Gas water heater power vent

thatguy · May 12, 2018

We inherited my in-laws home that has a natural gas water heater that has a power vent (that I assume that pulls fumes out of the combustion chamber before the burner ignites).. the burner does not stay lit

The power vent comes on and off every 5 to 10 minutes and will run for 2 to 3 minutes each time.. it does this all the time, no matter if we have used (or are using) hot water or not.. I dont see how the water would cool down enough to trigger the heating cycle within this short time..

Is this power vent operation normal or something that I need a plumber to check out?

brian

ultrarunner · May 12, 2018

I'm guessing the burner is cycling?

mddorange · May 13, 2018

If the burner is cycling that often, then it needs adjusting.

grm61 · May 13, 2018

What kind of water heater is this?
Tank type or tankless?
What is this power vent?

I have a high efficiency Ream tank type.
It has a electronic butterly at the top of the tank before the flue to hold the heat in when it is not running.

ultrarunner · May 13, 2018

The higher efficiency gas appliances have lower stack temps and to ensure the all is vented properly a small blower is required.

I see it more on gas furnaces.

If the blower doesn't function the or at least if the sensor doesn't see a functioning blower the gas valve for the burner will not open.

grm61 · May 13, 2018

ultrarunner said:
The higher efficiency gas appliances have lower stack temps and to ensure the all is vented properly a small blower is required.

I see it more on gas furnaces.

If the blower doesn't function the or at least if the sensor doesn't see a functioning blower the gas valve for the burner will not open.

Right, my furnace (PRO[ANE) is that way, vents through pvc high effiency, 1991 era.
Had a problem with it lighting then shutting off blower, it would keep running then relight...primary and secondary fans kept running,
It was the flame sensor, pulled out, cleaned with scotchbrite
2 years good now

mcfarmall · May 13, 2018

Sounds like the air flow proving switch isn't working. there should be a diaphragm switch with a small piece of flexible tubing going over to the stack. Pull the tubing off the stack and then suck/blow on it and you should hear the switch click on and off. If you don't it's not functioning properly. The burner goes through a set sequence for firing. Purge, which runs the blower to evacuate any flammable concentrations of gas in the combustion chamber. Main flame trial for ignition and then a post purge after the burner shuts off.

thatguy · May 13, 2018

couple things i noticed - it does not cylce on/off at night..

this is a tank (50 gal-ish i guess) natural gas unit.. with on demand ignition (no pilot light)

ill go down this morning and get more info..

thanks for the ideas so far

brian

radioman · May 13, 2018

My bradford powervent only comes on when its being used during the day. Perhaps your setting is a little too high.
These new hot water power vents is the way to the future and i love it due to fact you have more places to put it without worrying where chimney is.