I have a A.O. Smith Power-shot water heater. It heats fine when it needs to but the p

**reasonerj** · 10-09-2012, 02:34 PM

I have a A.O. Smith Power-shot water heater. It heats fine when it needs to but the power vent runs all the time. Why?

**Dana** · 10-09-2012, 02:39 PM

That feature was provided to suck all the heat back out of the tank during standby so it can fire up again sooner burn more natural gas!

Seriously- if the blower is stuck on that's literally what it's doing- fix it (or pay someone to fix it), or it could end up costing as much as your heating bill.

**reasonerj** · 10-09-2012, 02:56 PM

Yeah our electric is going threw the roof. Is the fan to suck the heat or is it to power vent the gas? How do I fix it?

**Gary Swart** · 10-09-2012, 03:23 PM

As its name implies, it's a power VENT. Has nothing to do with heating the water. It replaces the flue through the roof vent. The problem is probably in the control unit which is not signaling the vent fan to turn off. It will not fix itself, and would best be dealt with by a professional repair person. I really doubt if the added electrical use is going to send you to the poor house, but this should be repaired.

**jadnashua** · 10-09-2012, 03:53 PM

It's blowing air from the burner out the vent. This is continually pulling cooler air from the room around where the WH is, and throwing it outside. That air must be replaced, so during the cooling season, it's dumping air you've paid for to cool, during the heating season, it's dumping air you paid to heat. In both cases, it's pulling air in through cracks or other openings in your house.

It should only run while the burner is on, and for a short time afterwards, then shut itself off. A more ecconomical version uses closed combustion, and would have an additional pipe pulling in air from outside so it doesn't suck air from the house.

**Dana** · 10-10-2012, 07:17 AM

It's not just blowing conditioned air out of the house, MUCH more importantly it's pulling ~70F conditioned through the heat exchanger inside the 120F-140F tank, cooling water in the tank and throwing that heat out along with the conditioned air infiltration drive. The combined effect on gas use is the same order of magnitude as the space heating requirements.

The blower itself is probably on the order of 100-150W, which would only add 75-100kwh to the monthly power bill- not nothing, but not "through the roof" unless it's been 115F outside all month, adding a significant load to the air conditioning bill.

If you can't download the maintenance manual (which hopefully has a schematic for the burner & blower controls to help determine which sensor or relay has failed), kill the power to the sucker and call in a repair tech to debug it for you. If you need to take a shower in the meantime, turn it back on 10-20 minutes ahead of time and back off later.