Isolation Switches

[Barney12]

35 minutes ago, SteamyTea said:

Thanks for the tip about Googling DP, I may be gone some time

 

Well all I get is a link to Dorothy Perkins so I can only assume it's something about wearing women's clothes?  

[SteamyTea]

Just now, Barney12 said:

it's something about wearing women's clothes?  

Not for long

[Nickfromwales]

Thread tidied up ( to focus on the topic  ). 

Nick. 

[Jeremy Harris]

What our electrician installed and how the design changed because of the late change in oven supply requirement (something outside our control at the design stage, before first fix) seems unclear, so I thought a couple of very rough sketches might help make things clearer.  First off, the plan was to minimise the clutter above the worksurfaces, and in particular we didn't want or need stuff on the short length of wall to the right of the tall oven unit, which is on the end of a "C" shaped run of cabinets.  However, we needed to be able to isolate the supply to the hob, on the island, so had to fit a cooker isolating switch on that wall.  Because the ovens we had ordered both came with fitted 13A plugs, we decided to run the two spurs for these down the wall to the left of the tall oven unit, so that they were accessible but not behind the cooking area.  This is how the original installation looked, very roughly (please accept there is some artistic licence with these rough sketches):

 

 

The hob cable is massively over-sized for the simple reason that I had half a roll of 10mm² left over from something else, and didn't have a roll of more suitable cable to hand.  All three of these spurs were protected at the CU in the upstairs service room.

 

The new oven was supplied with a flat, black, three core cable, with eyelet terminations that were fitted via Torx head screws to the connection panel at the rear.  This cable was around 2m long, and the MIs said to connect it to a suitably rated and protected outlet.  Had we just replaced one of the 13A outlets to the left with a 20A DP switched outlet, then we'd have had to enlarge the cable entry to take the flat three core cable, and the cable grip would not have worked well, I think.  It would also have looked pretty dire, in my opinion.

 

So, after a long chat with our electrician, we (rather reluctantly) decided to rip out the two spurs to the left, make use of the capacity we had in the cable to the right (allowing for diversity) and relocate the connections to the oven and microwave to the space above and behind the microwave unit (there was very little free space behind the oven - probably why it was supplied with the odd, flat, heat resistant, three core cable).  We then had a problem in that we needed to be able to have accessible switches to isolate both the oven and the microwave, plus we needed protection on those two circuits.  We couldn't easily run cables across to the left from the old spurs, as it would have meant ripping a big hole in the wall for access.  We (rather our electrician) suggested that we use the hob isolator switch as the isolator for the whole lot (within it's rating, so OK), and add protection for the new spurs by DP MCBs in a small box in the adjacent cupboard, at the top and mounted on the side.  This worked out well, as it just meant cutting a slot in the wall under the existing hob switch (to fit the new cable) and cutting a hole through the wall behind the cabinet and behind the oven unit to hook the cables through (luckily both were in the same bit of service void).  This is what the final installation looks like:

 

 

It's OK in terms of neatness, although we've lost a bit of cupboard space where we fitted the new box.  At the moment the old outlet boxes just have blanking plates on, but the plan is to cut some bits of plasterboard to fit, fill the surface and redecorate (when I get around to it).

 

So, the bottom line here is that we had a good initial plan, that would have worked fine if the manufacturer hadn't decided to change their product range between the time we ordered and the time we took delivery.  I think it's just one of those things with any self-build, you have a schedule and often can't accept delivery of some things too early, because you don't want to have to store them somewhere whilst other work is completed.  In our case, the order of work was first fix, then plasterboard, plastering and painting, then flooring, fitting the kitchen and then second fix, and even at the time of second fix we still thought we were getting both ovens with 13A plugs and leads.  It wasn't until a couple of weeks after the electrical installation had been signed off that we discovered the change in oven spec.

 

Could we have predicted it, or pre-empted it with better planning?  I really don't think we could.  We could have cancelled the oven order and looked for another pair that would fit the space and the power outlets we'd already fitted, but frankly that was not something my other half wanted to think about, having made her choice originally.  We could have originally arranged the spurs for the ovens to be adjacent to the main switch, but we didn't like the idea of that area of wall being cluttered up.  We could have fitted outlets on the wall behind the microwave slot, with separate isolator switches on the wall, but when we did first fix we didn't know where the access gap was in the back of the tall oven unit, as it hadn't been delivered and none of the cabinet drawings had that level of detail.

 

The odd thing is that the spec of the new oven is near-identical to that of the old one, and it's rated at 2.2kW, which was the rating of the original one, too (which is slightly over the 2kW power for a 13A socket powered one, but the original would have been supplied with a moulded on plug and lead, so it would have been a case of the MIs superseding this, in this particular case).  It is slightly deeper, front to back, and has a different looking front panel, but it seems to have all the features the original one had.  I can only think that a regulatory change caused them to change it to a 16A rating.  Maybe it's supplied in Germany, and the rest of the EU that use Schuko 16A plugs, with a 16A cable and moulded plug.

Edited February 10, 2017 by JSHarris

[Barney12]

I really don't like these regulatory what knots! So picking up on @Onoff comment about isolators being within 2m of the appliance........

 

We intending to have a built in bank of units. Like the image below. I assume then I've got to stick an isolator on the section of the wall to the left or right! Just how rubbish will that look!! Grrrr

 

 

I'm sure putting them in the glass tambour units on the side would be OK though?

 

What about if they are behind a small panel that opens?

 

You may be getting the general idea that I DON'T LIKE SWITCHES!

 

 

[Onoff]

Couldn't you have just kept one of the single gang plug top outlets and replaced the other with 1-gang cooker connection plate that has an oval cable grip anyway? Were the "20A spurs" in fact radials off their own mcbs? 

 

[Steptoe]

I don't understand why the sockets weren't put behind/inside the unit in the first place with just a switch outside,

That would have looked terrible with trailing flexes through the side of the unit.

Then one of the sockets could have been changed to an outlet plate as @Onoff suggests.

And I think this is another one of those occasions where proper terminology needs to be used, as it does appear they were indeed radials and not spurs.

[Jeremy Harris]

 

 

25 minutes ago, Onoff said:

Couldn't you have just kept one of the single gang plug top outlets and replaced the other with 1-gang cooker connection plate that has an oval cable grip anyway? Were the "20A spurs" in fact radials off their own mcbs? 

 

 

Yes, it was the first option, but I just didn't like the aesthetics of it.  If I'm 100% honest I didn't really like the original plan much either, with two visible 13A leads coming out the side of that tall unit, but at the time neither of us could think of a way around it without adding switches to the right and it was the best plan we could come up with and still be compliant with the regs.  I didn't really want the hob switch on the right, either, but that was pretty much the only place we could put it.

 

The change in the oven spec by the manufacturer forced us to change things, and by then the kitchen units, worktops etc were all fitted so we knew exactly what options were available.  We were limited by the fact that the right most 13A box was up against  a 50mm x 50mm service void batten, so drilling across into the service void behind the oven unit was not going to be easy without cutting out a fair sized bit of plasterboard and making good, although I did think of it as a way of hiding the wide, flat, cable.  That cable's interesting, as it looks and feels identical to the blue, flat, three core cable that's fitted to the Grundfos borehole pump; maybe its a German thing. 

 

Having spare capacity on the cable to the hob switch, plus being able to hide the outlets to the two ovens, made the solution we opted for seem the best compromise, but I'm sure there are half a dozen alternative ways we could have solved the problem.

 

With hindsight, perhaps we should have ordered the kitchen units and appliances before first fix, and found someone to store them for us, as that way we could have taken measurements for the access at the rear of the oven unit and come up with a neater solution from the start.  The problem was that the units were all pre-assembled and would have taken up a lot of space somewhere.  We couldn't have had them in the house when it was being plasterboarded out and plastered, or when the floors were being laid, either.

 

Edited to add:

 

Sorry, missed the point about radials.  Yes, three radials from the CU, two 20A, one 40A.  We gained two free slots in the CU, which is handy as the water heater was added later and would have taken the only free slot left, and it's useful to have one or two spare slots, I think.

Edited February 10, 2017 by JSHarris

[ProDave]

23 minutes ago, JSHarris said:

Yes, it was the first option, but I just didn't like the aesthetics of it.  If I'm 100% honest I didn't really like the original plan much either, with two visible 13A leads coming out the side of that tall unit, but at the time neither of us could think of a way around it without adding switches to the right and it was the best plan we could come up with and still be compliant with the regs.  I didn't really want the hob switch on the right, either, but that was pretty much the only place we could put it.

the usual idea would have been two two 20A DP switches where your 13A sockets are to the LEFT of the oven unit, feeding two 13A sockets behind the actual oven space. Usually the oven space does not have a back panel on it, so the sockets would have just been set into the wall behind the oven.  I don't see why you could not have converted the original layout to that and because of the rating of the oven and it's supplied cable, fit a CCU instead of a 13A socket behind the oven space. You have plasterboard walls and a service void so should have been able to fish a cable that short distance.

 

Often space is limited behind an oven, and you never know until you get the oven where the socket will fit, so in practice I tend to leave a long length of cable and not actually fit the socket (or ccu) until I have the oven and can work out where it can go.

 

A lot of the confusion was the fact you initially described the two radial circuits as "spurs"
 

[Nickfromwales]

4 minutes ago, ProDave said:

A lot of the confusion was the fact you initially described the two radial circuits as "spurs"
 

Yup. That's where I got lost 

Jeremy!

[Jeremy Harris]

17 minutes ago, ProDave said:

the usual idea would have been two two 20A SP switches where your 13A sockets are, feeding two 13A sockets behind the actual oven space. Usually the oven space does not have a back panel on it, so the sockets would have just been set into the wall behind the oven.  I don't see why you could not have converted the original layout to that and becuse of the rating of the oven and it's supplied cable, fit a CCU instead of a 13A socket behind the oven space.

 

Often sopace is limited behind an oven, and you never know until you get the oven where the socket will go, so in practice I tend to leave a long length of cable and not actually fit the socket until I have the oven and can work out where it can go.

 

A lot of the confusion was the fact you initially described the two radial circuits as "spurs"
 

 

Had we known at first fix where the opening slot was in the back of the oven unit, then that's what we would have done.  The problem then was that we hadn't yet finally decided on the kitchen supplier and when we did the drawings of the oven unit didn't include the dimensions of the rear opening slot anyway.  Remember I had metal back boxes fitted in the service void, that was 50mm deep, and I have a personal dislike of plastic back boxes, perhaps irrational, but there you go.

 

Great in hindsight, but when you're working with only limited information initially you're a bit constrained as to the options you have!

 

The spur/radial thing is my age.  Spurs were any cable run from the fuse box (as it was then) to a specific single outlet.  Radial was a term generally used to describe the wiring scheme with multiple outlets on a single radial cable, to distinguish it from a ring scheme.  With rings, spurs refer to single runs from a ring.   I agree, I was wrong, the terminology has moved on, everything does.  We even have more houses being wired with all radial circuits, a better solution in many ways than rings.  We're all human...........................

Edited February 10, 2017 by JSHarris
added clearer explanation about not fitting boxes behind the oven space

[Barney12]

12 minutes ago, JSHarris said:

 

We're all human...........................

 

I'm with Jeremy. A radial was always known as a spur to me until this forum enlightened me.

 

Now can you clever minded folk please tell me how I can completely hide revolting spurs, isolation switches and such other "electrical gubbins" from the walls of my lovely designer kitchen.  

[Jeremy Harris]

 

23 minutes ago, Barney12 said:

 

I'm with Jeremy. A radial was always known as a spur to me until this forum enlightened me.

 

Now can you clever minded folk please tell me how I can completely hide revolting spurs, isolation switches and such other "electrical gubbins" from the walls of my lovely designer kitchen.  

 

If you go back in the mists of time, radials used to feed things like immersion heaters, directly from the fuse box, were very often colloquially referred to as spurs.  Officially, there was a tightening of terminology in the regs many years ago, so that a spur now refers specifically to a single cable to an outlet fed from a ring and a radial refers to a single cable, with one or more outlets, fed by one end from a consumer unit termination.  I made an error, but frankly it was an age related one.  Words and their meaning change with time, and terms that were perfectly well understood 40 years ago may now have a very different meaning, in all aspects of life.

 

Edited to add:

 

Sorry, forgot the answer - age again................

 

You can hide switches as long as they are readily accessible, and generally the Part M accessibility rules are pretty good guidance.  So putting them behind easily accessed panels is OK, but think about wheelchair users and the like.  I've been told (by my electrician) of a case where the oven isolating switches were allowed to be fitted at the back of the top cupboard, and were passed by a building inspector, but I took the view that that would be unacceptable, because my dad was a wheelchair user, as is a good friend, and I had a bit of insight into how un-wheelchair-user-friendly things can be.

Edited February 10, 2017 by JSHarris
forgot to try and answer the question...........

[Onoff]

1 hour ago, Barney12 said:

I'm sure putting them in the glass tambour units on the side would be OK though?

 

You mean on the returns immediately round from the grey cupboards? Sounds OK (without getting into the suitability of what you're mounting them on) I've seen it done. You'll obviously have to have any back box projecting into the cupboard so will want to achieve a neat detail there with conduits etc as required.

 

[Steptoe]

If the back boxes are metal, fixed to the rear of the 50mm service void, how has @JSHarris enclosed the cables between the back box and the accessory,? Even with a massive 47mm back box its still not enclosed,??? 

I'm just not understanding anybif the logic here whatsoever , obviously I'm missing something very simple, like not seeing the wood for the trees kinda thing. 

 

@Barney12 I have seen them surface mounted on the underside of wall cupboards, but that requires a rather large pelmet,,,    ,,,,,, 

[Onoff]

MK grid, other makes are available:

 

GridPlus.pdf

 

A typical grid back box:

 

https://www.fastlec.co.uk/893alm-mk-grid-plus-6-or-8-gang-flush-back-box-with-knockouts.html?gclid=CIzY17b-hdICFcQV0wod5cEAIA

 

[Jeremy Harris]

I like the idea of grid units like this.  We fitted a combination plate in the living room with a grid sector in one of the four isolated quadrants, and it was really useful to be able to pick and mix speaker connections, ethernet etc in one panel.  My only criticism of the MK system would be the price.  The combination plate was reasonable, but the four quadrant steel back box was a ludicrous price, something like £40 or more.  It was also slightly more awkward to fit, as all our back boxes are fitted to glued and well-sealed ply spacers onto the airtight/vapour tight membrane, with all the securing screws individually sealed to maintain the integrity of the vapour barrier.  Not an issue for the smaller boxes, as a squirt of sealant behind followed by prompt placement on to the ply spacer was pretty easy, but the electrician did need an extra pair of hands to fit the big grid back box before the sealant started going off - it was one of those "three hand jobs" (stop sniggering.............).

Edited February 10, 2017 by JSHarris
typos galore, yet again

[ProDave]

1 hour ago, JSHarris said:

Had we known at first fix where the opening slot was in the back of the oven unit, then that's what we would have done.  The problem then was that we hadn't yet finally decided on the kitchen supplier and when we did the drawings of the oven unit didn't include the dimensions of the rear opening slot anyway.  Remember I had metal back boxes fitted in the service void, that was 50mm deep, and I have a personal dislike of plastic back boxes, perhaps irrational, but there you go....................

I'm not sure I understand  this "slot" in the back of the oven housing?  Just about every oven I have ever seen is way to deep to allow the housing to have a back panel. Sure some are supplied with a back panel, but you almost always have to remove it to allow enough depth for the oven. You can probably allow the back panel to remain behind the microwaver shelf as they are not so deep.

 

so all you needed was to get the cable exiting the wall somewhere behind the oven housing, and chose the final location of the socket or CCU once it's ready to put the oven in, then using a plasterboard fast fix box which personally I much prefer for this type of install.
 

[Onoff]

Have a look too at Click Minigrid & Varilight for instance. Best to make sure the range actually includes the ready engraved appliance switch you want such as "Dishwasher" etc. You can if course get them custom engraved with "Quinoa Mill" or whatever you loaded types want!

Edited February 10, 2017 by Onoff

[jack]

1 hour ago, Barney12 said:

Now can you clever minded folk please tell me how I can completely hide revolting spurs, isolation switches and such other "electrical gubbins" from the walls of my lovely designer kitchen.  

 

We talked this through with our electrician and he mentioned the "accessible" requirement.

 

In the end we mounted them in a bank out of (direct) sight on our pantry wall.  In our case it was probably the easiest place to put them in terms of cable runs, because it's inline with the more direct route from the CU and roughly central for all the appliances.

[Jeremy Harris]

12 minutes ago, ProDave said:

I'm not sure I understand  this "slot" in the back of the oven housing?  Just about every oven I have ever seen is way to deep to allow the housing to have a back panel. Sure some are supplied with a back panel, but you almost always have to remove it to allow enough depth for the oven. You can probably allow the back panel to remain behind the microwaver shelf as they are not so deep.

 

so all you needed was to get the cable exiting the wall somewhere behind the oven housing, and chose the final location of the socket or CCU once it's ready to put the oven in, then using a plasterboard fast fix box which personally I much prefer for this type of install.
 

 

 

Sorry Dave, but the unit we bought wasn't really very open at the back at all.  I don't know whether that's unusual or not, I've never fitted a tall double oven unit before.  Ours had a solid back, with two slots around 200mm high in the back above each of the two oven compartments.  These slots were shown on the 3D sketches of the units in the catalogue, but I couldn't get the dimensions of them from the supplier.  The shelves to support the ovens was firmly fixed to the lower edge of the back panel in each section, to add some stiffness I guess.  It meant I had to do some faffing around to get the top oven to fit, as it was about 2mm too high, so I ended up cutting four shallow rebates in the shelf where the metal "feet" (really just projecting parts of the bottom panel) were, to get things to line up neatly, with an even gap all around.

 

Originally I wanted to get the whole electrical installation signed off in one go, and didn't want to bother the electrician to come back to wire up the outlets behind the kitchen unit later, so the plan was for all outlets to be fitted by him, tested and signed off, and then it would be fine for me to just fit the ovens and plug them in.

 

Best laid plans and all that..................

 

 

Edited February 10, 2017 by JSHarris

[Jeremy Harris]

OK, I've just checked all the correspondence we had back in 2014 with the appliance suppliers, and found a spreadsheet I made up to compare all the dimensions of different combinations of units, as there seems to be little in the way of standardisation.

 

The oven is 542mm deep, which tallies with what I remember, as the ventilation gap at the rear of the oven housing is around 30mm to 40mm deep and leads to a grill at the rear edge of the top panel and is open to the space under the unit at the bottom.  According to my spreadsheet, the maximum depth of oven we could fit was 555mm, from the edge of the front edge of the unit to the rear panel.

Edited February 10, 2017 by JSHarris