Hi, I am finally getting around to building a new garage and am in discussion with the builder about the electrics I require in it. I was thinking of having a 13a ring main, lights and also a higher power supply for my mig and arc welders. I have always used the latter on 13a three pin plug supply but every so often a welder can trip the fuse. Can anyone advise on the spec that I should install? Thanks in advance!
A dedicated 25A or 30A radial circuit. Or a cooker circuit in general terms. You can use a spot welder on that if you so wish. 16A plug. Check if your consumer box/fuse box has the capacity? For so called 13A socket outlets you can spur off with a fused spur. lighting also. Depends on length of run from your incoming supply? 6mm csa cable should be up to it.
Thank you for the quick reply. My consumer unit has plenty of spare fuse ways if that is what you mean by capacity? The supply currently goes into the existing integral garage. That will be converted and the distance to the new garage will be effectively the width on the existing single garage so 8-10 ft. Would it be best to run supply form the existing consumer unit to a consumer unit in the new garage? I have not fitted and used a 16A plug before, I will have to investigate those. Thanks for your very helpful reply.
My builder insisted the new build garage electrical wiring was totally separate to and independent of the house wiring. This was to avoid having to treat the house and new build garage as a whole new entity requiring all wiring to be certified. If your new build garage is attached to the house, check the building regs for smoke alarms being mandatory. Andy
Currently whatever wiring you do in your own property is not illegal. Unless an electrical inspector comes along and reports it to your house insurance. ie HMO's council property.
Make sure you run a 10sqmm cable from the consumer unit to the garage. Should you ever get an EV then this will open up the options when it comes to wall chargers. (ask me how I know!).
If the new build garage is subject to planning permission and building inspection, Part P certification applies. Andy
Is your arc welder kit old-school (i.e. big coil type)? If so, they can cause a large switch-on current surge, so talk to your electrician about maybe using a type-D MCB in the consumer unit that can handle the surge. Also - this is what a 16A single-phase mains connector & wall socket looks like:
Excellent, thanks everyone for the input. The arc and mug welder operate off 13a fused three pin plugs but all be it rarely have tripped the protection. The garage build had planning permission granted ten years ago and because we started the work by laying the slab/foundations/ constructed a retaining wall required can proceed with the build after talking to our building control chap. Does that change anything?
If it is the same as mine, your build will require staged inspection and approval by building control but he should have told you that. Andy
It is the final phase of a three stage development - only waited for my new garage for the past ten years, finally getting it now the kids are gone and I took early retirement. Better late than never!
My advice would be get the builder to install / dig the cable run if going in the ground. As I found out a 25m trench 2ft deep generates a lot of soil and takes longer than expected. When I had my house rewired years before I added a garage I had an additional (smaller) consumer unit added for future expansion and to keep it separate from the house as mentioned. Also had outdoor sockets added simultaneously
Hi, thanks for the advice. As the garage will be integrated into the bungalow no ditches will be needed but the builder will be installing the electrics 13a and 25/30a, lighting, ev charging point etc via a separate consumer unit. Having waited this long for my garage I don’t want to delay its usability by doing some of the work myself! The building work is booked in and will start mid spring which is probably just as well because the amount of roofing work is pretty big.
I have spoken with my builder re ev charge points and he has commented as follows - do you have any comments? “With regards to the cable size, while most of the home charging stations are 7.4kw even the level 2 fast chargers, and they are okay with a 6mm supply cable ( 32A ), unless the distance from the consumer unit to the charging station is over 20 metres, however, there are some level 2 fast home charging stations that are 17kw - 22kw as a result, we would recommend a 10mm 3 core CAT6 SWA EV cable ( 32A ) as a lot of the new home charging stations are Smart, the 3 core CAT6 cable has a data cable that provides a permanent data supply from you internal smart device , and prevents the drop out in signal from your smart devices to the charging station.” cheers
It looks like your builder is treating the garage as a separate installation and therefore you will need a means of isolation at both ends and appropriate protection at the supply end, probably a 40A Type C MCB. As it is a garage/workshop then RCD/RCCB are required and I would suggest, as a minimum, 6A for lighting, a 20A radial for sockets and another 20A Type C for the welder. A 7.4kW charger will require a 32A. Anything bigger will need 3 phase supply, which it is unlikely that you have. And yes, it will all need testing and inspecting but any decent sparky will do this as he goes along.
