Radial Circuits

[Barney12]

I thought I post this for a)interest b)to seek the views of the collective!

I'm planning on radial circuits and my draft list is as follows. My first thought is it seems like a lot of circuits requiring a big CU!

The last two columns are incomplete.

Thoughts?

 

(Circuit 16 is for fail safe only. No plans to install the electric rads initially. I've gone with 4 core as that matches the electric radiator control system we have in the flat (it uses the 4th core as a comms/control).

 

Edited August 29, 2017 by Barney12
Table didn't appear! Now a JPG.

[Barney12]

OK, cant do a table!

Edited August 29, 2017 by Barney12

[Jeremy Harris]

The need for an industrial size CU is one reason I think most stick with ring finals, rather than radials.  I like the idea of radial wiring a lot, but there is no doubt that it does need a lot of wall real estate to house the kit, and allow room for all the cables to come in neatly.  My workshop is radial wired, with contactors to remotely switch circuits, and emergency stop switches that kill the contactors, but even that used a pretty big box, just for two lighting circuits and three power circuits, by the time the contactors were fitted.

Edited August 29, 2017 by JSHarris

[Barney12]

Just now, JSHarris said:

The need for an industrial size CU is one reason I think we still stick with ring finals, rather than radials.  I like the idea of radial wiring a lot, but there is no doubt that it does need a lot of wall real estate to house the kit, and allow room for all the cables to come in neatly.  My workshop is radial wired, with contactors to remotely switch circuits, and emergency stop switches that kill the contactors, but even that used a pretty big box, just for two lighting circuits and three power circuits, by the time the contactors were fitted.

 

Yes, I've been browsing the larger CU's and frankly its bewildering! None of the product sites/catalogues make it clear if they meet the 17th Regs.

[ProDave]

Most industrial (3 phase) boards are outside the scope of these new fangled fireproof CU's that are only a domestic requirement.

 

A good compromise might be one CU downstairs and a submain to an upstairs CU?

 

I have a 20 way Hager board in my house. Deliberately fitted a few weeks before the new regs came in. It has a metal back part and plastic front.

 

P.S I would hope all your circuits are on rcd's now?

[Nickfromwales]

9 and 11 need to be unified IMO,mas the controls of a device should be fed from the same breaker as the device. 4mm2 cable going to the plant room, and the ashp isolator and feed there. ?

[Jeremy Harris]

My guess is that you may need to look at using an industrial type metal switch gear cabinet, rather than a domestic CU.  The advantage is that you can fit all your home automation switch gear in the same cabinet, as long as it has the required separation barrier between the ELV and LV circuits.  IIRC, this is the solution that @jack has used, a large wall mounted industrial type housing.

 

An alternative may be to use two domestic CUs, but I reckon it could end up looking messy.

 

Compliance with the regs is easy enough, you don't need a box that's advertised as "17th Ed compliant", as you can make pretty much any board compliant by just wiring it correctly.

 

 

[Nickfromwales]

Same for 15&16?

1 minute ago, JSHarris said:

My guess is that you may need to look at using an industrial type metal switch gear cabinet, rather than a domestic CU.  The advantage is that you can fit all your home automation switch gear in the same cabinet, as long as it has the required separation barrier between the ELV and LV circuits.  IIRC, this is the solution that @jack has used, a large wall mounted industrial type housing.

 

An alternative may be to use two domestic CUs, but I reckon it could end up looking messy.

 

Compliance with the regs is easy enough, you don't need a box that's advertised as "17th Ed compliant", as you can make pretty much any board compliant by just wiring it correctly.

 

 

Aren't you not allowed to put differing manufacturers equipment inside a CU?

[Jeremy Harris]

12 minutes ago, Nickfromwales said:

Same for 15&16?

Aren't you not allowed to put differing manufacturers equipment inside a CU?

 

 

Any DIN rail bit of kit can be fitted in a box with a DIN rail, the only slight issue is with switched line busbars, as some manufacturers position their terminals at different heights.  Not insurmountable, as you can get stepped busbar connectors, anyway.  There's a mix of stuff in my workshop box, a DP RCBO on the incomer and SP MCBs feeding the line side of DP contactors.  Off the top of my head I think there's at least two different makes of kit in there, maybe three.

 

The manufacturer-specific stuff applies to oddball CUs, like the Crabtree Starbreaker series, that use a proprietary plug in busbar, that nothing else (AFAIK) will fit.  There's also the issue of aesthetics, in that a row of MCBs that are the same make look neater.  Other than that you can mix and match, as long as all the connections are OK and safe.

Edited August 29, 2017 by JSHarris

[dpmiller]

I'll put a vote in for a submain up the stairs.

[Barney12]

3 hours ago, Nickfromwales said:

9 and 11 need to be unified IMO,mas the controls of a device should be fed from the same breaker as the device. 4mm2 cable going to the plant room, and the ashp isolator and feed there. ?

 

Yep that can work. CU is in plant room and that SWA is also already in the plant room as it was one of the slab insertions. 

[Barney12]

3 hours ago, ProDave said:

Most industrial (3 phase) boards are outside the scope of these new fangled fireproof CU's that are only a domestic requirement.

 

A good compromise might be one CU downstairs and a submain to an upstairs CU?

 

I have a 20 way Hager board in my house. Deliberately fitted a few weeks before the new regs came in. It has a metal back part and plastic front.

 

P.S I would hope all your circuits are on rcd's now?

 

So is a metal industrial cabinet acceptable under the domestic regs? Surely that's just as fireproof as a metal consumer unit for residential? 

 

 

[Nickfromwales]

3 minutes ago, Barney12 said:

 

So is a metal industrial cabinet acceptable under the domestic regs? Surely that's just as fireproof as a metal consumer unit for residential? 

 

 

As long as the breakers are covered by a metal door?

[Barney12]

3 hours ago, ProDave said:

 

P.S I would hope all your circuits are on rcd's now?

 

Id like to use RCBO's if I can make the cost stack up. 

Any negatives to that idea?

[ProDave]

19 minutes ago, Barney12 said:

 

So is a metal industrial cabinet acceptable under the domestic regs? Surely that's just as fireproof as a metal consumer unit for residential? 

 

 

I think this metal CU thing was rather proved wishful thinking when that big stately home burned down due to a CU fire in it's metal 3 phase board......

[ProDave]

2 minutes ago, Barney12 said:

 

Id like to use RCBO's if I can make the cost stack up. 

Any negatives to that idea?

That's the best solution, only downside is cost, but it's what I have.

[PeterW]

2 minutes ago, Barney12 said:

 

Id like to use RCBO's if I can make the cost stack up. 

Any negatives to that idea?

 

20 ways for less than £15 each ...

 

http://m.ebay.co.uk/itm/Metal-Board-Main-Switch-20-Way-Consumer-Unit-RCBOs-17th-Edition-Amendment-3-/232303133274?hash=item361658825a%3Ag%3A94YAAOSwFqJWqd0p&_trkparms=pageci%3A96074cfe-8cf0-11e7-97b9-74dbd1809ed2%7Cparentrq%3A2f79b72115e0aa411ac07660fffdf826%7Ciid%3A1

 

[Onoff]

24 minutes ago, Barney12 said:

 

So is a metal industrial cabinet acceptable under the domestic regs? Surely that's just as fireproof as a metal consumer unit for residential? 

 

 

 

All day long.

 

This metal cu thing is a load of bs in my personal; opinion. If there is a fire in there it just contains it on the wall better and uses all your ducts etc to spread it. There was a big fire happened in one of the stately homes (Clandon Park) a while back, this exact scenario I think. Think someone had left a knockout open and something had nested in there. 

[ProDave]

3 hours ago, JSHarris said:

 

 

Any DIN rail bit of kit can be fitted in a box with a DIN rail, the only slight issue is with switched line busbars, as some manufacturers position their terminals at different heights.  Not insurmountable, as you can get stepped busbar connectors, anyway.  There's a mix of stuff in my workshop box, a DP RCBO on the incomer and SP MCBs feeding the line side of DP contactors.  Off the top of my head I think there's at least two different makes of kit in there, maybe three.

 

The manufacturer-specific stuff applies to oddball CUs, like the Crabtree Starbreaker series, that use a proprietary plug in busbar, that nothing else (AFAIK) will fit.  There's also the issue of aesthetics, in that a row of MCBs that are the same make look neater.  Other than that you can mix and match, as long as all the connections are OK and safe.

The issue with that is "Manufacturers instructions"  If MK say you can only use their mcb's in their board and no other make, then by fitting a different make you have potentially taken on the task of type approving the whole consumer unit.

 

Yes it's a load of baloney in the real world. If a crabtree mcb is happy to work alongside a load of other crabtree mcb's then it's highly unlikely it would suddenly catch fire if you put it in between two MK mcb's (assuming it would fit) but by doing so you would have been assumed to have taken on the task of verifying it is safe.

[Onoff]

I enquired to Dave at SBS ref his Compact RCBO boards in this sceanario, he's come back:

 

"The biggest size of double decker (in fact, the only size that LiVE do) is a 24-module / 22-way box.

This would not give you the 24 circuits you need, unless there is a circuit rethink. Attached, is one I did for a customer, with 22 circuits.

A good solution would be stacked 2 x 14-mod boxes, giving you 26 usable ways, if using 1 x Main Switch, or 24 usable ways, if using 2 x Main Switches.

They could be coupled together, using brass or plastic bushes, giving room for all cables to pass through. Alternatively, they could be coupled them together with, say, 2 small bushes and bring all the cables, including tails, through the back knockouts, using my Stand Off Frames.

 

Let me know if I can be of further assistance and I look forward to hearing from you again.

 

Regards

David"

 

 

 

 

 

[Barney12]

9 minutes ago, ProDave said:

That's the best solution, only downside is cost, but it's what I have.

 

Not for the smoke alarm circuit though I assume? MCB only? 

[ProDave]

2 minutes ago, Barney12 said:

 

Not for the smoke alarm circuit though I assume? MCB only? 

The smokes should have battery backup as well.

 

The only thing making you fit an rcd is the <50mm rule. Put all cables on the smoke circuit >50mm deep or in earthed metal conduit and you can indeed connect them to an mcb with no rcd protrction.

[Onoff]

Are you TT up there?

[Barney12]

6 minutes ago, Onoff said:

I enquired to Dave at SBS ref his Compact RCBO boards in this sceanario, he's come back:

 

"The biggest size of double decker (in fact, the only size that LiVE do) is a 24-module / 22-way box.

This would not give you the 24 circuits you need, unless there is a circuit rethink. Attached, is one I did for a customer, with 22 circuits.

A good solution would be stacked 2 x 14-mod boxes, giving you 26 usable ways, if using 1 x Main Switch, or 24 usable ways, if using 2 x Main Switches.

They could be coupled together, using brass or plastic bushes, giving room for all cables to pass through. Alternatively, they could be coupled them together with, say, 2 small bushes and bring all the cables, including tails, through the back knockouts, using my Stand Off Frames.

 

Let me know if I can be of further assistance and I look forward to hearing from you again.

 

Regards

David"

 

 

 

 

 

 

That looks bloody ideal. I'm down to 22 circuits if I combine 9 and 11 as per Nick's advise? 

Will he supply me (my sparky is labour only with me supplying all materials)?

 

The next challenge is I then need to house:

 

8 channel dimmer with 1amp MCB's (Total: 16 ways)

 2 x 12 channel relay with MCB's (Total 48 ways)

 

(Note the actual dimmer and relay modules are an 8 way block)

[Barney12]

2 minutes ago, Onoff said:

Are you TT up there?

 

Currently TT but only because Western Power won't allow anything else for a 'site supply'. 

I can swap back to TN once the CU in the house is connected. 

 

(This info is what my sparky has told me)