Should I add a vent damper?

Hap_Hazzard

I notice that most people have automatic vent dampers on their boilers. Mine doesn't have one, but it seems like a good idea; it would keep the warm air in the basement from rising up the flue and bringing cold air into the house.



This is a gas-fired atmospheric boiler with a standing pilot and an open vent hood with a seven inch flue pipe. It seems like a pretty big hole to have open to the great outdoors in the dead of winter. I can't imagine why there isn't a damper on it.



As I understand it, it should be wired up so the vent opens when the thermostat calls for heat but independent of the other controls so it doesn't close every time the Pressuretrol or CycleGard turns off the burner. I realize this means the pilot would still be on while the damper is closed, but that much exhaust gas can probably leak by it. Would I be running any risks by installing one?

crash2009

Barometric Damper

I looked into a barometric damper for atmospheric steam boiler last fall.  I was told that they can help reduce high draft problems.  I even went so far as to have a combustion test done, to see if I would benefit from having one installed.  Unfortunately, or fortunately, depending on how you look at it, in my case it would have taken 10 years for a ROI.  So I passed on the idea.



The shortcut below has a link in it to The Comfort Institute, Jim Davis's website.  He is an expert on this subject.



http://www.heatinghelp.com/forum-thread/137968/Barometric-Damper-Upgrade-to-Atmospheric-Gas-Steam

ChrisJ

damper

Crash, I think hes talking about the automatic dampers like I have rather than a barometric damper.



I know when I installed mine which came with the boiler it had a hole in it which you could leave open if you had a pilot, or install a plug for EI which I did because I have EI.



Point being you can definatly use it with a standing pilot as long as you leave that hole open and I'm sure it reduces losses quite a bit.  You go from a 6" opening to a tiny like 3/4" hole which I guess lets enough draft through for the pilot.  Mine is wired so it closes when the pressuretrol trips.  It came this way from the factory and I don't mind it as the burner shuts off for quite a while in the rare event it actually does trip from pressure.  Also it stops the heat from going up the chimney during this event.

crash2009

Oh

 you mean one of those kind of dampers.  Yea, get one.

Hap_Hazzard

Yeah, one of those. :-)

On the one hand it seems like a no-brainer. On the other hand, if it's such a no-brainer, why isn't there one there already? But then, there are a lot of things like that in this house. I can't believe I paid somebody to inspect the place before I bought it. :-/



Some of the wiring diagrams in the IOM show a damper motor, so I should be able to figure out how to hook it up. All I have to do is figure out how to get the plug without having to buy their fancy universal wiring harness.

Hap_Hazzard

I wish I'd done this years ago.

Finally got around to it about a week ago. Just to give you some idea of what a huge difference this makes: my upstairs used to be about 2 degrees warmer than the downstairs; now it's about 2 degrees cooler.



My thermostat is on the first floor, set at 70 degrees with a 1 degree swing. The basement used to fluctuate from warm to very warm, depending on how recently the boiler has run. (The steam pipes are partially insulated.) The upstairs temperature has gone from 72 to 68 since I installed the damper.



I knew that air was leaking in at the back door, and I'm planning to replace the door, but I never made the connection between the air leaking in and the air going up the flue. Now that I've installed the damper, it doesn't feel cold by the back door, and the boiler isn't running as much. The basement is now constantly much warmer than before, without the fluctuations. When I go down there I often find the pipes cold while the basement is still warm, and since the boiler isn't running as much, it's now becoming obvious how much heat is being lost from the upstairs.

pipeking

ALL BOILERS

should come with auto vents. even wet base.

edit: automatic vent damper.

ChrisJ

auto vent?

Whats an autovent?





Nevermind, I guess I should've assumed we were talking about the subject in the thread.

I kind of confused it with maybe being the kind used on hot water boilers to vent air and got confused.

Steamhead

Part of the reason for the vent damper

which is also known as a stack damper, on a house with steam heat, is that the chimney was almost certainly built for a coal-fired boiler. In such a boiler, the chimney has to pull air thru a bed of coal, which takes a lot of draft to do. So chimneys were designed and built to develop a lot of draft. These things can pull pets and small children up to the roof.



With oil or gas firing, that kind of draft is not needed. So the barometric and the draft hood were developed to limit the draft at the burner while it was running. This gives more-stable combustion, but does nothing about the off-cycle losses from all that draft.



Stack dampers are most effective on atmospheric boilers since these boilers are wide-open at the base and draft hood. They were also quite effective with older oil burners because these had wider air passages than today's oil and power gas burners do- that is, until they sooted up and quit working.



Modern oil and power gas burners have smaller air passages so they don't admit so much air during the off-cycle. But a stack damper is still a good idea with these units- if you can find one approved for such use. I think Field was marketing one for a while but haven't seen anything on it recently.

ChrisJ

Huge chimneys

Which is what still confuses me about the brick chimney my house had. It had an opening large enough to fit 1 brick in, I guess around 4x7" ?



The only guess I have is the house was only 700sqft or so before all of the additions were done, but it still seems like it was really on the tiny side for coal stoves which I think it had 3 of connected to it.

Steamhead

How tall

is your house?

ChrisJ

Tall

Don't remember but the chimney was around 30 feet tall.

Jamie Hall

Two kinds of dampers...

totally agree on barometric dampers -- it is necessary to control the draught, and some of the older bigger taller stacks can, as Steamhead noted, just about suck the family pet up and out.  Amazing.  If you don't have one, controlling the over fire draught is almost impossible.



The powered automatic dampers, though, which close the stack when the burner is off are another story.  Yes, they do reduce the losses up the chimeny when the boiler isn't firing -- although with a properly set barometric damper, these losses may not be that much, as the air has to come through the boiler and burner.  But for the utmost efficiency... problem which I have with them (I used to have them, but took them off) is that of all the gadgetry on a boiler, they are by far the least reliable -- and reliability in a cold climate is a significant item.

Pughie1

Stupid Question

Hap,

This is probably a stupid question because you sound very knowledge,

but did you follow the manufacturer's wiring instructions exactly? Or perhaps

the damper has a harness that simply plugged into your control circuit.

Then did you test the fail safe operation of the damper? Sorry if I affended

you, but you can't be to safe.

                                                            John Pughe

Steamhead

The taller the chimney

the more draft it will produce. That might be why it worked. 

Hap_Hazzard

Field

The damper I installed is made by Field. I'm not sure if anyone else makes them. Even the ones I looked at that were sold as replacements for Burnham or Weil-McLain looked just like the Field units.



I'm not sure if this house was ever heated with coal. It was built in the 1930s. Of course that doesn't mean the bricklayers weren't still building chimneys as if they were still used for coal. I can testify that the fireplace chimney draws like a son-of-a-gun. Even with the glass doors shut, it gets going like a blast furnace.

JeffM

powered

I've been thinking about a powered damper myself. I had a Carlin EZGas put on my Weil-McLain SGO last fall, and the new double-swing barometric damper is partially open even with the boiler off, which sends a lot of basement heat up the flue (and leads to cold first level floors). I haven't added weights to the damper chain to hold it closed, assuming that the weights are used to tune the flow when firing - is that right?

At any rate, I've wondered if putting a powered damper downstream of the barometric in the flue to close it more tightly when things are off would help reduce my standby loss up the chimney. It's about a 35 foot chimney with a 6 inch stainless liner in it, and could probably suck my little dog up it if she got too close. If recommended, what brand/model would be good for this setup?

Hap_Hazzard

Safety

Yes, I followed the wiring instructions and tested it, then I left it wired in but not connected to the flue pipe for about two weeks just to make sure it didn't do anything crazy.



The boiler IOM didn't give any indication as to where to put it, but a more recent IOM downloaded from Peerless did, so apparently they weren't an option when mine was made, but it does have a redundant gas valve, and that's the critical thing. If it hadn't I'd have had to install one.

ChrisJ

Yep

When I bought my EG-45 its sold with and without the damper. I went with spark ignition and the damper because it seemed wise. Even if I went with a pilot I would've got the damper which was also an option.



I think one thing that gives an idea of what the damper saves me is when it closes right after a cycle. The first time I ran the boiler it smoked some and when it shut off and that damper closed the daft hood got super hot and smoked a lot because the draft stopped cooling it. To me, that shows an example of the heat its stopping from leaving the basement even for a few seconds worth.