My Thoughts on Power Venters and Barometric Dampers

OK, No expert here but I would say I'm pretty versed in the concepts of draft and the operation of a forced draft system. in my month of monitoring my manometer and power venter I have had a three day stretch that changed my views on Baros.

I WILL be installing a Baro damper, BUT it will be capped 90% of the time.

90% of the time the PV has no problem maintaining the .04" draft. But, when the noreaster blew through and the wind was 20-30kts and gusty there was no way to maintain the draft. Even an automated system would not have been able to keep up with it.

I don't think it is worth it to me to leave it uncapped because I DO loose room heated air out the damper even when closed. And again 90% of the time the draft is stable. But those few days it would be better to run the PV at .08" - .1" or so and let the Baro open to relieve the vacuum. Better than having to shut down or risk exhaust gasses enter the house.

leaving this here for any other PV/coal folks that come along!

Happy Heating!
Dan

Hi Elfmaze, I understand your point but I wanted to add one item that I think you failed to follow through with. You mention that when the high winds came through your power vent was unable to keep up, do you mean keep the draft down too -.04? If it was running at -.08 - -.10 then considerable heat was going up the flue instead of the baro. I am only an expert on my set up and one of my stoves runs without a baro and mpd and one has both a baro and mpd so I see the best of both worlds. I don't mind if some heated air goes up through the baro because with out it I would not have the radiant heat that the baro has saved me and that radiant heat warms everything it reaches. Example: You are in a tanning bed and the room has a window cracked, do you still get a Tan? Mike.

Each install has slightly different characteristics and you will find what works best after some experimenting. I foil my baro during any warm spells just to make sure the draft stays strong enough. In cold weather I keep it uncovered like MA says because I feel the room air I am losing there is more than made up for by the heat not 'rushing' out of the stoker and up the flue.

I re-read the tanning bed thing about 5 times and I still cant figure out the correlation to baro's and draft and poweventers!!

titleist1 wrote:I re-read the tanning bed thing about 5 times and I still cant figure out the correlation to baro's and draft and poweventers!!

I think he meant that you will still get the radiant energy even with the window open.

franco b wrote:

titleist1 wrote:I re-read the tanning bed thing about 5 times and I still cant figure out the correlation to baro's and draft and poweventers!!

I think he meant that you will still get the radiant energy even with the window open.

Right on!

Blast, Despite my best efforts to write that correctly. The PV can pull ten times the draft I need at full power. So power is not an issue. Its control. The draft when set for .04" would be rock steady for the two weeks I was watching it. But durring the storm it bounced from -.02 - .08" The negatives are the ones that concern me because air was coming back down my chimney.

I figure setting the PV draft for .10" and letting the Baro vent down to .04" would prevent the negative draft..... Unless of course the wind gets above 30kts....... Would still suck a lot of air out of the room, But would keep it safe! Negative draft is not acceptable in any case.

Elfmaze wrote:Blast, Despite my best efforts to write that correctly. The PV can pull ten times the draft I need at full power. So power is not an issue. Its control. The draft when set for .04" would be rock steady for the two weeks I was watching it. But durring the storm it bounced from -.02 - .08" The negatives are the ones that concern me because air was coming back down my chimney.

I figure setting the PV draft for .10" and letting the Baro vent down to .04" would prevent the negative draft..... Unless of course the wind gets above 30kts....... Would still suck a lot of air out of the room, But would keep it safe! Negative draft is not acceptable in any case.

After ready this I now understand your situation. The high winds are making your draft go positive and causing a dangerous situation. What kind of chimney do you have? Is it metal pipe on the outside wall of the home?...and is it tall enough? A baro won't cause a down draft but having one, (down draft that is), is reason NOT to use a baro for safety sake.

I reread the thread and I realize you have a power vent exiting the home so no chimney...can a power vent be sheltered from the wind but still exhaust?

Elfmaze wrote:Blast, Despite my best efforts to write that correctly. The PV can pull ten times the draft I need at full power. So power is not an issue. Its control. The draft when set for .04" would be rock steady for the two weeks I was watching it. But durring the storm it bounced from -.02 - .08" The negatives are the ones that concern me because air was coming back down my chimney.

I figure setting the PV draft for .10" and letting the Baro vent down to .04" would prevent the negative draft..... Unless of course the wind gets above 30kts....... Would still suck a lot of air out of the room, But would keep it safe! Negative draft is not acceptable in any case.

Actually, your chimney draft is a negative and -.06 is what you are looking for for example. If the wind is blowing into your stove it has gone positive. There has been some confusion over this and if I am correct, a baro won't do anything for that as it only limits maximum draft to a negative environment.

coaledsweat wrote:

Elfmaze wrote:Blast, Despite my best efforts to write that correctly. The PV can pull ten times the draft I need at full power. So power is not an issue. Its control. The draft when set for .04" would be rock steady for the two weeks I was watching it. But durring the storm it bounced from -.02 - .08" The negatives are the ones that concern me because air was coming back down my chimney.

I figure setting the PV draft for .10" and letting the Baro vent down to .04" would prevent the negative draft..... Unless of course the wind gets above 30kts....... Would still suck a lot of air out of the room, But would keep it safe! Negative draft is not acceptable in any case.

Actually, your chimney draft is a negative and -.06 is what you are looking for for example. If the wind is blowing into your stove it has gone positive. There has been some confusion over this and if I am correct, a baro won't do anything for that as it only limits maximum draft to a negative environment.

Elfmaze,

What you experienced with the wind storm is one of the hazards of a PV. If you had your stove connected to a regular chimney, you probably would have noticed an increase of your draft. This occurs as the wind blows over the top of the chimney pushing the air past the top of the flue thereby sucking more air out of the stove. A baro acts as a safety valve in that if the draft increases past your set point on the baro, the flapper opens and air is drawn through the baro rather than sucking it through the coal bed . On a hand fired stove, this can lead to overfiring if there is no way to control that increase in draft. Or it is just sucking the heat through the stove too fast for it to radiate into the steel of the stove.

Now with the PV, think of it as a window fan blowing the air out of the room to the outside. Along comes thunderstorm blowing directly into that window fan. If the thunderstorm wind is strong enough, the fan will no longer be blowing air from the room to the outside. In your case you could have increased the speed of the PV to counter the force of the air blowing against the PV.

In the case of your PV, is there any way to prevent the wind from blowing into the PV ?? Perhaps a shield of some sort to allow the PV to work at the speed you set ?? Having a baro in conjunction with a PV is there to prevent a wind source from revving up your PV past your set point. If the wind would over rev the PV, the baro would open again preventing the above scenario.

Did that make sense ???

Rick