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Old 01-09-2020, 12:51 AM   #21
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9 amp with no load is too high, there is a problem with motor or connections
I agree......I can't read the nameplate but I'd expect a 1 HP single phase motor to draw about 10 amps full-load at 115 volts and maybe 3 or so no-load.

If both speeds were engaged at the same time, it'd be a lot more than 9 amps, same thing if the start winding was not cut out. About the only thing I can think of is shorted windings on adjacent coil turns. That would cause higher no-load current and much higher full-load current.

P.S. Whatever dunce decided to get rid of the 3Ø and go with single phase should be given a fair trial then shot.
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Old 01-09-2020, 06:04 AM   #22
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I agree......I can't read the nameplate but I'd expect a 1 HP single phase motor to draw about 10 amps full-load at 115 volts and maybe 3 or so no-load.

If both speeds were engaged at the same time, it'd be a lot more than 9 amps, same thing if the start winding was not cut out. About the only thing I can think of is shorted windings on adjacent coil turns. That would cause higher no-load current and much higher full-load current.

P.S. Whatever dunce decided to get rid of the 3Ø and go with single phase should be given a fair trial then shot.
Most likely the utility was pitching a fit about the second transformer and the metering of it probably without a demand meter for a residence. But I thought the same thing, WHY would you tear out three phase and install single, what a step backwards.
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Old 01-09-2020, 08:00 AM   #23
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I agree......I can't read the nameplate but I'd expect a 1 HP single phase motor to draw about 10 amps full-load at 115 volts and maybe 3 or so no-load.

If both speeds were engaged at the same time, it'd be a lot more than 9 amps, same thing if the start winding was not cut out. About the only thing I can think of is shorted windings on adjacent coil turns. That would cause higher no-load current and much higher full-load current.

P.S. Whatever dunce decided to get rid of the 3Ø and go with single phase should be given a fair trial then shot.
Most likely the utility was pitching a fit about the second transformer and the metering of it probably without a demand meter for a residence. But I thought the same thing, WHY would you tear out three phase and install single, what a step backwards.

Yeah the new service was free if single phase and was going to be be a significant cost of 3 phase. The discussion never got far enough to hear how much more expensive.


As far as belts, pulleys, etc I am not very experienced with that stuff. That’s why I told the GC get your HVAC guy to install it and I’ll wire it. But the HVAC guy they hired told them to suck it so they threw it on me. I threw it back on them. And here we are.
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Old 01-09-2020, 01:09 PM   #24
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Both motors are the same HP 3phase or 1phase is not part of the HP equation.

New motor FLA is 12.4A at high speed, you mentioned it draws 20A after the starting current settles down and that is not right. The motor is overloading. You have either wired it wrong or there is something drastically wrong with the motor itself.

My guess is that you connected it for 120V and are feeding it 240V, that will make the motor over saturate and pull high current that is just making heat, not torque, but it will appear to run “normally” because doubling the voltage does not affect the speed on this type of motor.

PS: noticed that the motor can ONLY be wired for 115V, so if you ran 240, there’s the problem. But also, the way a starter/controller changes speeds on a 2 speed 3 phase motor is totally different than on a 2 speed 1 phase motor, so it you didn’t totally change out the speed selection method, it may be what is causing the problem.
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Last edited by JRaef; 01-09-2020 at 01:19 PM.
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Old 01-09-2020, 06:31 PM   #25
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P.S. Whatever dunce decided to get rid of the 3Ø and go with single phase should be given a fair trial then shot.
Judge is out skiing, can we shoot him first then give him a fair trial.
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Old 01-10-2020, 12:43 AM   #26
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Judge is out skiing, can we shoot him first then give him a fair trial.
Yes we can....and since he refuses to answer any questions, we'll take him out back and shoot him again.
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Old 01-10-2020, 02:54 PM   #27
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...P.S. Whatever dunce decided to get rid of the 3Ø and go with single phase should be given a fair trial then shot.
JRaef for the defense, in absentia.


It could be that a previous owner had 3 phase equipment for a home machine shop business, then sold the house. The new owners don't need the 3 phase for anything else and don't want to pay the surcharges that some utilities put onto 3 phase residential service drops and/or the demand meter charges just to run a couple of attic fans. My father had his own home based industrial business and had a 3 phase service drop when he built his house so that he could test machines. After he passed away and we went to sell the house, none of the potential buyers wanted the 3 phase drop once they found out that PG&E was going to charge them a demand charge. So I had to rip and replace his panels.


If you must shoot him anyway, shoot him in the leg but try to miss his femoral artery...
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Old 01-10-2020, 10:18 PM   #28
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JRaef for the defense, in absentia.


It could be that a previous owner had 3 phase equipment for a home machine shop business, then sold the house. The new owners don't need the 3 phase for anything else and don't want to pay the surcharges that some utilities put onto 3 phase residential service drops and/or the demand meter charges just to run a couple of attic fans. My father had his own home based industrial business and had a 3 phase service drop when he built his house so that he could test machines. After he passed away and we went to sell the house, none of the potential buyers wanted the 3 phase drop once they found out that PG&E was going to charge them a demand charge. So I had to rip and replace his panels.


If you must shoot him anyway, shoot him in the leg but try to miss his femoral artery...
The PUCO around here doesn't have a demand charge for my 120/208 3Ø 4 wire resi service. My bill has KWHR only.

Also, back in the 70s there were several subdivisions that had 240 ∆ 3 Ø services. They were a basic single phase split-bus panel with a ∆ breaker that fed the A/C unit. Always FPE.........

And again, the bills had only KWHR on them.

I guess different PUCOs have different charges for different services.
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Old 01-10-2020, 10:26 PM   #29
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3 phase to single phase-cooair-fan-01.jpg

3 phase to single phase-cooair-bulletin-01.jpg To get those fans up and running won't be cheap. The original HVAC guy knew it and quoted accordingly. That's why he was bumped. Those fans are vintage and are probably constructed of steel and cast-iron. If you can get your wiring sorted. You could run each fan with its own 115v motor. Possibly wire one motor on HIGH speed and the other on LOW. That may add some adjustability to the two motor scheme. There appears to be motor mounting slots prepunched in the centre of each fans support braces. OR you could run a larger HP 230v motor for both. Good luck
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Old 01-11-2020, 02:13 AM   #30
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P.S. Whatever dunce decided to get rid of the 3Ø and go with single phase should be given a fair trial then shot.
Judge is out skiing, can we shoot him first then give him a fair trial.

Thought I Said it earlier but the service was moved about 500’ on the property. It was free to move it single phase and it was going to be very expensive to keep the 3 phase. When told this the homeowner decided to go with single phase.
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Old 01-11-2020, 02:16 AM   #31
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Attachment 139654

Attachment 139656 To get those fans up and running won't be cheap. The original HVAC guy knew it and quoted accordingly. That's why he was bumped. Those fans are vintage and are probably constructed of steel and cast-iron. If you can get your wiring sorted. You could run each fan with its own 115v motor. Possibly wire one motor on HIGH speed and the other on LOW. That may add some adjustability to the two motor scheme. There appears to be motor mounting slots prepunched in the centre of each fans support braces. OR you could run a larger HP 230v motor for both. Good luck
Yeah I felt from the beginning the motor is too small but the “motor guy at Grainger says it should work” is what I have heard.
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