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Old 12-24-2012, 09:51 PM   #1
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Unhappy Atwood Elect/Gas water heater two switches problem

Hi. We have a 6 gal Atwood Elect/Gas water heater in our 5th wheel. We just purchased this in September. We have discovered that the previous owner had wired the relay on the back of the tank backwards and fried it. While replaced this and rewired it we could not figure out why he had two switches to run the water heater one that just (he said) to be turned on to heat up using the electric and the other switch was to turn on to use the gas. Now these switches are not even close to each other. We discovered that from the breaker for the water heater to the switch for the electric part then back down to the water heater. Shouldn't it be ran from the breaker to the tank directly? because the other switch is a dual switch which you have to flip on the one side for the electric and one side for the propane. Taking into consideration that he wired it backwards and also had to replace the water heater 3 times in the 7 years he owned it gives me a hint that it is not supposed to be wired up to the one switch. Also tonight while in the kitchen I heard a pop and the main breaker flipped and the water heater breaker flipped. We smelled a burning smell, used a flash light and looked around but couldn't find anything. So my husband flipped the breakers on and I saw a flash her the pop and they flipped off again. We left the water heater breaker off and I turned both switches off and the main breaker was able to be reset. We smelled the smell again and we looked at the one weird switch and the screw in the top was burnt and the wall was warm. So needless to say we don't have hot water right now until tomorrow and we can look at it in the daylight. (of course it is christmas eve night). Wondering if maybe the circuit was overloaded? or there is a wiring problem? what should we be looking for? and should we omit that switch entirely?
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Old 12-25-2012, 02:33 AM   #2
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On my Attwood the 110V system is completely separate from the propane system.

110 from the breaker goes to the mains switch and then to the rear of the heater tank where the mains thermostat and element are.

The propane system is controlled by 12V.

Both switches can be on at the same time if fast recovery is required.

The attwood circuit diagram is available on the web site and is fairly easy to follow.

If there is a relay involved in the 110V system, perhaps it is operated by 12V via a changeover switch so you can only have one source of heat running at one time. Since that might be peculiar to your brand of RV, some more info might help others sort out the problem.

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Old 12-25-2012, 05:03 AM   #3
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12 vdc current is used to control (small switches) the LP gas and the electric modes of operation of the water heater. Multiple in line current switches can (although not usually) can be used in the electric heating element circuit. If the relay is burnt, it is usually from loose wiring connections on high current devices. The operating t'stat controls the relay coil and the small wall switch will supply power to the control board for either or both modes of operation. The large switch is an inline ac current switch that does NOT HAVE to be in the circuit but if wired correctly CAN work the electric mode just fine. It appears as though yours is burnt and will need replacing; if for no other reason but to keep any splicing of the conductors in an approved device.
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Old 12-25-2012, 06:39 PM   #4
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Attwood water heaters use an assortment of connection schemes,, You need to download the service manual or the install manual for your unit.

On mine for example. both the Propane and the Electric switch only switch 12vdc, this goes to the control board which then activates either the gas solenoid, and the Direct Spark Ignighter or the electric heat element,,, or both.
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Old 12-25-2012, 07:12 PM   #5
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One other possibility might be that the previous owner installed an electric heating element i.e. hot rod in place of the drain. It adds an additional heating source and some additional wiring. Unless done well the potential for shorts from un (not well) protected wiring is great. This would also explain the additional switch 'elsewhere'. This one is easy to check by looking outside at the drain on the water tank and if it has a couple of wires sticking out, ya got one.
I ditched the Atwood switch and added heavy duty lighted switches. I carry a VOM with us when camping and it has been used a number of times to find shorts where the manufacture did a poor and in one case a very dangerous wiring job.
Good luck, the release of the magic smoke is seldom a good thing.
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atwood, heater, water

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