Three Phase to Single Phase

[Dairyspark]

Hi everyone, wee question for you. my latest job entails converting a pub attached to a hotel into a beauty salon, the supply for the pub is fed from the hotel by the means of a 4 core swa which was fed 3 fuses which have now been removed and the cable rerouted. now my question is, as I only need one phase and neutral, can I terminate the cable into a box with an 4 pole isolator and take off my single phase tail from one of the phases?

kindest regards

Bobby

 

[Andy™]

or you could double up on the conductors

 

[Dairyspark]

So double live and double neutral sufficiently marked at both ends? lol also, will what at a glance looks like 25mm cables doubled up fit into DP isolator?

 

[Lurch]

You say the fuses have been removed and the cable rerouted, so if it isn't connected to anything why connect it back up the 3 phase if you want single phase?

will what at a glance looks like 25mm cables doubled up fit into DP isolator?

Depends on the size of the terminals, but that's the wrong way to do it anyway. I would possibly double up on cores, but all depends on whether you need to or not. I'd keep it as 3 phase anyway for future use, also means you don't need to double up any cores and will have plenty of capacity.

 

[rapparee]

Three phase is a great thing to have. I wouldn't be too quick to do away with it. Can you not just put in a 3 phase distribution board.

 

[phil d]

You need to think this one  through properly, it may start as a hairdressing salon but how long before they add a few sunbeds or something else? Also if the supply was 3 phase before then making it potentially a high load single phase you may severely imbalance the load on the main supply to the hotel. With 3 phase there is more scope for expansion later, think of it as future proofing the install.

Last year we did some work on a church, the sub board was single phase and way too small for what they were adding, the main contractor had been let down by the original spark, after the quote had been done and with what had been spec'd it just wasn't going to happen. Anyway by making the new board 3 phase, we were still able to utilise the new cable that had been bought (6mm swa) but we were able to run everything that was required.

 It was either a case of the other spark hadn't a clue or he'd really messed up his calculations, either way the new load was not going on a 6mm single phase supply.

Personally I think you'd be nuts to sacrifice a perfectly good 3 phase in favour of a single phase supply. 

 

[Dairyspark]

The cable has only been rerouted at the user side, the hotel side is still configured for 3ph, I did suggest to the owner about keeping it 3 phase but he isn't caring about who moves into the place his exact words were "thats their problem not mine" 

 

[Lurch]

I did suggest to the owner about keeping it 3 phase but he isn't caring about who moves into the place his exact words were "thats their problem not mine"

So if he is doing the electrical design then why not ask him what you should do with the isolator and tap off?

 

[rapparee]

The cable has only been rerouted at the user side, the hotel side is still configured for 3ph, I did suggest to the owner about keeping it 3 phase but he isn't caring about who moves into the place his exact words were "thats their problem not mine" 

It'll be his problem if the hotel becomes unbalanced and he loses a phase in the hotel.

 

[Dairyspark]

No he isn't designing the installation, I've suggested that he keep it three phase but he doesn't want too, so I'm trying to think of future proofing solutions

 

[phil d]

It'll be his problem if the hotel becomes unbalanced and he loses a phase in the hotel.

Exactly what I was getting at, trouble is some people don't care, until it causes problems.

No he isn't designing the installation, I've suggested that he keep it three phase but he doesn't want too, so I'm trying to think of future proofing solutions

I would politely suggest that he leaves it up to you, you are the electrician and therefore the expert, how would he feel if you started telling him how to run his hotel?

 

[apprentice87]

So double live and double neutral sufficiently marked at both ends? lol also, will what at a glance looks like 25mm cables doubled up fit into DP isolator?

You do realise, that you cannot join two of the phases.... [I hope...]

john..

 

[Dairyspark]

You do realise, that you cannot join two of the phases.... [I hope...]

john..

Not without reconfiguring at the supply end as well......be a good fireworks show lol Phase to phase and phase to neutral brown to black and blue to.....fffffff

 

[binky]

The cable has only been rerouted at the user side, the hotel side is still configured for 3ph, I did suggest to the owner about keeping it 3 phase but he isn't caring about who moves into the place his exact words were "thats their problem not mine" 

it will be his problem whan his bills go up for being out of balance. I don't know exactly how it works, but an out of balance supply can incurr higher charges, hence the specialist companies who install Power Fcator Correction.

 

[Rob.]

it will be his problem whan his bills go up for being out of balance. I don't know exactly how it works, but an out of balance supply can incurr higher charges, hence the specialist companies who install Power Fcator Correction.

You're not usually charged for a supply being out of balance. 

You are correct in that you will incur charges if you're network has a leading or lagging powerfactor out of the DNO's tolerated bands. 

 

[Andy™]

it will be his problem whan his bills go up for being out of balance. I don't know exactly how it works, but an out of balance supply can incurr higher charges, hence the specialist companies who install Power Fcator Correction.

PF correction has nothing to do with phase balance. you could have all 3 perfectly balanced but a PF of 0.5. or you could have 80a on L1&L2 with 5a on L3 and PF of 0.98

 

[binky]

still a good argument to convince a tight wad to extend the 3 phase :^O

 

[Lurch]

From what I can see the costs would be negligible as the supply is already in. I don;t understand why you wouldn't just stick a 3 phase board on the end of it.

 

[Tony S]

I’ve got to agree with the others, a 3Ø supply would be the way to go.

 

[Dairyspark]

Well....an update to this haha, after some convincing he has agreed to fit a 3 phase board and let me do it the way I want. Yay!