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dlcorley · 10-09-2012, 05:11 PM

Propane / Electric Hot Water Tank Question:
I just bought a used 2003 Coachman 248 TBG and it has this type of hot water tank. The previous owner defeated the autoselection system that would use electric over propane because he said that the propane was already on and would not switch over. There are 2 sensors that are involved in this. He disconnected one and connected a wire to put 120 vac to the heater. I have found the sensors, one marked "ECO" but I can't read the other markings. I've attached a pic of the existing wiring and I need help to figure our what electrical connections to change or add. My preference is totally propane since it is faster and hotter. Can anyone help me?

trackman · 10-09-2012, 05:38 PM

Your best bet is to post this in the "products and appliances forum". If I read your post correctly the previous owner has this set for propane. If that is so your post that that is what you want. Looks like you may have to get a new unit to correct this maze. Good luck on resolving this issue

Rjhuser · 10-09-2012, 06:45 PM

Based on the model number seen in picture 4, you have an Atwood G6A-8E water heater, which is a 6 gallon propane only DSI (Direct Spark Ignition) unit.

It appears the PO installed an add-on electric heating element like a Hott-Rod or similar (the two red wires in the drain plug fitting in the lower left of picture 1) to the water heater.

One confusing thing in your pictures is the absence of the brown wire on the ECO switch in picture 2 that can be seen in picture 1.

Based on Atwood's wiring diagram, the brown wire on the thermostat switch (the one to the right of the ECO switch) is the 12 VDC + from the remote switch. The brown wire from the control module should be on the other connection of the thermostat switch.

Just a side note, based on the visual appearance of the gas valve and burner assembly, the propane side of the water heater may be non-functional, even if the wiring issues are corrected. Also, the control module may be bad too. Another item, the thermostat switch also looks questionable (corrosion on the switch and rusting on the terminals). Perhaps the PO disabled propane operation due to one of these items!

dlcorley · 10-10-2012, 05:07 PM

I really, really appreciate the responses, they are very helpful.

I noticed that in taking the pics, I moved the brown wire from the controller (it is not connected now) between taking the pics. I forgot that I had done that. My bad! They say that with age, the memory goes second.

Now, I have already bought new ECO and T-Stat switches and if I understand all this, I should just replace both and connect all the Red wires to the ECO on the left and the brown wires to the T-Stat on the right.

I will have to verify the brown wire coming in from the top. The PO had installed a separate switch on the inside of the unit so I will have to trace that out. The electric heater works the tank with just this one switch new switch.

rjhuser mentioned that this was 12vdc to the electric element, are you sure? I am an electrical engineer and computer geek but if this were 12 vdc, the wiring would have to be a lot bigger. Home HWT's use 1200 watt elements or larger and operate at 208 vac. If they were on 120 VAC would need 10 amps for 1200 watts. On a TT connected to a 120 vac source could easily do 10 amps on that if the elements were on AC but if they were on DC, the amps would be 10 fold at the same wattage and those wires look to be #12 at best which is rated at 20 amps max. So, I will check to see what type of power is there.

So, my plan is to replace both switches, reinstall the Reds on the ECO and the Browns on the T-Stat and see what happens as I stand by with a fire extinguisher just in case. I want propane heating on this. I know to look for a "Thermistor" which can cause the unit not to work. Fun, Fun, Fun!

And Thanks Again to those who have responded, I really appreciate your assistance.

Rjhuser · 10-10-2012, 05:28 PM

Sorry for any confusion - the propane side is 12 VDC, the electric side is 120 VAC.

The electric aftermarket heater should have its own thermostat somewhere, probably on the back of the water heater.

Looking around after my last message, the electric heater looks like it might be a Camco Hybrid Heat. If so, its only 400 watts - about a 4 amp draw.

Do a search on the Camco Hybrid Heat and Atwood water heater for more information on each.

Gary RVRoamer · 10-10-2012, 08:02 PM

rjhuser is giving you good advice.

The ECO has nothing to do with auto changeover from gas to electric - there is no such function. The ECO is an Emergency Cut Off, which is intended to shut down LP gas operation if the water tank is in danger of overheating. The adjacent sensor is the LP gas mode thermostat. Both of those are simple thermal switches that open/close a path for 12v electric power, which is what the LP gas mode operates on.

You can download a copy of the Atwood Water Heater Service Manual here - it will help you sort out the gas operation and wiring.

http://manuals.adventurerv.net/Atwoo...er-Service.pdf

The 120v electric wiring is an aftermarket add-on, as rjhuser describes.

dlcorley · 10-10-2012, 09:59 PM

All of you guys are TERRIFIC AND I THANK YOU VERY MUCH. With all this info I should be able to get this thing squared away.

Maybe I can return the favor some day.

dlcorley · 10-16-2012, 04:41 PM

Again, thanks to everyone for your help. And just a little explaination of why this is dragging on some - I live in NC but the camper is in WV so I have gone up there for the last 2 weekends. We are putting new siding on our house there so I go when the workers are there. It looks like I will be going up there tomorrow though. Bridge Day in Fayetteville WV this weekend. Come and join 100,000+ new friends.

Anyway, I replaced both the ECO and the T-Stat and voila, the gas fired and continued for a few minutes, then shut off. And I cannot get it to fire again.

I checked the power but there is no 12 vdc coming in. Both switches (ECO & T-Stat) are closed. I checked the breakers and the fuses including the one on the control module inside the heater but the brown wire coming in from the top of the unit, there is no power there. This wire "should be" fed from the switch inside to turn on the water heater but how do you take that switch apart and shouldn't that wire be a direct run from the switch to the heater?

Given that this unit is about 10 years old and only 6 gallons, I beginning to consider replacing it with a tankless propane unit. Any thoughts or experiences with these. I have found 2 that are for RV's, Girard and Precision. Pricing is a little high but the performance would be extraordinary. Thoughts / Experiences?

Thanks
Denver

Gary RVRoamer · 10-16-2012, 06:58 PM

Buying a new heater because of some missing +12v seems a bit extreme. Can you jumper +12v to the power wire and see if everything runs once again? If so, at worst you have to run a new wire or maybe replace a switch.

The power feed may not be a direct run - could well be via a relay. And there will surely be a fuse on the power source as well.

dlcorley · 10-16-2012, 07:50 PM

Gary, I checked every fuse and circuit breaker that I could find. Most were in the power panel as I expected and one on the controller inside the heater. There may be one in the wall switch but I didn't see how to get inside it without breaking it - probably really simple, but I didn't see it.

I didn't have a long enough wire with me to jumper from the battery to the heater but I will this next time.

As to replacing the water tank with a tankless, that is more for a better shower, I don't really enjoy 2 minutes of barely hot water at least while using the electric heat side. Note that this combo (electric / propane) was from Atwood, the original manufacturer. So, it is not an "add-on". But 2 hours for recovery also doesn't work. But of course, the electric heater just doesn't get it period.

But I'm not going to put "lipstick on a pig" so I will look for a direct replacement at a reasonable cost and one that I can remove when I sell the camper. Some of the prices I've seen today are fairly reasonable ($250) but I will really have to check the specs to be sure.

Thanks
Denver

Tony Lee · 10-16-2012, 10:17 PM

Quote:

Note that this combo (electric / propane) was from Atwood, the original manufacturer. So, it is not an "add-on".

I don't think so because the factory unit has the 120V system completely separate on the back of the heater tank - accessible through a cupboard or panel inside. That 120V hotrod element is installed in the drain hole which usually has a removable nylon screw plug andd is the sort of thing people add to a propane-only model
What might have happened (if it was originally a propane/120V model) is the original element inside might have failed and he couldn't get the element out (from experience can take far more torque than you can apply with the standard tube spanner) so he fitted the hotrod and supplied it via the original thermostat mounted on the back of the tank. There has to be a thermostat somewhere unless the hotrod has one included.

As for the 12V circuit - normally a switch inside and an indicator light and basic wiring so not very complex Legible wiring diagram available for download. Four wires to the switch inside - positive and negative 12V from the battery, switched 12V that goes to the circuit board via the ECO and a switched 12V from the board to the flame failure indicator. No fuse inside the switch/light unit. Any fuse is elsewhere