Buying a new house - is this too much for a domestic supply?

[bayzoo]

Evening,

I’ve just put an offer on a house without thinking too much of the electrics. It currently has 2 electric showers and an electric oven.

If we buy it I’d like 2 x 16A commando sockets installed in the garage so I can run my air compressor (2.2kW) and MIG welder. I calculated that the welder will draw a max of 21A though I’ll never be using it at this level, and the air compressor will draw around 10A.

I know I’ll need to get a spark to check it out for me but before I go ahead I want to know how likely they’ll tell me that it won’t be possible on a domestic supply to have points for my compressor and welder installed when there are already the 2 electric showers and an oven. I don’t know the cut out size but I know the max that can be installed is 100A so even at this it seems to be pushing it.

I will know not to run everything at once though but not sure if that makes a difference from a regs/safety point of view.

Any advice is much appreciated, thanks.

Fraser

 

[littlespark]

We have a system called “diversity” which basically assumes that not all cooker rings, ovens, electric showers etc will be on at the same time…. And if they are, the built in thermostats will be cycling on/off as it smuttiest to stay at temperature.

Some houses have 3 or 4 storage heaters running all night…. An EV charger…. Any number of high power appliances.

Yes, the showers, if both on together could be quite heavy. Do you know what size they are?

Quick rule of thumb for easy maths, is 4 amps per kilowatt of load…. But it could be fractionally more or less depending on actual supply voltage.

Even if the main fuse has a sticker saying 100A, it might only be a 60 fitted… but you’de have to ask the supplier to confirm.

Saying that, a 100A fuse will carry quite a bit more than that for some time before rupturing.

 

[James]

It will be fine, let’s face it, any other property you buy will still have the same issues, you still want up to 20A in the workshop.
worst case scenario, put a load sharing device on one shower so it can’t be used at the same time as the other shower. But gut feeling and a few years in the trade says you will be ok.
p.s. This is not a professional evaluation of your proposed electrical setup, just a comment from a half cut sparky.
enjoy your new home.

 

[bayzoo]

We have a system called “diversity” which basically assumes that not all cooker rings, ovens, electric showers etc will be on at the same time…. And if they are, the built in thermostats will be cycling on/off as it smuttiest to stay at temperature.

Some houses have 3 or 4 storage heaters running all night…. An EV charger…. Any number of high power appliances.

Yes, the showers, if both on together could be quite heavy. Do you know what size they are?

Quick rule of thumb for easy maths, is 4 amps per kilowatt of load…. But it could be fractionally more or less depending on actual supply voltage.

Even if the main fuse has a sticker saying 100A, it might only be a 60 fitted… but you’de have to ask the supplier to confirm.

Saying that, a 100A fuse will carry quite a bit more than that for some time before rupturing.

Cheers littlespark - I believe the showers are 8.5kW so going by your formula that’s 34A for each shower. Diversity sounds interesting, would this set up be common knowledge to most sparks?

If I get the house I’ll need to find out what size the cut out is, I have a feeling it’s 60A because the current owner told me he was advised not to run both showers at once. Is a DNO fuse upgrade a simple swap for a bigger fuse or can there be limitations?

 

[bayzoo]

It will be fine, let’s face it, any other property you buy will still have the same issues, you still want up to 20A in the workshop.
worst case scenario, put a load sharing device on one shower so it can’t be used at the same time as the other shower. But gut feeling and a few years in the trade says you will be ok.
p.s. This is not a professional evaluation of your proposed electrical setup, just a comment from a half cut sparky.
enjoy your new home.

haha cheers mate - hope we get it!

 

[littlespark]

The 60A fuse could be sized to protect the size of cable feeding the property, so having it changed to 100, or even 80, the middle size, might be impossible.

 

[DPG]

Could always consider swapping one of the showers to a combi-fed one. Much better than an electric one.

 

[bayzoo]

Could always consider swapping one of the showers to a combi-fed one. Much better than an electric one.

Yeah I have thought about that - it’s oil central heating though, do they do oil combi boilers? I’m in Northern Ireland.

I’ve also gone down the rabbit hole on looped supplies so if we do get our offer accepted I’ll be taking another look at their supply to see if there are 2 cables… I doubt it being a detached property but best to check as we’d likely be upgrading to an EV in a few years