Best way to add Garage circuits

[Joeka101]

Hi,

I am a keen DIYer (dangerous phrase - I know) but will NOT be doing this work myself and will be getting a local sparky (Part P etc) in. However I'd like some advice as I want to check its the best way of doing things.

I have a Tenby split load Consumer Unit (circa 2005) in the Garage with usual 100A main isolation switch, Non-RCD side and an 80A RCD protected side each having >4 unused ways. All inspected a couple of years ago and OK.
- Non-RCD side = 2 x 6A Lighting Circuits [Circa 1960 wiring so no earth wire and are on non-RCD side (I changed all light fittings etc for Class 2 double insulated and all switches have nylon screws)]
- RCD side = 2 x 32A Ring Main (1960s detached house not a mansion!) and 1 x 32A Cooker Radial

I am looking to add the following circuits in the Garage:
- 32A 2.5mm ring main (6 x double sockets) - to power 3 x Fridge / Freezers and occasional single power tool
- 2 x 32A 6mm radial circuits to 2 x Cooker Isolation switches used to feed my homebrew setup (2 x 5500W heating elements)
- 16A Radial / Ring main for an outdoor socket (would prefer not to have on same ring main as above due to load as all 3 freezers may go on at same time etc and outdoor socket is for charging an electric car so heavy load)

The electrician I had in was not keen on adding MCBs to RCD side, increasing RCD to 100A or using RCBOs non-RCD side so quoted for getting a separate garage consumer unit (to go next to the original) and splitting the feed from the main fuse.

The high power heating elements are only on for maximum 2 hours every few weeks and when I do this I switch all the fridge / freezers off.

What does the extra consumer unit add?
Are you within regs to add circuits to a consumer unit like I currently have (with non-earthed lighting etc)?

Thanks!

Joe

 

[Octopus]

I would say the advice the spark has given you is what I would say.

Adding more MCB's to the RCD side of the board means that when the RCD trips ............. you will loose more circuits

Adding RCBO's is an option - if they are available from Tenby ..... not product line I'm familiar with

The non earthed lighting circuit is irrelevent IMHO

So adding a 2nd board, with RCBO's for each circuit will add a little to the costs but mean any 1 circuit tripping won't affect any other circuits

I would say consult a couple more sparks and make sure that they confirm in writing to you that they will provide an EIC and Part P certificate...

Hope this helps

 

[buzzlightyear]

MCB - http://www.legrand.com.sg/products/protection/circuit-breakers-accessories/mcb/ not tenby any more .

 

[Joeka101]

Thanks guys. Point taken about RCD on existing board will trip all circuits if these are added on, however given that the heating elements are rarely used and I would be with them in the garage whilst in use (where the CU also is) this wouldn't be a big problem to me.

The Tenby CU has a mixture of legrand and MK MCBs (which is as we bought the house 5 years ago!) already.

I guess my question is if the combined load of Main and Garage CU can still only be 100A at once (I appreciate diversity but with 2 X 24A elements on the go, it's not beyond possibility), why not just add circuits to the existing CU (neater for my OCD!) or even replace it with a new dual 80A RCD one? (sparky implied they couldn't replace or "mess" with CU due to the non earthed lighting circuits being outdated - though I believe still acceptable).

I will check certificates, Part P etc.

Cheers.

 

[Toneyz]

If it was me I would check if the Legrand protective devices can be used in the Tenby consumer unit.
circuit for fridges/ freezers & power on non protected with RCBO s
RCBO non protected side 32A for each of the heating loads
An MCB circuit on RCD protected side for car charger/electric vehicle.