Static Pressure

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Carbon12
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Posts: 2230
Joined: Tue. Oct. 11, 2011 6:53 pm
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice/Anthracite
Other Heating: Heat Pump/Forced Hot Air Oil Furnace
Location: Harrisburg, PA

Post Sat. Dec. 07, 2013 12:48 am

Agreed on the BTU content. The equation gets more difficult when consideration for amount of heat extracted from the coil at different fan speeds is added. Higher fan speeds result in less heat per CF of air being transferred to the air. Not enough fan speed doesn't move enough BTU's. Each coil has a sweet spot between fan speed and water temperature. I've been recording coal usage per degree day. Will see if the fan speed change makes any difference. The fan seems to run for a shorter amount of time each time the TT call for heat. That also means the stoker is running for a shorter amount of time to satisfy the call for heat. I'll be watching it closely. Slower fan speed uses less electricity and is easier on the fan, especially if the external static pressure is decreased. Haven't tested that yet. Delta T across the coil is almost exactly 20 degrees now. I believe that's desirable. House is nice and toasty and that's what, ultimately, really matters :D
The A/C circuit ramps the fan up to high speed regardless of how it's wired for heating. I did put a note on the furnace jacket alerting anyone working on it to what I did,.....and to remind myself! Lol!

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Lightning
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Posts: 8453
Joined: Wed. Nov. 16, 2011 9:51 am
Hand Fed Coal Furnace: Overmodified/Bored out Clayton 1537
Coal Size/Type: Anthracite/Awesome Size
Location: Olean, NY

Post Sat. Dec. 07, 2013 12:51 am

Carbon12 wrote:Agreed on the BTU content. The equation gets more difficult when consideration for amount of heat extracted from the coil at different fan speeds is added. Higher fan speeds result in less heat per CF of air being transferred to the air. Not enough fan speed doesn't move enough BTU's. Each coil has a sweet spot between fan speed and water temperature. I've been recording coal usage per degree day. Will see if the fan speed change makes any difference. The fan seems to run for a shorter amount of time each time the TT call for heat. That also means the stoker is running for a shorter amount of time to satisfy the call for heat. I'll be watching it closely. Slower fan speed uses less electricity and is easier on the fan, especially if the external static pressure is decreased. Haven't tested that yet. Delta T across the coil is almost exactly 20 degrees now. I believe that's desirable. House is nice and toasty and that's what, ultimately, really matters :D
The A/C circuit ramps the fan up to high speed regardless of how it's wired for heating. I did put a note on the furnace jacket alerting anyone working on it to what I did,.....and to remind myself! Lol!
Perfect :)

User avatar
Carbon12
Member
Posts: 2230
Joined: Tue. Oct. 11, 2011 6:53 pm
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice/Anthracite
Other Heating: Heat Pump/Forced Hot Air Oil Furnace
Location: Harrisburg, PA

Post Sat. Dec. 07, 2013 11:30 am

Here's an interim report: With the lower fan speed my external static pressure is .5 WC instead of almost 1 WC. .5 is where the furnace manual says it should be. According to the fan curve chart, the high static pressure reduced CFM so even though I lowered the fan speed I'm essentially moving the same amount of air. With the higher register temperatures it appears I'm moving a lot more BTU's into the heated space. Higher fan speeds apparently don't necessarily equate to higher air flow. It depends on many factors. Will continue to monitor the amount of coal I'm burning per degree day. It may be more, less or the same. Curious to determine which :D FYI,.....all this static pressure, fan speed, flow rate crap is making my head hurt,......I do find it interesting so it's all good. :lol:


Rigar
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Posts: 857
Joined: Tue. Dec. 04, 2012 6:30 am
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace
Location: central new york (syracuse area)

Post Sat. Dec. 07, 2013 1:17 pm

Carbon12 wrote:Here's an interim report: With the lower fan speed my external static pressure is .5 WC instead of almost 1 WC. .5 is where the furnace manual says it should be. According to the fan curve chart, the high static pressure reduced CFM so even though I lowered the fan speed I'm essentially moving the same amount of air. With the higher register temperatures it appears I'm moving a lot more BTU's into the heated space. Higher fan speeds apparently don't necessarily equate to higher air flow. It depends on many factors. Will continue to monitor the amount of coal I'm burning per degree day. It may be more, less or the same. Curious to determine which :D FYI,.....all this static pressure, fan speed, flow rate crap is making my head hurt,......I do find it interesting so it's all good. :lol:
....its a fuzzy science.
...glad to see its improved for you

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Carbon12
Member
Posts: 2230
Joined: Tue. Oct. 11, 2011 6:53 pm
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice/Anthracite
Other Heating: Heat Pump/Forced Hot Air Oil Furnace
Location: Harrisburg, PA

Post Sat. Dec. 07, 2013 1:39 pm

Thanks Rigar! I'm going to have someone local come out in the Spring, if not sooner and do all the measurements and calculations that should be done. The house has a heat pump and I know virtually nothing about those. I just want someone knowledgable about the whole system to suggest changes to make it as efficient as feasible. Unfortunately, the company that installed the system went belly up. Hmmmmm???

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