PD drop over tails to CU

[davelittlewood]

Sorry, yeah you're right, 80A fuse and switch.

I also want to run a 3kW single phase compressor in the garage (which is currently an unfused spur on the kitchen ring main) so I'm concerned that the 16 sq mm from the switch to the CU isn't up to it.

As I said, I'm not an electrician, hence the request for some advice before I start getting quotes to put in larger cable.

As the CU is right in the middle of the house it's going to be a PITA to get access to run the new cable.

 

[davesparks]

Well this thread is taking a rapid change of direction isn't it.

We've gone from a concern over a bit of voltage drop to advice on how to proceed with a supply for a compressor!

I would be more concerned about the unfused spur than the 16mm submain.

You need an electrician to visit and make an assessment of what is needed and provide a quote.

 

[Octopus]

What do you mean by the "main supply board"?

Can you post a picky?

 

[Dave OCD]

A 7 metre run of 16mm T&E ought to cope fairly comfortably with the demand in an average home, the volt drop under fairly small loads does seem a little high though, that could be indicative of a poor connection anywhere upstream of your CU or a number of other things,might be nothing at all wrong even.
The 3kW compressor should be fine IMO, but ideally it would be better if the garage was on its own circuit, would that also be an awkward cable run from the CU ?
All things considered your best bet would be to get a decent electrician around to check it out properly and discuss the best course of action.

 

[davelittlewood]

We're going to rebuild the garage (as the foundations are knackered) so I'm already planning to get a sparky to put in a dedicated circuit for the garage rather than the spur from the kitchen ring main.

Picky below of the board with the main switch, meter etc.
The mcb in the bottom left supplies a separate circuit for my car lift (this might end up being the circuit for the complete garage as it's over spec'd for the load. I asked the electrician to put in a larger cable just in case).

You can see the T+E leaving top left.

 

[Octopus]

W

Picky below of the board with the main switch, meter etc.
The mcb in the bottom left supplies a separate circuit for my car lift (this might end up being the circuit for the complete garage as it's over spec'd for the load. I asked the electrician to put in a larger cable just in case).

You can see the T+E leaving top left.

View attachment 30381

Thats a bit of a dogs dinner isn't it!

 

[Dave OCD]

With all due respect the supply job for your car lift looks a lash up , the supply to the enclosure looks like 6mm straight off the outgoing side of the house sub main switchfuse - and apart from the MCB in the enclosure bottom left of the photo there should be a proper DP isolator, depending on the cable run/when the work was done there should really be an RCD also.

 

[davesparks]

With all due respect the supply job for your car lift looks a lash up , the supply to the enclosure looks like 6mm straight off the outgoing side of the house sub main switchfuse - and apart from the MCB in the enclosure bottom left of the photo there should be a proper DP isolator, depending on the cable run/when the work was done there should really be an RCD also.

The mcb is after the main switch so no other isolator is needed.
And SWA rarely requires RCD protection

 

[Dave OCD]

But is it really good practice to have to isolate the whole house in order to properly isolate the other separate supply , the thoughts on RCD protection were based on what's at the other end but of course I haven't seen the other end of the SWA.

 

[davesparks]

But is it really good practice to have to isolate the whole house in order to properly isolate the other separate supply , the thoughts on RCD protection were based on what's at the other end but of course I haven't seen the other end of the SWA.

It's no different to feeding it from a way in a CU.
DP isolation is only required for the main switch, after that single pole isolation is all that is required.

There is a car lift on the other end of it.