Bit rusty on this... after some help please :-)

[sythai]

Hi All

Just trying to put together a household/diversity calculation for a new supply to a 2 bed/ 2 bath 'fully electric' barn conversion.

Figures are working out way too high! done as per OSG.

Here's the final set up:

32a ring 1
32a ring 2
4a lighting
40a wall heaters (infrared panels)
26a water heater (Electric boiler)
13a oven
13a hob

After diversity

32a ring 1
13a ring 2
3a lighting
40a wall heaters
26a water heater
11a hob
11a oven

136 amps!!!! (don't think so)

What am I missing, if anyone could give me any assistance would be really grateful ?

Thanks Sy

 

[Octopus]

"what am I missing"

The OSG "guidance" on diversity dates from a time when properties had 4 or 5 circuits .....

What happens if you add up all the breakers and multiply by 0.25?

 

[sythai]

"what am I missing"

The OSG "guidance" on diversity dates from a time when properties had 4 or 5 circuits .....

What happens if you add up all the breakers and multiply by 0.25?

Thats better 45amps

Where does that calculation come from then? Thanks Sy

 

[Octopus]

Thats better 45amps

Where does that calculation come from then? Thanks Sy

My "creation" and I think is more sensible with bigger CU's .....

Never been questioned about it on my assessments

The reality is that a ring would never pull 32A unless its doing space heating.... a lighting circuit won't pull 3A ........

How big is the main fuse?

 

[sythai]

My "creation" and I think is more sensible with bigger CU's .....

Never been questioned about it on my assessments

The reality is that a ring would never pull 32A unless its doing space heating.... a lighting circuit won't pull 3A ........

How big is the main fuse?

I see... know what you mean, does seems more realistic. There is no main fuse as of yet, I'm doing the calculation for new supply coming in

 

[Wilko]

Hi - I agree the ring won't have much on it compared with cooking, hot water and heating - for what it's worth, my choice would be 100A service.

 

[Deleted account]

There is an accepted calculation of 0.4 of total breaker values.
I've never heard of the 0.25 rule, but in some installations I feel it would be more than acceptable.

However it's up to the individual spark to make there own judgement call for an individual Property.

Edit: posted before I'd read "your own creation" Murdock.

 

[Leesparkykent]

Why they even opting for infrared heating? Madness imo. Infrared won't necessarily heat the room, it will heat objects, so when it's on it will be just floging away. They may as well dig a hole in the ground and chuck £20 notes into it and Set it on fire. I've installed a few of these with wet systems Heatrae Sadia Electromax Electric Flow Boilers | Electric Boilers - https://www.plumbnation.co.uk/site/heatrae-sadia-electromax-electric-flow-boilers/?gclid=CjwKCAjwgr3ZBRAAEiwAGVssneSUIxF-rzASmrW42sEDmOt95x73_qa5hrlRQGjdKSqJ3gbJ2CN-7RoCAAwQAvD_BwE

 

[123]

"what am I missing"

The OSG "guidance" on diversity dates from a time when properties had 4 or 5 circuits .....

What happens if you add up all the breakers and multiply by 0.25?

That's similar to what I use...but not with Electric Heating and Electric Boiler.

 

[HandySparks]

What's the 13A supply for the hob? Is is gas (with electric ignition)?

 

[123]

What's the 13A supply for the hob? Is is gas (with electric ignition)?

Could be Induction...seen loads of them with plugs.

If gas, why all the electric heating unless LPG

 

[HandySparks]

Could be Induction...seen loads of them with plugs.

If gas, why all the electric heating unless LPG

Yes, I wondered whether there was bottled gas for the hob.

 

[w0z]

I'm not party to the actual power rating of whatever heaters and water heater will be fitted, but surely you would have to assume no diversity is applied to the actual ratings for these as it's almost certain that all the heaters and the water heater will be on at the same time?
I agree you could reasonably assume some diversity for the other circuits.

 

[Richard Burns]

Looking at a basic all electric house without storage heating it might be considered on average over a range of houses to consume about 30A as a maximum demand value, this is the sort of level that would be applied for a network design.
So you are generally looking to see if you are near this level.
32a ring 1 any ring is likely to only take a 13A load on a kettle for short time and most other applications (some cooking equipment excluded) will be much less than this, any other loading will be exceptional in most houses.
32a ring 2 as ring 1 but if upstairs then a lower loading is much more likely.
So rings at about 20A demand
4a lighting, all LED lighting might draw about 1A and can be pretty much ignored.
40a wall heaters (infrared panels), these will consume a lot of power but in bursts the primary long time period is when first switched on, but 9kW of heating is a lot for a modern insulated house so they would likely not be all on at once and with thermostatic control say half the power demand on average.
So heating at 20A
26a water heater (Electric boiler) this would hopefully be on most of the time so operating occasionally but you would need to account for an initial switch on so not a lot of diversity here.
Boiler 20A
13a oven and 13a hob these two together would use a similar load profile to a 6kW cooker so about 15A
Total load on average about 75A, but overcooked to allow for the boiler at times. This is over the 30A network design but would indicate an 80A supply could be suitable.
I would normally not consider a 60A supply suitable for an electric house (a flat, maybe).
This is just how I might approach things on a practical level.

 

[sythai]

Thanks Richard.... extremely helpful and appreciated, looking more realistic now than the osg method.

Hob and oven fully electric and both come with 13 amp plug tops on already.

Infrared heaters were Clients spec, bonkers I know but they've got some strange ideas and didn't want any alternative suggestions ! Believe me I tried.

Cheers Sy