Installing 3 Phase supply to new 5/6 Bed house

[Martin Kerr]

Even so , will still probably house 2 adults ,4 kids at most

 

[davesparks]

Is that at 100A per phase out of interest?

No, I used 80A and all values as per the datasheet from batt with no factors or other corrections applied.

But reading through the thread a bit further it appears that the design load is getting less and less as the thread goes on.

 

[davesparks]

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:

A quick calculation from the data sheet has 150m of 120mm four core tipping the scales at just over 1000Kg

 

[davesparks]

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

Make your mind up, you started at 100, then 80 now you're saying 60. These are all suspiciously round numbers for a calculated demand and look more like you are guessing at the numbers.

Have you done any calculation of the design load for this circuit?

 

[davesparks]

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

Based on what information?

 

[Leesparkykent]

Even so , will still probably house 2 adults ,4 kids at most

Yeah but could have single phase loads that require more than 40A like showers or similar.

 

[Martin Kerr]

I believe circuit breakers are designed at 1.45 times ib , assuming some of these loads are very short duration ,unless some people spend an awful long time in the shower?

 

[davesparks]

I believe circuit breakers are designed at 1.45 times ib , assuming some of these loads are very short duration ,unless some people spend an awful long time in the shower?

Eh? Relying on the operating characteristics of downstream circuit breakers to design a submain in this way is bad practise and far from sensible.

 

[Leesparkykent]

I believe circuit breakers are designed at 1.45 times ib , assuming some of these loads are very short duration ,unless some people spend an awful long time in the shower?

And that would make for bad design from the designer of the installation Imo.

 

[Darkwood]

I believe circuit breakers are designed at 1.45 times ib , assuming some of these loads are very short duration ,unless some people spend an awful long time in the shower?

With all due respect here Martin, regarding this comment of accepting overload in design just because you hope no one has a long shower -- well I'm rather worried by that.

@ The OP - before we go any further with help here, can you show your calcs for estimating the house demand and also your calcs for your supply SWA, it seems you plucking numbers and figures out of thin air here and changing them to suit the response.

 

[Martin Kerr]

Sorry folks
Maybe I have been to long with Pierre today, I have no calculations to back any of my posts up ,but the point I am trying to get across is that most large houses are supplied with a single phase 100a , which seems to be adequate for their needs , adding a couple of bedrooms should not add a ridiculous amount of maximum demand, divide this up over three phases and you should not exceed much more than 40a per phase on balanced ,load this is based on diversity to calculate VD ,and not the CCC of the cable
PS I Am going to bed now before I suffer the same fate as Paul the magpie

 

[Leesparkykent]

Sorry folks
Maybe I have been to long with Pierre today, I have no calculations to back any of my posts up ,but the point I am trying to get across is that most large houses are supplied with a single phase 100a , which seems to be adequate for their needs , adding a couple of bedrooms should not add a ridiculous amount of maximum demand, divide this up over three phases and you should not exceed much more than 40a per phase on balanced ,load this is based on diversity to calculate VD ,and not the CCC of the cable
PS I Am going to bed now before I suffer the same fate as Paul the magpie

Haha the PS bit made me chuckle

 

[Kamikaze]

Sorry folks
Maybe I have been to long with Pierre today, I have no calculations to back any of my posts up ,but the point I am trying to get across is that most large houses are supplied with a single phase 100a , which seems to be adequate for their needs , adding a couple of bedrooms should not add a ridiculous amount of maximum demand, divide this up over three phases and you should not exceed much more than 40a per phase on balanced ,load this is based on diversity to calculate VD ,and not the CCC of the cable
PS I Am going to bed now before I suffer the same fate as Paul the magpie

Your added problem with regards to the cable size is that it will have to be based on the neutral current unless you can perfectly balance the phases. So you might end up going up two sizes anyway.

 

[SJD]

A high spec 5/6 bed house (the sort of house than might be down a 100m drive) will often have a lot more appliances than typical.

I've worked recently on one such house, e.g. the kitchen has 2 built-in ovens, built-in warming drawer, built-in steamer, built-in microwave, 6-ring hob. The plant room has a couple of big water tanks with backup heaters in case the gas boiler fails. Every bedroom has an en-suite (though depending, the showers might not be electric). It needed a lot more than 100A.

 

[Darkwood]

Sorry folks
Maybe I have been to long with Pierre today, I have no calculations to back any of my posts up ,but the point I am trying to get across is that most large houses are supplied with a single phase 100a , which seems to be adequate for their needs , adding a couple of bedrooms should not add a ridiculous amount of maximum demand, divide this up over three phases and you should not exceed much more than 40a per phase on balanced ,load this is based on diversity to calculate VD ,and not the CCC of the cable
PS I Am going to bed now before I suffer the same fate as Paul the magpie

Sorry Martin that was my bad - I didn't segregate my post, its done now though, I should have multi-quoted :blush5: