Sanity Check Required - Do I really need 3 Phase Upgrade?

[philnixon]

I am doing a full renovation on a 4 bed house and once the electrician had got hold of all of the kitchen specs, he reckons we need to upgrade from a single phase to a 3-phase supply. He reckons max demand will be 150-160A.

I was under the impression that it is quite rare for domestic properties to be on 3 phase and if I could avoid the the additional cost and time (6-8 weeks waiting list for install) I'd prefer to!

I have 4 floors, basement, ground, first and loft conversion. Heating is underfloor with mains pressure hot water cylinder, so all powered by gas.

The main issue are the ovens and induction hob in the kitchen, but I would have thought with diversity the load would drop accordingly?

Would anyone be able to provide a sanity check for me? I think it is a close call! Below is my list of the main connected loads taken from the appliances:

Cooker Ring
60cm Pyroclean Right Hinged Oven 3.7KW (16A)
60cm Pyroclean Left Hinged Oven 3.7KW (16A)
Combination Microwave / Oven 3.1KW (16A)
Steam Combi Oven (Reservoir system) 2KW (10A)
Induction Ring
Induction 5 zone hob 10.8KW (45A)
Kitchen Ring
Downdraft Extractor 0.3KW
Warming Drawer 0.81KW
Warming Drawer 0.81KW
Fridge Freezer 0.3KW
Wine Cabinet 0.13KW
Dishwasher 2.3KW
Quooker tap 1.6KW
Double Drawer Dishwasher 1.8KW (9A)
Utililty Room Ring
Washing Machine 2.4KW
Tumble Dryer - Heat Pump 1KW
Ground Floor Ring
Nothing specific
First Floor and Loft Ring
Crosswater digital shower valve (not electric shower) .03KW
Spa bath 3.6KW (16A)
Basement Sump Pump and Alarms
V3 Foul pump 1.2KW (6A)
V3 Sump pump 0.43KW (1.9A)
V3 Sump pump 0.43KW (1.9A)
Alarm unit (2A)
Alarm unit (2A)
Lights - all LED
Basement 30 @ 10w 300
Ground 30 @ 10w 300
First 30 @ 10w 300
loft 10 @ 10w 100

Thanks in advance as always!
Phil

 

[JohnW2]

I am doing a full renovation on a 4 bed house and once the electrician had got hold of all of the kitchen specs, he reckons we need to upgrade from a single phase to a 3-phase supply. He reckons max demand will be 150-160A.

I think that you probably need a different electrician. This one appears to have simply added up the maximum current demands of absolutely everything (i.e. assuming that everything would be drawing 'maximum current' simultaneously). If one did that for most houses, one would probably end up with a ridiculously high number, and would hence conclude that a standard 60/80/100A single-phase supply would not be adequate!

Kind Regards, John

 

[Gerrydelasel]

What kind of alarms draw 2 amps?

 

[securespark]

He has just taken the recommended fuse size from the manufacturer's instructions (ADE for one recommend a 2A fuse in the spur supplying their panels).

There is diversity on cooker circuits. This is how it is possible to wire a 15+kW cooker onto a 30/32A circuit.

The ovens are no good on a ring final circuit, though.

Ask him to apply diversity to all applicable circuits, as laid out in the On-Site Guide, then see what the figure is.

 

[EFLImpudence]

As you say, the cooking appliances are the only things which are out of the ordinary but with diversity work out at 36A so would all be alright on a 40A circuit.

Therefore I would agree that the 'electrician' is the only part which needs replacing.

 

[philnixon]

What kind of alarms draw 2 amps?

They are alarms for failure of the sump pumps - I couldn't find a wattage on the manual so just assigned a nominal amount from the specification. Looking closer at the doc (http://www.deltamembranes.com/wp-content/uploads/Foul-V3-Sump-Installation.pdf) the last page shows the alarm.

 

[JohnW2]

They are alarms for failure of the sump pumps - I couldn't find a wattage on the manual so just assigned a nominal amount from the specification. Looking closer at the doc (http://www.deltamembranes.com/wp-content/uploads/Foul-V3-Sump-Installation.pdf) the last page shows the alarm.

The reality is that the current drawn by that would be totally trivial - nowhere near 400-500W. However, in terms of the big picture, that is of no consequence - it's the 'adding up of everything' (particularly the cooking appliances) that's wrong. You're lucky that you don't have an electric shower - the 'electrician' would probably have added another ~45A on for that, taking the alleged total to over 200A!!

Kind Regards, John

 

[bernardgreen]

How much of your waste water and / or sewage is going into the foul water pump ? It looks like a very small tank for a whole house sewage pumping system.

 

[philnixon]

How much of your waste water and / or sewage is going into the foul water pump ? It looks like a very small tank for a whole house sewage pumping system.

It is just foul from the basement (a WC and kitchen / utility wastes). The rest of the house flows straight to the mains sewer.

 

[JohnW2]

How much of your waste water and / or sewage is going into the foul water pump ? It looks like a very small tank for a whole house sewage pumping system.

Indeed - sounds more like a macerator/pump to me (maybe for a loo in the basement?).

Edit: typed too slowly - but at least I was right
Kind Regards, John

 

[deadshort]

What is the existing supply ?

Thanks,

DS

 

[philnixon]

What is the existing supply ?

Thanks,

DS

According to the sticker on the fuse installed by UKPN about 6 months ago (when replacing 'dangerously' located lead sheathed cable with newer stuff) "100A Fuse Fitted"

 

[JohnW2]

According to the sticker on the fuse installed by UKPN about 6 months ago (when replacing 'dangerously' located lead sheathed cable with newer stuff) "100A Fuse Fitted"

In that case, I would think that your present supply is probably plenty adequate for your needs.

Kind Regards, John

 

[securespark]

But don't tell Ban that we're advising putting a 100A+ load onto a 100A fuse......

 

[JohnW2]

But don't tell Ban that we're advising putting a 100A+ load onto a 100A fuse......

... but I don't think we are, after diversity. As I said to the OP, there probably aren't that many installations for which adding up all the potential 'maximum loads' would not produce a figure in excess of the rating of the cutout fuse. Don't forget that the DNO would probably regard the average load of the OP's installation (apply the sort of diversity that they do) as about 10A !!

Kind Regards, John