SpudFiles

I want to install an AC fan on top of my chimney to improve the draw so we can actually use it in winter. I figure this fan even on the high setting probably won't draw more power than the heat pump and associated fan, so we should save money! Only trouble is that it comes from the same device I got my compressor from, so I'll need to do some reassembly, and help relating the device to the diagram. I have the original capacitor, and I don't see anything other than that and the fan in the diagram, so I think I have all the parts I need, it's just an issue of what to connect to what.

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Yes, I realize I'll have to find a way to reverse the fan, since the current configuration would probably overheat the motor.

It seems that you can choose the power level (hi, med, low) by switching between the three cables

now would you really save money ?? I don't know

it would be a better idea to install some sort of recuperator that would save energy

saefroch wrote:
Yes, I realize I'll have to find a way to reverse the fan, since the current configuration would probably overheat the motor.

Why would it overheat the motor.

I'd have to reverse it to draw air up, no? I could try wiring it backwards...

Or you could just turn the whole fan around.

Also, have you looked into maybe using something like a gable fan?

To reverse the motor the phase of the main winding needs it's polarity reversed from normal. Because the main is 3 windings for 3 speeds, the simple job is to reverse the two leads of the start winding. This is the winding with the cap. This will require internal work on the motor and a meter. Internally one end of the run and start windings are connected together and are brought out on wire 20. Inside the motor the Wire connects to both the windings. Find the connections and separate them. Move wire 21 to the start winding removed from the connection and take the winding lead that was connected to wire 21 and connect it into the common. This will reverse the start winding polarity and make the motor start in reverse.

The bad news is this connection is often buried in the winding and requires surgery to expose it. It is rarely brought out on it's own lead so it is easy to swap.

To run the fan in the current configuration, simply refer to the diagram. Connect Line (power to the two leads as marked. One power lead goes to the cap and the motor wire #20. The other end of the cap connects to wire #21 as shown. The other power lead connects to only one of the remaining 3 wires depending on which speed you wish to use. #22 for Hi, #23 for Med and #24 for low. Two of the three leads have to remain not connected.

What is a gable fan? I'm sure I could purchase and install one, but that costs money... and this could be free.

Tech, it seems like you drew inductors, which leaves me horribly confused. Is it even possible to wire this up with just a switch and a capacitor, or do I need other elements from the original device?

^I think tech was just drawing the windings, saefroch. The top is the start and the bottom are the three run coils... but yes, technically they are inductors

Just to clear this up... is your fireplace/woodburner getting its air directly from the outside, or is it sucking it in from the room? I'm not sure you'd save much money if it's drawing cold air into the house when it's burning.

But in any case you might want to put an oven thermometer where the fan will be... it could potentially get pretty hot.

The fireplace draws in from the room.... but that's moot if I need circuit elements I chopped them off and recycled them all.

Could this fan run on DC? Is that what the windings are for, rectifiers?

The windings are what cause the fan to rotate... ya know, electromagnetism an all that rot.

The AC motor will run at 0 RPM on DC. RPM and AC frequency are related. DC on an AC motor is often used as a brake, such as on skill saws and chop saws.

I'm no expert, but you might want to somehow make the installation temporary before you think of permanently adding the fan to your chimney for several reasons. This is mainly conjecture, but it's possible that some of these points might be a concern.

1. Increased air draw might make your fire burn hotter and thus save energy, but it will also eat up more firewood, potentially costing more money if you're like me and you don't have access to lots of free firewood.

2. How loud is the fan? If you have to run it whenever you build a fire to keep the motor from overheating, the nice crackling of your fire might be drowned out by the noise of the fan.

3. Wouldn't increasing the air draw mean that more of the fire's heat would be sucked up into the chimney?

4. With air from the house being forced out of the chimney, wouldn't cold air have to be sucked in from outside, potentially cooling the house down more?

The issue with the chimney right now is that there is not enough draw to get all the smoke to go up the chimney. It just goes backwards into the house, and fills the downstairs with smoke. Not pleasant.

What are these mysterious windings? Are they just inductors that need to be in series with the AC power source?

See this for an explanation for multi speed PSC AC motor typically used for blower fans.

http://www.electrical-contractor.net/fo ... Post148744