Installing 3 Phase supply to new 5/6 Bed house

[dmelec]

Why run a separate earth?

Just easier to terminate

 

[Martin Kerr]

That's some house that needs 80a per phase?

 

[dmelec]

That's some house that needs 80a per phase?

Its a big 5/6 bed house, with a few outbuildings. 80 amps is probably a slight overkill haha

 

[davesparks]

Just easier to terminate

How is it easier to terminate?

Do you really think that laziness is a good basis for design over any technical or regulatory considerations?

 

[dmelec]

How is it easier to terminate?

Do you really think that laziness is a good basis for design over any technical or regulatory considerations?

Not sure how this wouldn't meet any technical standards as i would run a 4 core armoured with a sufficient separate earth?

 

[Flanders]

Just easier to terminate

I would not run a seperate earth just because its easier to terminate and over that length of run , but it would help get your zs down , when you did your calcs did you check for volt drop, and resistance of the cable .as then size you mention seams a little small for that size of supply over that length of run

 

[davesparks]

Not sure how this wouldn't meet any technical standards as i would run a 4 core armoured with a sufficient separate earth?

I didn't say it wouldn't comply, just that laziness is not a good reason for doing it.

You could have given any number of technical reasons for your decision, but instead you chose to cite laziness. Don't be surprised to catch a bit of stick for that

 

[Leesparkykent]

Not sure how this wouldn't meet any technical standards as i would run a 4 core armoured with a sufficient separate earth?

You would probably be looking at something like a 70mm earth if your basing your calcs on 80A bs88 fuses with a Ze of 0.35. That's why it would be an advantage to know the Ze when the the supply's installed as you could be grossly oversizing it.

 

[SJD]

I agree with Flanders, the cable size seems a little on the small size - without actually doing the calculations I'd have guessed at more like 70mm CSA.

 

[davesparks]

I've done a quick rough calculation and come up with a 120mm four core SWA giving a VD of 4.4V and a Zs of 0.5ohm, which I would say is probably cutting it quite close on the voltage drop if working to the 3% rule for the lighting circuits in the house

 

[Leesparkykent]

I've done a quick rough calculation and come up with a 120mm four core SWA giving a VD of 4.4V and a Zs of 0.5ohm, which I would say is probably cutting it quite close on the voltage drop if working to the 3% rule for the lighting circuits in the house

Is that at 100A per phase out of interest?

 

[dmelec]

Is that at 100A out of interest?

Thanks for the feedback
i think the property would only need a 60amp 3 phase supply

 

[Kamikaze]

I've done a quick rough calculation and come up with a 120mm four core SWA giving a VD of 4.4V and a Zs of 0.5ohm, which I would say is probably cutting it quite close on the voltage drop if working to the 3% rule for the lighting circuits in the house

That S.W.A. will probably weigh around ¾ of a tone. I hope he’s got some butch cable jacks and bouts of energy.:yes:

 

[Martin Kerr]

I would be basing my design load at no more than 40a per phase.

 

[Leesparkykent]

Is there gas being installed?