I understand how 208v in North America is derived, and I understand that it's not the same as 240, but what about UK 220 volts?

We have 208/120 available and a 3rd party crew from Britain is coming here to do a project and their stuff is all 220 vac.

Can they plug right up to our stuff? If I remember correctly, 220 vac in the UK is one phase of 380 volt, three phase and a neutral. Will they experience any problems?

 

208 is 94.54% of 220
In most cases, 5% off is not a problem but I suggest you read the labels and see if the equipment is really 230V or 240V. 14% low could cause problems.
I have been so embarrassed in a moment I could have solved the problem by merely reading the label on the equipment.

 

One thing I didn't think about: the frequency. Theirs is all 50 Hz, not 60.

 

The frequency difference can cause serious problems. Read the labels to see if their equipment is rated for 50Hz/60Hz.
Please check your settings and include something about your location so we don't have to guess where you are on the planet.

 

In case I wasn't clear: Our power generation and distribution equipment is North American-made 480 > 208/120 volts at 60 Hz. A subcontractor from Britain is coming here and they want to plug their stuff up to ours. Their equipment is made in the UK. It's 220 volts ac.

 

You mention US 208v so you must be deriving your supply from a 208 3ph transformer instead of the residential 240.
Generally the items affected by 50hz/60hz will be rpm of any AC motors, other than the Universal variety.
What is the nature of the equipment.
Max.

 

208 is 94.54% of 220
In most cases, 5% off is not a problem but I suggest you read the labels and see if the equipment is really 230V or 240V. 14% low could cause problems.

The difference in voltage isn't worrying to me (actually, none of it is, because it's their equipment, not mine: I'm just supplying them with power). What does concern me is the configuration of their power. To get 208, you must take two phases of power from a wye-wound transformer (or generator) with no neutral. In the UK, if I recall correctly, their 220 is obtained by taking one phase of 380 three phase and a neutral. If this is the case, their equipment will probably not work. And, if they have their neutrals tied to ground, they'll be sending 120 vac straight to ground, which puts them in a very dangerous situation.

 

To get 208, you must take two phases of power from a wye-wound transformer (or generator) with no neutral.

I disagree. I have wired plenty of stuff in the U.S. with only the 208V line in the breaker box and the Earth grounded neutral.

 

The equipment should still work.
The equipment will not normally have the neutral tied to ground, this is done in the service panel, as long as the 208 transformer has the star neutral at earth ground the equipment should be safe to operate.
But knowing the type of equipment would help.
Max

 

You mention US 208v so you must be deriving your supply from a 208 3ph transformer instead of the residential 240.
Generally the items affected by 50hz/60hz will be rpm of any AC motors, other than the Universal variety.
What is the nature of the equipment.
Max.

Well, it's hard to explain, in a way: I work in the middle of nowhere in Saudi Arabia. This company is coming here from England to do some data logging work. They'll be bringing (what we call) skids here. Their skids will look like extremely heavy duty single wide mobile homes, mounted on large I beams. The crane will put their skids into place, and they'll (theoretically) run long, large cables to our power plant and connect to our power.

So, they'll have data logging equipment (computers receiving input from sensors of various types, some shop equipment (a small drill press, a bench grinder and maybe a welder), air conditioning (for the humans and the equipment), etc., not to mention mundane items like coffee pots, microwave ovens, etc.

Modern computer equipment shouldn't have a problem with different Hz, but what about the air conditioner? That's what I'd worry about.

 

I disagree. I have wired plenty of stuff in the U.S. with only the 208V line in the breaker box and the Earth grounded neutral.

Well, I'm not going to say that it's impossible, but I've never seen that. If you take one phase of 208 and one neutral, you have 120, not 208.

 

The HVAC equipment will run faster on 60hz so it may present a problem.
The other bench tools, appliances and P.C's should not be a problem
The important thing is there is a grounded neutral at the supply.
Max.

 

Well, I'm not going to say that it's impossible, but I've never seen that. If you take one phase of 208 and one neutral, you have 120, not 208.

No you take the two phases for 208 1ph and ground the star point.
Max.

 

I didn't use any phase theory to make my circuits. I just looked in the circuit breaker box, found a 208V leg, ran it through a circuit breaker and connected the appliance.

You take this one, Max. I have 204 LEDs going in the Chat room.

 

Well, I'm not going to say that it's impossible, but I've never seen that. If you take one phase of 208 and one neutral, you have 120, not 208.

Are you supplying the 3 phase 208 transformer or is it already in place and an existing installation?
Max.

 

No you take the two phases for 208 1ph and ground the star point.
Max.

Correct. He's that he's taking "the" 208 phase and a neutral and getting 208. He's not.

Unless there's an entirely different way of getting 208 volts than this...

...but this is what we have here and this is what I've seen for years. I don't see how he could take "the" 208 phase and a neutral and come up with 208.

Maybe I'm misunderstanding him and he's saying that he's taking A and B (or B and C or A and C) + neutral, but that's not how I read it.

 

Are you supplying the 3 phase 208 transformer or is it already in place and an existing installation?
Max.

We have 208/120 power available in our power plant.

 

The equipment should still work.
The equipment will not normally have the neutral tied to ground, this is done in the service panel

Right. And they'll have their own service panel. They will run a cable to our distribution center and that cable will supply the service panels in their skids. I would bet dollars to donuts that the neutrals will be tied to ground. So, if they are taking 208 from us, one phase of our 208 is going to be going straight to ground, unless they isolate the neutrals from the grounds, in which case... ???? What happens then? I have no clue, but then again, it's not my problem; it's theirs.

I think I'm going to tell them to bring a genset.

 

I don't see how he could take "the" 208 phase and a neutral and come up with 208.

The power company provided the voltages to the meter. A "real" electrician wired that to the breaker box. I just connected a circuit breaker to a line that measured 208 volts compared to the planet. There were also some higher voltages, like 240v across 2 hot wires, but I can't remember exactly.

Here's a bit from a website:
http://www.ccontrolsys.com/w/Electrical_Service_Types_and_Voltages
Three Phase Four Wire Delta
[URL='http://www.ccontrolsys.com/w/File:3_phase_4_wire_delta_240.png']
Also known as a high-leg or wild-leg delta system. Used in older manufacturing facilities with mostly three-phase motor loads and some 120 volt single-phase lighting and plug loads. Similar to the Three Phase Three Wire Delta discussed above but with a center-tap on one of the transformer winding to create neutral for 120 volt single-phase loads. Motors are connected to phase A, B, and C, while single-phase loads are connected to either phase A or C and to neutral. Phase B, the high or wild leg, is not used as the voltage to neutral is 208 volt.
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The power company provided the voltages to the meter. A "real" electrician wired that to the breaker box. I just connected a circuit breaker to a line that measured 208 volts compared to the planet. There were also some higher voltages, like 240v across 2 hot wires, but I can't remember exactly.

Here's a bit from a website:
http://www.ccontrolsys.com/w/Electrical_Service_Types_and_Voltages
Three Phase Four Wire Delta

Also known as a high-leg or wild-leg delta system. Used in older manufacturing facilities with mostly three-phase motor loads and some 120 volt single-phase lighting and plug loads. Similar to the Three Phase Three Wire Delta discussed above but with a center-tap on one of the transformer winding to create neutral for 120 volt single-phase loads. Motors are connected to phase A, B, and C, while single-phase loads are connected to either phase A or C and to neutral. Phase B, the high or wild leg, is not used as the voltage to neutral is 208 volt.

Man, that is absolutely fascinating! Thanks for posting that.