Atwood marine water heater

boybach

boybach

Well-known member
Dec 9, 2020
1,033
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I usually only park up for a day or two before moving on and my heat exchanger keeps my hot water plenty warm/extremely hot.

I never bothered switching on the power to the Atwood marine heater, except this last week I was at a campground with hookups (first time ever hooked
up) so I plugged in. After a couple of days, the hot water from running the engine was used up/cold so I switched on the power to the unit. After
about 3 hours, I turned on the hot water tap and the water hadn't warmed up at all so it looks like the heater isn't working.

Is there a reset button on this unit or some switch other than the main switch near the breaker box?

TIA

Larry

--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
> I usually only park up for a day or two before moving on and my heat exchanger keeps my hot water plenty warm/extremely hot.
> I never bothered switching on the power to the Atwood marine heater, except this last week I was at a campground with hookups (first time ever
> hooked up) so I plugged in. After a couple of days, the hot water from running the engine was used up/cold so I switched on the power to the unit.
> After about 3 hours, I turned on the hot water tap and the water hadn't warmed up at all so it looks like the heater isn't working.
>
> Is there a reset button on this unit or some switch other than the main switch near the breaker box?
>
> TIA
> Larry

Larry,

Many have a resettable over heat control that is tripped by a 190° thermostat. Get in there and look for a red button.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
Thanks Matt, will do!

Is it possible that the engine temp exceeded 190° via the heat exchanger and THAT tripped the thermostat even though the heater wasn't actually
"on"?

Or is that impossible?

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
Yes. The safety sat does not know where the heat came from, just it’s over temp.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
I found the reset switch, molto buried and not super convenient to use without a pretty good teardown - but ANYWAY - I reset the switch and the heater
worked when I fired up the Onan.

What I'm concerned about is that the over-temperature switch may trip again every time I go for a drive; is there a way to limit the engine temp
coming into the heater?

If the reset switch was more accessible, I'd just leave it as it is and reset it when I ran out of engine warmed water.

OTOH, It may be ok and not trip again. I haven't driven the coach since the reset but I have a hunch what I describe above could very well be the
problem. The manual says something about matching the temps but I'm no plumber, that's for sure ... :roll:

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
Larry,

You don't know the conditions that made that over-heat trip. It may have happen years ago and you won't know more until you try it. Mine has been
known to trip when it really should have.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
Will report back after next trip, next week. Thanks Matt

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
Saw this label on my water heater today as I was getting ready to fit the winterizing bypass hose ...

"Caution - If the water heater has been retrofitted with supplemental heating equipment you must adjust both the thermostat controlling the
supplemental heat source (located in the water piping) and the thermostat on the water heater (behind the access panel) to the same temperature.
Failure to adjust both thermostats to the same temperature can cause loss of proper temperature control."

Pretty sure the PO didn't do that and as far as I can tell there isn't any stat "in the water piping" unless I'm looking in the wrong place. So
presuming there isn't a stat fitted in the heat exchanger lines, what would it look like and where would I get one?

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
If I understand correctly, you're considering a thermostat for the engine
water heater lines feeding the house water heater. There was never one
from GMC. Presumably the plan was for the house water to reach the
engine's water temperature, or close to it, while there was no other heat
source (or overwhelming and effectively disabling propane if left on).
That's worked well for the past 45+ years except for the need for caution
with engine-heated water.

Unless you're concerned about the high temperature of engine-heated water,
don't worry about it. If that is your concern, look for a "mixing valve".

Ken H.

> Saw this label on my water heater today as I was getting ready to fit the
> winterizing bypass hose ...
>
> "Caution - If the water heater has been retrofitted with supplemental
> heating equipment you must adjust both the thermostat controlling the
> supplemental heat source (located in the water piping) and the thermostat
> on the water heater (behind the access panel) to the same temperature.
> Failure to adjust both thermostats to the same temperature can cause loss
> of proper temperature control."
>
> Pretty sure the PO didn't do that and as far as I can tell there isn't any
> stat "in the water piping" unless I'm looking in the wrong place. So
> presuming there isn't a stat fitted in the heat exchanger lines, what
> would it look like and where would I get one?
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach 40,000 miles, PO said everything working but forgot the
> word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
> 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
> You don't need to reset the breaker
> on the heater every time you start the engine. Only if after running the engine you want/need hot
> water heated by electricity.

mmmm ...that's a little bit like saying you only need to start the car if you want to go somewhere, isn't it?

I want hot water when I switch on the 110V., that's the whole point.

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
Larry, I only recently started following this thread but have a comment that may or may not help. I have similar unit and when I bought my coach this
year the PO advised me that the hot water heater did not work on 110V. I pulled the panel off and found the reset button need ing reset. Did so. Then
each time I started the engine it and the coolant got up to temp, it popped (and a bear to get at if you have put things back together). Not knowing
much yet about the problem, I ordered a new high low switch and installed it. It did the same thing... blew each time I ran the engine up to temp.
Someone, I remember not who, suggested I go back and recheck ALL MY ASSOCIATED wiring was wired correctly to the hot water heater and make sure it is
all tight. I did so and did not note any particular errors but it now appears it is no longer popping the reset button. I cannot figure out why nor do
I know if it will last.... I do know, though, that the new thermostatic switches are different from the older version.
Rod
--
Bandit
MONTANA
 
Hey Rod - Thanks for the tip - at least I now know I'm not alone or in a unique situation. The reset button sure is a bear to get to alright.

If I could rig up some kind of remote button pusher, that would seem to be a good way to go ...meanwhile ....(crickets)

thanks

Larry

> Larry, I only recently started following this thread but have a comment that may or may not help. I have similar unit and when I bought my coach
> this year the PO advised me that the hot water heater did not work on 110V. I pulled the panel off and found the reset button needing reset. Did so.
> Then each time I started the engine it and the coolant got up to temp, it popped (and a bear to get at if you have put things back together). Not
> knowing much yet about the problem, I ordered a new high low switch and installed it. It did the same thing... blew each time I ran the engine up to
> temp. Someone, I remember not who, suggested I go back and recheck ALL MY ASSOCIATED wiring was wired correctly to the hot water heater and make
> sure it is all tight. I did so and did not note any particular errors but it now appears it is no longer popping the reset button. I cannot figure
> out why nor do I know if it will last.... I do know, though, that the new thermostatic switches are different from the older version.
> Rod

--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
I've linked to this old thread because the situation with my Atwood EH-6 is very similar to what was discussed on the forum 9 years ago.
check it out:
http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&th=24371&goto=192194&rid=0

When I was googling around looking for tips on how to deal with my reset switch I noticed that the Camco Kuuma heater was pretty much an exact copy of
the Atwood EH6 in my rig - apart from the case material and ...wait for it ...THE RESET SWITCH!

The Kuuma hi-limit "switch" doesn't have a reset button, apparently (or at least my guess is) the switch is a bi-metal strip or something that resets
itself when things cool down. The Kuuma manual says to trip the breaker on and off to do the reset. As these two heaters are practically identical in
design, I'm wondering if I pick up a Kuuma hi-limit "switch" and fit it to the Atwood, it might simplify my problem - I could just go to the breaker
panel to do the reset.
The other option would be fitting an extension to the existing reset button and drilling a hole for the extension through the cover - as Rob did 10
years ago, see clipped post below.

Larry.

> Tom,
>
> I did a Google search and found this:
>
> http://www.kuumaproducts.com/6gal.html
>
> This heater looks just like the Atwood EH-6 I removed from Double Trouble and replaced with a Seaward unit.
>
>
>
> The high temperature regulator on my Atwood has a little red button to reset it. I drilled a hole through the cover that goes over
> the electrics so I could reset it without having to take the cover off. See the picture below: (PICTURE LINK DOES NOT WORK)
>
> http://www.gmcmhphotos.com/photos/xantrex-inverter-install/p31262-xantrex-sw-2000-instal.html
>
> If you look in the upper left hand corner of this picture you'll see the wiring schematic for the unit. If you'd like I can send you
> the owners manual for an EH-6 Atwood Water Heater.
>
> Regards,
> Rob M.

--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
So first real test on a cold system this morning - fired up the Onan and switched on the water heater
Much to my surprise the reset switch held and the water heated up, so I guess another thing sorted out for the moment.... Still I'll drill s hole and
extend that reset switch button next week when I install the by pass hose.

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
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