Combustion Air for Solo Innova- Advice Needed

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dogwood

Minister of Fire
Mar 22, 2009
825
Western VA
I will be framing off a boiler room for a Solo Innova 50 in the back of our garage. It will be completely walled of from the garage, door to the outside only. Per code I need to vent 175 square inches of combustion air into the room, either from the main body of the house or from the outside. There are drawbacks to using either outside or inside air. The drawback to the use of inside air is that any smoke from the boiler that escapes could circulate into the house. On the other hand outside air would be cold and would cause heat loss in the boiler room, so I'd prefer to use inside air if possible. Also don't want to take any chance on frozen pipes on days I have to work away from home.

I purchased the Solo Innova specifically as it is supposed to power exhaust any smoke right up the flue when you open the boiler's door (Froling's supposed to do that too). Could anyone with a Solo Innova say if this is true in practice? Do you have any smoke issues with your Solo Innova? If there is a significant amount of smoke that escapes, I'll go with outside combustion air. If not, inside combustion air it is. What would your advice be?

Mike
 
Will the code people let you do a "heat trap" style loop on the outdoor air vent? My feeling is that you'd be better off pulling from the outside air, as pulling from the house just means that you'd be pulling in air that you've already gone to a great deal of effort to heat... Can't do a lot about the cold air coming in when the boiler is running, but a heat trap loop should greatly reduce the heat loss when the boiler isn't running and pulling in combustion air...

In addition, quite aside from any smoke issues, I suspect the code people would be happier if you were pulling from the outside anyway, just because it would mean less chance for any CO put out by a malfunctioning boiler would have less chance to get into the house, and it would mean better integrity in the (presumably required) fire barrier wall between the boiler and the rest of the house...

Gooserider
 
Got an Innova 30. I can open door at anytime with very little to no smoke rollout into room. My unit located in my garage, next door.

I don't have any vent, it just pulls air from the room. I would tend to think you want to use outside air, for the reasons Goose mentioned. Should be able to find a motorized damper which wired to power open, tied into unit. Start fire, fan comes on for boiler combustion, damper opens. When unit shuts down, power off(once power is taken away from damper, the springs will close it), damper closes.

I'm assuming you're doing storage also? I've really like my unit, performs very well.
 
I would recommend the outside air, heat trap design mentioned, if you want outside air. A properly sized duct with its bottom about half way down into a trash bin is all you need. The cold air will be trapped in the bottom of the bin and air will flow only when air is being drawn out of the boiler room.

OTH, is there a way to test your Innova for smoke leakage before you put in a permanent vent to the outside? Remember, that with inside air supply the air moves from the house to the boiler room and out the stack; with a separate boiler room, this might eliminate smoke leakage into the house.

Regardless, combustion air has to come from somewhere, inside or outside.
 
Thanks Jim, Gooserider and Flyingcow. I'd never heard of an outside air heat trap before. Sounds like a good idea. I also like your idea, Flyingcow, of putting motorized dampers on the combustion air duct openings, wired to open when the boiler is running. Are motorized dampers readily available. Any ideas where to get them? I'd like to check one out. Also encouraged that you get negligible smoke when you open your Solo Innova's door. Looks like outside combustion air it is, one way or the other, heat trap or motorize dampers. Thanks again.

Mike
 
dogwood said:
Thanks Jim, Gooserider and Flyingcow. I'd never heard of an outside air heat trap before. Sounds like a good idea. I also like your idea, Flyingcow, of putting motorized dampers on the combustion air duct openings, wired to open when the boiler is running. Are motorized dampers readily available. Any ideas where to get them? I'd like to check one out. Also encouraged that you get negligible smoke when you open your Solo Innova's door. Looks like outside combustion air it is, one way or the other, heat trap or motorize dampers. Thanks again.

Mike

I know that the motorized dampers can be gotten at Graingers, probably lots of other places as well... However I should point out that the ones I've seen don't seal all that tight, so I would suggest that even if you do the motorized damper, you should still do a heat trap as well...

Gooserider
 
I have seen the outside air vent into a garbage can or bin of some sort... it works suprisingly well... very effective, low cost and no mechanical parts to wear or require service.

cheers.
 
The issue with a motorized damper is "fail safe." It works OK with an LP, gas or oil boiler because the firing mechanism can be set not to go unless the damper is open. Not so easy to do this with a wood boiler. I still would recommend the cold air trap.
 
I will likely do both. The local code requires one combustion air intake within a foot of the ceiling. the other nearer the floor. I like the idea of the heat trap but would like to avoid hanging a garbage can near the ceiling. If you've actually seen a heat trap could you give me a rough idea of minimum dimensions, or cubic footage, a heat trap would need in order to be effective for a roughly hundred square inch vent opening. Does it need as much volume as a garbage can to be effective? I will frame a plywood box for the upper vent to function as the garbage can will for the lower vent, code permitting. Thanks for the idea. I would have never thought of it. I had considered putting a flapper over the inside opening, like a clothes dryer's exhaust vent flapper. Might cut down on unnecessary air infiltration on days where it isn't windy. Thanks for the reminder on having the walls meet fire barrier standards too. I think I'll only have to go with 5/8' sheetrock to meet code but I'd better check before they make me rip that out. So many rules, so much to remember.

Mike
 
The air volume of the heat trap isn't all that critical as long as it doesn't become LESS than the wall opening (If it does, then the size of the heat trap becomes the effective size of the opening) Essentially what the critical idea involves is making the air do a "U" bend so that the cold air falls down into the bottom of the trap and then doesn't want to rise back up... You are essentially after the same function as the drain trap under every sink...

My understanding is that the trap will work best if it goes down several times the height of the opening, and then comes back up to exit at the same height or a little higher, but I'm not sure just what the critical minimum dimensions are.

Gooserider
 
I think I get the picture Gooserider. I can create the equivalent of a "U" shaped pipe trap behind the boiler room's sheetrock with some "two-by" material or plywood easily enough. Air enters the top of the "U" on the exterior side of the wall, goes down several times the height of the opening, and then travels up to the top of the other side of the "U" to enter the boiler room. Outside vent on the exterior side of the wall on one branch of the "U", inside vent on the interior side of the wall on the other branch of the "U". Sound right to you? No garbage cans required and will look neat as a pin. If it works well enough I'll forego the mechanical damper. You all have great ideas. Thanks for sharing.

Mike
 
Sounds like it should work to me, long as the cross section of the "U" is the same as the area of the opening. Probably wouldn't hurt to have at least the outer surfaces of the U box insulated, but I don't know that you'd need to go to extremes on that - maybe an inch or two of foamboard in the middle of the sandwich?

Gooserider
 
I ended up using a dryer vent for my boiler room combustion air. It goes through the wall about 3 feet from the floor, and goes up the inside wall to the ceiling. I was told that this way, the warm air will not go down the vent pipe and outside, and the air would be pulled up the pipe when needed.
 
BioHeat Sales Guy, what are your concerns about the mechanical damper that make you strongly recommend against it. You sold us our boiler, so if you think there could be an issue I will certainly follow your advice. Thanks.

Scott your arrangement makes good sense along the same lines as recommended above by others. And thanks Hanson too. Bummer about Baxi moving their manufacturing to Turkey. Hope that's not the equivalent of American businesses being shipped to Mexico and beyond with the consequent drop in product quality. Cheap labor seems to rule. HS Tarm must be turning over in his grave about now.

Mike
 
Bummer about Baxi moving their manufacturing to Turkey. Hope that’s not the equivalent of American businesses being shipped to Mexico and beyond with the consequent drop in product quality. Cheap labor seems to rule. HS Tarm must be turning over in his grave about now.

Mike

I think the original Tarm folks may still be making the same units in Denmark. I think that's the Scantec line that Bioheat offers.
 
I currently use a motorized damper (Honeywell ARD6) that is powered through a transformer connected to the boiler draft fan power. If the draft fan is running, the damper opens and lets air come into the basement. I have an elbow pointing the air upwards so it does not just flood into the basement. Works OK, but overly complicated. I am going to change it to a direct connect air inlet to the wood boiler and use the damper elsewhere on an HRV. BTW: These dampers have a gasket and seal quite well.

My boilers instructions want the air inlet run from the boiler to almost the floor before going anywhere. I think this is to contain any smoke in a back puffing situation. I think that most gassifiers are prone to this issue where the fire is ripping and there is not enough air coming in. They start to breathe in and out of the air inlet and will push smoke out the air inlet if it gets severe. For this reason they also recommend that a dedicated direct connect combustion air inlet be treated as if it were an exhaust vent for clearance purposes.

If the area the boiler is in meets certain volume requirements, then the dedicated combustion air inlets are not a requirement. If they are not required, you have more flexibility on how you implement them.
 
I am going to change it to a direct connect air inlet to the wood boiler

I do not believe that all gasifers are engineered for direct connect to cold outside air. They may perform better or more properly with preheated inside air.
 
You're right Jim. The directions for my Solo Innova state you cannot direct connect. I wish you could. It would certainly be more energy efficient to direct vent in your combustion air.

Mike
 
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