Tip & How-To about Heating & Cooling

A Tip to Remember when Electrical troubleshooting

If you're troubleshooting HVAC electrical problems

230 volt single phase ac
The Common wire or circuit on an A/C or heat pump never has a run capacitor in that line.
The Run wire always has the run capacitor in that line or circuit.

115 volt ac
The Run or Hot wire has the run capacitor and the neutral wire does not.

So if you are tracing wires out in a circuit, if there's a run capacitor, it's the Run wire or Run circuit.
The Start wire always goes to the opposite side of the run capacitor than the Run wire and it is the only wire on that side of the capacitor.
The Run wire goes to the run capacitor, then goes to contactor, compressor, start capacitor or fan, so there's usually two wires on the Run side of the capacitor.

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2 Answers

replace compacitor on Carrier 5 ton 3 phase AC


Your 3 phase unit should not have a capacitor. I'm guessing it's single phase. If it's a single capacitor than the compressor should not be going to it also. To test the motor, common to start plus common to run should equal the ohms you get between start and run. For instance, 1.2 ohms+ 2.2 ohms= 3.4 ohms. Follow the wiring diagram on the inside of the door, send model number!!

Aug 29, 2017 | Carrier Heating & Cooling

1 Answer

wiring of 2hp motor


You need to take advice from the motor manufacturer or reconditioner to ensure you are wiring it correctly.

Typically a basic single phase motor will have a start winding and a run winding. That usually makes four wires for a reversible motor but that can be cut to three if the motor must run in one direction only so the three wires would be start, run and common.

The run is connected to the hot side of the supply and the start similarly connected to the hot side except the start capacitor will be in series. The common wire will require connecting to a neutral and of course the motor body will need a ground unless it is double insulated.

It should be possible to sort which is which using a sensitive ohmmeter.

Jul 03, 2017 | Smith 2hp Pool Pump Motor A O Electric...

1 Answer

I have a miller cp 300. It is wired for 3 phase power. I need to hook it up to 230 volt power. How do I do this correctly.


You cannot do this... 3 phase and single phase cannot be inter used... see 3 phase is 440 V AC, single phase is 230 Vots AC. This is unless the unit has Dual capability, in this case the wiring could only be wired to a Single Phase. of the unit. You will need a slow blow breaker of the correct rating and also the cable must be similarly CURRENT rated. If it IS only 3 phase, you can purchase after market single phase to 3 phase converters, that will allow you to plug the 3 phase into a single phase circuit and work, they quite costly though.

Mar 22, 2010 | Welding Tools

1 Answer

is posible run a single phase electric motor from a source three phase 120/208 wye connection the motor is rated 230 volts AC


It is indeed possible to use ONE Phase to run a motor, You simply use One Phase and Neutral. BUT ONLY if the 3 phase is Double, more or less, the required usage Voltage, EG: 440 3 phase, will be OK, for 220 single phase, . But 220 3 Phase,will not run a 240. single Phase. So in your case is suspect not, it really will do no harm to try though. it just wouldn't work, if not enough "juice", be careful.
http://en.wikipedia.org/wiki/Three-phase_electric_power

Feb 24, 2010 | Heating & Cooling

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