Water Heater barely warm water - NO bypass valve

[DougMatthews]

Need some help.

I have a Suburban water heater (gas only, near as I can tell). Rig is 2008 Weekend Warrior 25' (super light?).

After WH is running for 20 minutes (or more) the water is detectably warm, but not anywhere near hot. Used to work fine.

Seems like all the search results for this type of problem call out the bypass valve as the culprit. This rig does NOT seem to have one (looked at back of WH behind cabinetry - hot, cold, NO bypass).

Winterized by compressed air (thorough purge), removing WH drain plug.

Water system is now full. No leaks. Good flow at faucets. WH fires up, seems like decent flame, gets lukewarm. After it's been running for a while, seems like decent flame (visual inspection), but sounds odd. Causes me to think moisture in gas line maybe affecting amount of gas through jet? Is that a thing?

Any other things I should investigate?

Thanks!
Doug

[enblethen]

Many people get the solution but never responds.
Thanks for letting us know you found and fixed the problem.

[DiskDoctr]

Great job, fellas!

I've stuck the end of a hand torch (actual "torch" not a flashlight!) into the burner tube to clear out cobwebs and stuff on a malfunctioning DHW.

Didn't have to remove it 😉

Thanks for returning to post the update.

[Old-Biscuit]

Thanks for the update.

Glad it was an easy fix.....those are the best

With such a 'low pressure' fuel system----FLAME condition is the key

[DougMatthews]

Hot showers this weekend courtesy of Old Biscuit!

Dunked the orifice in alcohol overnight, blew it out and all is right with the world.

Thanks!
Doug

[Old-Biscuit]

OP stated:

OK, so ran the WH for 30 minutes (never turned off on it's own), then popped the relief valve. Water that came out (caught it in a cup) was barely warm to the touch.




Water heater has water in it....so not bypassed
Water in WH was warm......after 30 mins
Cold/hot have to mix to cause 'warm'---OP took sample from T&P Relief Valve

OP stated:

The flame is interesting. It's blue, with large flashes of yellow at the exit of the tube. At the entrance of the tube (near the jet) it's like a super-fast sputter, but blue.

Flame is fuel rich so flame temp not as hot as it should be plus gas flow is not consistent ---dirty orifice and/or burner tube

OP also didn't let WH operate until heating cycle finished

[westend]

Winterized by compressed air (thorough purge), removing WH drain plug.

You were able to blow out the system with the water heater drain plug removed? If so, that indicates you had a bypass valve closed.

[Horsedoc]

I tend to think there is valve he has missed. Had that situation in a previous coach and it was hard to see in the dark hole the WH lived in.

[wa8yxm]

Where are you measuring the water temp?

If it is at the faucet the #1 cause of such things is a shower either inside or outside, the mixing valves are open and the head valve is cut off.

If the water in the tank is not getting hot.. I'd guess an obstruction, either in the burner orifice as others have suggested or in the flu/heat exchanger.

[Old-Biscuit]

enblethen wrote:
The orifice screws into the gas solenoid valve.

Not on Suburban ...it is part of burner tube


Recovery rate is 10.2 gal/hr (recovery----after initial heating)

[DutchmenSport]

I will agree, that it takes longer than 10 minutes to initially heat the water completely for the gas to shut off. More like 30-40 minutes for mine, depending upon how cold the water is to begin with.

Now, once it's already hot, recovery is much faster.

[RJsfishin]

RJsfishin wrote:
How long does it burn before the stat shuts it down.
If the tank is cold, it should burn nearly 45 minutes. If its shutting down too soon, jump the stat,....see what happens.

My post from page 1, completely ignored !
Some people don't deserve help.

[Chris_Bryant]

Late model Suburbans have the orifice built in to the burner tube. 45-60 minutes is not at all out of line- there are 50 pounds of water in the heater, the burner is 12,000 btu/hr, 1 btu raises the temperature of 1 pound of water 1 degree. A lot depends on the temperature of the incoming water. For the initial run, you are also heating the tank itself= more time. Once hot, recovery will be quicker.

Someone who still remember high school math can do the calculations. 🙂

[dougrainer]

DougMatthews wrote:

dougrainer wrote:
IF you are testing while the burner is ON. WHY????????? If the burner is ON, the Tstat has not reached its shut off temp. LET IT RUN UNTIL IT SHUTS OFF. Then test your water. Doug

The unit used to reach temp and shut off in under 10 min (anecdotal, never measured).

Seems that if it is barely warm in 30 minutes it's going to be hours (if ever) before the Tstat shuts it off. That won't support taking a shower.

/Doug

NO RV water Heater will reach temp in 10 minutes on LP. Let it run, see if the burner shuts off. What do you have to lose? Doug

[enblethen]

The orifice screws into the gas solenoid valve.