box with perhaps a six-space unit. Then I found out that some panel boxes can accommodate two circuits in some slots. What I needed was a Tandem Breaker (two individual circuits in the space of one normal height breaker.) But could only find a GE double-pole breaker. I tried to convert it to a tandem breaker by cutting the pin that linked the two handles. But it didn't work and blew the main breaker.

Then I found out the GE doesn't make tandem breakers! They just make thin individual breakers and you can replace one normal with two thin, if your panel box allows it. In the pic below, you can see the two thin breakers that have replaced a single normal-height breaker.

Note the new circuit #4. It is the lower of the two thin breakers, and is the yellow Romex in the upper-left corner of the photo.

How do you know if the box can handle two circuits in one space? Look at the sticker in the box. It might say 20 space, 30 circuits, which would mean that half the spaces can hold two circuits. Mine just had a schematic, where it clearly showed two circuits per slot.

Dual Switch wiring

The dual fuel water heater required a new switch. Rather than adding a second switch, I bought the Atwood Dual Switch. Since I already had a remote ignition switch for the propane, I already had three wires running from the heater to the switch up in the front of the galley. I only had to run one additional wire to the new dual switch, for ground and battery negative.

My airstream, and I think all airstreams, ground the battery negative to the chassis. This confused me a bit as the wiring diagram for the water heater showed a wire going to ground and another one to battery negative. After clearing up that those were the same for me, this was my solution.

The circle at the top of the pic shows where I added a wire (#2, black wire) to one of the battery negative cables. The green wire on the bottom (#1) goes back to the water heater. Those two are connected with a wire nut with another green wire (#3) that goes to the ground on the back of the switch with a female connector (lower circle).

Exterior Door

They don't come with a door, unless specified. I had a brushed stainless door from the old unit that attached to the new unit in the same way. I've seen people replace the door with new white plastic doors, but spray-paint them silver to a decent effect.

Apparently, wasps and mud daubers are attracted to propane, so you do need to have a mesh cover over the vent hole to prevent them from building nests in your water heater!

The Light and the Whistle

When I finally turned it on, the light didn't come on and I heard a high-pitched whistle coming from the water heater, so I immediately turned it off and hit the forums. I assumed the light indicated that it was lit, but I found out an illuminated light on the switch actually means that the unit is locked out due to failing to ignite on gas, or failing to switch AC power on. The whistle also ended up being normal. Some people deal with it, some try to minimize it, while others don't even notice it. Once I knew it was normal, it didn't bother me. I could hear it outside the trailer more than inside, and I only hear it while the water is actively being heated.

Since mine is dual-power, it seems to illuminate to indicate a problem with either system when used individually, but will not illuminate if one system fails while you're running on both gas and electric. From the instructions:


The unit can be run in both gas and electric modes simultaneously for quick recovery. note: if the gas fails to ignite, the gas mode will lockout, but the lockout lamp will not illuminate since the electric mode is still operational. Should you notice slow recovery, indicating the gas is not working, turn the electric switch off. The lamp will then illuminate indicating a lockout has occurred on the gas side. Correct the problem and turn the switches back on.


2. If remote switch light stays on longer than 15 seconds, place remote switch in OFF position and wait 5 minutes.


5. If heater fails to operate due to high water temperature, a lockout condition occurs (indicator light on). After water cools, reset switch in OFF position for at least 30 seconds, then turn to ON position.


When the gas switch is turned on, the unit will make three attempts to light. If for any reason there is no ignition, the unit will lockout and the red lockout lamp will illuminate. If the thermostat fails, the ECO will also lockout the unit, requiring resetting. Determine the reason for no ignition, correct it, and reset the gas ignition sequence by turning the switch off, then on.

Good stuff on the high pitched noise here.

The high pitched squeal comes from the circuit board itself (maybe the relay is on the circuit board, I never looked). It makes the noise both on electric and gas, but much harder to hear on gas with the burner lit. Our water heater is right under my daughters bunk, and the noise on our heater seemed extra loud and would wake her up at night. We just had to remember to switch the heater off at night, but it was a pain in the butt to remember.

I found that if I removed the 4 attaching screws from the circuit board and pulled the board away from the tank the noise would be much quieter. The tank was acting like a speaker and amplifying the sound. My solution to quieting down the sound was to put 4 big blobs of silicone on the heater where the screws hold on the board, then install the board using the screws but only tighten the screws enough to hold the board in place and squish the silicone a bit. Wait 24 hours and remove the screws. Now the board is held in place with the silicone, and no screws to transmit the sound to the tank. This has reduced the noise by about 75%.

Excellent troubleshooting info here.

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