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I built a couple of houses in a hilly wooded area, subject to occasional strong winds, which suffer from the same problem. The hot water heater pilot light is extinguished during windy storms. They are Brookfield White 75 gal natural gas models. I’ve extended the flues, added wind directional caps (like old Spanish helmets) and added down-draft preventers just above the heaters to some of them. Although they are more reliable they still go out once in awhile. The gas company checked the valves, gas pressure and electronics. They tell me the pilot’s work OK. All are connected to a common flu with the furnace. Any ideas?
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Electronic ignition.
*Your last sentence may contain the clue. The problem may have to do with the shared vent. Some appliances require a so-called "Barometric damper" be installed above each appliance, below the tee. Reason is, one appliance's draft condition, when common vented, affects the other's. Certain negative-draft appliances are far more tender to their specified draft than others.Possibly, when the furnace cycles on under a relatively cool vent, an inrush may be caused at the DHWH air intake wobbling the pilot enough so that it occasionally loses flame.A Barometric damper is a calibrated, weighted damper that maintains draft within a determined range. It might be worth a call to the tech folks at both water heater and furnace manufacturers to see if this approach holds any water. My hunch is that the furnace folks may be of surprising help, as it could have just as easily been their unit that was behaving wobbly.
*I agree. Check with your heating contractor. Also it's possible that the flue was sized incorrectly to accomodate such a large water heater(lotsa BTU's) and a furnace(my HVAC man told me of a similar situation just last week).John
*all the posts have good ideas. as a hvac guy,I would check around the draft diverters when the water her is on alone,then check around it when the furnace is on. most ewer furnaces will have the main blower come on after a time delay of the burners. if the furnace and water heaters share a common mach room and there is a door on it close it while doing all this. our company sees a lot of problems like this in too tight of houses with return air ducts that are not sealed up good. use a lighter or cigarette held just to the outside of draft diverter.another thing to look for is level main burners in water htrs and do they run htrs to the point of just cold water coming out.a tank that is just filled or run to the point of full of cold water will drip a lot of condensation down the tank flue.this water is supposed to drain down thru the burner thru a couple of small holes.rust on the top of the burners plugs holes and spills or boils off the water over the side and puts out pilot.also seen venting where water heaters tees into main venting.best is to go into main venting at 45 degree type fitting like plumbing does.one sign i always look at is the top of the tank around the venting for rusting usually a sign of backdrafting.
*Along the lines of Don's post: Add up the btu's for the combustion appliances in the room: as a rule of thumb, you'll need 50 cubic feet in the room for each btu, or 1 sq in of free vent space per btu.Consider having draft tests done on the appliances, in my experience the smoke/lighter test will only tell you if you have gross downdrafting problems, you'll get much more information with a draft guage.
*Here's a little first hand experience you might want to check into. Installed an attic fan in our house and noticed if only one window was open the pilot would blow out on the water heater. Since our house is new, and tight, the free air vents located above the furnace were the only additional place for air to be pulled from. I'd check to see if the house has a professional stove, as well as the matching powerful exhaust fan.
*You said you installed downdraft preventers to some of them, what about all of them?... It seems to me that when one of your heaters fires-up on the shared flue system, the other unit's pilot gets snuffed. A problem that could get amplified during a storm.fv
*Thanks for the idea, we were saving it for last to save the cost.
*Thanks. I'll pass it along to HVAC and Plumbing.
*Wow, sounds like you've seen this before! Thanks.
*Thanks for the input. We may have to try all the ideas!
*This house has a big exhaust fan but is almost 4000 sq.ft and the heater is in the basement. Thanks for the information.
*Out of maybe 20 houses only three have problems and they are different designs and in different locations. However the hot water heaters are all the same brand. The dampers seemed to help. Thanks for your ideas.
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I built a couple of houses in a hilly wooded area, subject to occasional strong winds, which suffer from the same problem. The hot water heater pilot light is extinguished during windy storms. They are Brookfield White 75 gal natural gas models. I've extended the flues, added wind directional caps (like old Spanish helmets) and added down-draft preventers just above the heaters to some of them. Although they are more reliable they still go out once in awhile. The gas company checked the valves, gas pressure and electronics. They tell me the pilot's work OK. All are connected to a common flu with the furnace. Any ideas?