2 phases in domestic bungalow??

[Toby Kuhnert]

Hi Guys, Popped over to a bungalow yesterday that a mate of mine has bought to renovate, asked me to have a look at electrics/what might need doing and I found this... 2 phases (red and yellow) in a bungalow with 2 bedrooms?? bit ott i'm thinking? lol. Although the DNO have only supplied a meter for red phase, leaving yellow phase fuse just sitting there. Has anyone seen more than one phase in such a small domestic building before?? It isn't a farm or anything that I see could require such a large supply... its in a small village in the middle of a few other bungalows...

 

[Marvo]

... its in a small village in the middle of a few other bungalows...

I believe you occasionally get 180 degree split phase systems in rural areas. What's the voltage phase-phase?

 

[Toby Kuhnert]

I believe you occasionally get 180 degree split phase systems in rural areas. What's the voltage phase-phase?

I didn't measure, will do when I go back there either tomorrow or next week. What would be the purpose of a 180 degree split? I'm intrigued lol

 

[MDJ]

Hi Guys, Popped over to a bungalow yesterday that a mate of mine has bought to renovate, asked me to have a look at electrics/what might need doing and I found this... 2 phases (red and yellow) in a bungalow with 2 bedrooms?? bit ott i'm thinking? lol. Although the DNO have only supplied a meter for red phase, leaving yellow phase fuse just sitting there. Has anyone seen more than one phase in such a small domestic building before?? It isn't a farm or anything that I see could require such a large supply... its in a small village in the middle of a few other bungalows...

one question Toby before saying my bit, how do you know it is red and yellow phases?

 

[Marvo]

No purpose as such apart from being cheap for the DNO i guess. It does open up a whole can of worms with the high phase to phase voltage for suitably spec'd OCPD's, isolators etc though if you have both phases in the same DB/CU. Maybe the DNO is using one 4-core cable to supple 2 single phase premises???

 

[babylonsBurning]

Hi Toby, my mate has exactly the same, Two cut outs, but only one utilised, His is a three bed.

Marvo, i think the split phase system was 440v between the two phases, I believe it was used for remote locations like farms, the DNO could save on cable cost because only two phase + neutral were required (3 cores opposed to 4). Induction motors that are specially wound for this system are available.

 

[Toby Kuhnert]

one question Toby before saying my bit, how do you know it is red and yellow phases?

Before the fuse heads, the DNO's tails have red tape on one, and yellow tape on the other. So I'm presuming this is correct...

 

[MDJ]

Before the fuse heads, the DNO's tails have red tape on one, and yellow tape on the other. So I'm presuming this is correct...

I have come across this before, however before going any further have you actually tested between the so called phases to see if 400 volts exists?

 

[Toby Kuhnert]

Hi Toby, my mate has exactly the same, Two cut outs, but only one utilised, His is a three bed.
UItII jII
Marvo, i think the split phase system was 440v between the two phases, I believe it was used for remote locations like farms, the DNO could save on cable cost because only two phase + neutral were required (3 cores opposed to 4). Induction motors that are specially wound for this system are available.

Ah ok , yeah it would make sense on a farm, but not on a small bungalow. There are farms in the local area, so whether it was easier just to carry 2 phases to every building (overhead lines) then I guess that would make sense

 

[Toby Kuhnert]

I have come across this before, however before going any further have you actually tested between the so called phases to see if 400 volts exists?

No not yet, I will be going back there either tomorrow or next week (I installed some site power on Monday, going to wire up a static caravan next week) I presume you can measure from the top of the fuse on the yellow phase (the fuse with no meter tail) without taking it out?

 

[Marvo]

I think you'll need to establish exactly what's what. I'd check the phase voltages wrt N/E and it would be worth checkng the phase-phase voltage, if it's around 480v then it's probably 180deg split phase in which case I'd suggest you seek further advice if you're unfamiliar with it. Without this info it's only going to be guesswork I'm afriad.

 

[MDJ]

No not yet, I will be going back there either tomorrow or next week (I installed some site power on Monday, going to wire up a static caravan next week) I presume you can measure from the top of the fuse on the yellow phase (the fuse with no meter tail) without taking it out?

Hi Toby, well until you can confirm you have measured the voltage present with calibrated meter there's not much I can do for you, the reason being we do not know for sure 2 phases are present really and it may just be the markings the DNO man did from the coloured tapes he had on his van.

 

[Toby Kuhnert]

I think you'll need to establish exactly what's what. I'd check the phase voltages wrt N/E and it would be worth checkng the phase-phase voltage, if it's around 480v then it's probably 180deg split phase in which case I'd suggest you seek further advice if you're unfamiliar with it. Without this info it's only going to be guesswork I'm afriad.

Yeah I will definitely have a look when I go back and let you know how I get on... Whats the major difference? Does it affect the use of the single phase that's currently being metered?

 

[Marvo]

No, if it's split phase being used as one phase and neutral supplying two separate premises then you can treat it as two normal single phase installations (L-N should be 230/240v). The problems start stacking up when you have two phases from a split phase supply in the same board supplying the same circuits. Then you need to find devices that are rated >490volts which are surprisingly few and far between.

 

[Toby Kuhnert]

No, if it's split phase being used as one phase and neutral supplying two separate premises then you can treat it as two normal single phase installations (L-N should be 230/240v). The problems start stacking up when you have two phases from a split phase supply in the same board supplying the same circuits. Then you need to find devices that are rated >490volts which are surprisingly few and far between.

Oh fine, thanks for clearing that up, that makes sense . no probs then!!

 

[ayjay]

just use the existing phase

 

[Toby Kuhnert]

Just been back today, measured between red and yellow phase and found 422 volts ... presuming it is indeed there are 2 phases and it isn't split phase...

 

[Marvo]

It is too low to be 180deg split phase I think but the way to be sure would be to calculate the expected phase to phase voltage from the phase to neutral voltage.