Introducing myself and some questions

[G Westmorland]

Are you doing this in your own house?

Yes, in my own house.

 

[westward10]

Three earthing systems generally apply in this country, TN-S, TN-C-S and TT. The latter, TT employs an earth rod/electrode and in almost all cases will employ rcds for fault protection. The first two are variations of a TN system and generally do not require rcds for fault protection if correct measures are in place.

 

[GeorgeCooke]

This is a clear example where manufacturers instructions are wrong. A 16 amp oven currently available in B & Q. Should never be on a FCU and 16a fuse for FCU!

 

[richy3333]

The house has no RCD protection (it was built in 2002). IMHO an RCD is desirable but not essential. Would folk agree?

Well they potentially save lives in the event of a fault and as of January 2019 you'll hardly be able to fart in a domestic property without RCD protection! At the end of the day way up if RCD protection is required against the value of yourself or a loved ones life and then decide.

Ring the manufacturers and ask but I bet they are vague or refuse to comment just in case something ever happens. I guess they refer to installation by a qualified electrician as a get out clause for them in respect of DIYers doing the work?

 

[Darkwood]

View attachment 46408 This is a clear example where manufacturers instructions are wrong. A 16 amp oven currently available in B & Q. Should never be on a FCU and 16a fuse for FCU!

This goes to show you have not reading what I posted, I have on more than one occasion expressed we are excluding where the manufacturers instructions are clearly wrong so I am somewhat bemused as to why you have posted an example of one that clearly is.

 

[telectrix]

This goes to show you have not reading what I posted, I have on more than one occasion expressed we are excluding where the manufacturers instructions are clearly wrong so I am somewhat bemused as to why you have posted an example of one that clearly is.

he posted that to make your hair turn white. looking at your avatar i see it worked.

 

[ipf]

he posted that to make your hair turn white. looking at your avatar i see it worked.

Yep..…...and still waiting for King Kong and Mighty Joe Young showing their ugly mugs...

 

[Deleted member 26818]

I believe the Red book, or perhaps the Green, brought in a requirement to comply with Manufacturer’s instructions.
That requirement has (as far as I am aware) been dropped.
All we have to do now, is take account of the instructions.

As for the OP.
Installing up front RCDs or RCBOs to protect multiple circuits, is not a good idea.
Individual circuit protection is much better.

 

[G Westmorland]

I believe the Red book, or perhaps the Green, brought in a requirement to comply with Manufacturer’s instructions.
That requirement has (as far as I am aware) been dropped.
All we have to do now, is take account of the instructions.

As for the OP.
Installing up front RCDs or RCBOs to protect multiple circuits, is not a good idea.
Individual circuit protection is much better.

Thanks - that's helpful info.

Thanks to all for the replies.

My take on the situation is now:

1. The manufacturer's instructions do not say that an RCD is required, they say "Make sure that a shock protection is installed."
2. Westward10 advises that TN-S and TN-C-S installations generally do not require RCDs for fault protection if correct measures are in place, unless the earth is TT in which he says "in almost all cases will employ rcds for fault protection".
3. My system would appear to be TN-S or TN-C-S, as:
a. There is no RCD protection installed
b. The earth cables for the three phases are connected to a common earth in the meter cupboard goes down to join the supplier's cable where it enters the meter cupboard at its base. (I can't see what the common earth cable connects to though, that is out of sight).
4. After installation, there will be no physical access to any live parts, only to the glass topped hob, with capacitative touch controls. So in the unlikely event that shock protection is not provided by the current installation via the mcbs and earthing arrangements, shock protection is still provided by the glass surface which is not conductive of mains voltages. Or to put it another way, there is no actual risk of shock in using the appliance, unless the glass surface is smashed by a person falling onto it, which seems a very unlikely eventuality indeed.

So my plan is that I WILL have an RCBO fitted to this circuit, but only as and when I require a visit from an electrician for an additional purpose.

(P.S. Manufacturer specced cable is H05BB-F and hob rating is 7.4kw, so I plan to use 6mm cable, which is required for flex cable to carry 32 A. Am not relying on diversity because cooker has 4 heating areas each of which can in boost mode draw 3.2 kw for up to 10 minutes - which is power managed by the hob down to 7.4 Kw max. So an actual draw of the full 7.4 kw seems entirely possible).

 

[G Westmorland]

Thanks - that's helpful info.

Thanks to all for the replies.

My take on the situation is now:

1. The manufacturer's instructions do not say that an RCD is required, they say "Make sure that a shock protection is installed."
2. Westward10 advises that TN-S and TN-C-S installations generally do not require RCDs for fault protection if correct measures are in place, unless the earth is TT in which he says "in almost all cases will employ rcds for fault protection".
3. My system would appear to be TN-S or TN-C-S, as:
a. There is no RCD protection installed
b. The earth cables for the three phases are connected to a common earth in the meter cupboard goes down to join the supplier's cable where it enters the meter cupboard at its base. (I can't see what the common earth cable connects to though, that is out of sight).
4. After installation, there will be no physical access to any live parts, only to the glass topped hob, with capacitative touch controls. So in the unlikely event that shock protection is not provided by the current installation via the mcbs and earthing arrangements, shock protection is still provided by the glass surface which is not conductive of mains voltages. Or to put it another way, there is no actual risk of shock in using the appliance, unless the glass surface is smashed by a person falling onto it, which seems a very unlikely eventuality indeed.

So my plan is that I WILL have an RCBO fitted to this circuit, but only as and when I require a visit from an electrician for an additional purpose.

(P.S. Manufacturer specced cable is H05BB-F and hob rating is 7.4kw, so I plan to use 6mm cable, which is required for flex cable to carry 32 A. Am not relying on diversity because cooker has 4 heating areas each of which can in boost mode draw 3.2 kw for up to 10 minutes - which is power managed by the hob down to 7.4 Kw max. So an actual draw of the full 7.4 kw seems entirely possible).

EDIT - Going for 4.0mm² 3183TQ which seems to tick all the necessary boxes. (Have read that HO5bb-F is difficut or impossible to get above 2.5mm).

 

[Edtwozeronine]

We were told that manufacturers instructions need to be followed in college, they have to follow the same guidance in as the installers do and if they don't they could be in legal trouble for supplying potentially dangerous equipment. I very much doubt any manufacturers producing goods to UK standards want to be in that position.

 

[G Westmorland]

The Butyl 3183 TQ is heat ressistant to 90C rather than 60C, is flexible, and resistant to fats and oils. So it meets and exceeds the spec for H05bb-f.
Plus, , see Spinlondon's post above which says:
"I believe the Red book, or perhaps the Green, brought in a requirement to comply with Manufacturer’s instructions.
That requirement has (as far as I am aware) been dropped.
All we have to do now, is take account of the instructions."

 

[FatAlan]

After all this discussion about what the manufacturers instruct or not. You say at the start that it’s a replacement for a ceramic hob on a 32A MCB. Do you know the current size of the cable feeding the the cooker connection point, length of cable run to MCB and fixing method? Presumably the cable size you were discussing was just for the hob to the connection point?

 

[G Westmorland]

After all this discussion about what the manufacturers instruct or not. You say at the start that it’s a replacement for a ceramic hob on a 32A MCB. Do you know the current size of the cable feeding the the cooker connection point, length of cable run to MCB and fixing method? Presumably the cable size you were discussing was just for the hob to the connection point?

Am assuming that cable capacity must be at least 32a as it is on its own 32a mcb. If less than that, mcb will not provide proper protection and hob spur would be improperly installed. Think it's safe to assume that it was properly installed.

As cables are all hidden in property syructure, there is no other way to assess it.

Yes, cable size is for hob to connection point. Very short run as connection point is just below hob.

Had to go for H07 cable 6mm in the end as only suitable cable I can get in reasonable time.

 

[FatAlan]

If you ‘assume’ it does tend to make an ‘---’ out of ‘u’ and ‘me’
You are more than likely right with a pre existing cooker having been connected but you never know until it’s normally too late.