How Many 10kw Showers?

[ED17]

Last year we rewired a bungalow on a large private estate which caters for mentally ill patients. It had 5 bedrooms each with it's own wet room. The builder wanted a 10kw shower in each wet room but as the incoming sub - main was only 16swa protected by a 60amp fuse we told him no. We ended up with one electric shower and 4 mixers off the combi. The client needed a back up in case of boiler breakdown.

There are six identical bungalows and now the next one is ready for refurbing. The builders had two other contractors in to price the rewires. One's told him that 3 x 10kw showers will be ok and this has made the builder happy.

I've spoken to staff in the original bungalow who inform me that the normal morning routine is for two showers to be used at the same time usually while breakfast is being prepared (with electric oven and hob)

I'm sticking to one shower so it looks like I'll not be getting this one.

 

[mhar]

In my area it is usually concentric (sometimes split concentric) supplying the property, not swa. It is quite usual to have a 16mm feed with an 80A service fuse.
It is usual for the supply to properties (certainly in my local area) to be an 80A supply so I would phone the DNO and ask if there is any reason for this smaller than usual supply and to see if it can be increased to 80A.

 

[ED17]

It's from their own private distribution system not DNO.

 

[Leesparkykent]

How well do you get on with the builder? I would call on a meeting and explain that you don't want to loose the job over some other dipsticks quote saying he can have 3 x 10KW showers. If he's a sensible guy then he will be able to see the maths doesn't add up if you put it in black and white in front of him. Due to the nature of the building It wouldn't be practical to use contractors/relays so if one shower was on the others couldn't be used. An unvented cylinder would be the ideal choice in this situation if the water pressure and flow rate is acceptable for the demand. you could use a direct cylinder or indirect cylinder. Indirect would be heated by a boiler for example and a direct cylinder would be heated by immersions. A 250 litre cylinder would feed 3 showers on the go at once for nearly 10 minutes. The reheat time for the entire cylinder would be around 2hours with two 3KW immersions so that would be a factor as to how frequent the 3showers were to be used.

 

[Wilko]

Ohm's Law hasn't changed overnight and a 10kW shower will still pull over 40A. How a competent designer thinks its ok to run 3 of them (and cookers!) off a 60A fuse does take tonight's biscuit. As Lee has said, hopefully the builder will get it. I'm staying optimistic for you, but sometimes you just can't beat stupid.

 

[Ian1981]

I'd be reluctant to even allow for 2 10kw showers never mind 3.
If they where getting used at the same time you'd be drawing around 80 amps and that's without taking into consideration any other demand being used at the same time , cookers, hobs kettles etc.

 

[ED17]

I've got a site meeting on Friday and I've asked the builder to bring the other contractors design calc's along.

 

[Dave OCD]

1 electric shower per 100a installation would be my usual limit,and I also try my best to steer customers towards a max of 9kW, anything bigger is just bragging rights really.

 

[Leesparkykent]

I've got a site meeting on Friday and I've asked the builder to bring the other contractors design calc's along.

Let us know how you get on.

 

[Dave OCD]

No Lee it's know not no.

 

[ED17]

Let us know how you get on.

Will do.

 

[ED17]

No Lee it's know not no.

It might be a "no" from the builder

 

[Dave OCD]

And Lee has sorted out his spelling now.

 

[Leesparkykent]

And Lee has sorted out his spelling now.

My spelling and grammar is awful....That's what you get for leaving school at 13 I suppose lol. My electrics are the bollox though

 

[Wilko]

My spelling and grammar is awful....That's what you get for leaving school at 13 I suppose lol. My electrics are the bollox though

My Other Half was an English teacher, oh the pain ...