How to provide fresh air to my boiler?

[Phantom]

I figure a damper similar to one on a gas water heater should work. It would work best to seal the inlet to the inlet chamber but I assume that if you do that you would need to calculate the amount of air that the pipe would need to be able to supply. I would also assume that you do not need to seal it but place the opening close enough that the majority of the air will come from the pipe.

If the area by the burner gets hot you should not use PVC as it gasses off when it heats up and for the last foot or so you might want to use metal. Make sure that the opening on the outside will not get covered by snow or debris that could block the flow of air and adding a screen to keep critters out would probably be good.

[Daox]

Can you get a picture?

[S-F]

You see the cover just hangs on there. There is nothing remotely sealed about it.

[Daox]

Yeah that is going to be a bit of work to seal up. You can do it, but its going to be a pain. Perhaps you can add some sheet metal in there? Just bent some pieces to fit in there, bend flanges on them and screw them to the outside sheet metal. Seal it up with some silicon. Add some weather stripping to the cover as best you can. It doens't have to be perfect, just the better you seal the more it'll suck from outside vs inside.

[herlichka]

What I've seen is the intake duct has a slight slope down to the outside, so that any condensation that forms simply runs to the outside, the pipe turns down via two 45's at the boiler. And as far as connecting the intake air duct to the burner, I think that if it is simply as close as possible to the louvers, it will actually supply outside air to feed any convection flow that may set up after combustion stops: when combustion stops the warm walls of the exhaust flue will draw warm room air up and out, so if outside air is available right there then it will likely flow into the appliance. The pressure balance is so subtle that you you may want to consider prevailing winds and so on. Also, consider the possibility of things like auto exhaust, opening the basement door at the wrong time may pull fumes in with the outside air.

[S-F]

Good point about condensation there herlichka. But, how do I air seal the duct?

Well, google helped me find this.

I wonder if I can get these in the US and how much they cost.

EDIT:

Well Amazon has it all!

[herlichka]

I don't know if you really have to, or want to seal the duct to the appliance, doing so would constitute a "modification" to the appliance, and may present a liability issue: Various inspectors (municipal building inspectors, gas company, Fire Department, Insurance companies, etc) are trained to look for these things.

I have seen a number of woodstoves where the manufacturer's instruction manuals illustrate the duct presenting combustion air near the air intake of the stove, but not physically connected to it.

[S-F]

Yeah. I'm not planning on trying to convert it to a direct vent apparatus. The boiler is just open everywhere. Everywhere.

I'll just deploy that thing previously linked to at the end of a 6" insulated flex duct right next to the louvers on the front panel.

[Xringer]

I wonder if you could modify a drier vent with some weights,

so it would be closed pretty tight, until there was a pressure drop in
the basement, which would cause it to open and let in some outside air?
(This pic is of a bathroom ceiling vent that dumps into the attic).


I was thinking of running some 2 or 3 inch PVC from the outside, over beside the oil burner.
If it turned out to be venting in some really cold air all the time,
then I would build something like the drier vent.
Weight down the hatch, until only the burner coming on would lift it.
(Unless my basement is really leaky)!!

We stopped heating the basement a few years ago. The geothermal effect
of the ground water flowing under the basement slab, keeps the floor
above 60F during the coldest winter days.
Just keeping the old single pane windows closed keeps the basement
between 60F and 65F all winter. (With some help from boiler heat loss).

Should be interesting this winter, when I plan to start using the exercise
equipment down there every night..

[Piwoslaw]

Originally Posted by S-F

Well, google helped me find this.

I wonder if I can get these in the US and how much they cost.

EDIT:

Well Amazon has it all!

So they actually sell those? I was thinking about making one myself. The linked device's fail-safe mechanism requires energy to keep the damper closed when the boiler/furnace is off, any idea about how much energy?

As for sealing the furnace, I took a closer look at mine, and here are some pics:

I have a hanging model (Ariston Genus 23RI), no louvers, only a small peephole to spy on the flame, but the whole bottom, top and back are open.

Inside is the combustion chamber, plus all the gizmos and doodads in the bottom section.

Now, imagine that the whole boiler is boxed in and an intake tube with fresh, cold air is hooked up. That air will be steadily flowing through the boiler and out the chimney. If that air is really cold, like as low as -30°C (-22°F), then the whole inside of the boiler will freeze, both the electronics and the water pipes.

So maybe only the combustion chamber can be sealed off?

Mine is totally open at the bottom, under the burner, and at the top, where extra basement air can be sucked into the chimney to mix with the exhaust.

Sealing the combustion chamber may potentially freeze up the heat exchanger, unless the intake tube had a damper mechanism (cold air is probably OK while the burner is fired up).