Suburban propane water heater

[Tommy guy]

I purchased a new Suburban gas/electric water heater. I don't use the 110 volt heater, propane only. (Suburban Advantage RV Tank Water Heater SW12DE) Spark ignition.

If I don't use the hot water for a day or so, the water goes cold. It's not maintaining hot like I would expect. When I turn the switch off and back on, it then fires up and heats to full temp. Can anyone here clue me in as to what's wrong or why this is happening?
Thanks in advance for any help you can provide

 

[Aussieguy]

I've never noticed this
we turn off hot water any time away from using the camper
and only run it always ON only if connected to 120v

If using propane we only turn it on after diner for showers / dishwashing
we never leave it ON ... using propane
------------------------------------------------------------------------
could be some sort of timer.... don't use the hot water it turns OFF ???
saves propane why heat water when you don't need to
sounds like a good idea....

if you want hot water after a day or two... you'll have to wait

or.... between showers use HOT to wash hands in the bathroom
it would reset any timer

 

[RhumbleFish]

If I don't use the hot water for a day or so, the water goes cold. It's not maintaining hot like I would expect. When I turn the switch off and back on, it then fires up and heats to full temp. Can anyone here clue me in as to what's wrong or why this is happening?

I see this is your first post - welcome!

Sorry you're having this issue. For the burner to come on for a reheat, your SW12DE will need:
1. Trailer power ON (shore power or battery), hot water heater switch turned “ON.”
2. Gas supply to heater not empty or turned off.
3. Reset button on ECO not tripped.
4. Thermostat to read water temp (and def below 110° for refire, based on ECO)

If the above is all true, and the trailer's main power is switched on during this time (providing the minimal electricity for the brains and the DSI/spark/respark), it sounds like a thermostat problem: like the system will sense when the tank needs to be heated at powerup, but not when it needs a re-heat. Frankly, I'd be tempted to reach back to your retailer/manufacturer with a warranty issue.

I'm also wondering a little but about the "day or so" for "cold" water. In particular, how long are you waiting, what are the actual water temps (hot and cold), and what's the temp differential from the cold water temp to air temp? Insulation on these units is fairly modest, but same day hot water is definitely something you should be able to expect (especially on a 12gallon unit). Should carry well into the next day, as well.

48 (or more) hours later, however, might be a lot to ask. This might be a lack-of-insulation issue OR a water temperature not getting to upper temp limit issue, but - depending on how long you're waiting - might simply be the limits of the system (again, especially considering temperature differential btw water temp and outside air). Have to say, depending on how long you're waiting, might be a little like putting ice cubes in a styrofoam cooler and being surprised to find water two days later.

Here's install, usage and trouble shooting guides for your SW12DE:

Suburban Water Heater Master Service and Training Manual.
Suburban Gas Water Heater Model SW12DE Installation and Operation Manual 1
Suburban Gas Water Heater Model SW12DE Installation and Operation Manual 2

Parts and more here:
Suburban SW12DE – PDX RV

Just my .02. I could be wrong. Hope this helps.

 

[GolfingDave]

Frankly, I'd be tempted to reach back to your retailer/manufacturer with a warranty issue.

X2

Could let it run and then once it shuts off run hot water to cool it down. See if you hear it try to kick on.

 

[Tommy guy]

I've never noticed this
we turn off hot water any time away from using the camper
and only run it always ON only if connected to 120v

If using propane we only turn it on after diner for showers / dishwashing
we never leave it ON ... using propane
------------------------------------------------------------------------
could be some sort of timer.... don't use the hot water it turns OFF ???
saves propane why heat water when you don't need to
sounds like a good idea....

if you want hot water after a day or two... you'll have to wait

or.... between showers use HOT to wash hands in the bathroom
it would reset any timer

My old gas water heater had a pilot lite for ignition. Since I live off grid in my cabin, I prefer to keep the water hot at all times. I use a 500 gallon propane tank for hot water, refrigeration and cooking. Anyway, this new spark ignition type won't even allow me to adjust the water temp thermostat. It's set at 130 F. No hotter. I see now that it not staying hot 24/7 is another safty thing so if one forgets to turn it off when their not using the RV, it won't burn up all the propane. I get it now. I thought there was something wrong with it. They don't offer the old pilot ignition type anymore. So, I'm stuck with the new fangled type! Thanks much for your input!

 

[5picker]

My old gas water heater had a pilot lite for ignition. Since I live off grid in my cabin, I prefer to keep the water hot at all times. I use a 500 gallon propane tank for hot water, refrigeration and cooking. Anyway, this new spark ignition type won't even allow me to adjust the water temp thermostat. It's set at 130 F. No hotter. I see now that it not staying hot 24/7 is another safty thing so if one forgets to turn it off when their not using the RV, it won't burn up all the propane. I get it now. I thought there was something wrong with it. They don't offer the old pilot ignition type anymore. So, I'm stuck with the new fangled type! Thanks much for your input!

I do not believe this to be the case with modern Suburban water heaters.

The water heater should stay on and provide hot water as long as you have it turned on and have propane and 12v DC to run the controls.
These units are not complicated and are usually very dependable.

With that said, if the unit is new, I'd reach out to whom you purchased from or Suburban.

The water heater for LP operation needs 12v DC and propane. When you turn on the LP side of the heater, the system (via the control module) checks to be sure the high limit switch is closed and the thermostat is closed. Once that is verified, the module opens the gas valve and begins sparking the electronic ignitor. Once flame is detected, the system provides flame until the thermostat opens saying the water temperature is hot enough and closes the gas valve. The system stays on, waiting for the thermostat to close and begin the process all over again. If the thermostat should stick, the overlimit switch opens and kills the system to prevent overheating. The control board also has a "lock-out" feature that prevents the water heater from continuous firing if no flame is present after three tries when calling for heat.

The thermostat "could" be the issue you describe either by a malfunction or poor contact to the water heater tank but because you say turning off the unit at the switch and the turning back on refires it, I tend to believe the control module has a sensing issue.

Also of note, BOTH the 120v element AND the LP side of the water heater can be used for quicker recovery.
They are essentially two separate systems, but can be used together. (or separate)

Here's a schematic... hope it helps you understand the system.
NOTE: disregard the astric (*) and the relay. It is only used if you have a 2nd switch inside to turn on the 120v portion of the heating.

 

[Larry-NC]

I believe that here is what is really happening.

The SW series has Direct Spark Ignition, no pilot light. Each time the thermostat (in the heater) calls for heat, the gas turns on and there's a continuous spark until the propane lights or the heater times out. After a couple of timeouts, the heater goes into "lockout" and gives up. The switch will turn red at this point and the heater won't retry until it is turned Off, then On again.

Next time this happens, turn the switch Off, then On while the door is open so you can hear outside (or someone is listening outside). You will hear a "clunk" sound as the propane valve opens, then click, click,... of the sparks, then "whoomp" as the gas ignites. If there's no ignition, you won't hear the whoomp ignition sound.

It's common to have ignition problems if you haven't used the RV for a while and the propane tank valves have been closed. The propane diffuses from the hoses and is replaced by air. Seasoned RVers always attempt to light the range burners FIRST, and don't attempt to light the water heater or furnace until the range burners are burning cleanly (and then turned off).

If this is not your problem, there are a couple of possible causes. Since the heater does light sometimes, the problem is intermittent and you are looking for an intermittent (sometimes) failure
Failing propane regulator (at the tanks).
Low ambient temperature at the tanks
Bad position adjustment of the spark electrode
Bad flame sensor or bad positioning of the flame sensor

Can you tell us more about the conditions under which it fails to relight?

 

[GolfingDave]

I do not believe this to be the case with modern Suburban water heaters.

Sure looks like they all use the same 520814 control board. Pretty much tells me they should all operate the same.

Do not see anything about this problem/feature in any manual but do see about the thermostat being 130 degrees.

I know I've gone 24 hours on propane without hot water use without any lockout. Can not absolutely say I have gone longer.

 

[5picker]

Sure looks like they all use the same 520814 control board. Pretty much tells me they should all operate the same.

Do not see anything about this problem/feature in any manual but do see about the thermostat being 130 degrees.

I know I've gone 24 hours on propane without hot water use without any lockout. Can not absolutely say I have gone longer.

I've gone well over a month on LP with several different Suburban water heaters.