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Mike Warner 10-19-2008 12:53 AM

Help with motor wiring
I have a single phase, 120V AC motor. It has only three wires, hot, neutral, and ground. I want to have a simple SPST on-off switch.

Green ground wire to green motor ground.
White neutral wire direct to white neutral motor wire.
Do I connect the balck hot wire to my 1HP 125VAC rated toggle switch, and the other side of my toggle switch to the black hot wire of the motor? I also plan on putting a 0.25 Amp fuse inline with the toggle switch, as this is the motor's amperage rating.

This is a Watts circulation pump model 500800, which simply plugs into a 120 volt outlet, and is normally controlled by a built in timer. I want to disconnect the timer and put in a switch.

Mike Warner 10-19-2008 01:00 AM

The motor is 25 watts, the toggle switch is rated for 1HP

theatretch85 10-19-2008 03:44 AM

Looks like you got it all figured out. Just make sure the switch is enclosed properly in an approved manner along with the fuse (though the fuse is probably not needed).

Mike Warner 10-19-2008 10:18 AM

Thanks theatretch85. By your handle it looks like you might be a home theater technician. Great field to be in now that the february 2009 digital broadcact date is fast approaching.

I'm going to drill a hole in a solid face non-shattering plastic switch plate, for the toggle switch.

J. V. 10-19-2008 11:00 AM

Hold on Buddy. Size the the fuse at 175% of nameplate. Amps X 1.75 = Fuse Size. You need a fuse that will allow the motor to ramp to full speed. An AC induction motor will draw approximately 8 times the nameplate rating during start.

theatretch85 10-19-2008 12:33 PM

It the motor truly is 25 watts, 1.75 X that would be .364 amps. So you'd probably need a .5 amp fuse if your going to even use one at all. Why do you need a fuse for this motor? Does the documentation for the motor require one to be connected? With such a low load I wouldn't be worried about it. Many appliances that use more power than .5 amps and don't have fuses in them.

Actually Mike, my handle is from working in an actual "theatre" where acting takes place. I also do a lot of work with theatrical lighting and sound for one of my part-time jobs. I do have a ton of experience in home theatre as well. Once I find my new house, it will be fully wired for a home theatre setup and completely wired for a computer data network.

Mike Warner 10-21-2008 11:09 PM

Thanks for the heads up on the fuse J.V. and theatretch85. I just supposed the capacitor alongside the motor provided the initial punch for start up rpm's. The motor is rated for 0.23 amps, so startup of X8 is 1.84 amps. I figured I needed a fuse for extra circuit protection just in case an overly wet finger flipped the switch. Maybe I'm mistaken. It seems from this discussion that a fuse is not needed. There is nothing in the documentation about installing a fuse. Remember I have removed an internal motorized timer from the motor that could be used to preset times when the water recirculator would come on. There was no provision to remove this timer and install a manual switch.

A possible concern is that the motor might be left powered on. It is almost impossible to detect it is running when standing right beside the motor. This motor is located two floors below in the basement from the bathroom location where the manually toggled on/off switch is located. Is there a circuit addition I could add to shut this off automatically similar to an electric laundry iron?

J. V. 10-22-2008 10:01 AM

I don't know if you need the fuse either. Can't hurt. I just wanted you to know how to size a fuse. Do not use my 8X comment for sizing. Name plate amps is what you always go by. The 1.75 multiplier is the correct method.

Your last question is not clear to me. Tell us what you are doing with this motor. You may not want to use a switch. If you only want the motor to run for a period of time and then shut off, a spring timer will work the best.

Mike Warner 10-23-2008 08:37 PM

Its a hot water recirculating pump I want to heat up the shower water so I don't have to let it run down the drain while warming up.

J. V. 10-24-2008 10:52 AM

How long do you want it to run? You can get a spring wound timer for 5-15 minutes or 5-60 minutes. You would just install this timer like a regular light switch. This way if you forget and leave it on, it will shut off by itself. They are usually used for bathroom fans. HD or Lowes has them for about $20.00.

Mike Warner 10-24-2008 07:36 PM

I want it to run for less than two minutes. I did consider an Intermatic spring-wound switch from Home Depot rated for a 1HP inductive load and 250VAC. This definitely would work, but when you need a shower, you don't want to wait for a timer. That's why I want a definite shut-off, with the possibility of a backup timed shut-off. I'm just unsure of putting a shut-off switch in series with the Intermatic spring-wound timer.

Mike Warner 10-24-2008 07:45 PM

My last post got me thinking about the primary and secondary loops on my boiler. Each has a separate pump, and both run when any zone calls for heat.Likewise the recirculating hot water pump can be running at the same time the shower is being used.

If this setup, using only a spring-wound timer, does not appreciably affects the shower water pressure, then I suppose this would be the best way to go. Plus, a series shut-off switch would not be necessary.

J. V. 10-25-2008 11:31 AM

Don't connect the timer in series with the switch. If the switch is off or the timer has timed out, the circuit will be open. Connect them in parallel. This way both devices will work together.

Mike Warner 10-25-2008 08:50 PM

Much obliged for all the follow up posts. Thanks!

beenthere 10-26-2008 08:33 AM

Just use a timer.
There is nothing wrong with the circ running while you are using the shower.

In commercial apps. The DHW loop circ never shuts of.
Its just a recirc.

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