Testing 480v system

dnjdnj9090 · Oct 7, 2009

Hi there,

i was called to a job by a customer to replace a distribution board that had suffered water damage within a farm building.

The DB i was presented with was 2 - phase, with a measured 250v per phase and 480v between phases. I have never seen these before and no-one in the wholesalers has either, so locating one is a problem in itself.

More importantly though, my test equipment will not carry out a PFC test on 480v equipment. Can i do this through calculation and is it done in the same manner as per 3 phase i.e

(pfc=v/ze)*2

??

Thanks in advance and any information regarding 2-phase 480v installations is much appreciated.

Mark.W · Oct 7, 2009

Dont't know alot about it but 2 phase just means you have 2 seperate 240 volt single phase supplies, a common neutral and earth!

You can obtain PFC by enquiry!

Hope this helps!

acvc · Oct 7, 2009

SPLIT PHASE
I came across an installation like this in a farm in Devon. It was something I had never seen before or since. The farmer said that when it was installed it was called a 'split phase' installation by the electricians.

Wallace-ISL · Oct 9, 2009

Is it not possible to use a standard 3 phase board and connect the 2 x phases and neutral to the same and mark up the 3rd phase ways as blank? / unused
Just a thoought...

is this possible ?

mrloy99 · Oct 9, 2009

dnjdnj9090 said:
Hi there,

i was called to a job by a customer to replace a distribution board that had suffered water damage within a farm building.

The DB i was presented with was 2 - phase, with a measured 250v per phase and 480v between phases. I have never seen these before and no-one in the wholesalers has either, so locating one is a problem in itself.

More importantly though, my test equipment will not carry out a PFC test on 480v equipment. Can i do this through calculation and is it done in the same manner as per 3 phase i.e

(pfc=v/ze)*2

??

Thanks in advance and any information regarding 2-phase 480v installations is much appreciated.

Must be very close to supply transformer,normally you would expect 240/460volts.But I don't see any
reason why you couldn't treat it as 3 phase provided you have it suitably labled up.You should try and balance your load as much as possable.It's unlikely that you would have many loads using both phases,
though I have seen a 400volt single phase welder,and it is also possable to get water heaters running at the higher voltage...They have similar set ups in other countries,eg Canada and USA etc,I think they are known as Edison or split phase as other poster suggests. I think we are lucky over here in that 99% of our supply over here has been standardized to 230/400 volt.

Tester Steve · Oct 9, 2009

Yep, standard 2 phase 3 wire install and common on farms agri etc. As others have said, treat as 3 phase unless both phases are being used, ie 2DB's, then as 2 seperates.

Steve.

Spudnik · Oct 9, 2009

The shop i have just finished was a 2 phase 3 - wire install, and that was in the middle of town.

Reason being,according to the DNO, there were only 2 phases available in the street, apparently.

mrloy99 · Oct 9, 2009

Jason.S said:
The shop i have just finished was a 2 phase 3 - wire install, and that was in the middle of town.

Reason being,according to the DNO, there were only 2 phases available in the street, apparently.

Hi,
There seems to be a little confusion over split phase and two phase.I will attempt to provide clarification.230/460volt would be split phase where the 460 volts are tapped off a supply transformer from a single phase sourse,ie the primary would be supplied at a higher line voltage(1 live wire and an
(earthed)neutral.On the secondary side the windings are centre tapped to earth giving 230volts from each leg to earth....and 460 between lines.
So on a two phase system(derived from two of your three phases) 230/400volt your voltage between phases is approx 400 volts..and your
voltage to earth is 400 devided by square root of three giving approx 231volts.
I came across one years ago in the centre of town but I'm not sure now which of the above categories it fell in,but 400,OR 460 volts on their own are pretty limited in their usage ie,no good for three phase motors.