gas side of water heater wont ignite

[big_russ]

well I screwed up thought there was water in the water heater ,fired it on gas and it ran for 2-3 minuntes.then nothing realized my mistake ,got the water valves turned on.went to refire nothing .switched to the electric side it works fine,what have I burnt out on the gas side? the igniter?thanks

[Old-Biscuit]

hohenwald48 wrote:
Use caution when you get in there near the thermostats and high limit switches. The 120V thermostat and high limit switch have -- well -- 120 volts on them if you haven't turned off the breakers.

Neither 120V AC T-stats or 12V DC T-stats have any power to them unless ON/OFF switches are ON.

Always best to have AC CB OFF or DC fuse pulled when removing/installing T-stats.

[old_guy]

you might take the black cover off the reset plate and wiggle the gas side of the switch. do this with the gas switch in the on position inside the TT. if it is a poor connection the gas should fire right up. happened to me on my suburban heater.

[74alex]

A few years ago I made the same mistake. Within a minute of firing up the dry tank the gas went off on my Suburban tank
The wire on the 12V. gas T. stat and limit switch had burned out.
Replacing the switch fixed the problem.
As others have said, please turn off all power before working on the tank.
Alex

[hohenwald48]

Use caution when you get in there near the thermostats and high limit switches. The 120V thermostat and high limit switch have -- well -- 120 volts on them if you haven't turned off the breakers.

[Old-Biscuit]

The above post is on the right tract...some clarification


IF your water heater is similar to the one pictured it has 'Push to Reset' .... cover in outside compartment. Under that is 2 sets of t-stats. The LEFT side is for 120V AC element and the RIGHT side is for the propane.
The High Temp T-stats are 're-settable' when they trip (170*F/180*F)
The Normal Temp T-stats Opens at 130*F (then recloses at 115*F for reheating cycle)
(Atwood uses a self resetting t-stat----just like normal the ECO/HI will reclose when water temp is cooled)

Between the upper t-stat and lower t-stat is a connector wire, Sometimes that wire will burn into.

So IF you have 'reset' (you can feel it when you push in on button) and have turned Propane switch OFF/ON (resets 'fault') and water is cold then it should refire on propane.

If it doesn't then remove the cover on t-stats and check that wire is intact.
Otherwise you will need to test for 12V DC.


Suburban T-stats


Atwood T-stats

[hohenwald48]

big russ wrote:

hohenwald48 wrote:

big russ wrote:

WyoTraveler wrote:
Watch the ignighter while your wife throws the switch. Are you getting spark? I'm not sure, maybe there is a reset if the tank gets too hot.

it has what seemed like two reset buttons ,it didn't work.what ignites he gas and how does it know when to ignite?

The gas is ignited by a spark generated by the control board when the thermostat says the water is cool. The control first opens the electric gas valve then generates the spark. It then monitors the flame (via thermocouple) to insure it has lit. If it has not, it will shut off the gas valve.

ok switch on control panel is on, LED indicator light is off., I have gas.its not firing .what could cause it to not fire after firing it on a dry tank?

There are basically two thermostats in the system. One that operates the control board on a regular basis. I don't know exactly but lets say it's set at 130 degrees. As you use water the tank cools and the thermostat closes allowing voltage to the control board and igniting the gas. As the water heats it opens at 130 degrees shutting off the flow of gas. This cycle continues over and over as you use the hot water.

The second "thermostat" is a safety device that operates only in the event of a failure of the first thermostat to turn off the gas when the water reaches 130 degrees. This second "thermostat" is also called a "limit switch" or "high limit". It is designed to open at say 140 degrees. Once it opens it will never close again and must be replaced. Some WHs have a resettable high limit but most do not.

As I said, I'm just using examples of the temperature setting of the thermostat and high limit. I don't know what the exact settings are. However, the high limit setting will always be higher than the thermostat setting.

The LED indicator is a fault light. If it is off that means the control board has not detected a failure to light fault after calling for the burner to light.

The electric operation of the WH is controlled by a separate set of thermostats and high limit switches. For control purposes there is no connection between the gas and electric operation.

Keep in mind that I am speaking in general terms. There may be WHs out there that operate completely different from what I've described.

[big_russ]

hohenwald48 wrote:

big russ wrote:

WyoTraveler wrote:
Watch the ignighter while your wife throws the switch. Are you getting spark? I'm not sure, maybe there is a reset if the tank gets too hot.

it has what seemed like two reset buttons ,it didn't work.what ignites he gas and how does it know when to ignite?

The gas is ignited by a spark generated by the control board when the thermostat says the water is cool. The control first opens the electric gas valve then generates the spark. It then monitors the flame (via thermocouple) to insure it has lit. If it has not, it will shut off the gas valve.

ok switch on control panel is on, LED indicator light is off., I have gas.its not firing .what could cause it to not fire after firing it on a dry tank?

[hohenwald48]

big russ wrote:

WyoTraveler wrote:
Watch the ignighter while your wife throws the switch. Are you getting spark? I'm not sure, maybe there is a reset if the tank gets too hot.

it has what seemed like two reset buttons ,it didn't work.what ignites he gas and how does it know when to ignite?

The gas is ignited by a spark generated by the control board when the thermostat says the water is cool. The control first opens the electric gas valve then generates the spark. It then monitors the flame (via thermocouple) to insure it has lit. If it has not, it will shut off the gas valve.

[downtheroad]

good idea about 'RESET"

[big_russ]

WyoTraveler wrote:
Watch the ignighter while your wife throws the switch. Are you getting spark? I'm not sure, maybe there is a reset if the tank gets too hot.

it has what seemed like two reset buttons ,it didn't work.what ignites he gas and how does it know when to ignite?

[big_russ]

downtheroad wrote:
Strange...should be the other way around.
Electric side should be burned up...if you turned it on without water in the tank.
Are you sure you haven't confused which switches turn on what?

no always ran it on the gas side.

[dave17352]

Maybe there is a limit switch that needs to be reset.

[WyoTraveler]

Watch the ignighter while your wife throws the switch. Are you getting spark? I'm not sure, maybe there is a reset if the tank gets too hot.

[downtheroad]

Strange...should be the other way around.
Electric side should be burned up...if you turned it on without water in the tank.
Are you sure you haven't confused which switches turn on what?