Replacing old electric shower

[Paullovell]

Hi,

I have a very old Redring 7000w electric shower that has broken down. I want to replace it with a low pressure 7.2w or higher watt model. All the existing cabling is fine - its 6mm 2 core twin and earth from a 20amp supply running from the mains supply.

I think i have to upgrade the fuse to take the extra load to 30amp? Will the wiring take the extra load?

Many thanks in advance.

Paul

 

[ericmark]

Thermoplastic insulated and sheathed flat cable can be rated as low as 23.5A to 47A according to how installed. In the main it is rated at 32A but the problem with any pre-installed cable is without the original installation certificate it is hard to work out if any part of the run goes through areas which would reduce it's current rating.

Reference Method 103 (in a stud wall with thermal insulation with cable not touching the inner wall surface) is nearly impossible to see. No electrician can know if the cable is or is not touching the inner wall surface without opening up the void.

7Kw is 30.5A and the question is why was a 20A Fuse/MCB fitted as clearly this is not the correct size for even a 7kW appliance. The Fuse/MCB is a thermal device and will not trip straight away but will take some time as will the cable to heat up. So using a 20A would mean the trip will open before the cable overheats allowing short showers only. Not the way it should be done but only reason I can see for 20A Fuse/MCB.

Maybe since you say fuse although it says 20A it has a larger fuse wire inside. Not the way it should be done but it was done and one has to be realistic. However there has been a requirement for RCD protection for some time now and to install RCD protection with a fuse is unusual although not impossible.

Both my old Wylex consumer units are protected by 30ma RCD's and I could fit re-wire-able, cartridge or MCB's into the unit but this is rare. In the main re-wire-able fuses are only now used where there is a electrician always on site they are not used in the home as too easy to end up with wrong size or type of wire.

I would guess that in your case a lot more than simple change is required.

 

[ban-all-sheds]

Will the wiring take the extra load?

• //www.diynot.com/wiki/electrics:mcbtocable
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://www.tlc-direct.co.uk/Book/4.3.11.htm
  
  
• http://www.tlc-direct.co.uk/Book/5.3.1.htm
  
  
• http://web.archive.org/web/20070327014113/http://www.kevinboone.com/cableselection_web.pdf
  
  
• http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
  
  
  
  
• http://www.tlc-direct.co.uk/Book/8.1.1.htm