Howdy. I have an England's 30-NC with an attached 3" vent pipe, ducted and well sealed which inhales fresh air from outdoors. I have plenty of automation going on which I will publish at a later time. My question is: what is the ball park range of CFM going thru the 3" intake vent pipe for this or similar stove. Thanks.
Air intake CFM value - 3" piped-in
- Thread starter Smokey-the-Canuck
- Start date
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Wow. My fan boost design has 6 CFM in there while the stove is running between the 175 Deg F & 350 Deg F range. I kinda under rated, adjustments required. Thanks. Will accept all feedback.
You are running forced combustion air on a stove designed for natural draft???? That probably isn't the best idea
I got this, my stove installation is becoming fully automated including air intake damper and fan control. I read the stove top temperature within 1/2 a degree and my circulation fans control has an integral Alarm to the Damper Control as well there is a thermal cutout on the stove pipe also offering Hi-Limit feedback for that point. My draft is good. Just trying to determine the CFM value for various stove temperature range, mostly the mid operating range. Thanks.
One problem with doing this is that you can get pretty extreme temperature differential between areas of the stove leading to cracks. You can also pressurize the firebox leading to leakage.
Yes, this can turn the stove into a forge if one is not very careful. Flue temps should also be monitored closely.
I was hoping to receive more CFM value related feedback. Thank you for your advice
To ease the discussion, I will say that my automated damper will fully close at the adjustable setpoint of 315 Deg C (600 Deg F) on the stove top and at that time the only air accessing the inner stove is from the stove integral air port holes. That protects the stove fairly well. My electronics also monitor a signal via a thermal cutout for 300 Deg F on the stove pipe 40 inches away from the stove collar. The air intake mini fan application is to supply some additional air only if the stove is between the 85 Deg (185 Deg F) and 125 Deg C or somewhere in that range (tunable). These are all tunable setpoints based on the stove top temperature.
Air intake CFM values for particular stove temperature ranges is the info I'm looking for or anybody's best guess is good enough. Thanks
To ease the discussion, I will say that my automated damper will fully close at the adjustable setpoint of 315 Deg C (600 Deg F) on the stove top and at that time the only air accessing the inner stove is from the stove integral air port holes. That protects the stove fairly well. My electronics also monitor a signal via a thermal cutout for 300 Deg F on the stove pipe 40 inches away from the stove collar. The air intake mini fan application is to supply some additional air only if the stove is between the 85 Deg (185 Deg F) and 125 Deg C or somewhere in that range (tunable). These are all tunable setpoints based on the stove top temperature.
Air intake CFM values for particular stove temperature ranges is the info I'm looking for or anybody's best guess is good enough. Thanks
I really don't know the answer and if I did I wouldn't feel comfortable advising you on how to do something with so much potential danger. Not saying your setup is unsafe I have no idea but there are lots of potential dangers
Stovetop temperature is a lagging indicator. There will need to be correction involved for the hysteresis. Flue temp would be a better primary input with stovetop temp as a secondary input. There really should be no need for additional air with a properly drafting flue system on the stove, especially if the stove already has a boost air intake, which the 30-NC has multiple.
Have you read any of the previous threads on stove automation in this forum?
Have you read any of the previous threads on stove automation in this forum?
I have read a bunch on this forum and many posts regarding pellet stoves of which I am familiar with regarding fresh air / cold air / oxy / combustion and tons on draft. My surface mounted Platinum RTD reads temperature accurately and is linearized even.
I say that the intake fan is set not to come on if the stove top temperature is less than 85 Deg C (185 Deg F). This means that the stove is either on startup and warming (it feeds itself first BTW) or that it is cooled down to a point where there isn't much fuel left to offer any substantial BTUs. At these staged there is little lagging of thermal conductivity .
I say that the fan will not operate above a stove top temperature of 125 Deg C (257 Deg F) because of the tunable setpoint that I have chosen. Beyond that temperature who needs a fan operating in their intake.
For safety, a separate module monitors for temperature alarms on the stove pipe in conjunction with the stove top and will close the air intake damper sealing it very well. My rigid 3" intake duct run has aluminum wrap around every join and Hi-Temp silicone fully seals things at the stove's coupling and its weld spots. The alarm module was primary build to prevent runaways in my case beyond 315 Deg C (600 Deg F) stove top temperature. The same apply to the Stove Pipe sensing device that triggers at 155 Deg C (310 Deg F) situated a foot from the Stainless Steel liner that speaks for itself.
I did read an article about a fellow using a can-processor board and programing to regulate physically the air intake manual lever proportionally to the temperature dictated by his wall stat. Impressive effort. I may go back to comment. I'm not sure about any of his safety features and it does alter the stove. Thank you all for your advice, it is really appreciated and shows that you care. Merci.
Note that I am making external adjustments to the cold side of the stove, not the hot side. I'm still seeking for any data on CFM values for wood stove vents. In my next project I will be controlling the atmospheric pressure, just kidding.
I say that the intake fan is set not to come on if the stove top temperature is less than 85 Deg C (185 Deg F). This means that the stove is either on startup and warming (it feeds itself first BTW) or that it is cooled down to a point where there isn't much fuel left to offer any substantial BTUs. At these staged there is little lagging of thermal conductivity .
I say that the fan will not operate above a stove top temperature of 125 Deg C (257 Deg F) because of the tunable setpoint that I have chosen. Beyond that temperature who needs a fan operating in their intake.
For safety, a separate module monitors for temperature alarms on the stove pipe in conjunction with the stove top and will close the air intake damper sealing it very well. My rigid 3" intake duct run has aluminum wrap around every join and Hi-Temp silicone fully seals things at the stove's coupling and its weld spots. The alarm module was primary build to prevent runaways in my case beyond 315 Deg C (600 Deg F) stove top temperature. The same apply to the Stove Pipe sensing device that triggers at 155 Deg C (310 Deg F) situated a foot from the Stainless Steel liner that speaks for itself.
I did read an article about a fellow using a can-processor board and programing to regulate physically the air intake manual lever proportionally to the temperature dictated by his wall stat. Impressive effort. I may go back to comment. I'm not sure about any of his safety features and it does alter the stove. Thank you all for your advice, it is really appreciated and shows that you care. Merci.
Note that I am making external adjustments to the cold side of the stove, not the hot side. I'm still seeking for any data on CFM values for wood stove vents. In my next project I will be controlling the atmospheric pressure, just kidding.
But why force air into the stove? It isn't needed and comes with lots of potential dangers
I doubt that a 5 CFM boost is going to blow anything otherwise we would neve be able to open the door.
Thank you all for your feedback. I'm thinking that our moderators are probably squinting about this post. I didn't thing it would cause any ruckus or take up bandwidth. Perhaps my next post will be about the smoke inhibitor I put together. Cheers & thanks.
You have 2 very experienced moderators telling you forced combustion air is very risky on a stove designed around natural draft.
Ok, the reason why is, I wish a higher flame for a short period when the stove cooling down because it is almost finished burning the load. That's it. Not interested in coals.
With your displayed knowledge , can you not rig up a device to gage the natural CFM your particular stove draws in a given cycle from start up to embers?
Because of the forge effect causing large temperature differential between the bottom of the stove where the coals are and the rest of the stove. This leads to stress and can cause premature failure. Also forcing air into the stove at the end of the burn when exhaust temps are low (meaning low draft) and you are burning charcoal which produces the largest concentration of CO can lead to co leakage.
Yes I can. One issue is that the CFM sensing device physically obscure the flow, It doesn't restrict it much but even 5-10% accuracy and deviation makes data poor. I could measure via differential pressure, but I'm not extremely interested in the curve because it will vary with atmospheric pressure and of course the load, hard wood fuel. As per the displayed knowledge, not that much there. I still ague with myself and loose the argument. My design will permit me not to use this feature just by turning the set point to a million degrees. I've seem posts on here that others have been successful in adjusting the natural air flow. A 5CFM fan is less than I can whistle. Not much of a flame thrower nor a high pressure device.
Yeah I doubt a 5cfm blower will make much difference one way or another.
Very interest, right cool feedback. I would hope that the small increasing in air flow would increase the heat enough. I have developed and have both a CO & CO2 sensing device. Thanks dude. Will consider this for sure. Could be the deal break I was looking for where the other snowball on temperature fall is more creosote, chit. temp rise would be ok.
You won't be producing any creosote at that point in the burn at all. You are just burning charcoal
You are clearly very intelligent and tech savvy. I don't doubt you will make this work. I just really don't see that forcing air in has that much benifit. Especially considering the risks
Everybody is right. I think that my set constraint of the operating temperature being above 85 Deg C (185 Deg F) as I specified, could potentially still have burning wood. I think I will test it on a few burns and take some various measurements. The project is not complete yet anyway.
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