vent damper

Billy_3

One of my customers has a hydrotherm boiler in the attic of the house. It has one burner tube and it's a millivolt system. Whoever put it in didn't use the draft hood and they put in a vent damper. The flue is done exactly like if it was oil. It seems to be drafting ok. I have never seen this before so I shut it off and told her I needed to call the manufacturer to see if it was ok. Can it stay like that or does it need to be changed

Jim Davis

Are you referring to a barometric as a vent damper? Did you do a combustion test? How did you verify it was drafting OK? This could have been done to correct a dangerous condition and if you change it, only you can be sued, not the manufacturer, regardless of what they say.

Billy_3

I tested it

By putting a smoke bomb in the burner tray.

Jim Davis

Is it a vent damper or a barometric?

Mark Hunt

Smoke bombs?


Did you do ANY other test?

I'm not sure what you're asking here.

You can't tell anything about combustion and venting from a "smoke bomb" test.

Now why is a barometric damper OK for oil but not for gas?

There is more to this than what you have been told.

Mark H

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Dale

Attic installs

One thing to look for on an attic install is no single wall vent connector, it must be B vent.,a common mistake. I would get the install instructions and check them. A barometric may be OK if installed correctly but an electric vent damper or a bimetal and no draft diverter is not OK.

Billy_3

barometric. sorry I keep calling it a vent damper

Jim Davis

barometric

Freddy was you saw is more common than you think, but is only done by a certain group of trained and skilled technicians that do combustion diagnostics. It should not be done by anyone else. This installation was verified by field testing to be acceptable by the American Gas Association in 1993. If holes are drilled in the flues for testing, it was most likely done correctly and is the safest of installations.

Unknown

I've heard that said before

What part, by number, of the 2002 NFPA 54 National Fuel Gas Code can I read that in?

Noel

Jim Burke comfort zone

DAMPER IN ATTIC

THE REF. # IS 7.12.4* IN THE BOOK .
must be done with proper test equiptment.
must be a listed double -acting barametric draft regulator
installed in accordance with manufactures instructions.
I would contact them. hope this helps.

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Unknown

Exactly.

Contact the manufacturer. That's my point.

Noel

Billy_3

holes

There are holes drilled in the flue

Jim Davis

NFPA

The problem with NFPA or the Vent-II tables is that they leave open an infinite amount of ways to be interpretted and is full of contradictions. Yes, it is a start and we need something that is initially standard but then all similarities disappear on each job. In the end and legally it is on the shoulders of the installer or service tech to determine the correct design in the field. NFPA-54 states "anyone using this document should rely on his or her own independent judgment". The Vent-II tables state "Good engineering judgment should be used in making allowances for all disturbances in the field." Obviously I believe verified operation, not just a judgment call. NFPA 7.12.1 does state that all equipment must use a drafthood unless the equipment requires draft for venting. I have yet to see any vented appliance work with zero draft in the flue. It also states in 7.15 that no device should be used in the flue that obstructs the flow of flue gases. This is the definition of a drafthood(ASHRAE-drafthood isolates appliance from venting disturbances). The key is to test and verify all possible conditions that can affect venting and then correct these things so no interference can occur. Having been involved in many court cases, it was always the installing or servicing contractor that had the ultimate liability. Field corrections should only be made and verified by the best equipped and trained field personnel. If one installs the same piece of equipment in 100 different buildings, 100 different conditions will be encountered. Each and everyone must be verified to be functional and most of all safe.
Noel I do not know if you are familier with products like Therma-Stack, Coil-Mac or Cain. These are hot water coils designed to be put in flues of boilers to capture lost heat up the chimney. The installation of these, back in the 80's required the removal or relocation of drafthoods on all atmoshperic boilers. All powers to be had to accept this whether they approved it or not. My problem is that unqualified contractors were allowed to install them. That will and should always be the everyone's main concern. After this week in Boston, you will see some posts to address this issue again. Pro or Con???