Extend existing 40A unused circuit to shed

Discussion in 'Electricians' Talk' started by dtexh, Oct 22, 2021.

  1. bright_Spark

    bright_Spark Screwfix Select

    Then you are not adding the circuit so is not a new circuit albeit it has a different name from shower to shed.
     
  2. dtexh

    dtexh Member

    Yes, but the council could argue on a technicality that the shed consumer unit isn't just a big switch!
     
  3. The Happy Builder

    The Happy Builder Screwfix Select

    Is this so called shed is actually a substantial new building that has already been brought to the the attention of the council by a neighbour?

    Do you really think that if the council gets involved with inspecting the electrical installation they will accept that the entire electrical installation in this new building is just an extension to an unused circuit in the main house?

    If I were the inspecting electrician working for the council the first thing I would ask for would be the design calculations for this installation and a written specification, do you actually have them?

    You appear to have spent several months differing about try to decide how to install this electrical installation and the proposal you have come up with seems to be a bodge job, a 40 amp socket circuit and a couple of SFCU with a potentially underrated circuit cable.
     
  4. Jimbo

    Jimbo Screwfix Select

    If it were me, I'd use a a 5-module CU like this from our hosts: Wylex 7-Module 5-Way Part-Populated Main Switch Consumer Unit | Consumer Units | Screwfix.com

    Then use:

    - B16 for UFH
    - B6 for lights
    - B20 for a radial for the sockets in 2.5mm

    Use 3-core SWA terminated in a gland directly in the CU. Leaves a couple of spare slots for anything in the future. As you're paying the fee anyway may as well just do it the conventional way IMO. If the resulting loop impedance comes out too high can always down-rate the source to B32.
     
  5. bright_Spark

    bright_Spark Screwfix Select

    The way the OP has described this in his first post, I have assumed just a shed. If this is merely a shed with a couple of sockets and a light in it, then why go to all of the trouble by notifying it in the first place? You won't gain anything by notifying a shed unless you are a registered electrician. It costs us a couple of pounds to self certify the job so we do it because that is part of the deal. If I was not registered I would certainly not go to the expense of notifying this. I am not saying bodge it up but do it properly and leave it at that. You are not a registered electrician so the hassle and expense outways any benefits you would gain. If you ever sell the house then the shed would go on the EICR and if it is wrong then it simply gets this added to the report. Even if you notify this job and it gets passed it is not going to add any value to the house.
     
    rogerk101 and Jimbo like this.
  6. Tony Goddard

    Tony Goddard Screwfix Select

    Exactly this, the council will not be even slightly interested in a shed, LABC offices are universally under staffed and busy with loads of big building projects, nor will a prospective buyer, the electrics in most sheds and garages are appalling even if the house is perfect, becuae often even when a house is re-wired the spark just re-connects the cable to the shed that has been in place for 40 years - yours already sounds much better.

    You are over thinking it, you clearly seem to have enough knowledge to make a decent job of it, so honestly, just press on with it, save lots of cash and agro.
     
    rogerk101 likes this.
  7. The Happy Builder

    The Happy Builder Screwfix Select

    That’s more like it, the UFH could be on a B10 as it’s only a 7 amp load.
     
  8. dtexh

    dtexh Member

    Thanks everyone. Going to do it properly, yes would be totally stupid to deliberately bodge it just to get around Part P on a technicality.
     
  9. The Happy Builder

    The Happy Builder Screwfix Select

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