Interconnecting electric shower and conventional hot water system

We've got a bathroom refurb project under way, throwing out the bath (cast iron - that was heavy!) and installing an electric 10kW shower.

Builder is proposing a joint method of connecting the shower so that heated water to the shower head either comes from electric or the existing hot water system (Gas fired S-plan 20yr old Potterton lump).

The logic is that the electric is unnecessary if the gas system has already heated a full tank of hot water, but if that's gone then we'll switch over to electric heating.

I'm shaking my head negatively as it sounds a bit complicated, and would much rather it was just kept electric, but SWMBO and the builder is a bit keen on this - so I'm currently being overruled.

Are there any water regulations precautions peculiar with this kind of switched arrangement. The DHW system heats tanked water, the electric will be running from mains pressure. Lots of pressure from both, we don't need pumps.

Reply to
Adrian C
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My investigations today into shower cabinets has found some that need hot and cold water *and* a 15A supply...

E.g. This unit:

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don't have (nor want) electricity, but do have plenty of 1.8 bar pumped hot & cold!

Gordon

Reply to
Gordon Henderson

Well, if you only end up with HW from a single source I'd certainly jump at the chance of moving to the gas-fuelled shower rather than the electric one... you'll get a far more effective shower from the HW tank, and AFAIK it's still much cheaper to heat your water with gas rather than electricity.

In terms of having a 'back-up' in the event of the gas system failing - well, most tanks will have an electric immersion heater to cover that eventuality anyway, so I'd suggest forgetting all about the separate electric shower unit... or maybe that's the same solution your builder is proposing?

David

Reply to
Lobster

Don't know. Our gas system was designed for heating huge volumes of water. For small uses of water like hand washing dishes it's probably inefficient, and in the great scheme of things it's probably not too efficient with volume - but until it breaks it won't be replaced.

Maybe there is a chance we may turn off the gas system during the summer, and get an instantaneous water heater for the kitchen (or use a kettle).

She's worried if it came to that, and we'd have to use an immersion heater (which at the moment we haven't got) - it would be more expensive electrically heating the whole tank than running an electric shower.

so I'd suggest forgetting all about the separate

Nope. Combined system is on the menu. I'm expecting to be seeing more taps and controls than the engine cabin of your average steam locomotive.

So really the original question, is there anything dodgy about interconnecting the two systems.

Reply to
Adrian C

Point taken - but OTOH do you know how long your system takes to heat enough water in the tank for a shower? I mean, we have a pretty large HW tank, but you certainly don't need to heat anything like the whole thing in order to get a shower's-worth off (if that's all that's required).

For sure - but this is for emergency use only (ie to cover the time between boiler failure and repair, if that's ever needed) so running costs not really an issue. If you haven't got an immersion heater already (isn't that a bit unusual? I thought it was pretty well standard for HW cylinders to have them?) then you'd have to bear the cost of a new circuit for that; however I must say I wouldn't want to be without the 'insurance' of our backup immersion heater; not only for showers but washing up, baths etc)

Personally, not a clue I'm afraid - still think it's the wrong answer myself but that's your call (and SWMBOs, natch!): but if this was a more commonly adopted solution wouldn't there be more kit generally available?

David

Reply to
Lobster

At the moment I'm a bit of a soak in the bath creature, and she is the

10mins shower type - so useage of hot water at the moment is average on at least using one 140lt cylinder a day.

The (rather inflexible) timer is set for 1 hr water heating in the morning, and 1 hr in the evening. I don't actually know when the 70degC tank thermostat decides to overrule the timer and call it quits to heating so say I wave finger in the air and guess probably around 40mins in the morning for my bath and another 15mins heating in the evening.

That's gonna change to about 20 mins of water heated electrically per day for both our showers if we turn the gas off during the summer - and if electric is a bit more expensive per joule, the process of heat conversion for a small amount of water is probably more efficient than that big tank. And high heating temperatures are not required.

So I'm OK with electric - and could do with that all year.

But in the winter, with the gas heating going full pelt she says we may as well heat the water as well - hence this dual system malarky.

SWMBO has mentioned she is taking liability if the new scheme doesn't save money.

We're looking at doing this

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but if this was a more

Yup my worries as well. The two way diverter valve as a common shower room friendly thing? I've seen something in hotels for switching between water for the bath or for the shower hose. Googling it comes up with some very expensive prices for that item. I don't know what the builder is thinking off.

Thanks BTW for the comments - think I'm going to sod off and do a few countrywide jobs and leave both of them to figure it out.

Reply to
Adrian C

electric shower. Although I'm sure you wouldn't deliberately turn the electric shower on with the diverter valve in the DHW position, the random Triton shower instructions I just looked at say:

"DO NOT ?t any form of outlet ?ow control as the outlet acts as a vent for the heater can."

Rich.

Reply to
Richard Skeen

I've not read the whole thread but my first instinct would be to pass the output of the shower mixer through the electric shower with no valves. If the mixer output is too cool then the electric shower will add heat, if the gas fired DHW is on and the mixer set sensibly, the electric shower will not need to add anything. No special components. Simples! I can't see a snag to this at the moment.

Bob

Reply to
Bob Minchin

how about this:

(AFAIK electric showers will have a one-way valve built in anyway, for compliance with water regs)

David

Reply to
Lobster

I lived in a flat where the landlord had plumbed the electric shower into the hot instead of the cold pipe.

The electric shower overheat tripped if we had the immersion on, regardless of setting, so we never had the immersion on.

Owain

Reply to
Owain

That implies that the electric shower did not have a thermostat as such but regulated the output temperature by flow rate (I think earlier ones did this) but in any case my suggestion should work in as much as if the input water is hot already then the electric shower will trip but the water will still come out OK. If the input water is at cold pipe temperature then the heater will do it's bit and give a hot shower.

It might not be working as designed but should achieve what the op seems to want.

Bob

Reply to
Bob Minchin

That implies that the electric shower did not have a thermostat as such but regulated the output temperature by flow rate (I think earlier ones did this) but in any case my suggestion should work in as much as if the input water is hot already then the electric shower will trip but the water will still come out OK. If the input water is at cold pipe temperature then the heater will do it's bit and give a hot shower.

It might not be working as designed but should achieve what the op seems to want.

Bob

Reply to
Bob Minchin

That implies that the electric shower did not have a thermostat as such but regulated the output temperature by flow rate (I think earlier ones did this) but in any case my suggestion should work in as much as if the input water is hot already then the electric shower will trip but the water will still come out OK. If the input water is at cold pipe temperature then the heater will do it's bit and give a hot shower.

It might not be working as designed but should achieve what the op seems to want.

Bob

Reply to
Bob Minchin

Just an update:

The idea of interconnecting wotsits between the two systems has been abandoned and we've now gone for two shower heads and hoses, each mounted on parallel rails. It's all going to be a lot of gubbins to clean when it starts attracting chalky water deposits - but that's what she wants ...

Happily, there is another bathroom with a normal bath that I'm going to live in. Have to break the news gently to the toy duck that it's soon moving to another pond ...

:-)

Reply to
Adrian C

Bless... ;-)

Thanks for the update!

Reply to
Lobster

Wouldn't one shower in each bathroom be, erm, well, more conventional?

Owain

Reply to
Owain

Yeah. Erm, SWMBO is, well, not conventional...

Reply to
Adrian C

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