Water Heater Function

JohnDar · Aug 14, 2012

I normally run the water heater on just the 120V element, but decided to use the propane (alone) for a bit, just to check it out. Seems the system doesn't want to cycle as automatically as it should. To the point that unless I manually recycle the switch, I end up with cooler water from the tank. Works OK on the element, though. Methinks the controller board may be at fault. The switch lights up when you turn it on, but the small indicator light doesn't seem to act "right." When the burner is lit, the flame is clean/blue, and there is no debris in the gas system, so I don't suspect any problems there.

I think I'll check the module board, maybe the plug connections are tarnished from lack of use, for a better word. But, if push comes to shove, I've located a replacement board, online, for the SW12DE unit for about $150.

Ray LeTourneau · Aug 14, 2012

So John, are you saying it fires on LP but won't stay lit?
Like you, we ran on mostly 110 for quite some time. Last year I tried LP but the unit would not remain lit. Worked fine on LP. I took apart the burner assembly, cleaned the orifice and made sure the burner sensor was clean and positioned properly. I ended up with a new board. I can't imagine not using LP for any length of time should affect the lifespan of the board.

danemayer · Aug 14, 2012

Suburban Sequence of Operation
Power from the on/off switch flows to the E.C.O. switch (rated the same
as a Atwood, 180oF (82oC), and continues on to the thermostat.
From the thermostat, power continues onto the circuit board and from the circuit board,
to the propane valve. When the thermostat recognizes the water has reached the set temperature,
it opens, stopping power from going to the circuit board, and the propane valve.
In the event of thermostat failure, the E.C.O. switch will open, stopping power from going
to the thermostat, circuit board and propane valve. This configuration will have a manual reset
button installed on the E.C.O.

• The on/of switch controls the operating circuit to the water heater. If the
heater fails to ignite or is in the lockout mode, the light will appear. Also,
on startup and during the purge cycle, the light can appear for approximately
15-18 seconds.

• The thermostat-limit controls the power to the module board. At a preset
temperature the thermostat, will open shutting off the burner. If the thermostat
fails, the limit or E.C.O. switch will pen and must be manually reset.

• The ignition of the burner is controlled by the direct spark ignition. As
module board power is applied to the DSI board, the system will do the following:
1. The DSI board will delay for 5-7 seconds before ignition occurs. The
board will then apply current to the gas valve and at the same time also
create a high voltage current to the electrode, creating a spark for ignition.
2. The module will then confirm the presence of a flame. If the flame is
not detected within 6 seconds the module will stop the firing sequence.
The DSI board will try for ignition two times, and will then go into the
lockout mode.
3. To reset the water heater turn the on/off switch to the off position for
about 10 seconds and then turn back to the on position.

John, if the light is on, indicating a lockout, and it operates sometimes, indicating presence of spark and propane, possible causes include:

Propane pressure incorrect
Low voltage (10.5VDC min)
Poor electrical ground
Electrodes out of flame pattern
Electrodes sparking to screw fastening burner to flue tube
Dirty electrodes
Partial obstruction in main burner
Partially obstructed main burner orifice
Improper air adjustment
Flame spreader on main burner
Manifold not aligned with main burner
Partially opening solenoid valve
Defective circuit board

JohnDar · Aug 15, 2012

Thanks, Dan, I've put your post in my "Instructions" folder.

What seems to be happening is that when I first turn on the propane switch on the monitor panel, the small indicator comes on. But, if the burner lights, it (the indicator) goes off and does not come back on. Unfortunately, the burner does not reignite later on its own when the tank cools off. I don't hear any attempts by the system to try igniting, either. Tried "forcing" it by running the hot water into a sink to drop the temp (element off), but still no joy. I've examined the flame, when it's on, and it is a clean, blue. So it doesn't look like the air/fuel mix is off or there are obstructions.

Replacing the board is the simplest route, I think. I did find one on Ebay for $85. If that doesn't correct it, then it's off to the dealer at the end of the season.

danemayer · Aug 15, 2012

John,

If the light didn't come back on when it should have reignited, then it sounds like it's not in lockout mode - which would probably clear the gas pressure and gas valve/solenoid. Since it initially fires up, and then shuts off when the water is hot, it sounds like the electrical path through the thermostat to the board is ok. No mention of having to press the reset button, so the ECO sounds like it's passing power to the board.

I think I agree with you that it's likely the board.

JohnDar · Aug 15, 2012

danemayer said:
John,

If the light didn't come back on when it should have reignited, then it sounds like it's not in lockout mode - which would probably clear the gas pressure and gas valve/solenoid. Since it initially fires up, and then shuts off when the water is hot, it sounds like the electrical path through the thermostat to the board is ok. No mention of having to press the reset button, so the ECO sounds like it's passing power to the board.

I think I agree with you that it's likely the board.

Thanks again, Dan. I'll be ordering the one I found on Ebay to be sent to the CG. Should be here for our next visit, so it may be a while before I can report on the outcome.

JohnDar · Sep 8, 2012

Re: Water Heater Function - Follow Up

Well, I replaced the circuit board and was still getting the lock out after the water heater was on for a day or so. What to do?? Went out and wiggled the wires on the gas valve enough to partially remove and reseat them and now the thing has been working fine for several days. Maybe I was premature on the board and should have just wiggled the wires in the first place.

Makes me feel a bit like the astronaut Dave in the 2001 Space Odyssey movie. "HAL, you can get your momma to take another space walk to replace that board!"

Willym · Sep 11, 2012

Re: Water Heater Function - Follow Up

The wire wiggling trick will not work until you've spent some money on replacing a perfectly good component.

JohnDar · Sep 11, 2012

Re: Water Heater Function - Follow Up

Willym said:
The wire wiggling trick will not work until you've spent some money on replacing a perfectly good component.

Yep, I think the simplicity of the repair is inversely proportional to the amount of money you spend on fixing it. But at least it continued to work until I shut it off this morning to return home. Once again doing my part to help the economy, one vendor at a time.

boatto5er · Sep 11, 2012

Re: Water Heater Function - Follow Up

JohnDar said:
Yep, I think the simplicity of the repair is inversely proportional to the amount of money you spend on fixing it. But at least it continued to work until I shut it off this morning to return home. Once again doing my part to help the economy, one vendor at a time.

I think the GDP must have ticked up at least.00000000005%.

Water Heater Function

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