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Does duct size really matter when using ECM2 motor?

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Does duct size really matter when using ECM2 motor? Double A-Ron 01-19-2007
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Posted by Double A-Ron on January 19, 2007, 11:14 pm
Recently replaced my forced air oil furnace with a 5 ton dual speed
WaterFurnace Envision. My HVAC guy told me the not to worry about my
ducting as the ECM motor will overcome the lack of duct size. I mainly
concerned about my return air vents.
Here are some details;
- 2 story house - 2800 sq/ft
- Near Toronto Ontario
- Two supply ducts 12"x8" and 12"x7"
- Two return duct 14"x6" and 12"x8"
- 18 heat registers feed by 5" dia ducts
- 4 return air vents 15"x7" (2 up stairs, 2 downstairs)
- Design heat loss of 63,312 btu/h
- Heat gain 30,000 btu/h
- Furnace blower settings - 1st stage CFM=1500, 2nd stage CFM=1950
Quite honesty everything seems to be working fine...... slight noise
from downstairs return vents, however we're warm. Defiantly much long
run times over oil.
I've read many times the CFM should be 400 per ton (cooling?)..... I'm
nowhere close. So I having trouble sleeping at night not know if I my
ducting is incorrect or I shouldn't worry as the ECM motor overcomes it
by pushing more air. Also adding to my confusing is the supply duct on
the furnace measures only 14"x14".
I'd very much appreciate your thoughts and advice,
Thanks
Posted by <kjpro on January 20, 2007, 12:21 am
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It doesn't matter eh... ? you better get a new HVAC technician!
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12 x 8 & 12 x 7 with a plenum that's 14 x 14... for a 5 ton unit... Oh MY.
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Posted by Steve Scott on January 20, 2007, 9:32 am
Why? His tech is looking to replace that ECM motor down the road.
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--
Make love, not war -- but be prepared
for both.
Posted by <kjpro on January 20, 2007, 2:30 pm
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Retirement plan, Eh? LOL
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Posted by Bob Pietrangelo on January 23, 2007, 7:06 pm
The warranty rreplacement from WFI isn't that great of a $$
--
Bob Pietrangelo
bobp3@comcast.net
bob@comfort-solution.biz
www.comfort-solution.biz
On Time or Your Service Call is FREE
Preventive Maintenance Specialist
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