What Kw electric showers can safely be run from 6mm

[Justin_Scotland]

Hi All,

I just purchased a house that currently has a Heatrae Sadia (Saphire) shower installed. I pressume its 7Kw as during winter I get only a very weedy drible of hot water.

My next job is to get this replaced with a better equiped and better performing shower however I do not want to have to get wiring changed. I therefore presume it will have std 6mm cabling (haven't looked inside yet)

My question is what Kw rating for electric showers could I safely run from this feed. I was looking at the Mira Sport range of showers and believe 9Kw would be okay but wondered if I could use 9.8 or 10.8Kw?

Any help would be very gratefully received.

Regards

Justin

 

[ChrisR]

10mm seems to be the recommendation tho it seems OTT to me. Try the sparks forum?

Even 11kW showers are piddling at about 4 litres/min.

Consider using a Triton T40 or similar - small pump for your mixed H&C, usually give around 8 l/min. The "feel" is different though cos the mains is higher pressure, which means faster water if the jets are appropriately small.

 

[Justin_Scotland]

Due to he artic tempratures up here in bonny Scotland I think the heating unit in the shower has to melt the water before it can actually heat it up.

Unfortunately changing the existing plumbing to hot and cold feed would mean ripping out all the tiling and replumbing which is extra cost I don't want to pay out for.

So is 9kw the best I can go for with the 6mm cable?

Thanks

Justin

 

[Bahco]

You can go up to approx 18 metres of 6 mm up to an 8.5 kw shower.
A 9 kw should be wired with a 10 mm cable.
Don't forget the RCD which every shower should have.
Sparks will give you chapter and verse if you ask nicely

 

[ban-all-sheds]

Hi All,

I just purchased a house that currently has a Heatrae Sadia (Saphire) shower installed. I pressume its 7Kw as during winter I get only a very weedy drible of hot water.

Might just be an old under-performing heater can.

My next job is to get this replaced with a better equiped and better performing shower however I do not want to have to get wiring changed. I therefore presume it will have std 6mm cabling (haven't looked inside yet)

There's nothing "standard" about 6mm² cable, any more than there is any other size. If it is a 7kW shower then the cable might well be 4mm². You need to check and make absolutely sure. Also, you need to find out what the rating of the fuse/MCB is, how long the cable is, and how it is installed (i.e. surface, in plaster, in insulation, bunched with other cables etc), as these factors all affect how much current it can carry.

My question is what Kw rating for electric showers could I safely run from this feed. I was looking at the Mira Sport range of showers and believe 9Kw would be okay

If your cable is 6mm² it might be OK, or it might not, it depends on how the cable is installed.

but wondered if I could use 9.8 or 10.8Kw?

No way.

Any help would be very gratefully received.

http://www.tlc-direct.co.uk/Book/4.3.1.htm

 

[Justin_Scotland]

Thanks Bahco, ban-all-sheds.

I finally took the front cover off the old shower last night to have a peek inside and work out what wiring I actually have. Unfortunately what I was doesn't actually mean a lot to me.

There's nothing "standard" about 6mm² cable, any more than there is any other size. If it is a 7kW shower then the cable might well be 4mm². You need to check and make absolutely sure. Also, you need to find out what the rating of the fuse/MCB is, how long the cable is, and how it is installed (i.e. surface, in plaster, in insulation, bunched with other cables etc), as these factors all affect how much current it can carry.

The fuse box for the house is only about 4-5 metres below where the shower unit is. The cable will run through plaster walls for half the length and then through the floorboard space and down into the understairs cupboard into the circuit breaker.

Now it has a separate isolator switch on a pull cord from the ceiling therefore I guess the total length of cable to be considered is from the main breakers -> isolator -> shower? In this case it could be up to 8-9 metres

What does a 6 mm cable look like (apart from 6mm wide) is there a certain number of strands to each of the positive / negative feeds? Mine seems to be made up of 4/5 thick wound strands of wire to +ve and -ve.

Or can 6mm and 10mm be supplied in different formats?

Maybe I will take digi image and try to embed an image into the thread.

Thanks

Justin

 

[Bahco]

Start a new post on the Electrics UK forum as they will be better to advise you.
My opinion (for what its worth) is to fit Rcd , 10mm cable, and a 10.5 Kw shower. You will get a better flow and is worth the extra cash

 

[Bahco]

Start a new post on the Electrics UK forum

Didn't realise the mods had already moved it

 

[Careful_Bodger]

Justin........

What does a 6 mm cable look like (apart from 6mm wide)

Erm - I think this actually refers to cross sectional area of the L & N conductors.

 

[ban-all-sheds]

The fuse box for the house is only about 4-5 metres below where the shower unit is. The cable will run through plaster walls for half the length and then through the floorboard space and down into the understairs cupboard into the circuit breaker.

If it's 6mm² cable, I wouldn't advise a loading of more than 38A.

Now it has a separate isolator switch on a pull cord from the ceiling therefore I guess the total length of cable to be considered is from the main breakers -> isolator -> shower? In this case it could be up to 8-9 metres

Length is not a problem re volt drop.

What does a 6 mm cable look like (apart from 6mm wide) is there a certain number of strands to each of the positive / negative feeds? Mine seems to be made up of 4/5 thick wound strands of wire to +ve and -ve.

1) As C_B said, the size refers to the cross-sectional area of the phase conductors, nothing to do with the overall size of the cable. If you hae a look here: http://www.tlc-direct.co.uk/Main_Index/Cable_Index/Twin_and_Earth/index.html , they tell you the typical overall dimensions of Twin & Earth cable. Couple of pointers:

1) I expect yours has 7 strands, not 4/5. 4mm² and above has stranded conductors. When you get to 10mm², the earth conductor becomes stranded as well.

2) It's not positive/negative - it's live/neutral. The actual voltage of live with respect to neutral varies from +325V to -325V 50 times a second....

Or can 6mm and 10mm be supplied in different formats?

No.

Edited to correct a spelling mistake I only just spotted. Shame on me.

 

[Justin_Scotland]

Surprising the range of answers I got from plumbers who came round to quote for actually swapping the unit. General was 8.5KW but couple came in at 9KW and some even 9.5KW. That was without them even taking the front of the shower off. Must have xray eyes..

Fortunately as you can tell from my

positive/negative

I won't actually be doing the work myself as anything that involves electricity and water I would much rather leave to the professionals. However the useful information you have given me has now made it clear which of the plumbers not to go for.

Thanks all for your time and patience with a newbie.

 

[dingbat]

Surprising the range of answers I got from plumbers who came round to quote for actually swapping the unit...


However the useful information you have given me has now made it clear which of the plumbers not to go for.

Ah... then no wonder you got a range of answers. I dare say you'd get a range of answers if you asked a few electrician which lights best matched your curtains. If you had a mixer shower then I'd say you need a plumber every time, but when it comes to electric showers... well the clue is in the name.

 

[jenki]

Surprising the range of answers I got from plumbers who came round to quote for actually swapping the unit.

Maybe you should ask for some quotes from electricians?? - after all, you'll only get wet if they get their 'second' trade wrong

EDIT: Beaten to it by Dingbat , drat

 

[dingbat]

EDIT: Beaten to it by Dingbat , drat

 

[t4msy]

Maybe you should ask for some quotes from electricians?? - after all, you'll only get wet if they get their 'second' trade wrong

I fully agree unless the plumber is also a qualified electrician i wouldn't let him touch it. I once saw a plumber try to run a 9Kw on a fused spur off the ring and couldn't work out y the fuse kept blowing.