2 x Main Switches in on consumer unit

[KashBag]

I wondered if it is OK to have 2 x Main Switches in the same consumer unit. One feeding the RCBOs in the House and one feeding the CU in a garage, so that the outbuilding stuff can be isolated from the House CU?

 

[DefyG]

Yes but a main switch to BS 60947-3 doesn't provide OCP in itself for the circuit to the garage.

 

[KashBag]

I wondered if it is OK to have 2 x Main Switches in the same consumer unit. One feeding the RCBOs in the House and one feeding the CU in a garage, so that the outbuilding stuff can be isolated from the House CU?

Thanks, but the consumer unit in the garage has its own 100A main switch and 2 RCBOS. This on is for isolting the supply to it.

 

[Avo Mk8]

Thanks, but the consumer unit in the garage has its own 100A main switch and 2 RCBOS. This on is for isolting the supply to it.

Something has to protect the cable to the garage other than the DNO's fuse (which is probably a bit over-rated for that!)

 

[davesparks]

I wondered if it is OK to have 2 x Main Switches in the same consumer unit. One feeding the RCBOs in the House and one feeding the CU in a garage, so that the outbuilding stuff can be isolated from the House CU?

You should have one main switch which isolates the whole installation.

After that you can add any other means of isolation you need/want.
You can use another 2 pole switch in the CU, in addition to the fuse/MCB, to isolate the garage or you could add an isolator next to the CU, it cannot replace the fuse/MCB. You could even use a 2 pole MCB.

 

[KashBag]

Something has to protect the cable to the garage other than the DNO's fuse (which is probably a bit over-rated for that!)

oh, yes, I have allowed a 40 A mcb. Does the attached sketch make sense if practical? Second option is let the Garage Switch to be fed through the House Switch but then if I need to disconnect the outbuilding then I the house will be disconnected as well.

 

[nicebutdim]

Could maybe keep this in one thread, so it's easier for people providing advice to see all available information.

Feeding LogCabin from Shed CU

Hi guys, I have supplied my Shed with a 6mm SWA cable into a nice consumer unit. In there I have a 6Amp MCB for the lights and a 16 A supplying a single socket for a freezer unit. I also have an additional 32 Amp (idle). Now I have a log cabin 10m away. I am going to install a new consumner...

www.electriciansforums.net

 

[KashBag]

You should have one main switch which isolates the whole installation.

After that you can add any other means of isolation you need/want.
You can use another 2 pole switch in the CU, in addition to the fuse/MCB, to isolate the garage or you could add an isolator next to the CU, it cannot replace the fuse/MCB. You could even use a 2 pole MCB.

, Yes, so a double pole mcb to isolate both the N and the L, N should be isolated as well. By using a double pole MCB I will save space (instead of the 40A MCB and the Main Switch).
Another option is use 2 x Henley blocks to add a separate CU in the House to feed the Garage CU?

 

[mainline]

, Yes, so a double pole mcb to isolate both the N and the L, N should be isolated as well. By using a double pole MCB I will save space (instead of the 40A MCB and the Main Switch).
Another option is use 2 x Henley blocks to add a separate CU in the House to feed the Garage CU?

 

[KashBag]

View attachment 113555

question! are the 2 additional 100A Switches fed through the main one, or are all three connected in parallel?

 

[mainline]

question! are the 2 additiona Switched fed through the main one, or are all three connected parallel?

The main switch isolates the other two basically the same as a dual rcd cu

 

[KashBag]

The main switch isolates the other two basically the same as a dual rcd cu

Cheers, it does make sense, but it is not incorrect to connect them in parallel right? Or is there a requirement to have one main disconnection point in the CU?

 

[Risteard]

Cheers, it does make sense, but it is not incorrect to connect them in parallel right? Or is there a requirement to have one main disconnection point in the CU?

The actual main switch must isolate everything.

 

[EricMark]

You should have one main switch which isolates the whole installation.

I was told that for years, however my house has a few, the DC isolators, the UPS isolator, the DNO isolator etc. And at work one building has at least three DNO supplies, maybe four.

 

[Rockingit]

My issue with this thread isn't about design aspects of combinations of isolators, it's about who is installing, testing and certifying a Part P notifiable project.......

 

[mainline]

I was told that for years, however my house has a few, the DC isolators, the UPS isolator, the DNO isolator etc. And at work one building has at least three DNO supplies, maybe four.

If a board is marked up as having a main switch then it should isolate that DB so that there is nothing live after that main switch.

 

[davesparks]

I was told that for years, however my house has a few, the DC isolators, the UPS isolator, the DNO isolator etc. And at work one building has at least three DNO supplies, maybe four.

Yes, I was referring to simple installations such as domestic as that is what the thread is about. I also said should rather than must because I know it's not always possible.

But as a general rule there should be a main switch to isolate the whole installation, If there isn't then suitable labelling to identify the multiple sources of supply and their respective isolators is required.

Outside of a simple installation it obviously can get a lot more complicated.
For one of my customers the only way to fully isolate the building is a phone call to UKPN to get the 2x 11kV incoming supplies switched off.