Plastic switch in external meter box

It is raining......

 

TPN boards, even where they do comply with BS EN 61439-3 can't be described in BS 7671 as consumer unit simply because BS 7671's definition of a consumer unit only applies to single phase equipment (i.e. having DP incomer).

Of course, due to them being "similar switchgear" as opposed to Consumer Units. Principally, consumer units are a particular type of Distribution Board used in domestic [household] premises and, yes, they have to have a DP incomer, but the "similar switchgear", a distribution board, does not necessarily have one.


 

As I read it, 421.1.201 isn't saying that the requirement for non-combustibility applies to BS EN 61439-3 equipment - rather it's saying that where ordinary persons are about (domestics) then it must both comply with BS EN 61439 as well as having an non-combustible enclosure - the BS EN 61439-3 is part of the requirement rather than part of the condition.

Agreed. That is what was said.


 

If a householder is following instructions to 'turn off at the main switch' surely the switchfuse is exactly the place they should be doing it. So really I don't buy that the existence of a downstream CU means that the householder wouldn't have any cause to operate the switchfuse.

But there is not always a switchfuse. There may be a separate isolator, say a DNO supplied one. For a domestic [household] premises there will be a consumer unit. What is labelled "main switch" will determine where someone operates the main switch. Instructions for turning off the main switch are usually for isolating the consumer unit; there will be a label on it saying to do so before removing cover, for instance. There will not be a consumer unit without a main switch in the same enclosure in domestic [household] premises.


Never say never, but the consumer unit main switch would be the "go to" device, it being the most obvious to a consumer.


The point is "resetting a device" like an RCD or MCB in a consumer unit. Turning off a main switch is isolation.

The consumer unit will have things that are in the off position if there is a fault or overload. That is consumer friendly, hence the moniker consumer unit for domestic [household] premises. 


A 800KMF has a more " only an electrician should be fiddling with that" look than your bona fide, consumer friendly, consumer unit?


 

I didn't know about the 63A limit for outgoing ways for CUs - and am a little surprised about that - since the BSI site in the overview of BS EN 61439-3 says rated current (Inc) of the outgoing circuits does not exceed 125 A and the rated current (InA) of the DBO does not exceed 250 A"

Like I said "consumer units" to BSEN6143-9 are limited to 63 amp / way. I never said the standard stated that. Your "similar switchgear" are distribution boards and could be up to 125 amp/way, but I would suggest that at this point we have probably gone beyond a domestic [household] premises and 100 amp supply.

 

and some examples of 80A/100A switchfuses appear to claim some sort of compliance with BS EN 61439-3 as well as 60947-3.

I am glad the language used above as a descriptor of the particular wylex product does not infer absolute compliance with BS EN61439-3. 

Is that due to the product being described as a Switchfuse? If it is manufactured to comply with BSEN61439-3 it is a distribution board as that standard  defines the specific requirements for distribution boards intended to be operated by ordinary persons (DBO). To my mind something built to comply with that standard is a distribution board. That Wylex product should be described as a one way distribution board.


I note the literature posted a little way back from Wylex is 2015. They have their interpretation of "similar switchgear" in print; many had various interpretations at that time. If nothing else, it hopes there is a demand for a new product that is really only a distribution board and not a switch fuse.


 

I'm still struggling to see why a 3x12 way TPN DB with 125A incomer and perhaps several 63A outgoing MCB is considered to be similar to a CU, but a 1-way SP distribution board with a 100A incomer and a 63A outgoing fuse isn't.

Of course, a 1 way SPN  distribution board is "similar switchgear". As is the TPN when intended for domestic [household] premises.


 

Fortunately building regs have their own definitions of things (and often didn't align with BS 7671 ones anyway) - as far as I can tell the notification requirement applies only to consumer units (not similar switchgear) - so perhaps there's no need to notify a TPN board replacement in a domestic?

But the "similar switchgear" are distribution boards and when used in domestic [household] premises they are principally called consumer units. The notification requirement is for dwellings where there is a presumption of there being a consumer unit present. "Similar switchgear" is in BS7671 only, as the standard is not just for dwellings.


I do not think we should be condemning the use of KMFs in domestic installations. There are many, many thousands installed, they are compact and manufactured as a switchfuse, usually for a specific purpose where a distribution board is not suitable.

It is raining......

 

TPN boards, even where they do comply with BS EN 61439-3 can't be described in BS 7671 as consumer unit simply because BS 7671's definition of a consumer unit only applies to single phase equipment (i.e. having DP incomer).

Of course, due to them being "similar switchgear" as opposed to Consumer Units. Principally, consumer units are a particular type of Distribution Board used in domestic [household] premises and, yes, they have to have a DP incomer, but the "similar switchgear", a distribution board, does not necessarily have one.


 

As I read it, 421.1.201 isn't saying that the requirement for non-combustibility applies to BS EN 61439-3 equipment - rather it's saying that where ordinary persons are about (domestics) then it must both comply with BS EN 61439 as well as having an non-combustible enclosure - the BS EN 61439-3 is part of the requirement rather than part of the condition.

Agreed. That is what was said.


 

If a householder is following instructions to 'turn off at the main switch' surely the switchfuse is exactly the place they should be doing it. So really I don't buy that the existence of a downstream CU means that the householder wouldn't have any cause to operate the switchfuse.

But there is not always a switchfuse. There may be a separate isolator, say a DNO supplied one. For a domestic [household] premises there will be a consumer unit. What is labelled "main switch" will determine where someone operates the main switch. Instructions for turning off the main switch are usually for isolating the consumer unit; there will be a label on it saying to do so before removing cover, for instance. There will not be a consumer unit without a main switch in the same enclosure in domestic [household] premises.


Never say never, but the consumer unit main switch would be the "go to" device, it being the most obvious to a consumer.


The point is "resetting a device" like an RCD or MCB in a consumer unit. Turning off a main switch is isolation.

The consumer unit will have things that are in the off position if there is a fault or overload. That is consumer friendly, hence the moniker consumer unit for domestic [household] premises. 


A 800KMF has a more " only an electrician should be fiddling with that" look than your bona fide, consumer friendly, consumer unit?


 

I didn't know about the 63A limit for outgoing ways for CUs - and am a little surprised about that - since the BSI site in the overview of BS EN 61439-3 says rated current (Inc) of the outgoing circuits does not exceed 125 A and the rated current (InA) of the DBO does not exceed 250 A"

Like I said "consumer units" to BSEN6143-9 are limited to 63 amp / way. I never said the standard stated that. Your "similar switchgear" are distribution boards and could be up to 125 amp/way, but I would suggest that at this point we have probably gone beyond a domestic [household] premises and 100 amp supply.

 

and some examples of 80A/100A switchfuses appear to claim some sort of compliance with BS EN 61439-3 as well as 60947-3.

I am glad the language used above as a descriptor of the particular wylex product does not infer absolute compliance with BS EN61439-3. 

Is that due to the product being described as a Switchfuse? If it is manufactured to comply with BSEN61439-3 it is a distribution board as that standard  defines the specific requirements for distribution boards intended to be operated by ordinary persons (DBO). To my mind something built to comply with that standard is a distribution board. That Wylex product should be described as a one way distribution board.


I note the literature posted a little way back from Wylex is 2015. They have their interpretation of "similar switchgear" in print; many had various interpretations at that time. If nothing else, it hopes there is a demand for a new product that is really only a distribution board and not a switch fuse.


 

I'm still struggling to see why a 3x12 way TPN DB with 125A incomer and perhaps several 63A outgoing MCB is considered to be similar to a CU, but a 1-way SP distribution board with a 100A incomer and a 63A outgoing fuse isn't.

Of course, a 1 way SPN  distribution board is "similar switchgear". As is the TPN when intended for domestic [household] premises.


 

Fortunately building regs have their own definitions of things (and often didn't align with BS 7671 ones anyway) - as far as I can tell the notification requirement applies only to consumer units (not similar switchgear) - so perhaps there's no need to notify a TPN board replacement in a domestic?

But the "similar switchgear" are distribution boards and when used in domestic [household] premises they are principally called consumer units. The notification requirement is for dwellings where there is a presumption of there being a consumer unit present. "Similar switchgear" is in BS7671 only, as the standard is not just for dwellings.


I do not think we should be condemning the use of KMFs in domestic installations. There are many, many thousands installed, they are compact and manufactured as a switchfuse, usually for a specific purpose where a distribution board is not suitable.