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Old 12-14-2010, 12:08 PM   #1
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Bryant 345MAV Size Matters?


Full model is Bryant 345MAV048100ACKA This has been in my home in Tahoe (elevation 6200) for 10 years but always seemed underpowered. Does anyone know if this is correct size for heating about 2500 square feet? I've replaced filters, checked for leaks and all the most obvious issues. Thinking of installing some in line fans in ducts furthest away. Curious though if unit is just bare minimum to begin with or what.
UPDATE: what I have so far figured is I need 3.5 ton to 3.7 ton, (88000BTU to 95000 BTU) for zip code 96150, 2500 square feet to 2700 square feet....all roughly speaking but I still cannot find the spec for this model furnace?
Next Update: I found my furnace to be 92,000 BTU so OK, size seems enough but what about fan speed. It is adjustable and one guy said don't use the "high" setting but maybe he's wrong? Should I try the high setting??


Last edited by TruckTahoe; 12-14-2010 at 07:44 PM. Reason: updated
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Old 12-14-2010, 05:33 PM   #2
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Bryant 345MAV Size Matters?


Besides the obvious furnace size question, a lot depends on the tightness of the house and how well the ductwork is insulated and how it was run. Are the duct sizes correct? Has anyone done velocity measurements at the vents?
This should be a fairly easy question to be answered buy someone who knows what he's doing.
Ron

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Old 12-14-2010, 06:19 PM   #3
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Bryant 345MAV Size Matters?


Thanks for the reply Ron. I can only assume the duct sizing is correct and the standard insulation. House is tight, only 10 years old. No velocity test but just feeling the air at the farthest register you can hardly feel the flow. Opinion on adding duct fans?
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Old 12-14-2010, 06:38 PM   #4
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Bryant 345MAV Size Matters?


More Information: In about 1/3 of the 2500 square feet this home has Cathedral ceilings, 20' or so, half of that area is loft though. I wonder if this unit has a BTU rating??
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Old 12-14-2010, 08:04 PM   #5
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Bryant 345MAV Size Matters?


Quote:
Originally Posted by TruckTahoe View Post
Thanks for the reply Ron. I can only assume the duct sizing is correct and the standard insulation. House is tight, only 10 years old. No velocity test but just feeling the air at the farthest register you can hardly feel the flow. Opinion on adding duct fans?
You can't assume the ductwork is the correct size if the flow to these registers vary by too much. Weak flow is an indication of incorrect duct size.
I think you would need the proper size fan. An adjustable speed fan would give you the flexibility to balance the system.
Ron
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Old 12-15-2010, 12:07 PM   #6
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Bryant 345MAV Size Matters?


Thanks for the reply. Any thoughts on changing my fan speed to "High"? I was told by one guy not to go to "high" but without any explaination. I have the manual and see where I move some connections in order to change fan speed.
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Old 12-15-2010, 01:08 PM   #7
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Bryant 345MAV Size Matters?


Quote:
Originally Posted by TruckTahoe View Post
Thanks for the reply. Any thoughts on changing my fan speed to "High"? I was told by one guy not to go to "high" but without any explaination. I have the manual and see where I move some connections in order to change fan speed.
I'd check with the guys in the HVAC forum, but if the only issue you have is a balance issue, the rooms with the correct duct size will now heat up quicker. If the room has a thermostat, it will reach the set temp and shut the furnace off and the cold room will stay cold.
Does the ductwork have dampers? It could be that the system just needs to get balanced.
I would personally bring in a competant heating guy to look at and evaluate the system in total. Right now,all of this is just guess work in the dark(at least for me). There might be other components that are also not working properly that is effecting the overall performance of the unit.
Ron
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Old 12-15-2010, 01:14 PM   #8
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Bryant 345MAV Size Matters?


Thanks, Next trip up to the home I'll try to meet with a guy to evaluate the entire system. I'll also try to change the fan speed setting and see what happens unless someone tells me I shouldn't. Not sure about the fused link eliminating the rollout switch still also?
I'll try to summarize all and post to the HVAC section too.
Thanks again and Merry Christmas!
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Old 12-15-2010, 02:50 PM   #9
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Bryant 345MAV Size Matters?


Quote:
Originally Posted by TruckTahoe View Post
Thanks, Next trip up to the home I'll try to meet with a guy to evaluate the entire system. I'll also try to change the fan speed setting and see what happens unless someone tells me I shouldn't. Not sure about the fused link eliminating the rollout switch still also?
I'll try to summarize all and post to the HVAC section too.
Thanks again and Merry Christmas!
Good luck. Let us know the results.
Ron

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