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| Subject - 3 phase service & 1 phase motor? | |
| JerryB52 |
I have a 120/208V 3 phase service and a 115/230V motor. Can I tie in the motor using only two legs of the 3 phase to make this work? I realize that I'll only have 208V by doing this. I already tried this and after 5 to 10 seconds it will trip the 20A breaker. The nameplate says that at 230V, the motor will draw 10.2A. Should I have the customer get the proper motor? This is for a rooftop exhaust fan. I appreciate any advise. Thanks... 
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| kbsparky | quote: This sounds like the motor is still wired for 120 Volts and as such, it will trip out the breaker as you described with a 208 Volt source.  Check those connections at the motor terminal box to ensure that it is connected for 230 Volt operation. Let us know how many Amps it is using. IF you still have problems with it on 208, you can either: 1) Wire it for 120 Volts, and use a large (30 Amp) circuit on a single pole breaker, OR 2) Install a transformer to boost the voltage to within the motor's tolerance range. |
| JerryB52 | Thanks, kbsparky for the reply. I went out yesterday morning after consulting my Ugly book and you were right. I just had to arrange the leads in the motor for 230 V. It runs fine now. Some of the wiring diagrams on these motors are not easily interpreted. It could also be that it's been a while since I've tied-in a motor like this and am a bit rusty at it. I'll know now in the future to check the leads closely. At least I didn't burn up the motor. Jerry B. |