Runnin in circles

[jetmec]

Hi, I recently changed my hot water heater up in my attic. When I checked it out I noticed alot of heat coming out of the vent hood. It failed the draft test. There are no obstuctions in the vent pipe. There is an attic vent fan nearby and I think this is causing a down draft in the pipe. Does anyone know what I can do to prove this, then fix it?

 

[Beni]

Well you can use a single sheet of single ply toilet paper, held near the vent hood, it should what to pull into the vent hood, if its negative pressure as it should be. If it puffs away from the hood its positive, and you have a problem.

Lucky the fix is to put a few more vent openings somewhere in the space, in the side eve or roof. Or turn the fan off.

 

[jetmec]

Thanks Beni, I unplugged the fan and no more heat from the hood. I gotta come up with a permanent fix now. The house is 25 years old and the fan and water heater are installed in the same place all this time, so it must have been going on all the while. I've only been the owner for 3 years. Do you know of any products that force air from the heater outside? Once again thanks for your response

 

[Beni]

There is Draft fans out there, but its been a while since I've seen a UL listed one. An easy fix is to turn the exhaust fan around and let it pressurize the attic. With maybe an extra roof vent cap or two. The air will find a way out. Some of the newer sealed combustion water heaters would work there too, but pricey.

 

[joshuameares]

If you turn the attic vent around it will cause poor attic circulation. Attic venting is designed to draw air up from the soffit vents and out the top. This actually occurs by natural convection since heat rises. In saying that you could just add a few more vents at the peaks and just leave the fan unplugged. Most new houses dont utilize electric attic fans anymore. They still make ul rated forced draft ventilators to go inline with flue piping. So you can do that too. But it would be way cheaper to install one or two attic vents.

 

[Beni]

Actually I'm betting his soffit vents are plugged or there's way too much insulation in the way to allow natural ventilation. Many times that's the case or so I've seen. My thought was to reverse the fan AND add additional roof vents near the ridge line. Really depends on how his attic space is vented

Its really against the code to locate a atmospheric vented heater in a negative pressure space. By pressurizing the space, that annoying code issue goes away. I'm not sure that putting a booster on the vent of a gas appliance located in a negative pressure pressure space, solves the code issue. Pretty sure it doesn't actually..

Simply adding a few roof vents, and keeping the exhaust fan running will not necessarily solve the negative venting issue.

Beni Bacon, PE, CIPE

 

[joshuameares]

By adding the roof vents near the ridge AND reversing the fan, you will cause poor circulation in the attic because you will only by circulating air at the top of the attic and not at the bottom. If you thought the soffit vents might be plugged then why not say so and fix the root of the problem rather than cause more problems. I'm pretty sure that if he still has a hit water tank in the attic or partially in the attic there's a good chance it's not being inspected nor up to new building codes and standards.

 

[Beni]

More likely there is lots O insulation in the lower roof area that completely blocks the flow of air from the soffet vents. Seen that many a time. Not suppose to be that way, but seen it far too often. I'm thinking the side eve fan was maybe added by a previous homeowner. Agree that reversing the fan is not perfect, but it solves the code issues and life safety issues with the water heater flue in a negative pressure space