Is my consumer unit adequate

[burnsey]

I want to install a 10.8kw mira shower but I'm not sure if my consumer unit is up to the job. I know from reading the other posts about the same topic that I need a minimum of 10mm2 cable and a 45amp MCB. my current shower is a 8.5kw so I'm guessing the cable will need to be changed but i'm not sure if my consumer unit will take a 45amp MCB.
Can anyone confirm if my consumer unit will take a 45amp MCB and if yes where can i get one from?

I'm not a sparky and my knowledge on electrics is almost zero so if you could keep your response in simple terms that would be much appreciated.

Untitled

• burnsey
• 4 Apr 2008
• 1

 

[daytona]

i assume the 32a mcb is the existing shower circuit?

CU looks ok but its hard to tell with the cover still on it,if your main bonds are present.

are you using a sparks for the work?

if not how will you get the cable from a to b ,bonding,notification etc?

most of the mainstream wholesalers will get the new mcb in for you not sure who has it as stock though

 

[GaryMo]

Depends if your 10.8kW rated shower is at 230v or 240v.
If it's rated at 230v then you'll require a 50A MCB, at 240v it's bang on 45A.

 

[comms]

www.thefusecompany.co.uk

The GE range E mcb's also fit Ashley cu's

Yes the cu will take a 45amp mcb but you need to check on the circuit cable size

 

[GaryMo]

Yes the cu will take a 45amp mcb but you need to check on the circuit cable size

He mentioned he needs a minimum of a 10mm2 cable so he has that one covered.

 

[kevnurse]

Burnsey,

As suggested, your CU appears to accept mcbs from GE, who also make 50A mcbs.

I'm not a pro lecky, but I reckon that a 10.8kW shower will need a bigger mcb than 45A on either 230V or 240V. IMHO the power spike when you switch it on to HIGH from off, even with 240V, will trip a 45A mcb. If you switch to LOW or MEDIUM before HIGH, the spike should not be so great. To allow for flexibility of operation, I would use a 50A mcb, which will give you the protection against a 15% increase in current, due to faults, and prevent nuisance tripping.

 

[GaryMo]

I'm not a pro lecky, but I reckon that a 10.8kW shower will need a bigger mcb than 45A on either 230V or 240V. IMHO the power spike when you switch it on to HIGH from off, even with 240V, will trip a 45A mcb.
To allow for flexibility of operation, I would use a 50A mcb, which will give you the protection against a 15% increase in current, due to faults, and prevent nuisance tripping.

Is this from experience?

A B type MCB will trip between 3-5xIn, for a B45 that's between 135A and 225A. I think there's a little headroom for an initial current spike!

Also why would you use a larger MCB to protect against faults?

 

[burnsey]

daytona
Yeah thats the existing shower circuit. I've turned it off because the shower is leaking internally. I'll run the cable from A to B myself but yes I will get a qualified sparks to do the final connection. I'll either try to run it where the existing one is which is down the dot and dab cavity (which I know will take alot of swearing) or I'll bring it down a stud wall and then through the ceiling above the CU.

GaryMo
I've found the instruction manual for the one I want and it states the following: -
"10.8KW 240V AC (9.9kw 230V AC) heater"

and then goes on to

"As a guide only 10.8kw = 45amps. It is strongly recommended that a 30mA RCD is included in the electrical circuit."

comms
Thanks for the link but from what I can see they don't do 45amp.


Thanks for the help everyone. I guess now my question is do I need a 45amp or 50amp MCB. If I need 45amp is it safe to use a 50amp?

 

[ban-all-sheds]

Thanks for the help everyone. I guess now my question is do I need a 45amp or 50amp MCB.

45A.

10800 ÷ 240 = 45

9900 ÷ 230= 43

If I need 45amp is it safe to use a 50amp?

Depends on cable size, and what it runs through. 10mm² might not be OK - would it run through insulation, or behind insulated wall covering?

 

[burnsey]

Thanks for the help everyone. I guess now my question is do I need a 45amp or 50amp MCB.

45A.

10800 ?0 = 45

9900 ?0= 43

If I need 45amp is it safe to use a 50amp?

Depends on cable size, and what it runs through. 10mm? might not be OK - would it run through insulation, or behind insulated wall covering?

No. The cavity between plaster board and block work wall is uninsulated and so are the stud walls if I went along that route.

If it's 45amp I need then that's the way I'll go, and if I can't get my hands on one then I guess it's an indendant 45amp consumer unit like this one.

http://www.toolstation.com/?r=f&feature=63252

Don't really want to take chances on the 50amp MCB when the cost is only an extra £22.00 to do it the correct / safe way.

Thanks for the input.