Showers on 5 core cable?

cgarrad · 10-02-2020 4:16pm #1

I'm building a house and have 3 en suites which all touch each other.

3 instant showers 9kw each.

House will have three phase.

Can the electrcian wire them with 5 core 10mm or will it need 3 lenghts of 10mm t&e?

BIG difference in price for the cable.

10-02-2020 4:54pm

Each shower is an independent single phase load. As such it would make sense to have a cable per load. If you had a 3 phase load then a 5 core may make sense.

The cable for each shower should be sized separately. It may not necessarily be a 10 sq. depending on a few factors (such as length of run) a larger cable size may be required.

cgarrad · 10-02-2020 5:11pm

The run length (15m x 3) is the reason I wanted to try and reduce the cable cost ;-D

So it's a definite no?

10-02-2020 5:13pm

cgarrad wrote: »

The run length (15m x 3) is the reason I wanted to try and reduce the cable cost ;-D

So it's a definite no?

How do you propose to terminate a 5 core 10 sq. cable at the isolator for the first shower ?
You won’t have enough terminals or space.

TheBully · 10-02-2020 5:15pm

Can I ask why your putting in a 3 phase connection? Are you running a guesthouse or something where there is potential to run 3 showers together?

Sorry I know I’m not helping just curious

TheBoyConor · 10-02-2020 5:18pm

Unless you have a very, very good reason to justify putting in 3p, then you should not be doing it. It costs substantially more in the long run.

TheBully · 10-02-2020 5:19pm

2011 wrote: »

How do you propose to terminate a 5 core 10 sq. cable at the isolator for the first shower ?
You won’t have enough terminals or space.

This could work if he put a sub board up outside one of the bedrooms but would look pretty crappy. And just ran the 10sq t+e from there but if it was my house I know what I’d be doing.

Also if cable ever fails you now have zero working showers

Xwebstar · 10-02-2020 5:24pm

TheBully wrote: »

This could work if he put a sub board up outside one of the bedrooms but would look pretty crappy. And just ran the 10sq t+e from there but if it was my house I know what I’d be doing.

Also if cable ever fails you now have zero working showers

The cable wont fail but there's no saving when you factor in a sub-board and the 3P cable has to be protected at the Main DB too

10-02-2020 5:25pm

TheBully wrote: »

This could work if he put a sub board up outside one of the bedrooms but would look pretty crappy. And just ran the 10sq t+e from there but if it was my house I know what I’d be doing.

True.
But as the cable runs are only 15m it is hardly worth it.

TheBoyConor · 10-02-2020 5:29pm

Better off running 3 cables.

A subboard introduces more complexity, additional components and more joints/connections - all additional potential failure points.

Keep it simple stupid. Even if it does cost a bit more on cable. Sure the subboard and the labour of installing it all will eat up any saving on cable costs. It is only 15 meters anyway.

Also, the heat will dissipate from 3 seaparate cables much easier than a 5 core one.

cgarrad · 10-02-2020 5:29pm

TheBully wrote: »

Can I ask why your putting in a 3 phase connection? Are you running a guesthouse or something where there is potential to run 3 showers together?

Sorry I know I’m not helping just curious

Was going with future proof, electric car and 3 showers. Think a lot of people will want it in a few years.

Xwebstar · 10-02-2020 5:29pm

Who's idea was this anyhow, there's no big saving on 45m of cable

Sure leave out the earthrod and the main isolator they're hardly ever used

dazed+confused · 10-02-2020 5:33pm

On one side there seems to be crazy spending here and penny pinching on another.

I would relook at your priorities.

As stated already, avoid three phase at all costs and I would also recommend a maximum of two instant showers in a house.

TheBoyConor · 10-02-2020 5:39pm

What is the reason for 3 instant showers anyway?

Would it not make no sense to make the main bathroom an instant shower, then mixer showers in the ensuites.

The ensuites will eb the ones most likely to be used at planned predictable times for which the HWC will be at temperature. Then for the unpredicatbel showers, visitors etc, they can use the instant shower.

Electric showers are very expensive to run.

Also, no power, no shower. Remember that. If you have a stove or whatever, your mixer showers will still work grand, albeit by candle light.

Xwebstar · 10-02-2020 5:44pm

I'm assuming op is making provision for car charging and maybe 3P heat pumps etc.

Xwebstar · 10-02-2020 5:47pm

An instantaneous electric shower on each phase of a domestic supply was all the fashion

About 20 years ago..

TheBoyConor · 10-02-2020 5:47pm

I can't see that ESB will be willing to install 3p supplies into private dwellings into the future. The demand it would place on the grid would be too great.

TheBully · 10-02-2020 6:40pm

TheBoyConor wrote: »

I can't see that ESB will be willing to install 3p supplies into private dwellings into the future. The demand it would place on the grid would be too great.

They will give it to you no problem if your willing to pay for it, nobody in their right mind would install it just for a few showers in this day and age though

Tuco88 · 10-02-2020 8:53pm

Are you allowed to use a common neutral over 3 showers like that? I wouldn't see it as good practice.

listermint · 10-02-2020 8:56pm

Tbh whatever about the showers 3 phase may well be the future in construction. With the move to electrical based heating and of course the vehicles as pointed out. The expense in the long run is old thinking.

slavetothegrind · 10-02-2020 10:34pm

You should really look at a plumbing solution here, much more cost effective in the long run.
A pumped hot water supply to all three showers from afully insulated pressurised cylinder, even an electrically heated one, is a better solution.
And only 6kw.

Xwebstar · 10-02-2020 10:41pm

Tuco88 wrote: »

Are you allowed to use a common neutral over 3 showers like that? I wouldn't see it as good practice.

I don't think there's any regulations that say you can't

No benefit over 15m runs

listermint · 10-02-2020 10:42pm

slavetothegrind wrote: »

You should really look at a plumbing solution here, much more cost effective in the long run.
A pumped hot water supply to all three showers from afully insulated pressurised cylinder, even an electrically heated one, is a better solution.
And only 6kw.

Not only better. But much nicer shower to use tbh. Thermostatic heads. Like a hotel.

Tbh I don't like electric showers and I've had a few and have a brand new silent Triton there. It's nothing in comparison to my pumped system.

Sleeper12 · 11-02-2020 9:34am

I'm in the shower repair business. Electric showers are 90 percent of my business. They are a wonderful invention. Very handy not having to heat a tank of water before getting into the shower. A energy rated. Cheaper to have a 10 minute shower in this than heating water in the cylinder by immersion or by gas. You use less water. So many positives but but they are a compromise at best.

There is nothing like a power shower. Yes you have to heat the water first, you use more water & it's not as cheap to run as an electric shower but it's invigorating. If I were you I'd have at least One of the showers on a bar mixer. with a diverter to a rain head & connected to a 2 or 3 bar pump. At least one & maybe Two. I definitely wouldn't have Three electric showers in the house. One or maybe Two. Install a priority board so only one can be used at a time & forget about 3 Phase. There are thousands of homes in Ireland manage perfectly with an EV & electric shower without issue

If you go down the road of Three phase you will save very little by not running three separate cables. Not a sparks here bet there is something in the regs saying that an electric shower must have it's own dedicated supply. You can't connect a bathroom fan to the supply for exapmle. I've no idea if sharing the neutral would break this rule or not. Plenty of good skarks here can answer that better than me.

Bruthal · 11-02-2020 10:01am

Sharing the neutral won't overload the neutral anyway. Current will be that of 1 shower with 2 showers on and be 0 with 3.

But 3 showers over 3 phases should be single phase circuits.

Tuco88 · 11-02-2020 11:04am

Id be more worried with the common neutral getting broken. Less risk with a separate cable for each one.

Xwebstar · 11-02-2020 11:14am

That risk is there for a 3P sub-board or panel in any type of installation with 1P loads

Certainly better to avoid the sub-board here as there is no need for it

JL spark · 11-02-2020 11:51am

3 phase heat pump / Air to water ,
Showers off that with a central pump for pressure, by far the best solution in my opinion,

Bruthal · 11-02-2020 11:54am

Tuco88 wrote: »

Id be more worried with the common neutral getting broken. Less risk with a separate cable for each one.

It wouldn't be a huge issue probably. Self monitoring etc.

Although not ideal if one shower was on cold only

Tuco88 · 11-02-2020 2:00pm

Would a 3phase RCD still work correctly in such case?

5 Core cable one phase for each shower and shared neutral across the 3...

Xwebstar · 11-02-2020 2:07pm

Tuco88 wrote: »

Would a 3phase RCD still work correctly in such case?

5 Core cable one phase for each shower and shared neutral across the 3...

It's not allowed or not recommended

I can't recall which

11-02-2020 2:15pm

Tuco88 wrote: »

Would a 3phase RCD still work correctly in such case?

5 Core cable one phase for each shower and shared neutral across the 3...

It would work, yes.

Xwebstar · 11-02-2020 2:19pm

It may also work but you'll be breaking another rule by creating a potential nuisance

I can't remember which specific rule that is but it's there somewhere

11-02-2020 2:26pm

Xwebstar wrote: »

It may also work but you'll be breaking another rule by creating a potential nuisance

I can't remember which specific rule that is but it's there somewhere

You are correct that it isn’t permitted but that is not the question thy was asked

Tuco88 · 11-02-2020 2:28pm

2011 wrote: »

It would work, yes.

Once the current in, is the same as the return current so..

I was just curious to if the current returning on the neutral would have any effect in different scenarios... As to when all or just 1 or 2 showers are on?

Bruthal · 11-02-2020 2:28pm

Tuco88 wrote: »

Would a 3phase RCD still work correctly in such case?

5 Core cable one phase for each shower and shared neutral across the 3...

They do.

11-02-2020 2:34pm

Tuco88 wrote: »

Once the current in, is the same as the return current so..

I was just curious to if the current returning on the neutral would have any effect in different scenarios... As to when all or just 1 or 2 showers are on?

Assuming the circuits are all healthy the phasor sum of the currents flowing in will be opposite and equal to the currents flowing out regardless of how many showers are switched on. As such the RCD will not trip.

Bruthal · 11-02-2020 8:21pm

Tuco88 wrote: »

Once the current in, is the same as the return current so..

I was just curious to if the current returning on the neutral would have any effect in different scenarios... As to when all or just 1 or 2 showers are on?

Yes the vector sum over the 3 phases and N will be 0 once no current is taking another path (earth fault).

If the neutral was left out and the 3 neutrals of the showers connected together in a star setup, the RCD still functions properly, as the vector sum of the 3 phases are still 0 with no neutral used.

So 3 phases to a motor with no neutral used, and an RCD will function properly to monitor the phases for residual current.

Ubbquittious · 11-02-2020 8:35pm

How much to get 3 phase in a house? Opens up possibilities so it does. Be tempted to get it for fluting around

11-02-2020 9:42pm

Ubbquittious wrote: »

How much to get 3 phase in a house? Opens up possibilities so it does. Be tempted to get it for fluting around

How long is a piece of string? There is no fixed price as there are so many variables. There is also an increased fixed fee. At this time our focus should be on reducing energy consumption and costs.

Tuco88 · 12-02-2020 12:02am

Thanks for the info lads.

cgarrad · 12-02-2020 7:36am

So it looks like while doable the 3 single phase runs would be better.

Thanks for all the info, way more than I expected

12-02-2020 7:59am

cgarrad wrote: »

So it looks like while doable the 3 single phase runs would be better.

Yes

Thanks for all the info, way more than I expected

If we see confusion we always add to it

autumnalcore · 15-02-2020 3:02pm

Just had three phase removed from my house added by previous owners you'd be mad to add it. invest the money in insulation, highly insulated water/buffer tanks, solar water heating. and you won't be needing a three phase heat pump, electric showers and will save a fortune in the long run

Effects · 15-02-2020 5:11pm

Ubbquittious wrote: »

Be tempted to get it for fluting around

What kind of fluting around do you want to do with 3 phase?

cgarrad · 15-02-2020 6:58pm

autumnalcore wrote: »

Just had three phase removed from my house added by previous owners you'd be mad to add it. invest the money in insulation, highly insulated water/buffer tanks, solar water heating. and you won't be needing a three phase heat pump, electric showers and will save a fortune in the long run

Had to get an upgrade as it was on a legacy 8kva, €1000 either way so mad not to get it in my eyes.

irishfire · 15-02-2020 8:30pm

cgarrad wrote:

Had to get an upgrade as it was on a legacy 8kva, â‚¬1000 either way so mad not to get it in my eyes.

Late to the game but once it's registered as a domestic connection the standing change should be the same for single/three phase. Your only variables are Urban/Rural & 24h/Dual Tariff meter

Obviously not the norm however so needs to be careful organised to make sure you don't end up registered as commercial, can be changed afterwards but easier to get it right from the start

cgarrad · 15-02-2020 8:39pm

I just signed up thru Bonkers for the cheapest bundle, paying standard standing charge and PSO.

14.8 cent unit rate as well.

autumnalcore · 16-02-2020 5:42pm

cgarrad wrote: »

Had to get an upgrade as it was on a legacy 8kva, €1000 either way so mad not to get it in my eyes.

Fair enough thats cheap there must have already been three phase on the pole.

8kva sounds terrible but in reality its probably fused 12kva at least at the cutout its a bit like a fair usage policy.

Xwebstar2 · 16-02-2020 5:59pm

autumnalcore wrote: »

Fair enough thats cheap there must have already been three phase on the pole.

8kva sounds terrible but in reality its probably fused 12kva at least at the cutout its a bit like a fair usage policy.

May have been an older setup

25amp ESB fuse was common in old houses

Xertz · 17-02-2020 8:40am

3P makes sense in most continental countries because that’s how they’ve opted to load balance on their networks. ESB just always preferred hefty single phase connections, even where 3P is available.

Single phase in say Spain is often limited to 16amps, which is ridiculously small. I know I had that in a studio apartment and tripped the main breaker quite regularly. In Ireland single phase is pretty beefy.

My view of it is you’re introducing a lot of unnecessary complexity and cost.

Also definitely consider a modern hot water storage system with a heat pump and solar inputs. You’ll have much more pleasant showers.

A lot of the calculations around immersions being hugely inefficient are based on the old copper tanks, which are ludicrously badly insulated and the use of just a resistance element.

A good tank is almost like a thermos flask and you’ll get very, very little heat loss, if it’s installed correctly. Add a pump and you’ll have very good water pressure and far more luxurious showers.

Also if you’re using locally pumped electric power showers they are very noisy. Whereas a central pump (well located and isolated on an anti vibration pad) is likely to be far less annoying.

Just be very aware of where you site the pump.

Ours is in a basement and you wouldn’t really know it’s running at all. However some are located right in the middle of the bedroom areas with a hot press. Definitely creates extra noise.

Also bear in mind a hot press with a modern hot water heater will neither have space to store towels nor will it be hot. They’re fridge freezer sizes units and they don’t bleed heat so, you’ll just have a big appliance in a press. If you can site or somewhere like a ground floor, a garage or a basement it makes a lot more sense noise wise.

Showers on 5 core cable?

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