208-Volt to 240-volt Machinery Conversion

Woodshop owner moves from a shop with 240-volt power to a shop with 208-volt power, and has to figure out how to adapt some older machinery to the new situation. March 3, 2009

We are moving some equipment from a shop that had a 240-volt delta service to a shop that has a 208-volt "Y" service. We want to make sure that we don't fry these motors when they get juiced up. I'm thinking the best source of information would be the manufacturer. We're having a problem locating two vendors. One of our machines is a 10HP whirlwind (model S-24004).

Can anybody point me to information about wiring requirements for this machine? We also have a SAC planer RS-63. Does anybody know who represents these machines these days?

Forum Responses
(Cabinetmaking Forum)
From contributor D:
If the mortors are rated 208/240/460 you should be okay, if they are 240 then you may need an electrician to rewire the motors.

From contributor K:
Check your motors to see if they are 208 wye or 208/240 delta. If they are 240 delta and your power is 208 wye then you will need a dry type transformer, no big deal but it will be needed to keep the motors happy.

From contributor P:
Dropping voltage from 240 to 208 will increase the amp draw. This means that you may need to use a larger supply breaker from the panel. You mentioned the SAC machine. It's made in Italy and as a rule they use a 230 volt motor (maybe 230/460 volt). If you work from a rule that motors will operate on plus or minus 10 percent of its rated value then you should be fine.

The real question is about the motor starter or switch that turns the machines on. If the machine is equipped with a magnetic motor starter/contactor, then you could possibility have the contactor chatter when you try to operate the machine.

If the machine has a magnetic switch/contactor and you have chatter when you operate on a lower voltage then you will need to change the coil inside the switch/contactor. Take it to Granger's or an electrical supply that handles these parts.

From contributor A:
The only problem I've ever seen was wiring down to 120 using the 208 leg, will fry the motor fast.

Ive never had an issue with three phase equipment. Ive never had any problems with starters either, all being 220 volt was most likely why.

From contributor D:
I just went through this but in the other direction. I have 208v and needed 230V its a very simple process of purchasing three voltage converters (one for each line). Depending on your system, you may need four if you have a four wire system. I get the Wye and delta mixed up in my head as to which one is three and four wire. I think they were $50 each at the local electrical supply house. Its pretty simple to hook up - three wires going in and three wires coming out. If you are not comfortable with electricity, definitely get an electrician and make sure everything is rotating in the correct direction when finished. If you get it wired backwards, everything is going to turn backwards.

From contributor J:
The electric company should be able to change the leads in the transformer and get you the required voltage. When they were putting power to my shop they had to do this it took them about an hour.

From contributor D:
It's not the leads, it is the transformer on the pole. If you go out and look on the transformer, there will be a sticker on the sides of them indicating the voltage (120/208 120/230 and etc.).