Phase B, the high or wild leg, is not used as the voltage to neutral is 208 volt.

That guy never met me...or the schmuck at the DAV that didn't want to pay for two circuit breakers.

He probably never met the transformers I use, labeled, "120/208/230"

 

By the way, here is my email to them. My boss doesn't want to supply them with power at all—he wants them to bring a genset— so he told me to write it giving them the worst case scenario. My suggestion was to write it into the contract that we have power available at this voltage and this frequency so that everyone knows what we're giving them—that way, if they come back later and say that this didn't work or something got fried, they can't blame us for it.

Here's the email...

Richard,

I don't mean this in an unkind or flippant way, but let me start by saying that, if I was in your shoes, I'd be looking at getting a power transformer, if not a genset to supply your power.

On the 208/120 panel, we have a spare 30 amp breaker, a spare 100 amp breaker, and a spare 60 amp breaker. Right away, the 30 amp is out of the running because, at a minimum, you need 32 amps. So, that leaves us with a 100 and a 60. To plug into our 60, you will need an ACP6044 Appleton plug (or equivalent), and to plug into our 100, you would need an ACP1044 Appleton plug (or equivalent). That part isn't a problem.

The part that is a problem is the difference between North American 208 volts and UK 220 volts (and I don't mean the mathematical difference of 12 volts).

208 volts is derived by having either a 208 wye wound generator or, in our case, a transformer that has a wye wound secondary. Each individual phase is 120 (nominal) volts when compared to earth, but when compared to one another, the voltage is (more or less) additive so that, between the two, you get 208 volts. Attached is a simple schematic that shows what I am talking about.

In the UK, if I recall correctly, your 220 is obtained by taking one phase (a wire that, when compared to earth, reads 220 volts) and one neutral (that ultimately ties to earth. And, to my mind, therein lies the problem: we would supply you with 208 (two wires that are about 120 volts each) and a ground (which is what you will get from us), but your neutral wire will be tied directly to earth so that, from our perspective, one phase (120 nominal volts) would be going straight to earth and, from your perspective, only 120 volts would be going to your computers, printers coffee pots, microwaves, etc.

Also, you have to take into consideration the differences between 50 Hz (what you need) and 60 Hz (what we generate). If I had to take a stab in the dark, I'd say that your computer equipment will be fine, but what about your ancillary equipment? What about your air conditioners? That would be something to investigate.

And this is why I started the email by saying that I would recommend either a transformer or a generator set.

We don't have enough ampacity on any one plug to supply all of your needs, so there would be no place to connect, say, a sufficiently sized isolation transformer or a 208 to 220 volt transformer, therefore, If you go with the transformer option, you'll have to procure one that's 600 volts (wye) on the primary side and you'll need an Appleton ACP1034 plug or equivalent, plus a 4-wire cable capable of handling more than 100 amps. To be clear: the cable and plug are for the primary side of the transformer to get our power to your transformer. What happens on the secondary side is up to you.

The only other option I can think of is to modify your service panels in your units so that the neutral is not grounded at any point. If you can make such a modification, then your equipment shouldn't see a difference between 208 and 220.

 

I'm a HVAC guy and I can tell you, you can't run a 50Hz compressor on 60Hz because the horsepower goes up with the frequency. A 5 ton compressor suddenly becomes a 6 ton compressor (by the volume of gas compressed), and the motor isn't wound for that much power. It's about a 20% increase in HP.

 

I'm a HVAC guy and I can tell you, you can't run a 50Hz compressor on 60Hz because the horsepower goes up with the frequency. A 5 ton compressor suddenly becomes a 6 ton compressor (by the volume of gas compressed), and the motor isn't wound for that much power. It's about a 20% increase in HP.

Ok, that's going in my email, too. Thanks again, #12.

 

If the star point is grounded all you need do is supply two phases for 208 and a ground.
No neutral involved.
This is identical to using a N.A. 240v supply with a ground and no neutral where the centre tap is grounded.
BTW I have an electricians license for UK, so I know the configuration there..
Max.

 

http://www.ccontrolsys.com/w/Electrical_Service_Types_and_Voltages
Max.