Main switch in CU optional?

[nevis]

In preparation to having my CU replaced, I've had an isolation switch installed between my meter and existing CU.

Is it necessary to have a 2nd main switch in the CU or could this space be used for a couple of extra MCBs?

Would not having a main switch present a problem terminating the incomming tails onto the bus bar?

Cheers,
Ed

(TNC-S, Scotland).

 

[JohnD]

If you are buying an ordinary domestic CU, you will find they all come with main switches. If you want space for more MCBs just buy a bigger CU.

The connection to the Phase busbar is through the main switch, it might be possible to bodge something up without one but this would defeat the type approval.

Some industrial distribution Boards are made to work without a main incomer, but they are made with steel enclosures and would be more expensive.

 

[Adam_151]

How many outgoing ways do you want?, I don't believe you would have trouble finding a big enough board unless you take things to extreme as BAS does

 

[nevis]

John,

Thanks for the swift response. So it looks like not having an incomer would be a bad idea.

I am a bit limited for space. The CU is in a flush mounted cabinet on the side of the house. The service head and the meter only leave room for a 9-way + RCD + incomer. This is sufficient, but not generous so I was just seeing what the options would be.

I'll go with the 9-way for now and if I get stuck in the future there's space above the existing CU for a secondary one (It's width that's the limiting factor).

Cheers,
Ed

 

[JohnD]

How many outgoing ways do you want?, I don't believe you would have trouble finding a big enough board unless you take things to extreme as BAS does

Somebody will cater for all tastes, even Ban's

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7631502377&rd=1&sspagename=STRK:MEWA:IT&rd=1

 

[JohnD]

I am a bit limited for space. The CU is in a flush mounted cabinet on the side of the house. The service head and the meter only leave room for a 9-way + RCD + incomer.

What are the dimensions? Manufacturers may vary.

Or you could put it inside the house.

 

[nevis]

Adam,

Pretty standard setup, I'm planning:

Non-RCD:

Downstairs lights & bell transformer
Upstairs lights & battery backed mains smoke detectors.
Kitchen fridge/freezer spur
Fish tank pump spur *

RCD:

Downstairs ring
Kitchen ring
Upstairs/garage ring **
immersion spur
Cooker spur

So this comes to 9

* I guess this one is a bit unusual, but If the RCD trips the fish would like the tank to keep pumping.

** Sounds a bit strange, but that's how it is at the moment.

Cheers,
Ed

 

[Adam_151]

MK do some stacking kits for their boards, could use two 12 module boards done in this way, not sure if the stacking kit allows the split load kit to be used (but I think it'd be rather crap if it didn't)

Also be careful about putting too many cicuits on the RCD, the harmless leakage from appliances adds up and causes nuisense tripping

Or you as john hints, use a switch fuse of some sort and locate the board elsewhere (or probably without the switch fuse if within 3m* tail length)


*varies between DNOs, 3m is the most common I belive though

 

[nevis]

John,

I've got about 310mm to play with between the service head and the edge of the cabinet.

Cheers,
Ed

 

[Adam_151]

I think you mean radial circuit where you said spur

I'd put the immersion heater and cooker on non-rcd, no need for RCD protection on them and when they get old they could cause nuisense tripping

How big is the gap, if you can spare 378mm then you can get a 16 (12 circuits) module MK board in, if not you are down to 12 module (which will take 10 circuits if you loose the RCD and use RCBOs on the rings)

or theres the stacking option

 

[nevis]

Adam,

If I start moving the CU then the scale of this project suddenly changes! The living room is on the inside of this wall, so SHMBO would have something to say about any new wall-mounted items next to the fireplace. Going further afield the hall cupboard is about 6m away, so I'm not very keen.

Cheers
Ed

 

[nevis]

Adam,

Thanks for the advice on the immersion and cooker radials . I was in two minds anyway about these. Opinion, particularly on cookers seems mixed.

Now I like the RCBO idea, that could be the way to go.

Cheers
Ed

 

[JohnD]

I think RCBOs are great. As well as saving two units by not having a separate RCD, you don't lose other innocent circuits if there is a fault on one circuit, and if you can afford it, you can put one on every circuit. (they do work out a bit expensive, I know).

Otherwise:

I see MEM do a metalclad two-deck unit at 296 wide and 370 high, 17 ways. Rather expensive at £166 list for the AS908HED split-load

They also do an insulated surface mount CU (plastic) 17-way AP908HED split load 9 ways on RCD which is a lot cheaper (haven't got the price here) and 296 wide x 370 high x 113

or the Insulated AP19 (no RCD) which is 296 wide x 370 high x 113 deep and has 19 ways. As it is not split-load and has no RCD you would need RCBOs

These are all from the Memora 2000 range (there is also a 2000 AD range which is different, I don't see one suitable for your needs)

 

[securespark]

I am a bit limited for space. The CU is in a flush mounted cabinet on the side of the house. The service head and the meter only leave room for a 9-way + RCD + incomer.

What are the dimensions? Manufacturers may vary.

Or you could put it inside the house.

I'm afraid you may well find the DNO will not allow you to refit a consumer unit in their cabinet. I know this sounds ridiculous, but as a Technical guy for my company, I have had this out with the organisation representing the DNO's around the country.

The conclusion was that if a consumer unit in an external cabinet is being replaced, the DNO would not be happy unless it were resited.

However, Wylex units are very space-effective. If you get the OK, they could even make you one specially to fit.

 

[ban-all-sheds]

How many outgoing ways do you want?, I don't believe you would have trouble finding a big enough board unless you take things to extreme as BAS does

Somebody will cater for all tastes, even Ban's

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7631502377&rd=1&sspagename=STRK:MEWA:IT&rd=1

Nah - looks like it's made of plastic....