Need for pedestal box under furnace

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  #1  
Old 04-13-20, 07:57 AM
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Need for pedestal box under furnace

I am upgrading my HVAC system. Received two bids. Exactly same equipment. One contractor said I need a pedestal box under the new furnace to allow for proper airflow. The other contractor said the existing ductwork is within specs. How would I know?

NEW (American Standard)
Gas Furnace : S9V2C100U4PSBA

OLD (Lennox)Gas furnace: G51MP-48C-110-01

Thanks for any advise!





 
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Old 04-13-20, 08:00 AM
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To start, do you really need 100k BTUs worth of heat, or are you just going off of what’s there?
What is the current duct setup?
 
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Old 04-13-20, 12:36 PM
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Regarding BTU’s, not sure how to tell. current system is a G51MP series unit.

The vertical return “duct” dimensions are: 26” x 13”. This connects to furnace via a horizontal segment (with filter) with dimensions: 24” x 19” x 6”.

Hope this helps.

thanks
 
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Old 04-13-20, 01:13 PM
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Ask the bidding contractors how they determined what size furnace to install.
The model number indicates you had around a 100,000 BTU furnace. That’s a large capacity unit, could go back with a smaller furnace that would operate better.
 
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Old 04-13-20, 01:41 PM
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Thanks for info. This will heat the main level of my house. It is 2600sf, with some ceilings up to 20ft. Do you think 100 000 btu too much?

Back to the original question, assuming I go with the new proposed furnace, do I need a pedestal or you think not?

thanks
 
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Old 04-13-20, 01:56 PM
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100,000 BTU could very well be too large of a furnace for that space.
Equipment isn’t sized via square footage.
It’s done via AHRI approved manual J calculations.
You can try your own here-

www.loadcalc.net

A furnace that’s too large is just as bad as one that’s too small.
 
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