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Discussion Starter · #1 ·
I bought a used Burnham 130K BTU boiler from a vintage store. It has a 6" exhaust vent (hole on top of the boiler housing) and my chimney stack is also 6". Burnham boilers are designed to work with a draft hood (mushroom-like air intake along the vent pipe right above the appliance), can't have straight pipe like my old boiler (Raypack). The draft hood it came with was 6" on the bottom, matching the appliance, but it reduces to 5" after the mushroom, which does not match my chimney stack. I suppose it was like that to suit the old implementation. The store had another draft hood, from another model that was 7" at the appliance side and 6" on the chimney side, the latter matching my chimney, which I am now working with:

Wood Milling Gas Cylinder Engineering


I understand it would be ideal to have a 6" straight draft hood but (due to the pandemic?) it seems impossible to get one. My question is, can I put a 6-7" adapter right out of the boiler before the draft hood (can be seen in the picture coming out of the boiler), for the time being, until I can procure a properly sized new draft hood? It would introduce an awkward sequence on the stack going from 6 (boiler) to 7 (bottom of draft hood) back to 6 (top of draft hood and into the chimney)? Will this adaptation cause impeded venting, risking CO hazard?

The adapter does fit in properly as male over the boiler tail and fits in as female into the bottom of the draft hood, to avoid fumes escaping.
 

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No. Draft is very sensitive to sizes and has to be installed correctly. Mixing and matching will not work. Everything there looks too close to the wood.

Why did you get a second hand boiler? The exchangers have fixed lives and is the most expensive part. When it leaks, you'll have to replace it. A 60% efficient boiler is not worth buying unless you barely use heat.
 

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Discussion Starter · #3 · (Edited)
No. Draft is very sensitive to sizes and has to be installed correctly. Mixing and matching will not work.
Can you explain, on a lower level than "won't work", how this particular adapter breaks the proper function of the vent, going from smaller to bigger (which is, as I understand, generally a permitted shift). I would like to know why, is it because the 7" hood opening is too big, etc.
Everything there looks too close to the wood.
I followed the specifications for clearances from the manual. The old boiler was also as close to the wood. The utility room is small.
Why did you get a second hand boiler?
it was making too much noise
 

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Can you explain, on a lower level than "won't work", how this particular adapter breaks the proper function of the vent, going from smaller to bigger (which is, as I understand, generally a permitted shift). I would like to know why, is it because the 7" hood opening is too big, etc.

I followed the specifications for clearances from the manual. The old boiler was also as close to the wood. The utility room is small.

it was making too much noise
I'm pretty sure the clearances for that boiler on the sides are more then an inch. That's what it appears to look like from the pictures.


You need to follow the instructions on the vent sizing. Too big and too small will cause problems possible carbon monoxide poisoning.
 

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Put the correct hood on. And then use a 5" to 6" increaser to go up to your chimney size.

Those hoods are designed to be X height above the boiler. By using the 7" with an increaser on the boiler side. You have now changed how well it will draft the boiler for you. So its a code violation.
 
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