cable size for shower

[John robertson]

Hi guys I have been asked to fit new shower and run new cable for it too, looking at regs book it would have to be reference method 103, which for 8.5kw shower would mean 16mm cable, can terminals in the shower take 16mm and the terminals in the isolator? I have tried looking for different cable routes but the board is downstairs and the bathroom is upstairs. 10mm is what is in at the moment. I don't usually do domestic electrical work so any advice would be great. I just thought 16mm was a bit overly for 8.5kw shower.

 

[telectrix]

cut some insulation out.

 

[buzzlightyear]

Hi guys I have been asked to fit new shower and run new cable for it too, looking at regs book it would have to be reference method 103, which for 8.5kw shower would mean 16mm cable, can terminals in the shower take 16mm and the terminals in the isolator?

Are you pulling sub main for it has well
what volt drop for this.

 

[Pete999]

What calculations have you done to arrive at 16mm2 for an 8.5 shower?
.

 

[telectrix]

irrc, 10mm ref.103 is down to 32A. shower is 35A (and a bit).

 

[John robertson]

I just used one of those online volt drop calculator things and they come up with 16mm also. just I was looking at the regulations book for 10mm ccc and noticed with method 103 that it would be rated to 32 amps therefore I would have to go to 16 as the shower is 35.4 amps. I was just going to run 10mm but I guess I should go 16 to be in line with regs. I cant see any other different cable route. I have spoken to other electricians and they have said to just run 10mm but I would rather be safe than sorry. I usually work offshore so this domestic side is something im not really familiar with. thanks for your help

 

[buzzlightyear]

just used one of those online volt drop calculator things and they come up with 16mm also. just I was looking at the regulations book for 10mm ccc and noticed with method 103 that it would be rated to 32 amps therefore I would have to go to 16 as the shower is 35.4 amps. I was just going to run 10mm but I guess I should go 16 to be in line with regs. I cant see any other different cable route. I have spoken to other electricians and they have said to just run 10mm but I would rather be safe than sorry. I usually work offshore so this domestic side is something im not really familiar with. thanks for your help

Rule with a big thumb stick in 10mm
For a up grade of shower.

 

[Pete999]

Hi guys I have been asked to fit new shower and run new cable for it too, looking at regs book it would have to be reference method 103, which for 8.5kw shower would mean 16mm cable, can terminals in the shower take 16mm and the terminals in the isolator? I have tried looking for different cable routes but the board is downstairs and the bathroom is upstairs. 10mm is what is in at the moment. I don't usually do domestic electrical work so any advice would be great. I just thought 16mm was a bit overly for 8.5kw shower.

You don't mention in your post the length of the run of this circuit.

 

[LastManOnline]

Hi guys I have been asked to fit new shower and run new cable for it too, looking at regs book it would have to be reference method 103, which for 8.5kw shower would mean 16mm cable, can terminals in the shower take 16mm and the terminals in the isolator? I have tried looking for different cable routes but the board is downstairs and the bathroom is upstairs. 10mm is what is in at the moment. I don't usually do domestic electrical work so any advice would be great. I just thought 16mm was a bit overly for 8.5kw shower.

Well there is a little bit of history in the making here for me. An 8.5 kW shower wired in 16mm?.Am really curious to know the installation conditions for this one. I must assume it is immersed in insulation and on the top floor of a 3 story structure?

 

[bill01803]

16mm goes in Mira showers and Crabtree pull switches

 

[Strima]

16mm for the run through insulation then 10mm from an isolator switch of you need to drop cable size.

 

[littlespark]

Think how many small showers have been originally wired in 6mm, then attics filled with scratchy wool, then the shower upsized to a 9.5kW.

the vd must be massive.

 

[telectrix]

leave the 10mm as it is. clear some of the insulation round it, fit new shower, grab the cash.(then go home and dry behind your ears).

 

[pirate]

Run the feed in the insulation with IrnBru bottles...made in Scotland from GIRDERS! No VD there!

 

[Pete999]

16mm goes in Mira showers and Crabtree pull switches

Bit of a tight fit though?

 

[Pete999]

Bit of a tight fit though?

So consequently unsafe, 4 by 16mm2 in a plastic accessory, get real Mate please.

 

[Welchyboy1]

Think how many small showers have been originally wired in 6mm, then attics filled with scratchy wool, then the shower upsized to a 9.5kW.

the vd must be massive.

And theystill probably running fine

 

[bill01803]

Bit of a tight fit though?

Fits fine

 

[LastManOnline]

And theystill probably running fine

Yes. I posed a question on a different forum as to whether any spark had come across a heat damaged 6mm cable supplying an electric shower.?. No one had. I personally never have. House I, m currently renting has our shower wired in 4mm (lying on top of, not under insulation) .To date every shower repair I have personally carried out has always been either a heat damaged pull switch or a heat damaged rcbo

 

[Grant1987]

Yes. I posed a question on a different forum as to whether any spark had come across a heat damaged 6mm cable supplying an electric shower.?. No one had. I personally never have. House I, m currently renting has our shower wired in 4mm (lying on top of, not under insulation) .To date every shower repair I have personally carried out has always been either a heat damaged pull switch or a heat damaged rcbo

It’s bad practice though isn’t it, when carrying out EICR’S I code it as a C3 with no thermal effects and downgrade mcb to 32A rather than the 40A installed. If I’m asked to replace faulty shower which is 8.5kw or above on a 6mm cable I will renew cable with 10mm it’s the right thing to do isn’t it.