Domestic remodel - Sanity check on a couple of things

[SparkyChick]

Hi all,

Currently quoting for a fairly extensive remodel of a kitchen diner, and I have a couple of things I'd appreciate a sanity check on.

1. Structural steel bonding - My brain is telling me based on what I've read and understood that I don't need to bond the new structural steels. They aren't in contact with the ground, but my heart is telling me that just seems wrong somehow. One of the beams is going to have it's cavity acting as trunking effectively since it's the path of least resistance from one side of the room to the other and so my thinking is, I should bond it to ensure a good earth path in fault conditions.

2. Sanity check on a cable size - New oven, 22.2A (max, no diversity factored in at all). 6mm can handle it, but obviously running a 20A breaker at that is not great long term, so 32A breaker required. Since 6mm can only handle 27A when in a ceiling with insulation (ref method I'm going to be encountering), my only choice is 10mm. Voltage drop is fine either way, it's just the potential overload situation. So 10mm is the correct choice as far as I'm concerned.

3. There is going to be some under cabinet lighting. To future proof, I am going to suggest that the supply for this (coming from a 6A lighting circuit) is exposed in the cupboards as 13A unswitched outlets since then the customer can change the lighting to their hearts content. My concern though is if they stick something other than lighting on it. 1.5mm is fine generally, and can handle 13A in the ceiling with insulation. So my brain is saying this is fine, but for some reason it just feels wrong. For that reason I was considering providing the supply by 5A round pin outlets, but that raises the issue of the 6A breaker. I have very limited experience of round pin outlets. 5A is obviously the continuous rating, try as I might, I can't find any information about overload characteristics, so I'm wondering what you guys think?

Whilst it's a fairly big job (by my standards so far), the rest of it is straight forward, it's just these three niggles I could do with a bit of feedback on.

Comments and thoughts welcome

 

[SparkyChick]

Like those spacers, will definitely be picking some of those up.

The sockets are laser levelled around the room. Yes, the conduit is for u/c lighting, still have to put one on the other wall.

Yes, the switch is supplying the RCD, then two MCBs. The original plan was to convert the existing board to two RCDs and use the new CU for some safety services only (smokes and a sprinkler system that's being installed). But, the existing board is lacking sufficient neutral bars (my mistake). So I've made do. And before anyone asks... yes there is a single point of isolation in the meter cupboard (not the DNO fuse).

 

[Midwest]

Yep the spacers are quite handy, if a bit expensive and not all wholesalers have them. Makes life so much more easier though

Just wondered if you could of ditched the main switch, and just used the RCD as main switch?

Like the idea of the oval conduit, but that would be a bridge too far for my kitchen fitters. Just convinced them to notch the back of the wall units, and attach supplied lead, before they install the wall unit. Bless em.

Seem to recall, the single point of isolation, is only relevant if the two (or multiple of) are not adjacent or not obvious, i.e. CU in garage, CU in hallway?

 

[madmaz]

The 10mm by the window is outside of any safe zone, as you say fit a blank plate to highlight the cable run

 

[charlie76]

The customer also had notes on the literature he showed me about the oven that stated it required a 32A breaker.

"134.1.1 - ....etc. The installation of electrical equipment shall take account of the manufacturers instructions"

 

[David M]

Like those spacers, will definitely be picking some of those up.

The sockets are laser levelled around the room. Yes, the conduit is for u/c lighting, still have to put one on the other wall.

Yes, the switch is supplying the RCD, then two MCBs. The original plan was to convert the existing board to two RCDs and use the new CU for some safety services only (smokes and a sprinkler system that's being installed). But, the existing board is lacking sufficient neutral bars (my mistake). So I've made do. And before anyone asks... yes there is a single point of isolation in the meter cupboard (not the DNO fuse).

(My bold) Nice to see pride taken in your work. Nothing worse than uneven accessories, especially in a kitchen where they can stand out against a tiled background.
As Midwest said, I've often come across uneven cupboard units, especially the wall hung ones.

 

[Midwest]

(My bold) Nice to see pride taken in your work. Nothing worse than uneven accessories, especially in a kitchen where they can stand out against a tiled background.
As Midwest said, I've often come across uneven cupboard units, especially the wall hung ones.

Luckily, both myself and kitchen fitters I do work for, have laser levels! They even mark the positions of the units, before I 1st fix.

 

[Specialist]

Blimey, you've got them well trained. Laser levels are a godsend though.

 

[Midwest]

The 10mm by the window is outside of any safe zone, as you say fit a blank plate to highlight the cable run

Course, 'we' could of just run it down the corner of the room, and everything would be tickety boo. Not dissing you madmaz, just this whole zone thing.

 

[Midwest]

Blimey, you've got them well trained.

Taken some time, but prevents cock ups. Doesn't matter who's fault it was, it's a lot to put right, when 'socket' is in the wrong place when the walls been tiled or plastered.

 

[SparkyChick]

The 10mm by the window is outside of any safe zone, as you say fit a blank plate to highlight the cable run

There is a 150mm safety zone created at the angles of two faces of the wall no? Therefore it is within a safety zone where the window is, but that zone stops 150mm below the window sill... at least that's my take on it.

 

[SparkyChick]

"134.1.1 - ....etc. The installation of electrical equipment shall take account of the manufacturers instructions"

It's on a 32A breaker

 

[Richard Burns]

There is a 150mm safety zone created at the angles of two faces of the wall no? Therefore it is within a safety zone where the window is, but that zone stops 150mm below the window sill... at least that's my take on it.

Because most people (except electricians) have no idea of safe zones I tend to try and limit the use to the most obvious locations where possible. Since the zone description is 150mm from the angle of two adjacent walls I do not think that this applies for a penetration through a wall such as a window frame.
You can also think that is someone is hacking out the window to change it they may well hit a cable; however a similar problem occurs with coving on the 150mm from the ceiling zone.

 

[HandySparks]

There is a 150mm safety zone created at the angles of two faces of the wall no? Therefore it is within a safety zone where the window is, but that zone stops 150mm below the window sill... at least that's my take on it.

Must admit, I'd never thought of a window opening as usable as a safe zone. Would you also regard a door opening in the same way?

 

[SparkyChick]

I guess it's one of those issues that's open to interpretation. I'm planning on adding an outlet at the bottom of the wall just in case and I'm annotating plans for the customer showing where the cable runs are along with junction boxes. Aside from a blob of dot'n'dab, that cable's of the only one that causes me concern in terms of location wrt the zones.

 

[Midwest]

Think the whole zone thing is a daft idea, only sparks know about it. Repaired loads of 'drilled into' cables directly above faceplates, nearly done it myself once

Incidentally, do plumbers have such zones?

Came across this doing kitchen refurb'. The gas pipe fed an unused gas outlet for kitchen cooker, which wasn't directly below it;



The three holes were for the old wall unit brackets, luckily the drill bit somehow managed to miss the pipe.

Edit, the cut oblong hole I did, so we weren't attempt the same thing.