208/240 off of Delta

[rookie4now]

Greetings,

I need to install power to some equipment tomorrow. The spec sheet that was just faxed to me says it requires 208v 30a single phase to the motor and 220v 30 single phase to the dryer.

Unfortunately, the journyman that usually works with me won't be there tomorrow. I can call him, but thought I would try and figure this out.

According to the owner, the building has four wire Delta service. I think I should be able to derive 208 volts from the "B" leg to ground and 240 volts from phase to phase, but I'm not sure how I would get 220v?

Any thoughts?

Thanks.

 

[Minuteman]

Rookie

First, let me say, that 220 volts is a misnomer for a nominal voltage. In most cases, 208 and 240 will work just fine for most motor loads. The only noticeable difference would be to resistive loads, and the difference would be ever so slight.

However, the 208 volt High leg from your Delta system is not a usable voltage and is unstable. Don't even try to connect it to your motor.

 

[sparkzilla]

You need to double check the specs for the equipment. You will only be able to get 120 or 240 from the building system. Motors are usually OK, but some equipment can't handle 240Volt, and you might have to use a buck/boost transformer. I had to install buck/boost transformers for some tanning beds that were rated at 230Volt in a building that had single phase 120/240, as the lamps were burning out from the excessive voltage.

 

[Minuteman]

Let me clarify that. I m talking about about 208 WYE and 240 Delta as nominal voltages that will work for most loads. The 208 volts found on a Delta "B" phase is not usable.

 

[rookie4now]

Thanks for the info. I wll talk to the manufcturer and see if a transformer will be required.

 

[coulter]

... the 208 volt High leg from your Delta system is not a usable voltage and is unstable. ...

Michael -

I would agree that the high leg is un-useable. Although I don't know the code prohibits it - probably can't find a commonly available circuit breaker with the required rating.

My question is: Why is the highleg unstable? I'm not seeing that.

carl

 

[coulter]

... The spec sheet that was just faxed to me says it requires 208v 30a single phase to the motor and 220v 30 single phase to the dryer. ...

Michael and sparkzilla are dead on. Call the mfg back, check the specs, question them close.

I've never seen a piece of equipment that takes two different nominal voltages in the same range. And, unless it was for 50hz, I haven't seen 220V on a new equipment spec sheet in 30 years (maybe 40).

carl