Double Garage 20A Power supply

[berniesquash]

Hello all, newbie here looking for help and advice. Despite knowing a few things about 'trons' I'm not performing this work myself unless it's cast iron non notifiable.

I need a minimum 20A supply operating in my new build (Nov 2012) attached double garage to run a light industrial woodworking bandsaw. The saw itself doesn't draw a constant 20A (more like 7A) but is prone to well documented start up loads. The 20A figure is as recommended by the saw manufacturer.

The current installation: CU to garage 2.5mm TE from a 16A Hager B Type MCB/RCD feeding a single dbl 13A socket on a radial circuit. Garage lighting is on a separate 6A 1.5mm TE circuit. The CU is located in the main house and not adjacent to the internal garage wall so running a new circuit would be difficult and may spoil the outside of my lovely new house! The kitchen and 6mm TE 32A cooker radial does however back directly onto the internal garage wall.

As I see it I have 2 potential options.

1. Have the 16A 2.5 mm CU Garage MCB uprated to 20A (Type C) and install a switched 16A Commando as an additional radial socket in the garage. Would this be notifiable?

2. Have the 6mm 32A cooker radial extended on 6mm through the garage wall to a new CU / DB splitting out to a commando socket. The cooker is a modern double oven with a gas hob and overhead extractor.

Expert views really appreciated! I've seen elsewhere that there is contention in having a 20A MCB protecting a 16A connector, but am I right in assuming that the 20A MCB is protecting the cable only?

 

[Richard Burns]

I see you have posted the same question twice in slightly different terms.
Effectively you are wanting to install a new circuit for your bandsaw, this is notifiable to building control as are all new circuits.
Using the cooker circuit for the cooker and for the bandsaw is not a good idea.
Changing the length of a circuit and upgrading the CPD may come under non notifiable work (though really you are installing a new circuit just happening to use some existing cable) however in all cases it would need to comply with the building and wiring regulations.
So long as you can undertake the correct cable calculations and correct circuit tests to ensure that the your new circuit design is safe to use then you are good to go.

 

[berniesquash]

Richard - Many thanks for the reply. I think I'll proceed on the basis of extending the existing garage circuit on 2.5mm TE. The bandsaw itself is rated at 1.5Kw at steady load (6.25A @ 240v) so provided the circuit can handle very short term start up loads - a 16A circuit should actually be man enough for the job. Plan will be to replace the B Type MCB with a like-for-like 16A C type MCB with a 16A Switched Commando socket. If I do the installation - I'll have my sparky buddy check it over also.
As an aside - I was very surprised that the existing 2.5 wiring in the garage is simply clipped to the internal garage walls without conduit or additional physical protection. As it's a new build installation I'm assuming it's all pukka and will install the same. What would 'best practice' be in your opinion?

 

[Deleted member 9648]

You will almost certainly find that a 16a type C will be adequate despite the manufacturer spec for 20a,try it before doing anything else.

 

[berniesquash]

Thanks Guys - Sounds good. I will still have to install a 16A (switched?) commando I think. What's the best way to achieve this? There's only a dbl 13A socket from 2.5mm TE (surface clipped) at the moment.

 

[Guest111]

Come out of existing socket in 2.5 twin and earth and clip round to new socket position,there is no need for the 16 A socket to be switched unless you have a reason for wanting it that way,also cost may be a factor,an unswitched is about a fiver whereas a switched is about thirty quid.

 

[telectrix]

agree with phil.d and wirepuller. unswitched commando socket is beat. isolation is achieved by pulling the plug. cable clipped direct is OK if not liable to suffer mechanical damage. if it is, then you could fit mechanical protection.

 

[berniesquash]

Guys - many thanks. Appreciated.