Looks like it will start up from cold, thenI guess it gets too hot? It locks out ignition and gas, and relief valve is dripping.This is my first rv, so Im trying to learnthis system.any help appreciated.groundhog

Dripping from TP valve is not uncommon, especially if it not seated well enough. Try opening and closing it a couple of times. If that does not work new valve from your local big box store will fix it.

So you are not thinking the thermostat?What does a thermal cut off do?Is that what cuts off the propane?

RV water heaters use 2 t-statsOne is the 'normal' temp t-stat. It is what allows heating & reheating (after cool down) of water.Suburban uses 130*F fixed temp t-statAtwood uses 140*F fixed temp t-statOther one is the ECO (Energy Cut Off) t-stat (High temp shut down). If normal t-stat should fail the ECO shuts down heating and 'locks' out further operation until 'fault' has been reset.Suburban uses 170*F fixed temp t-stat and has a reset button that allows t-stat to be manually resetAtwood uses 180*F fixed temp t-stat that will auto reset when water temp cools off enoughBoth have 'fault' lights and that has to be reset (Turn switch OFF then back ON)Atwood also has a thermal cutoff fuse.........it is a one shot device that trips at 190*F due to blow back out of combustion chamber. When it trips it shuts down all operation and device has to be replaced.It is connected to normal t-stat (has a clear tube over fuse)Weeping T&P Relief Valve can be caused by:*Weak T&P .........replace*Loss of 'Air Pocket' Water heater is designed with an air gap at top of tank. Air can be compressed so as water swells from being heated the air allows for this increase w/o a big increase in pressure. Lose the air pocket and pressure increases as water swells from heating causing T&P to weep.Establish air pocket1) Turn off water supply2) Open faucet hotside to relief pressure3) Open T&P via Lever....hold open ntil water stops running out then let valve snap close4) Turn on water supply5) Close faucet*Dirty T&POpen via lever let snap close couple times to clear valve seat (CAUTION: Do with water supply on so water blows out----water can be very HOT)Then re-establish air pocketWhich Brand/Model do you have and if Atwood which year (Changes made in 2004)

What is your make of water heater? Atwood or Suburban?Atwoods have two small devices that open the circuit. The thermostat and then the ECO. They also have a thermal fuse normally hidden behind some heat shrink tubing adjacent to the thermostats.The thermal cutout opens as a safety switch to prevent damage. The ECO or the thermal fuse can shut down the electric going to the circuit board.Both the thermostat and the ECO can be tested. You could wait for the unit to go into failure, test the thermostat and the ECO. The thermostat should not have continuity. The ECO should have continuity under normal operating temperatures.Dripping is normal. Not a real problem. I would get the unit operational, then think about replacing it. They are a standard relief valve available at most hardware stores. Just need to get one matching the name plate disc on your existing one.

T&P valves are easy and cheap to replace. I'd start there.

Hot water heater is blowing the relief valve...

18 Replies

DennisG9
Explorer
Oct 24, 2015
smkettner wrote:
Get a small expansion tank after you replace the valve.

http://www.amazon.com/SHURflo-182-200-Pre-Pressurized-Accumulator-Tank

IMO every RV should have one.

Expansion tank is the way to go. In an RV you have a check valve on your fresh water line coming in so it creates a closed loop on the side your water heater is on. You are building excess pressure where in a stick house you have room for it to go to but in an RV it is a much shorter run. I added an expansion tank on mine and it cured the same problem your having.
wa8yxm
Explorer III
Oct 23, 2015
Ok. as the water heats first the T-Stat should open, this is normal operation, and burners stops.. The water than cools, the T-Stat closes and it "Recycles"

Page 2: IF the T-Stat continues to heat the ECO should open, this will cause the lock outs you cite.. but should not blow the TPR.

IF it continues to heat, a plug in the TPR melts, when this happens it does not drip.. IT GUSHES, I mean Niagra Falls level Gushes. (Been there, Done that, not on an RV though) I mean Gallons per minute, Not drips per minute.

Dripping indicates a need to drain and flush the water heater.. (Routine maintenance) LET IT COOL, Remove drain plug, Install short 1/2 inch pipe (plastic, brass or metal) to extend flow past side of RV, if Suburban needing anode inspect anode and replace if needed. Flush using flush want (optional) and once drained close TPR and replace plug.

But check the T-Stats.

It is doubtful (Impossible on mine) that the dripping TPR is dripping water onto a circuit board and shorting it out. But I am basing that on MY water heater.. I've not seen yours.
RJsfishin
Explorer
Oct 23, 2015
Houston Remodeler wrote:
T&P valves are easy and cheap to replace. I'd start there.

Mine wasn't easy. First of all I had to make a special tool to remove and install. And 2nd, it was super tight,..... after 2 trys, I went for broke, figured on a new heater, but got lucky.
And if I recall, after I made the tool, I found one on line made for that purpose.
RJsfishin
Explorer
Oct 23, 2015
smkettner wrote:
Get a small expansion tank after you replace the valve.

http://www.amazon.com/SHURflo-182-200-Pre-Pressurized-Accumulator-Tank

IMO every RV should have one.

X 3 !!
time2roll
Nomad
Oct 23, 2015
Get a small expansion tank after you replace the valve.

http://www.amazon.com/SHURflo-182-200-Pre-Pressurized-Accumulator-Tank

IMO every RV should have one.
Old-Biscuit
Explorer III
Oct 23, 2015
Atwood G6A-6E ------ 6 gallon 'gas' only with electronic ignitor

Uses a front mount t-stat/ECO
T-stat OPENS at 140*F and CLOSES at 110*F
ECO OPENS at 180*F and CLOSES (auto reset) at 150*F

Normal operation ECO should always be CLOSED

T&P Relief Valve
OPENS on HIGH Temperature 210*F
OPENS on HIGH Pressure 150# ---resets 125#
IT is the fail safe device........normal t-stat fails then ECO, ECO fails then T&P
Depending on which tank was used T&P can be 1/2" NPT or 3/4" NPT threads. Available at most any hardware store

'FAULT' Light (Red light ON/OFF Switch Panel) Comes ON:
IF propane fails to light off and PROVE (no return signal to circuit board ---so voltage on gas valve gets dropped closing it)
IF 'Thermal Cut off' trips (190*F blow back ------dirty/obstructed combustion chamber)
IF ECO OPENS
Houston_Remodel
Explorer
Oct 23, 2015
T&P = temperature and pressure, which are the two reasons the valve will automatically open.

Read all about them
enblethen
Nomad
Oct 23, 2015
Yes, zero ohms for the ECO when operating under normal conditions.
The thermostat will open(no resistance) at the set value, roughly 130 degrees.
willi4nd
Explorer
Oct 23, 2015
PRV's weaken and calcium builds up, replace with correct one. Match specs on ring.
groundhogy
Explorer
Oct 23, 2015
Relief valve was tripped and then due to age didn't fully spring back