Atwood Water Heater Questions

[Mikesr]

What would cause the pressure relief valve to have a slow leak even after it was bleed off ? The unit will not fire on LP only works on electric. Could it be the thermostat? Would these issues be related ? It is as simple as a bad relief valve ?
Thanks for any input

[Old-Biscuit]

Weeping T&P Relief Valve...as noted.....is due to LOSS of Air Pocket in top of water heater tank (Suburban, Atwood and EVEN residential have them by design)
RV water heaters are more problematic due to small volume/size of tanks

During a normal fill the air pocket is naturally formed provided folks don't open T&P during fill.....air in system should be bled off via a faucet. Opening the T&P DURING filling doesn't allow for the air pocket to be established.

Water swells when heated...air pocket controls pressure increases because ai can be compressed..water can NOT.
W/O air pocket.....pressure increases as water swells and T&P weep

Under normal conditions with air pocket water is heated to 140*F (Atwood) or 130*F (Suburban)
IF normal t-stat fails to shut down heating the Hi Temp T-stats Open shutting down all DC power/heating
Atwood ECO (Energy Cut Off) 180*F
Suburban Hi Temp T-stat 170*F

If Normal fails, Hit Temp fails then T&P Relief Valves OPEN to relieve pressure build up and allow for COLD water input----heating still going on!!
T&P Relief Valves......OPEN 210*F/150 PSI (start closing when pressure drops to 125 psi or below)

Reestablish air pocket.
First....with water supply ON pop open T&P and let it blow (caution) to clear any build up on valve/seat (which are all metal)
Then let it SNAP closed

Now turn off water supply.....open nearest faucet to relieve pressure
Leave faucet OPEN
Open T&P via lever until water stops flowing out...let it SNAP closed
Close faucet
Turn on water supply....air pocket established in top of tank




As for LP not heating.
Your Atwood uses the SAME set of T-stat/ECO for BOTH electric/propane so issue is NOT with either t-stat OR the thermal fuse (device inside the clear tubing between circuit board and t-stat (Brown wires)

Electric works so you have DC Voltage to the ON/OFF switches and the circuit board UNLESS Propane ON/OFF switch is bad

Only separate components are the gas valve, burner, spark electrode...propane system

Weeping T&P can cause problems with gas solenoid connections....corroded terminals/spade connectors
Possible that one of the solenoids is bad (more common of Suburban)
Dirty gas orifice (soak in alcohol then blow dry No poking or high pressure)
Burner tube dirty......even a spider web will disrupt gas/air flow Remove and run bottle brush thru it...blowing air doesn't get rid of spider webs


Then there is the spark electrode.....
Strong spark (CLICK, CLICK, CLICK)....gap 1/8" MIN----3/16" MAX
Clean high tension wire connection
Clean/tight ground....mounting screw and/or green wire to exhaust shield/frame
Ceramic insulator not cracked (at night in dark watch Spark Electrode and any 'tracking' from ceramic..replace spark electrode if ceramic cracked



So does it even SPARK when water is cold and propane turned ON?
NO Sparking.....circuit board connectors. Remove/clean contact surface with pencil eraser and then make sure pins are not bent and make GOOD contact when pushed back onto circuit board

Got voltmeter.use it to trace DC path. Find where it stops...
Wiring diagram for your Atwood

[DownTheAvenue]

The pressure relief valve is doing its job. As the water heats, it expands. Without anyplace for that expansion to go, the valve opens to relieve the pressure. There is supposed to be an air gap inside the water hater, but it is often displaced by water.

The water heater not working on gas could be several issues. More information is needed to be helpful.

[SoundGuy]

westend wrote:
I never touch them as I've experienced failures by opening them. Sometimes, an O-ring will become unseated or tear when the valve is opened. Sometimes, accumulated mineral build-up will limit proper seating for closing.

Exactly - leave it alone, if it does leak replace it.

[westend]

Unrelated. The pressure relief valve is designed to open should a set pressure (temperature) be reached. A lot of folks use them as an air port to drain the heater or muck with them to recreate the interior air reserve. I never touch them as I've experienced failures by opening them. Sometimes, an O-ring will become unseated or tear when the valve is opened. Sometimes, accumulated mineral build-up will limit proper seating for closing.

Your LP igniting issues are related to the part of the heater that uses LP and is in the ignition sequence---orifice on gas tube, cleanliness of air tube, condition of ignitor, etc. You may also have a failed gas valve but that should be the last in a chain of diagnosis. Clean everything up in the LP firing area and see if you have success. There are a few threads on this Forum that deal with water heater repair and service manuals are available here:Bryant Service