CU as isolator box

[Brightonguy]

We have a dislike of switches all over the kitchen as you see today. The appliances are in housings with no worktops adjacent. Isolation switches would be on a the wall near the door to the cupboard with the CU just inside.

I was just musing:

1. Maybe having another main DP isolator, subbed off the main one of course that isolates the bank of three appliances. or;
2. Just a RCD (which is DP & an isolator and about £8 each) that has the three appliance mcb's on just that bank.
3. Each appliance with one RCD and mcb (3 ways per appliance). which means a CU with a lot of ways. The difference in price between a 10 way CU and 12 way is about £15.

No. 3 looks OK. BTW, is there any reason why CU cannot be turned on its side? Just curious.

 

[JohnD]

switches all over the kitchen

there is currently a fad for wiring all the appliances to a bank of gridswitches, often near the door. It is of course essential to have them correctly labelled.

 

[JohnW2]

A DP switch on the wall above or beside the appliance is perfectly suitable unless you have a dislike of switches.

It appears that the OP has such a dislike, and that's the reason he started this thread:

... precluding having ugly isolators next to the appliances.

IMO the idea of concealing switches is akin to putting bloomers on piano legs.

I agree up to a point. However, given that the most likely reasons for wanting to achieve 'emergency isolation' probably involve an appliance that has become very hot, is involved in a fire (e.g. chip pan) or has developed a live casing, I personally don't like having isolators too close to the appliances. For 'elective isolation' (e.g. for maintenance), having the isolators 'concealed' in a a nearby cupboard is, IMO, no big deal.

Kind Regards, John

 

[JohnW2]

1. Maybe having another main DP isolator, subbed off the main one of course that isolates the bank of three appliances. or;
2. Just a RCD (which is DP & an isolator and about £8 each) that has the three appliance mcb's on just that bank.
3. Each appliance with one RCD and mcb (3 ways per appliance). which means a CU with a lot of ways. The difference in price between a 10 way CU and 12 way is about £15.

(3) is obviously in some senses the ideal, being the same as using DP RCBOs - so it woulod only make sense if you could not find DP RCBOs and/or there was a substantial cost advantage in having separate RCDs and MCBs.

If you are contemplating only using the the 'isolator' facility in emergencies and to facilitate maintenance (i.e. extremely rarely), then I presume that it would be no great hardship/inconvenience to have to isolate all three appliances together - and either (1) or (2) would achieve that.

BTW, is there any reason why CU cannot be turned on its side? Just curious.

Not that I'm aware of; I've certainly seen it done. MCBs/RCBOs are fitted horizontally in most 3-phase boards.

Kind Regards, John

 

[Brightonguy]

Good points JohnW2. In a hospital of course local isolation is essential. But in a normal domestic house when the only isolation is mainly for maintenance then a switch in a local cupboard is no big deal. The serviceman will seek it out and if it is well labelled then it is easy. The only final safety aspect to me was getting DP isolation. I am warming to my musing of a RCD with an associated mcb for each appliance. Just for info, who do make DP mcb's or DP RCBO's in the UK?

I really do hate all these fused spurs scattered on top of kitchen worktops. And especially the big oven isolation switches. They are downright ugly. Which are rarely ever switched off by the users anyhow. You do not see such clutter in new German kitchens.

 

[JohnW2]

I am warming to my musing of a RCD with an associated mcb for each appliance. Just for info, who do make DP mcb's or DP RCBO's in the UK?

Wylex (which you seem to favour) certainly do DP MCBs for their NH distribution boards, but I don't know whether they would fit their standard 'consumer' CUs. You could ask them:

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• JohnW2
• 7 Sep 2013
• 1

Kind Regards, John

 

[Brightonguy]

1. Maybe having another main DP isolator, subbed off the main one of course that isolates the bank of three appliances. or;
2. Just a RCD (which is DP & an isolator and about £8 each) that has the three appliance mcb's on just that bank.
3. Each appliance with one RCD and mcb (3 ways per appliance). which means a CU with a lot of ways. The difference in price between a 10 way CU and 12 way is about £15.

(3) is obviously in some senses the ideal, being the same as using DP RCBOs - so it woulod only make sense if you could not find DP RCBOs and/or there was a substantial cost advantage in having separate RCDs and MCBs.

If you are contemplating only using the the 'isolator' facility in emergencies and to facilitate maintenance (i.e. extremely rarely), then I presume that it would be no great hardship/inconvenience to have to isolate all three appliances together - and either (1) or (2) would achieve that.

BTW, is there any reason why CU cannot be turned on its side? Just curious.

Not that I'm aware of; I've certainly seen it done. MCBs/RCBOs are fitted horizontally in most 3-phase boards.

Kind Regards, John

Pricewise No. 3 does fill the bill to get DP RCD isolation cheaply.

 

[JohnW2]

... and also DP RCBOs for standard CUs, but only in Type C:

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• JohnW2
• 7 Sep 2013
• 1

Kind Regards, John

 

[JohnW2]

Pricewise No. 3 does fill the bill to get DP RCD isolation cheaply.

Fair enough - but, as I said, if there is already RCD protection, your option (1) may be adequate.

Kind Regards, John

 

[Brightonguy]

Pricewise No. 3 does fill the bill to get DP RCD isolation cheaply.

Fair enough - but, as I said, if there is already RCD protection, your option (1) may be adequate.

Kind Regards, John

You have a point. So another idea. Three £8 incomers with an associated mcb for each appliance in a dual RCD CU. If an appliance has a fault (say N to E), the RCD will trip even if the appliance MCB is off taking out a full bank of circuits. So you throw the incomer (DP isolator for that appliance) and full isolation in case of maintenance. A second best No. 3, which is the ultimate.

ta.

 

[EFLImpudence]

I was tempted earlier to comment that you, Brightonguy, seem to have it already understood despite several posts citing unnecessary worries.

However, it is now, in my opinion, getting a bit silly.
Talk of double pole RCBOs/MCBs and fitting additional Incomers (just DP switches) is overcomplicating it all.

All you need is for a normal DP switch (grid switches already suggested) for as many appliances as you want placed anywhere you want.

 

[Ahtyrrell]

The only reason you may need double pole isolation is If you are on a TT system and have an upfront RCD before the consumer unit
Unless this is the case I can see no reason at all for double pole isolation.

Just have a socket for the appliance if any one needed to remove it they would remove the plug from the socket hence double pole isolation is achieved.
I would put all three appliances on a single RCBO or if you really wanted on separate ones
Having a huge bank of incomers/RCDs and MCBs in the CU just seems to be going far to OTT

 

[JohnW2]

However, it is now, in my opinion, getting a bit silly. Talk of double pole RCBOs/MCBs and fitting additional Incomers (just DP switches) is overcomplicating it all. All you need is for a normal DP switch (grid switches already suggested) for as many appliances as you want placed anywhere you want.

I agree totally, but the OP seems to have very specific views/wishes:

... precluding having ugly isolators next to the appliances.

I don't see the point of having a bank of DP switches next to bank of CU switch, when an RCBO is neater and does the trick?

I'm more-or-less with BAS on this one - a kitchen is a workplace, and I personally have no problem with visible switches in 'the obvious places'. However, some people are clearly more concerned about the aesthetics.

Kind Regards, John

 

[JohnW2]

The only reason you may need double pole isolation is If you are on a TT system and have an upfront RCD before the consumer unit. Unless this is the case I can see no reason at all for double pole isolation.

Well, an N-E fault in the appliance will obviously take out anything else protected by the same RCD even if 'SP isolated' - but, as you go on to say, unplugging the faulty appliance represents the ultimate in DP isolation!

I agree that most of the things discussed have been (IMO) way OTT, but the OP clearly understands most of the issues and possibilities, and there are clearly elements of 'personal preference' involved.

Kind Regards, John

 

[Brightonguy]

I was tempted earlier to comment that you, Brightonguy, seem to have it already understood despite several posts citing unnecessary worries.

However, it is now, in my opinion, getting a bit silly.
Talk of double pole RCBOs/MCBs and fitting additional Incomers (just DP switches) is overcomplicating it all.

All you need is for a normal DP switch (grid switches already suggested) for as many appliances as you want placed anywhere you want.

I never sussed anything out really. I just thought as the thread went along. I suppose one of the advantages of these forums.

I do not see the need for a bank of switches (grid switches) next to a bank of switches that does the same. I am trying to find out the best way, and most cost effective, using the one switch box, the CU box.

Drawing out the appliances from the housings is not easy. Also having a 3 pin plug with 13A fuse is another thing to go wrong - right behind the fixed in appliance.

I suppose having the fridge/freezer on a non-RCD circuit is a good idea in case of a trip when on hols. Then this leaves say one RC in a two mcb bank serving the integrated oven and m/wave. Much simpler. So a three RCD CU with one circuit not RCD'd. One RCD with two mcb's for the two integrated appliances.

You are right I, and the other half, do not wants big ugly electrical switches in the kitchen. Row of white switches above worktops ruin a kitchen and when you have one which is a bit special then they have to go.

Thanks fellas, thinking a bit and batting the ball can get results.

ta.