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Troubleshooting forced air blower

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68bucks

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I have a forced air wood burner to heat a shop. It sits outside and has duct to blow the air inside including a return air duct. The return is about 12' long 12" round. The supply is 10" round with about 9' of run and enters the building through a 12" duct. The blower is rated at 1800 cfm, has a 1/2 hp 1075, 3 speed motor. I don't have a real good way to measure the actual air flow but I don't thing there is any way this thing is putting anywhere near that much out.

I have checked rotation wiring etc and I can't put my finger on the problem. The motor is a direct drive, split Capacitor, OAO motor. I checked the capacitor and it was border line so I replaced it, no help. I'm not sure of any other way to determine if the motor speed is correct, I don't have a tach, and I'm not sure what the heck else to look for. I attached a couple pics of inside the blower enclosure and the over all layout. Please excuse the bucket duct supports I'm still working on the install.
 

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68bucks

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I figured out the problem. Tore the fan enclosure back apart and determined that the blower was in fact running backwards. I switched the leads for rotation and have all kinds of air flow.
 

oldognewtrick

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I figured out the problem. Tore the fan enclosure back apart and determined that the blower was in fact running backwards. I switched the leads for rotation and have all kinds of air flow.
Good deal, we love happy endings.

I have to ask, why the long duct runs on the supply and return?
 

68bucks

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The duct run was mainly determined by where I wanted to set the heater and where they had to go through the wall. The supply is only about 10', the return is about 12'. If I could have turned the heater 90 degrees I could have shortened them a bit and saved an elbow but there is a tree in the way. Beside the 90 it would have only saved a couple feet of run.
 

bud16415

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Most around here are using hot water, run underground in insulation. Yours is the first I have seen hot air.

Our friend has one he heats his house with and he put the outside burner in a good size pole barn and he stores a years worth of wood inside the pole barn.
 

68bucks

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I don't want to burn this every day so a boiler would require antifreeze and that has its own issues plus a boiler isn't the best thing to heat cycle a lot. That is what lead me to a forced air system. There are a lot more options for outdoor boilers. I'm thinking about putting a system on the house in the future. That would be a boiler set up similar to what you described only in a small shed.
 

bud16415

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I don't want to burn this every day so a boiler would require antifreeze and that has its own issues plus a boiler isn't the best thing to heat cycle a lot. That is what lead me to a forced air system. There are a lot more options for outdoor boilers. I'm thinking about putting a system on the house in the future. That would be a boiler set up similar to what you described only in a small shed.
That seems logical.

There is something nice about bringing the heat in but leaving the dirty wood and bugs and smoke outside.
 
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