Introducing myself and some questions

[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.

 

[G Westmorland]

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 structure, 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.

OK. Got the H07RN-F. Can't find a spec online from the maker (Prysmian), but Eland publish a spec for theirs, which says:

"The H07RN-F trailing duty cable has a temperature rating of -30C to +60C for fixed installations (rising to +85C for fixed protected installations) and from -15C to +60C when flexed."

Please forgive my ignorance, but, as the manufacturer specified "H05bb-F or H03V2V2-F which withstands a temperature of 70C or higher"

- am I ok with the H07? (As i can't source the specified cable, esp in a sufficient size).

This is for a very short run of less than half a metre, inside a kitchen cabinet, to the switched outlet. Does that qualify as a "Fixed protected installation"?

Also, what does "when flexed" mean? Does it mean if there is significant movement going on, or does it mean of the cable has to be bent? There will need to be bends in the cable, obviously.

The hob does require ventilation gaps underneath it, and the install guide warns about possible damage due to overheating if insufficient ventilation is provided. So I deduce that:

a. There will be some heat coming from the hob, although I don't know how hot, in the region of the supply cable,
b. That heat will be in the form of blown air, which presumably has some degree of cooling effect, even though the air will be hot, due to air movement.

Or should I just order and wait for 3183TQ 6mm, to be on the safe side?