Shower mains cable

[grim_d]

Hi all,

I know there are a few excellent sparks on here so just looking for a bit of advice. Have recently moved into a new house and the electric shower is terrible, water pressure is good though. I have a plumber coming Wednesday to advise if I could run one from the combi but I fear due to length of hot water run a meagre electric shower upgrade will have to suffice. Currently there a 9.5Kw one in, I would want to bump it to a 10.5Kw, anything would be better.

I've done some research but just looking to clarify to see if the current wiring is suitable, I just want to make sure things are safe.

So 10.5Kw/230V = 45.65A

I have a 10mm2 cable coming from the CU into a standalone 63A RCD, up some plastic trunking into the loft where is it not clipped onto anything then goes into the shower switch then from there down a cavity wall into the shower. The run from the CU to the shower is approx 8 metres.

There was some insulation in the loft on top the cable which can be permanently moved on put under the cable. The ceiling and walls are lath and plaster. I would say there is no insulation in the cavity wall based on the other walls having none but I cannot confirm. Which reference method should I use to determine the cable rating?

It wouldn't be a huge deal to replace the cable with 16mm2, but wouldn't that be hellish to terminate in the switch and shower? FYI I am pretty happy doing a bit of wiring usually but will probably have a spark deal with a shower if that's the way I have to go.

Thanks,
G

 

[Wendelspanswick]

Hi all,

I know there are a few excellent sparks on here so just looking for a bit of advice. Have recently moved into a new house and the electric shower is terrible, water pressure is good though. I have a plumber coming Wednesday to advise if I could run one from the combi but I fear due to length of hot water run a meagre electric shower upgrade will have to suffice. Currently there a 9.5Kw one in, I would want to bump it to a 10.5Kw, anything would be better.

I've done some research but just looking to clarify to see if the current wiring is suitable, I just want to make sure things are safe.

So 10.5Kw/230V = 45.65A

I have a 10mm2 cable coming from the CU into a standalone 63A RCD, up some plastic trunking into the loft where is it not clipped onto anything then goes into the shower switch then from there down a cavity wall into the shower. The run from the CU to the shower is approx 8 metres.

There was some insulation in the loft on top the cable which can be permanently moved on put under the cable. The ceiling and walls are lath and plaster. I would say there is no insulation in the cavity wall based on the other walls having none but I cannot confirm. Which reference method should I use to determine the cable rating?

It wouldn't be a huge deal to replace the cable with 16mm2, but wouldn't that be hellish to terminate in the switch and shower? FYI I am pretty happy doing a bit of wiring usually but will probably have a spark deal with a shower if that's the way I have to go.

Thanks,
G

If you use 90 C cable 10mm will suffice even if run through insulation.

Multicore 90°C Thermosetting Insulated and Thermoplastic Sheathed Cables, Non Armoured
Tables Apply to: 6241B, H6242B, H6243B

Voltage: 230V

Load: 10.5kW / 45.65A

Length: 8m

Method of Installation: Enclosed in conduit in thermally insulated walls

Cable Size: 10mm²

 

[steve_s]

It will still be rubbish ! electric shower are just a kettle mounted on the wall a will never be able to heat water fast enough for a decent show no matter how bigger cable you put in, just put a bar mixer in, length of hot water run wont be a problem (unless we are talking 3 streets over) and if it over a bath you will have all the necessary pipework already there,and that way you will get hot water at slightly lower (due to it going through the combi)than incoming main pressure

 

[Tigman]

shower from combi should work ok but you will have to wait for it to get hot if the pipe runs are long , must be thermostatic aswell for safety reasons !

 

[grim_d]

If you use 90 C cable 10mm will suffice even if run through insulation.

Multicore 90°C Thermosetting Insulated and Thermoplastic Sheathed Cables, Non Armoured
Tables Apply to: 6241B, H6242B, H6243B

Voltage: 230V

Load: 10.5kW / 45.65A

Length: 8m

Method of Installation: Enclosed in conduit in thermally insulated walls

Cable Size: 10mm²

So I would need to change to better 10mm2 cable, the current cable has a 70C rating. not a big deal.

It will still be rubbish ! electric shower are just a kettle mounted on the wall a will never be able to heat water fast enough for a decent show no matter how bigger cable you put in, just put a bar mixer in, length of hot water run wont be a problem (unless we are talking 3 streets over) and if it over a bath you will have all the necessary pipework already there,and that way you will get hot water at slightly lower (due to it going through the combi)than incoming main pressure

Oh I know, my last house had a tremendous gravity fed mixer from a hot water tank and I really miss it! Flow like a waterfall and 60C if you wanted to remove your skin!

Plan A is to run a mixer from the bath pipework as you say but at full flow the boiler can only get the water to about 40C at the moment and I suspect when the temperature really drops it will affect it. Pressure through the combi is fine and waiting for it to heat up is no problem as used to that from last house.

Have also read that thermostatic shower mixers also always mix a bit of cold water which would drop it further?

 

[Tigman]

needs a thermostatic because if whilst showering someone runs kitchen cold tap it can reduce cold to shower and scald the person in the shower

 

[p0689109]

I beg to differ steve_s as my electric shower is great. I have never had it at the top of the hot scale as that would burn but the flow is still great. It is a Mira Sprint by the way. Two flow selections though we always have it on the max. I like a hot shower too with loads of water flow and this does the bis!

 

[tlovatt]

Try some different shower heads, some are very good at making the flow rate seem better than it is. It will never be the same as a truly large water flow, but some of the large diameter heads can make a smaller shower feel like it is giving a higher flow than it does.

 

[DrDeAtH]

Mira Advance shower.
It won't reduce flow as you ramp up the temperature. It's also thermostatic.
Not cheap, but a decent bit of kit. Just put a scale reducer (sesi or limefighter) inline Max 2m from the shower unit

http://www.screwfix.com/p/mira-advance-thermostatic-electric-shower-white-chrome-9-8kw/7380g

 

[Kayos]

I have a Mira Sport electric shower with a Villeroy & Boch head I acquired some time ago...

One of the best showers I've ever had, no point running from a combi, as if it breaks you have no way of getting a shower, I did consider a Mira Excell but decided against it because of the above. My water pressure is around 10 bar (a lot of bradford is) so I have a pressure reducing valve on the cold mains, but the flow rate is still immense

 

[DrDeAtH]

I see a mira theme emerging

That's because Triton showers are unreliable rubbish nowadays. I stopped fitting them years ago.

 

[500e]

Big tank & 4 bar pump

 

[Justme]

A 1kw increase is not going to light your fire.

 

[grim_d]

Try some different shower heads, some are very good at making the flow rate seem better than it is. It will never be the same as a truly large water flow, but some of the large diameter heads can make a smaller shower feel like it is giving a higher flow than it does.

The whole thing is knackered, the rail cant hold up the shower head that's there as it is, and removing the shower head yield a woeful trickle when on hot. It is time for a new unit of whatever kind.

Our electric shower is good too (mira jump) and likewise never had the temp control to max (2/3 of the way up is enough to make skin red and tingly).

We had a shower off a combi before and it was awful, to get the water hot enough it had seriously reduced flow (so the boiler could keep up) - it was a little better than the gravity fed mixer one before that (header tank was like 2ft above the shower head).

The sole drawback to the electric one is the amount of electric it sucks through the meter...

That is my fear, our boiler can only heat the water to hot at about half flow.

I'm not particularly worried about the lecky cost as our last house had a very old conventional boiler system...£200+ a month for gas and lecky.

Big tank & 4 bar pump

Yes that would be ideal with a system boiler, Perhaps in future but as we have many changes planned including relocating the bathroom in future, we just want to improve for now.

A 1kw increase is not going to light your fire.

Correct but a better shower should work better, and if I'm replacing the shower I might as well go for the max available.

 

[DrDeAtH]

My mum's place is 6 years old, landlord fits triton electric showers.

When they work they're just fine.

She's on the 4th (I think) unit...

I rest my case...

 

[DrDeAtH]

The whole thing is knackered, the rail cant hold up the shower head that's there as it is, and removing the shower head yield a woeful trickle when on hot. It is time for a new unit of whatever kind.



That is my fear, our boiler can only heat the water to hot at about half flow.

I'm not particularly worried about the lecky cost as our last house had a very old conventional boiler system...£200+ a month for gas and lecky.



Yes that would be ideal with a system boiler, Perhaps in future but as we have many changes planned including relocating the bathroom in future, we just want to improve for now.



Correct but a better shower should work better, and if I'm replacing the shower I might as well go for the max available.

Click the link in my first post. It's what you need.

 

[WorkshopChris]

My water pressure is around 10 bar (a lot of bradford is) so I have a pressure reducing valve on the cold mains, but the flow rate is still immense

Wow, last time i looked our mains water pressure was around 3Bar on a good day. We have a water tower almost at the end of our garden so you might expect it to be better.

 

[Rig Pig]

The whole thing is knackered, the rail cant hold up the shower head that's there as it is, and removing the shower head yield a woeful trickle when on hot. It is time for a new unit of whatever kind.



That is my fear, our boiler can only heat the water to hot at about half flow.

I'm not particularly worried about the lecky cost as our last house had a very old conventional boiler system...£200+ a month for gas and lecky.



Yes that would be ideal with a system boiler, Perhaps in future but as we have many changes planned including relocating the bathroom in future, we just want to improve for now.



Correct but a better shower should work better, and if I'm replacing the shower I might as well go for the max available.

You don't need a huge flow of hot water to a shower, I suspect that you boiler is more that 10.5kW so it should be able to keep up.

 

[grim_d]

You don't need a huge flow of hot water to a shower, I suspect that you boiler is more that 10.5kW so it should be able to keep up.

Ok well that's reassuring, plumber should advise me on Wednesday. 30Kw DHW.

 

[brightspark]

I see a mira theme emerging

I bought a mira sport 10.5kw it had only been fitted and removed in someone's house for 6 weeks and I scored it for 20 quid its brill wired in 10mm cable