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Tanklets > Wind Issues

Q: We have a HUD home made in 1996. The water heater is a Rheem Warrior DV system similar to the one shown at this link. It has a exhaust vent to the roof and a air intake floor vent from the crawl space. http://www.rheem.com/documents/warrior-direct-vent-warrior-direct-vent-5-year-spec-sheet I can go months without re-lighting the pilot. Then when the mountain winds pick up I may have to light it 4 to 5 times a day!

It is in a closet with a sheet rock removable door to keep in enclosed. Sometimes the winds are so much that it will not only blow out the pilot but the burner flame too! Some suggestions I have seen is extending the roof vent stack pipe, adding a thermostat shield. My thinking: it has a floor air intake that it promotes down drafting from roof vent and down. I have gone to a smaller roof vent cap. It helps a little. Frustrated and ready to yank it out and go electric! Attachment: heater vent.jpg

A: Several manufacturers make flue vent caps designed for high wind situations. MetalBest's version is pictured below. Have you tried one of these? Chuck Attachment: HiWindTop.png -- LazyDevil

Q1: I have had a DuraVent like the one in my photo. Very popular in high wind areas but does not do well as far as I am concerned. I will look into the one you showed. Not expensive at around $18 bucks. Thanks!

A1: I looked at the link. Crawl space going negative relative to the WH and vent (roof) location will cause a back draft. WH location going negative relative to the vent (roof) will cause a back draft. I suspect most vent caps try to keep wind from blowing down the vent. Does it make sense to design a vent where wind will always cause low pressure at the vent?

Well, I tried to get a jpg sketch but it was always too big, so I'll try to describe. A 3 inch vent terminates into a very short tee above the ridge line. Add a one foot long asymmetrical funnel to each end of the tee. The funnel will be 3 inch diameter on the small end to connect to the 3 inch tee. Over the one foot length, the funnel which is straight on the top (relative to the 3 inch tee) with the flare on the bottom flares to 4 inches diameter.

Then a 2 inch long 4 inch diameter piece is attached to the 4 inch diameter end. The tee is mounted parallel to the closest ridge line. Wind coming over the ridge will move perpendicular to the tee creating low pressure inside the tee (and the end of the vent pipe). Wind moving parallel to the tee will increase velocity as it moves through the tee, which again creates low pressure at the end of the vent pipe. -- EnergyExpert

Q2: From what you are saying you have described a cap similar to my wood stove chimney cap ....which can take all kinds of winds! (wood stove cap photo) They come in 3" sizes which is what the WH vent pipe is. Even though it's $75 for one of these compared to $17 for the MetalBest cap I am tired of lighting this pilot and may opt for getting one. -- (1/19/12)

Q3: I have had my new High-Wind Top cap from Metal-Best on for about 2 weeks now. It has not prevented the pilot from going out, In fact I don't think it is any better than the one I had one before. Winds up hear were not that bad, some days 30 MPH would blow out the pilot. This water heater is a DV direct vent Rheem Warrior.

Question, I have heard of a "Pilot Baffle". What do they look like? Where can I get one? My next attempt at a fix is the extend the 3" pipe above the roof from 24" to 36" and try another cap. I have read some post at other forums that extending the vent pipe may help.

A2: Hello: Thinking out loud here: Normally for a balanced flue appliance, both intake and exhaust are very close to the same location. Thus, they both experience the same pressure from wind and remain balanced. What you have promotes air flow through the heater because intake and exhaust are at such different pressure points when wind is gusting. The heater only needs enough air for combustion. How about putting an air filter on the inlet side of things to baffle and slow down air flow? It would need cleaning if it proved out, but if the pilot quit blowing out, this would be a step in the right direction. -- Larry (2/2/12)