electric shower problems

georgemorgan · 24 Nov 2007

Hello,

I've got a problem with my new electric shower. The old one would sometimes emit warm water but then would trip the circuit after you were soapy. But mostly it just ran cold.

So I bought and fitted a new BnQ essentials 8.5kW one. I got a low power one in case there wasn't enough water pressure for a higher power one. The problem is that in the mornings, on a reasonable temperature it cycles between warm and cold.

I'm guessing that at peak times there isn't enough water pressure to maintain the modest temperature. Even later on in the day there isn't much pressure. The unit is run off the mains, on the third floor, and seems to share its pipe with where you top up the water into the central heating.

Our lodger is moaning about the shower and suggested fitting a pump. Most shower pumps seem to be for mixer showers, and I read that you aren't allowed to put a pump in a mains flow. Is there one I could get? They all seem to be massively expensive, like £300!

Would a more powerful shower help? Or should we just have baths?

Thanks,

George.

hi-spec plumbing heating · 24 Nov 2007

you can't fit a pump to the mains cold water.

georgemorgan · 24 Nov 2007

Thanks for your reply.

Why can't you fit a pump into the mains? Would it suck up other people's water supply, leaving them with a trickle?

I'm not sure if it is the real mains anyway: we live in a 1950's maisonette block, with two huts on the roof that you can sometimes hear filling with water. Would all the water go up to these, and then come down again proporting to be mains? The stopcock turns off the water to everything so I don't think there's a seperate supply to things other than the kitchen sink from these tanks.

We've got a combi boiler, with a reasonable flow of hot water. Could I get a different sort of shower, like a mixer one? Or would the easier option of getting a more powerful shower help?

hi-spec plumbing heating · 24 Nov 2007

it's illegal to pump mains water.
like you say it sounds like you are supplyed by tank and kitchen by mains.
if you have a combi boiler you can fit a mixer supplied of that and have balanced hot/cold pressure.

get your incoming mains pressure checked for pressure. is your kitchen sink tap powerful ?

georgemorgan · 24 Nov 2007

I suspect that all the water is from the roof tanks, since the under sink stopcock turns off all the supply everywhere. The kitchen tap is pretty fierce, actually all the taps seem fine. I just assumed the pressure to the shower was the problem because it has quite a low flow at the best of times.

simond · 24 Nov 2007

One of the major manufacturers, Galaxy I think or Triton has just brought out a mains pumped electric shower.

It is not illegal to pump from the mains; there is a maximum flow rate you are allowed to extract which conveniently is less than a typical eleccy shower.

hi-spec plumbing heating · 24 Nov 2007

simond said:
One of the major manufacturers, Galaxy I think or Triton has just brought out a mains pumped electric shower.

It is not illegal to pump from the mains; there is a maximum flow rate you are allowed to extract which conveniently is less than a typical eleccy shower.

how about trying again

yes 12 litres per min a pump can draw from mains before you need approval.

an average 9.5kw electric shower will give 3.4 l/m at 35 degrees, 12l/m at 5 degrees.

so it is illegal for what he wants. if you want to be funny.

simond · 24 Nov 2007

I wasn't trying to be funny.

Instantaneous electric showers are flow limited so you won't ever see 12l/m. At 12l/m 40C Delta you would need an approx 30kW electrical supply, about 120amps. Domestically that would be challenging, the electricity supply authority would want you to be on 3 phase with that load. So I can't see your point at all.

The manufacturer would fit a pump below 12litres, there is no point in them pumping more than 4 litres per min as nobody will pay extra for a cold shower

Which is perhaps what you need

hi-spec plumbing heating · 24 Nov 2007

simond said:
I wasn't trying to be funny.

Instantaneous electric showers are flow limited so you won't ever see 12l/m. At 12l/m 40C Delta you would need an approx 30kW electrical

no one said 12 l/m at 40c, it 12 l/m at 5c 3.5 l/m at 35c

georgemorgan · 24 Nov 2007

I don't really understand all that. How does flow rate relate to pressure? Is there a formula? The pipe is 15mm, and the shower says it needs 0.7 bar.

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electric shower problems

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