Thought I had it this time

FranklinD

Well crud.

Woke up to a cooling house this morning...about 30 seconds after I awoke I knew the boiler was having a "seizure" of sorts. Ran downstairs, tossed on my shoes, and ran out into the snow and -5 wind chill to knock the frost accumulation off of the boilers air inlet screen. Had to remove the screen from the 3" PVC altogether as it frosted over again within 20 minutes. The wind was *just* right, blowing a combo of snow fluff and boiler exhaust up to the intake (4 feet above and 3 feet laterally away) and frosting the bug/bird screen I installed in September. Back to the old drawing board! Anyway...thought I'd share with you two very different forecasts from the last year. This area can get some interesting weather...Lake Superior does some strange things and drives forecasters crazy. We were just predicted to get 10-16", ended up with 2". That's happened 3x this winter so far. It's been a balmy -1 to -9 all week long. We're predicted to be at -20 to -30f tomorrow morning. Gotta love them big cast iron radiators!

FranklinD

Forgot to specify...I'd be at the "Duluth" part of those weather maps. I believe the first one was from last January, and the second was from July or August this year.

Paul48

Snow fencing?

hot_rod

Can you pull intake air from inside the building ?

I noticed all the boilers in commercial buildings that I visited in Fairbanks had intake air from inside, piped up near the ceiling

Gary Jansen_4

Did I read your post correctly? It sounds like your exhaust is below your intake? Can you post a picture?

JUGHNE

I put a PVC wye in the inlet near the furnace/boiler. It is installed so as to collect any moisture or dirt....somewhat like a strainer configuration. The lowest portion has a CO plug. The plug is drilled with an 1/8" bit to allow any moisture that forms to drip and be noticed. In a horizontal run it adds no fittings to the resistance flow calculations and if in the vertical then the 45 is used to transition to the horizontal. The unused run opening gets the CO. If air inlet plugs the HO can remove that plug for inside air until the problem is corrected.

On a couple of difficult cases I installed a single or double Tee just inside the building allowing some inside air or mix of both.

Solid_Fuel_Man

I've thought about pulling combustion air from a well vented attic space. Go straight up with exhaust like a sewer vent with intake below the roof decking. Never have asked any manufacturer or code compliance though. Have yet to try it or see anyone else do it.

hot_rod

Solid_Fuel_Man said:

I've thought about pulling combustion air from a well vented attic space. Go straight up with exhaust like a sewer vent with intake below the roof decking. Never have asked any manufacturer or code compliance though. Have yet to try it or see anyone else do it.

The boiler in my house I have intake air from the attic, just under a ridge vent. I put regular window screen over it to keep bug out.

If the volume is adequate I believe the manufacturer allows intake from within the room, Would an attic be the same?

Solid_Fuel_Man

We get lots of wind driven snow which finds its way into places water never should be. When I was first married we lived in a small apartment which was previously a free standing two car garage. 20x24' slab with 4000 watts of electric baseboard. My father-in-law was our landlord (we paid rent) and he allowed me to install a Rinnai wall furnace and a propane clothes dryer.

Well that slab-on-grade and the Rinnai's concentric vent 16" off the ground in northern Maine was a bit problematic. I kept it shoveled out well but the snow would make it go out on flame failure when we had some wind. My cheap as possible solution was to build a little plywood dog house over the near ground level vent and that solved the snow intake problem. Don't miss that place. But we saved enough money to build our own home 2 years later.

Solid_Fuel_Man

@hot rod I would consider an attic the best snow filter and with good ventilation no matter the size will have infinite air supply. In my tight house when the clothes dryer is on I have trouble starting a fire in our woodstove. Reverse draft in the chimney until I open a window. My wood boiler is induced draft so not an issue, but combustion air is at a premium.

I just don't know if a manufacturer would object to a vertically vented boiler with a shorter intake or maybe it wouldn't matter. Or some type of code issue, when I go with a mod-con as backup in my own house my plan was attic air.

@Hatterasguy I would put an increaser on the end of the intake and then put the screen on with a large zip tie for more surface area.

hot_rod

Solid_Fuel_Man said:

@hot rod I would consider an attic the best snow filter and with good ventilation no matter the size will have infinite air supply. In my tight house when the clothes dryer is on I have trouble starting a fire in our woodstove. Reverse draft in the chimney until I open a window. My wood boiler is induced draft so not an issue, but combustion air is at a premium.



I just don't know if a manufacturer would object to a vertically vented boiler with a shorter intake or maybe it wouldn't matter. Or some type of code issue, when I go with a mod-con as backup in my own house my plan was attic air.



@Hatterasguy I would put an increaser on the end of the intake and then put the screen on with a large zip tie for more surface area.

I have a small pot belly wood stove in the living room. I installed a combustion air vent directly to that also, from the attic.

It has a damper and a round connection underneath, so I used some large EMT to make a nice one piece intake tube.

FranklinD

Thanks for the comments!

The arrangement is far from ideal, honestly. It's a power vented burnham esc, so the pipe comes out and drops on a 45* to their vent cap...about 24" off the ground. I know it's not high enough. The air inlet comes out about 12" to the side of the exhaust, goes up 60", and then there are 2 90's. There's a fence about 15' down from the vent/intake. The problem crops up when the wind is just right, windmilling fluffy snow up off of the fence. It kind of cyclones around and reaches the intake, slowly plugging up the heavy wire screen in the PVC opening. I guess I just have to leave the pipe open...the oem intake and the screen both "grab" the frost and snow, gradually plugging up, though I can see it building up on the sides of the PVC too.

I may end up installing a wye in the basement, just so the interior air is an option. Interesting thoughts about non-conditioned attic space.

rick in Alaska

Our local gas company will not let us use combustion air from the attic. They say too much heat will migrate up it in the off cycle and cause condensation issues on the roof decking. Not sure how much warm air can go up a combustion air intake, but guess it is possible.
Might be a good idea to check with the local powers that be first.
Rick

Gordy

rick in Alaska said:

Our local gas company will not let us use combustion air from the attic. They say too much heat will migrate up it in the off cycle and cause condensation issues on the roof decking. Not sure how much warm air can go up a combustion air intake, but guess it is possible.
Might be a good idea to check with the local powers that be first.
Rick

That would certainly seem to be a concern to me. Especially up in your climate. Any condensation in the attic space could lead to future issues unknown to the owner until it's to late.

I'm sure the intake could pull air from the conditioned space during non operating periods.

JUGHNE

-15 here this morning. Had HO clean outside air inlet of powder snow. He will leave the basement CO plug out until the heat wave of +30 hits here Monday.

BobC

A screen only has 63% of ope space so it can restrict the airflow if used on the air intake.

I use outside air for my Carlin ezgas. I ran a 4" duct from the ezgas shroud to a 4" hood connector in one pane of a cellar window (has 3 panes). That 19x32" window has a widow screen over it but the area of the screen is so much larger than the duct it does not restrict the air flow.

Bob

Fred

Isn't there an operational and code requirement that the intake and exhaust have to be in the same atmospheric zone?

BobC

This is on a cast iron steam boiler. A sealed combustion system would be a different kettle of fish.

Bob

hot_rod

Different opinions on air from inside and at a different location. Lochinvar Knights suggest intake air for commercial applications?? Not sure how a commercial application differs from many of the McMansions these days as far as boiler size, building square footage, etc.

The boilers I saw recently were at wholesalers in Alaska in commercial applications. And yes they were loud when pulling air from inside.

rick in Alaska

Hey Hot Rod is that cpvc vent or polypro? I can't get any of our suppliers to get us cpvc, and I can't stand the look of the clamps that the polypro uses. Just looks tacky, and I still don't trust the o-rings. Seen too many around here on various systems where the o-ring was just gone.
Rick

Solid_Fuel_Man

Same here Rick, there was a recent boiler room picture and I had never seen cpvc before. Only in the CTS that is used for potable water.

hot_rod

rick in Alaska said:

Hey Hot Rod is that cpvc vent or polypro? I can't get any of our suppliers to get us cpvc, and I can't stand the look of the clamps that the polypro uses. Just looks tacky, and I still don't trust the o-rings. Seen too many around here on various systems where the o-ring was just gone.
Rick

Poly on the vents I think, and ABS for the intake air. New boilers this summer at Frontier in Fairbanks.

I've heard the gaskets are the weak link with the poly, especially on horizontal runs. I think adequate support to prevent droops, and a steep pitch, more like 1/2" per foot to keep the condensate off the gaskets.