Saturday, March 5, 2016

120- Volt Electric Conversion to Suburban Gas Water Heater

Warning: The post below is for informational purposes only and does not constitute an endorsement or recommendation to modify your water heater and other products mentioned here. I will not be liable for any direct, indirect, incidental, or consequential damages or personal injury that may result from following this blog post.

I recently installed an aftermarket 120-volt electric heater element to my Suburban gas water heater. This mod should help cut my water heater propane usage when shore power is available. I opted for the "Lightning Rod" brand as it is the only electric conversion unit with built-in anode rod. Suburban does recommend using an anode rod in their porcelain lined steel tank for corrosion protection. Although the anode that came with the electric conversion is a lot smaller than the OEM anode rod, it is still a better option than no anode at all with the competing aftermarket products. I'm not sure how well the small anode will last or perform. I will update this post after a few months of water heater use.

First thing I did is to add a dedicated AC line/ outlet wired from the AC/DC fuse panel. I added a 15 amp single pole AC breaker, and then run a Romex wire from the fuse panel to the water heater area. You don't really need a dedicated AC line for this mod as the electric element only draws few amps, the unit can be directly plugged into nearby AC outlet.

Routing the Romex wire is a little envolved as I have to remove some of the fabric covered panels to fish the wire.
You'll probably noticed that I was using a heavier 10-gauge wire which is not really needed for this mod but that's what I had in hand at that time.
The Romex wire is routed down the driver side rearmost pillar then terminates next to the water heater as shown above. I ended up removing the pillar panel covering and the upper seat belt post in the process just to fish the wire down into the water heater area.
The new 120-volt switched outlet. I use a solid state relay with DC input control to remotely switch the AC outlet on-off. I like the electric water heater switch installed to the factory switch panel and wiring a 120-volt into this area along with the DC switches is not ideal or safe in my opinion that is why I opted for the solid state relay approach.
The solid state relay on the right and the DIY cover on the left.
With the cover on.
Solid state relay wired. Basically, a 12-volt power input to the DC control side enables  the AC current to pass thru the relay.  
Modified the factory water heater switch and added an on-off switch to activate the solid state relay.
With the switch wired and installed. 12-volt power was tapped from the adjacent water heater propane switch.
Instead of using the thermostat switch that came with the conversion unit, I decided to use a Suburban 120-volt 130 degree thermostat/ limit switch. I like the Suburban thermostat switch as it is mounted under the weatherproof factory plastic thermostat cover (with modifications) unlike the "Lightning Rod" thermostat which is recommended and designed to be mounted on the outside pressure relief valve. The Suburban Thermostat switch also has a high limit switch to prevent the water heater from overheating.
Suburban thermostat/ Limit switch. I added a copper mounting bar to secure it against the water heater tank using the gas thermostat/ limit switch threaded post. The Suburban non-electric gas water heater version does not come with a second threaded post for the electric thermostat (see below)
Backside of the modified Suburban thermostat/ limit switch.
With the 120-volt thermostat/ hi-limit switch installed next to the gas thermostat/ hi-limit switch.
All wired up.
A minor modification is needed to the factory thermostat cover to clear the new thermostat mounting bracket.
Made a hole into the upper corner of the water heater flange for the electric heater wires, I then added rubber grommet to protect the wires from the sharp metal edges.
With the electric element brass adapter/anode rod threaded into the factory anode rod hole.
With the electric water heater element installed and wired! The gas and electric operates independently and can be switched on at the same time for faster water heater recovery time.


  1. Great article! Did you pull a wire from the control panel switch to the relay, for the 12 volt input to the relay? Thanks

    1. Yes, a (+) and (-) wire was fished thru the headliner. It was not that hard as the switch panel is just on the opposite side of the AC/DC fuse box. Thanks.


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