Mallard M210RB Water Heater

[Paul.Wuerch]

My granddaughter recently purchased a Mallard Rv with gas/electric water heater. It will only ignite on gas if the electric switch on control panel is also turned on. Heartland customer service told me that is correct. I have other rv that will operate on gas without electric switch on and other family members also have campers that operate like mine. I think either Heartland didn't want to address the issue or this is a very poor set up. Has anyone else had this problem with a Mallard M210RB or similar trailer with Dometic water heater?

 

[John From Detroit]

How the switches are wired is kind of up to the builider.

NORMALLY you wire 12 volts to the control board
And a pair of leads one for gas one for electric (At least on Dometics)

But you could just wire the 12 volt for the board to a "Master" switch.. jumper it to the "Electric" and then swich the gas as the option . You want Gas only (30 amp park) Turn off the breaker for the thing that way it can't draw 120V.

 

[Paul.Wuerch]

How the switches are wired is kind of up to the builider.

NORMALLY you wire 12 volts to the control board
And a pair of leads one for gas one for electric (At least on Dometics)

But you could just wire the 12 volt for the board to a "Master" switch.. jumper it to the "Electric" and then swich the gas as the option . You want Gas only (30 amp park) Turn off the breaker for the thing that way it can't draw 120V.

Thank you for your reply. That makes sense but still not happy with the way the builder did it.

 

[John From Detroit]

Thank you for your reply. That makes sense but still not happy with the way the builder did it.

That... I fully understand
If you get a copy of the install manual for the water heater
(Google make model manual PDF) you may be able to modify the install...

Another suggestion (Helpful on 30 amp sites) Replace the 1500 watt 120 volt heat element with a 1500 watt 240 volt element.
What's the difference.. Well the 240 volt element will be only 375 watts when fed 120 so it will take 4 times as long to heat the water but you simply turn on gas if you need fast re-heat (I never did but I used park showers)
But at only 3.change amps instead of 12.5 it will take a whole lot longer to pop the park breaker.

 

[Kirk]

It will only ignite on gas if the electric switch on control panel is also turned on.

While what switch is used does depend on the coach builder, the way that it operates does not, if connected properly. If you would post the model number of the water heater and perhaps a picture of the switch that she has, it would help us to give accurate information. The current Dometic switch for their water heaters that have both gas and 120V electric heating looks like this:

 

[John From Detroit]

It could just be improperly wired switch.. Now that I think of it.

If I am not mistaken the switch will have 3, 4 or 5 wires (one or two just for the lamp) 12 volt (or ground) Gas and Electric (Likely 12 volt not ground)

12 volt is common to both
BUT if you hooked the 12 volt to the "Electric" and the "electric" to the common (12 volt) terminal. Then it would work... exactly as it works,.

your volt meter is your friend on that one.

 

[Paul.Wuerch]

Thanks for your suggestions. I have been busy the last couple days and just had a chance to try it again tonight. It seems the best way to make it work on gas only is to turn off the 120 voltbreaker for the water heater and then turn both the electric and gas switches on the control panel on then it will work on gas only . I really think the 12 volt switches are wired wrong but its not my camper and have never seen any other camper work that way.

 

[RayIN]

Who's to say a previous owner hasn't modified that wiring?? Kirk offered sound advice.

 

[Paul.Wuerch]

While what switch is used does depend on the coach builder, the way that it operates does not, if connected properly. If you would post the model number of the water heater and perhaps a picture of the switch that she has, it would help us to give accurate information. The current Dometic switch for their water heaters that have both gas and 120V electric heating looks like this:
View attachment 1107058

 

[Paul.Wuerch]

This is the control panel. Water heater model is WH6gea

 

[RayIN]

The Dometic WH6gea service manual will contain everything about that water heater, including wiring diagrams.

 

[Paul.Wuerch]

Thank you. I will check out that wiring diagram.

 

[Kirk]

This is the control panel.

In the picture that you posted, there are two switches, one to the left corner says LP water heater and the other on the right side says electric water heater. Are you saying that both turn on if only the LP switch is on? It is intended that you would be able to use both at the same time if/when you wish. Many RV folks do that for a faster temperature recovery when showering but only use one the rest of the time. Of course, the electric side only works at all if you are connected to a source for 120V alternating current. The electric side does not operate if you are not plugged in.

If you look at that electric diagram it shows 2 switches, and they are both 12V and send a signal to the control circuit board, which operates on 12V only. That circuit board then sends 12V to a relay to turn on the 120V power to the electric heating element, if that power is available.

 

[Paul.Wuerch]

Gas burner will only operate if electric switch on right is turned on also so I am sure something is wired wrong but haven't had time to check it out.