[mike136]

The motor I have is a 230v with 3 wires and a capacitor I have it working now and would like to install a thermostat. My main question is do I need a two pole thermostat or can the wires be connected to one pole..

[bitters]

Single pole stat is what you need. Your talking 230V so you will need to look on the motor for the amps and then find a stat with contacts rated for the amperage.

[mike136]

So I can connect both lines together at the Stat then to the capacitor. The don't need to remain apart through the cap? I can't find specific literature on this topic.. I am repurposing a ac condenser fan from the outside unit for a attic exhaust fan.

[bitters]

So I can connect both lines together at the Stat then to the capacitor. The don't need to remain apart through the cap? I can't find specific literature on this topic.. I am repurposing a ac condenser fan from the outside unit for a attic exhaust fan.

Is it a 3 or 4 wire motor?

[mike136]

The motor has 3 wires. One is purple and goes to the cap only.. other two go power source -cap -fan.

All wires have separate terminals on the cap. I guess I'm just not sure if the wires can be combined before the cap or do they need to remain separate.

[bitters]

The motor has 3 wires. One is purple and goes to the cap only.. other two go power source -cap -fan.

All wires have separate terminals on the cap. I guess I'm just not sure if the wires can be combined before the cap or do they need to remain separate.

Sorry I missed that on your first post. You will put the stat in series with the black wire.

[mike136]

So the Stat will interrupt one leg of power only. What will the power that is still flowing on the other leg do? Or because one leg of 110 is removed there is no circuit. And in turn no 220.I'm trying to build a understanding of the way the current flows.and don't want to wreck my fan.

Your pic doesn't work

[bitters]

So the Stat will interrupt one leg of power only. What will the power that is still flowing on the other leg do? Or because one leg of 110 is removed there is no circuit. And in turn no 220.I'm trying to build a understanding of the way the current flows.and don't want to wreck my fan.Your pic doesn't work

Hi Mike, With one leg open you won't have any power flow. If you measure from one wire to ground you get 120 Volts. If you measure across the two wires you get 230 Volts. Some AC units use a single pole contactor, it works. Don't know what is going on with the pic, I can see it.

[mike136]

Thank you. That does make sense. Maybe the pic doesn't work on phones. It's OK.
I was not fully sure if removing one wire was sufficient to safely open the circuit. With power going to the capacitor on the other leg. Is it still charging the capacitor with the one wire connected. Can you explain or know where I can read about this.

[ma0641]

A capacitor holds a charge, electricity doesn't flow through, it flows in and then out to the motor when starting. If you remove the power lead from a capacitor, it will still give you a big shock. The power lead has the thermostat and has nothing to do with the capacitor. When the thermostat opens, no power flows through the circuit. Think of a 120 VAC line, power in on black and out on white. The 120 lines on a 240 VAC system are opposite phase, they are not on the same line, that's why they are connected together, each other breaker goes across to the other side. If you try to make 240 from 2 120VAC lines and they are not phased, you will only get 120VAC. It is true that the leg without the thermostat will show 120 VAC to ground but nothing between the lines with the thermostat open. BTW, this would have been a much easier project with a 120 VAC fan.

[mike136]

Now the fan was free and works great so easier is not free ma6041. There are three wires on the fan purple that goes between cap and fan only and two others that go from the fan to the panel with power from each going to the cap on separate terminals (3 on the cap).

The power lead is connected to a terminal on the cap.

[mike136]

Thanks for the info you gave ma0641.I still have more questions though.but I don't know how to ask

[mike136]

Been trying to get this straight..researching what I can find..
It's a dual run capacitor. The black wire don't need to be connected to the cap. Is that correct? It was in the condenser but I'm thinking it was only for the compressor.
So one line to common on cap thru to fan
Other line to black on fan
Purple on fan to fan terminal on cap as it was.
And the proposed single pole thermostat on the black fan wire??
And it's OK that the other line remains hot to the cap and motor all the time why..

[bitters]

Been trying to get this straight..researching what I can find..
It's a dual run capacitor. The black wire don't need to be connected to the cap. Is that correct? It was in the condenser but I'm thinking it was only for the compressor.
So one line to common on cap thru to fan
Other line to black on fan
Purple on fan to fan terminal on cap as it was.
And the proposed single pole thermostat on the black fan wire??
And it's OK that the other line remains hot to the cap and motor all the time why..

If you are using a dual cap, use only the fan and common terminals.
Yes stat will open the black wire.
Even wonder how a bird can sit on a 13,000 volt power line? The air around him is insulating him from being grounded. So the bird is not ""hot". Think of the cap as that bird.

Hope this helps.

[ma0641]

Mike 136-Read #10 again. No phasing with 1 line not hot.

[mike136]

Yes bitters it does very much. I was just not understanding that phasing is the circuit. Now I do. Just wanted to be sure. For safety. Thank you

My problem was with the phasing part. In my mind I pictured each line as a independent thing not realizing that without one the other won't work. Through the line out the ground.. but it goes line to line back and forth.. I'm still intrigued by how two hot lines pass power back and forth.

[hkstroud]

Your original question was whether you should use a single pole or a double pole thermostat. A single pole thermostat will make the system work because you only need to interrupt one of the input lines to break the circuit. From a functional prospective it will work just fine. However, because this is a 240V circuit I recommend a double pole thermostat. While interrupting the circuit any where will stop the motor from running, it will not stop the capacitor from charging and discharging with each cycle. Therefore, for the life of the capacitor I would use a double pole thermostat.

Your wiring with a single pole thermostat would be;
Line-In 1 to the thermostat.
Line-In 2 to one of the motor leads
Output terminal of thermostat to the common of the fan start capacitor
and to the other motor lead.
Fan terminal of capacitor to fan start lead (purple).

Note that with this arrangement, one plate or the other of the capacitor is continually being charge and discharged. Even though you have interrupted the circuit to the common of the capacitor, the other plate of the capacitor (the one marked "fan") is contentiously being charged and discharged from the common of the motor, through the start windings and the centrifugal switch (because it is closed when the motor is not running). This would have to have an effect on the life of the capacitor.

Therefore, while a single pole thermostat will work, I recommend a double pole.

Footnote.
Presumably you are putting an on/off switch in this circuit. This must be a double pole switch.
For personnel safety, since the capacitor will most likely not be enclosed, you should insulate the unused compressor terminal of the capacitor.

[mike136]

Hkstroud.. that was the thing I was concerned about.. if it is only a danger to the life expectancy of the capacator that's OK by me.. but if it can damage the motor or be a fire hazard that is obviously not. Form what I gather from you and everyone else I'm good to go here.. and now have a good understanding of what's going on here..