UK Garage electrics - analysing quotes

[np12345]

Hi everyone.

I have had two quotes for work but one is twice as expensive as the other and I can't determine which is the better of the two. I believe both are valid and can explain some of the differences, but I'd appreciate some feedback please.

Work required: I have a 13A fused spur in the kitchen to an outside junction box on the wall of my house, which comes off the existing downstairs circuit. This was to provide power and lighting to the detached garage (1m from house) but that piece of work was never finished. I want 2 x double sockets and 2 x LED light strips with one way switch to control both at the same time. The power would be used for a speaker, possibly small TV, charging the drill battery - nothing extreme. In the future, i.e. not part of this quote, I would like an outside double socket and some LED lights for decking when that gets done.

Quote 1: Half cost of quote 2. Plastic boxes and trunking/conduit. SWA from junction box into garage via catenary wire. Lighting will use fused connection unit.

Quote 2: Twice cost of quote 1. Metal boxes and trunking/conduit. SWA from junction box into garage via new channel in concrete ground between the two which will get filled (and eventually paved over). Mini consumer unit in garage to split power and lighting circuits.

Questions:
1. Any concerns about either option?
2. Any concerns about my future plans if I go with one or the other?
3. For quote 1, is a fused connection unit different to a fused spur? I know you can't have a spur off a spur.

Any comments gratefully received. I can explain some cost of quote 2 easily (metal, CU, channeling concrete) but I don't see why it's twice the cost. I am happy that both electricians are competent and have the required qualifications.

Thanks in advance

 

[Risteard]

You haven't stated what the quoted costs are.

 

[davesparks]

A switched fused spur (or SFCU, fused connection unit, fused spur, any other rname for it) is all that is needed for the lighting.
The whole thing will be limited to 13A by the switched fused spur in the kitchen which feeds it, so a small consumer unit is pointless (assuming the circuit has RCD protection already). The consumer unit would probably have a 16A MCB for the sockets and a 6A MCB for the lights, the 16A MCB would do nothing as the 13A fuse before it is of a lower rating, so you may as well not have it and just have a fuse for the lights.

 

[np12345]

You haven't stated what the quoted costs are.

I didn't want to influence any replies in case you thought one was way too cheap. I'm ok with either cost, just want to make sure the approach is ok.
[automerge]1584986859[/automerge]

A switched fused spur (or SFCU, fused connection unit, fused spur, any other rname for it) is all that is needed for the lighting.
The whole thing will be limited to 13A by the switched fused spur in the kitchen which feeds it, so a small consumer unit is pointless (assuming the circuit has RCD protection already). The consumer unit would probably have a 16A MCB for the sockets and a 6A MCB for the lights, the 16A MCB would do nothing as the 13A fuse before it is of a lower rating, so you may as well not have it and just have a fuse for the lights.

Ok, but that was my point in Q3. Wouldn't that result in the lighting being connected by a spur off a spur (one in the kitchen, one in the garage)?

Understood about the 13A limitation. I guess this wouldn't hinder the future plan for a double socket outside and LED decking lighting?

 

[davesparks]

I'd normally go for an underground cable in a suitable duct rather than an overhead cable, you might be able to get the price down by digging the trench yourself if you are able.
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Ok, but that was my point in Q3. Wouldn't that result in the lighting being connected by a spur off a spur (one in the kitchen, one in the garage)?

You cannot have more than one point (single or twin socket, switched fused connection unit) connected to an unfused spur, or in other words you cannot have an unfused spur off an unfused spur.

However from the switched fused connection unit (often referred to as a fused spur) you can have as many points as you like as everything after it is protected by the 13A fuse.

 

[np12345]

I'd normally go for an underground cable in a suitable duct rather than an overhead cable, you might be able to get the price down by digging the trench yourself if you are able.
[automerge]1584987152[/automerge]


You cannot have more than one point (single or twin socket, switched fused connection unit) connected to an unfused spur, or in other words you cannot have an unfused spur off an unfused spur.

However from the switched fused connection unit (often referred to as a fused spur) you can have as many points as you like as everything after it is protected by the 13A fuse.

Ok, thank you. In that case it's down to me to consider the pros and cons of the quotes and that gives me what I need to do so.

Cheers for the help.

 

[peterhyper]

In domestic garages I always put in metalclad sockets and would only use plastic conduit as metal conduit is a complete overkill in 99% of home garages.

 

[littlespark]

Plain t&e clipped at high level and pvc conduit drops to either metal clad or pvc surface boxes with regular sockets.
buried cable through duct, and no need for CU if coming from a 13A fuse