D
dayrider3883
I have installed a fan from the lighting switch to bathroom do i need to use a spur for the fan or can i go direct
The extractor fan doesn't neccessarily need an isolator.
Please read:
Bathroom extractor fans and 3 pole isolation, a source of much controversy
Please read:
Bathroom extractor fans and 3 pole isolation, a source of much controversy
J
JUD
This is the third time I've asked this and you haven't even mentioned it.
WHY, if you can't have a circuit using a BS 1362 fuse, do they provide Zs values for them in the regs. I've never seen a distribution board with 3A and 13A plug-top fuses in them.
D
Deleted member 26818
It may well be the third time that you've asked the question, I'm still struggling to see it's relevance.
I'm not aware of any Regulation prohibiting the use of a BS1362 fuse in a circuit.
As far as I'm concerned, there are many instances where the use of a BS1362 fuse is quite acceptable, in fact Appendix 15 indicates that devices which use such fuses may be supplied through both ring and radial circuits. For instance where the current carrying-capacity of a conductor is reduced, when spuring off of a circuit.
Judging from your arguments, it appears that you accept that RCD protection must be provided for the whole circuit if that circuit is of a location containing a bath or shower.
Your argument appears to be whether the origin of the circuit is as the information contained in Appendix 15 indicates at a DB; or as you contend, at an FCU.
As I posted earlier, I accept that an FCU meets the requirements of an overcurrent protective device as per the definition of a circuit in Part 2.
However Regulation 314.4 requires that final circuits be conected to a separate way at a distribution board and unless I'm mistaken, an FCU is not a DB.
Do you have an argument that allows us to disregard Regulation 314.4?
J
JUD
We do not need to disregard Regulation 314.4 as the lighting final circuit itself complies with it as it's origin is the distribution board.
The FCU is supplied by the final circuit and itself supplies a circuit for the light and fan in the bathroom.
The reg you're referring to regarding RCD protection says that "Additional protection shall be provided for all circuits of the loacation...."
If what you're suggesting was true then surely it would say "Additional protection shall be provided for all final circuits supplying equipment in a location containing a bath or shower...." or something along those lines.
At the end of the day it's down to how each individual interprets the regulations.
The FCU is supplied by the final circuit and itself supplies a circuit for the light and fan in the bathroom.
The reg you're referring to regarding RCD protection says that "Additional protection shall be provided for all circuits of the loacation...."
If what you're suggesting was true then surely it would say "Additional protection shall be provided for all final circuits supplying equipment in a location containing a bath or shower...." or something along those lines.
At the end of the day it's down to how each individual interprets the regulations.
D
Deleted member 26818
So what exactly is the circuit the FCU supplies, is it not a final circuit?
Why would the wording be all final circuits? That would then allow distribution circuits to be unprotected.
In fact, it could be that the Regulation is not just for circuits that supply equipment in such locations, but also for circuits that pass through to supply equipment in other locations.
It used to be in the 16th edition, as you probably know, that in zones 0, 1 and 2, cables either surface mounted, or concealled in walls at a depth less than 50mm, had to have additional protection, if they did not supply equipment in their respective zones.
It may well be down to how an individual interprets the Regulations, although how you can interpret 314.4, and the very clear information provided in Appendix 15, in any other way than as it is written, is a mystery to me.
Of course, it may just be the case that you do not want to comply with 701.411.3.3 for whatever reason and are trying to make excuses?
J
JUD
It's a circuit as defined in Part 2 the regulations. The final circuit already exists and complies with Regulation 314.4 as I said in my previous post.
The reg is for all circuits of the location, not all circuits supplying the location.
If other circuits were passing through the location they would probably be concealed in walls or above ceilings so they would not strictly be in the location. If these circuits were installed before the requirement for RCDs then you have no obligation to bring them upto current standards as you haven't worked on these circuits.
Appendix 15 is not a regulation. I'm not making excuses, an RCD FCU would comply with 701.411.3.3 as the lighting circuit would be RCD protected.
D
Deleted member 26818
JUD, this is becoming very tedious.
I suggest that if you can't put up then shut up.
I've answered your pointless question about Zs valus for BS1362 fuses, why won't you answer my question about what type of circuit is being supplied by the FCU?
Is it just because you know that the circuit must be a final circuit and as such is not accepted by BS7671 to be supplied from anything other than a distribution board?
A kettle meets the requirements of the definition of a circuit in Part 2, but I wouldn't call it a circuit.
I have no idea why you have stated:
Should we then ignore the Tables for time/current characteristics of overcurrent protective devices in Appendix 3, the Tables for current carrying-capacities of cables in Appendix 4, the figures for voltage drop in Appendix 12, etc. as they also are not Regulations?
Or is it we just ignore the information that doesn't tally with your point of view?
I suggest that if you can't put up then shut up.
I've answered your pointless question about Zs valus for BS1362 fuses, why won't you answer my question about what type of circuit is being supplied by the FCU?
Is it just because you know that the circuit must be a final circuit and as such is not accepted by BS7671 to be supplied from anything other than a distribution board?
A kettle meets the requirements of the definition of a circuit in Part 2, but I wouldn't call it a circuit.
I have no idea why you have stated:
Or:
I know Appendix 15 is not a Regulation, it is there to provide information in relation to the Regulations.
Should we then ignore the Tables for time/current characteristics of overcurrent protective devices in Appendix 3, the Tables for current carrying-capacities of cables in Appendix 4, the figures for voltage drop in Appendix 12, etc. as they also are not Regulations?
Or is it we just ignore the information that doesn't tally with your point of view?
O
Octopus
Gentlemen, may I suggest that we agree that you have different interpretations of BS7671 and leave it at that!
:6:
J
JUD
I agree and this will be my last post.
There's no need to get offensive just because somebody doesn't agree with your point of view. Looking back through all the posts, I see that there's only you who thinks that the whole circuit needs RCD protection.
Everybody else who's commented thinks the same as I do i.e. RCD protection only necessary for the circuit in the location.
I've answered your question twice. Where does it say that a circuit must be labelled as a final circuit? As I've said, the lighting circuit as a whole is a final circuit and complies with Regulation 314.4.
I suppose the best way I could describe it would be a sub-circuit. I know it's not in the definitions, however the definitions in Part 2 are for the purposes of the regulations only as it says at the top of the page.
You use Appendix 15 as an argument that all circuits must start at a distribution board. It refers to Regulation 433.1. Nowhere in 433.1 does it say a circuit must start at a distribution board. If we're to take Appendix 15 as literally as you do then that means that all radial final circuits should be connected to 30A or 32A overcurrent devices because Appendix 15 says they are.
Not sure why you've brought any of that up.
Again, I'm not alone in my point of view.
Have a read of Q2 in the link:
http://www.esc.org.uk/industry/industry-guidance/industry-guidance-on-the-wiring-regulations/alterations-and-additions-in-domestic-and-similar-premises/.
That should clear things up for you.
Last edited by a moderator:
D
Deleted member 26818
Sorry, I wasn't intending to be offensive, just trying to get you to answer my question, which you now have.
I'll try and put my case as consisely as possible:
We all know that locations containing baths and showers are areas where the risk of electricution are increased.
I won't bore you with explanations as I know you are well aware of the risks.
By placing an RCD anywhere other than at the origin of a circuit, an earth fault occurring upstream from the RCD will bypass the RCD and enter the location.
As such, the RCD is only providing protection against an earth fault occuring on the part of the circuit downstream from the RCD.
If for instance a supply was taken from a RFC then any earth fault current caused by a fault in the wiring of the RFC or by any appliance plugged into the RFC, that current would bypass the RCD and enter the location.
I ask you what would be safer, installing the RCD at the DB, or somewhere along the circuit?
BS7671 defines two sorts of circuits, Distribution and Final. It does not have a definition for a sub circuit.
A fused spur meets the definition of a circuit, and also that of a final circuit, but not that of a distribution circuit.
As such if we accept that it is a circuit then we must also accept that it is a final circuit.
Regulation 314.4 as I have already pointed out, requires all final circuits to be connected to separate ways at a DB.
As such if we accept a fused spur as being a circuit, then it will not comply with BS7671.
With regard to the typographical errors in Appendix 15.
These errors were addressed in a corrigendum, and the corrigendum is available for download from the IET website here:http://electrical.------.org/wiring-regulations/updates/bs7671-2008-corrigendum-jul08.cfm?type=pdf
As can be seen, the reference to '30A or 32A' overcurrent protective device has been struck through.
I'll try and put my case as consisely as possible:
We all know that locations containing baths and showers are areas where the risk of electricution are increased.
I won't bore you with explanations as I know you are well aware of the risks.
By placing an RCD anywhere other than at the origin of a circuit, an earth fault occurring upstream from the RCD will bypass the RCD and enter the location.
As such, the RCD is only providing protection against an earth fault occuring on the part of the circuit downstream from the RCD.
If for instance a supply was taken from a RFC then any earth fault current caused by a fault in the wiring of the RFC or by any appliance plugged into the RFC, that current would bypass the RCD and enter the location.
I ask you what would be safer, installing the RCD at the DB, or somewhere along the circuit?
BS7671 defines two sorts of circuits, Distribution and Final. It does not have a definition for a sub circuit.
A fused spur meets the definition of a circuit, and also that of a final circuit, but not that of a distribution circuit.
As such if we accept that it is a circuit then we must also accept that it is a final circuit.
Regulation 314.4 as I have already pointed out, requires all final circuits to be connected to separate ways at a DB.
As such if we accept a fused spur as being a circuit, then it will not comply with BS7671.
With regard to the typographical errors in Appendix 15.
These errors were addressed in a corrigendum, and the corrigendum is available for download from the IET website here:http://electrical.------.org/wiring-regulations/updates/bs7671-2008-corrigendum-jul08.cfm?type=pdf
As can be seen, the reference to '30A or 32A' overcurrent protective device has been struck through.
J
JUD
I understand the point you're trying to make.
Putting aside definitions of circuits and regs about separation of circuits you have to remember the reason for the RCD in the first place, that reason being Additional protection.
The RCD is there to limit the touch voltage between exposed and extraneous-conductive-parts of the location to ≤ 50V should an exposed-conductive-part become live while a person is touching it and another exposed or extraneous-conductive-part simultaneously.
This is achieved weather the RCD is at the origin of the circuit or not.
Good point about the corrigendum by the way. I've actually already got it on the computer but forgot all about it.
No hard feelings I hope.
I'm sure Luke Skywaler will be here soon to correct us both....:hurray:
Putting aside definitions of circuits and regs about separation of circuits you have to remember the reason for the RCD in the first place, that reason being Additional protection.
The RCD is there to limit the touch voltage between exposed and extraneous-conductive-parts of the location to ≤ 50V should an exposed-conductive-part become live while a person is touching it and another exposed or extraneous-conductive-part simultaneously.
This is achieved weather the RCD is at the origin of the circuit or not.
Good point about the corrigendum by the way. I've actually already got it on the computer but forgot all about it.
No hard feelings I hope.
I'm sure Luke Skywaler will be here soon to correct us both....:hurray:
J
JUD
A fault current on a part of the circuit before the RCD will take the path of least resistance i.e back to earth through the cpc and along the normal earth fault loop path and, if Zs for the circuit is within limits which it should be, take out the main breaker/fuse.
D
Deleted member 26818
JUD the fault current won't only take the path of least resistance, it will be distributed across all paths according to their resistance.
The maximum permisable Zs values for an overcurrent device are determined to allow disconnection times to be achieved where there is a fault of negligible impedance.
Any fault which has a high resistance will not necessarily cause an overcurrent device to operate within the applicable disconnection times.
A fault may be of such a high resistance, that the current will not be enough to cause an overcurrent protective device to operate at all.
Consider a shower circuit, it might have a 50A type B MCB. The current required to cause instantaneous operation is 250A. If the current is below 70A the device will not operate. A current between 70A and 250A willl cause the device to operate anywhere between 16 minuites and some tenths of a second.
The point of using an RCD is to achieve disconnection within thousandths of a second.
Then of course there's the fact that the CPC will only provide the path of least resistance, if it is intact.
An RCD is additional protection, it is installed to provide protection in cases where an overcurrent device is not deemed to provide sufficient protection, and other forms of additional protection are not being used or not deemed acceptable.
Where cables are concealled in walls at a depth less than 50mm, an RCD will provide protection against penetration by screws or nails.
Socket-outlets require RCD protection, not to protect the socket-outlet, or the cables supplying the socket-outlets, but to protect appliances that are plugged in to the socket-outlets.
Circuits of locations containing baths or showers, and circuits in other special locations, such as on building sites, agricultural/horticultural premises require RCD protection, not just to protect appliances which may be connected to the circuit, not just to protect cables concealled in walls, but to protect in the event of any fault which may present a danger to persons.
Even where other forms of addition protection are used such as SELV in locations containing baths and showers, BS7671 still requires the LV circuit that supplies the SELV to be RCD protected.
What makes you think that BS7671 which requires an LV circuit supplying a source of SELV to be RCD protected, would then allow an LV circuit supplying an FCU to be unprotected?
Last edited by a moderator:
D
Deleted member 26818
Murdoch, have a look at this: Young mother electrocuted by bath taps - Telegraph
The OPD didn't operate in time, in fact it didn't operate at all, as the resistance of the earth fault path was not low enough, and the woman was dead and collapsed disconnecting the earth fault path before the OPD had time to operate.
Now installing an RCD as suggested by JUD would most likely have saved the woman.
However if the earth fault had been upsream from th RCD, it wouldn't have made any difference.
This is not a simple matter such as should conductors be sleeved with the correct colour at a light switch where a competent person should be aware that any conductor at the switch could be live, this is a matter that could cause fatalities.
The OPD didn't operate in time, in fact it didn't operate at all, as the resistance of the earth fault path was not low enough, and the woman was dead and collapsed disconnecting the earth fault path before the OPD had time to operate.
Now installing an RCD as suggested by JUD would most likely have saved the woman.
However if the earth fault had been upsream from th RCD, it wouldn't have made any difference.
This is not a simple matter such as should conductors be sleeved with the correct colour at a light switch where a competent person should be aware that any conductor at the switch could be live, this is a matter that could cause fatalities.
J
JUD
I thought the info in the link to the ESC website I provided would have made mine and others cases.
spin, I agree with Murdoch, let's just agree to disagree.
At the end of the day only the IET could give a definitive answer as to what is required.
D
Deleted member 26818
The IET do, and it is that the the circuit requires RCD protection.
As for the ESC, they don't even recommend a code for lack of RCD protection for these circuits in their BPG for PIRs.
Heres a link to an article issued in wiring matters by the then IET Chief Engineer Mark Coles: http://electrical.------.org/wiring-matters/30/additions.cfm?type=pdf
His advice is that not only should the circuit you are working on be protected, but all other circuits, even if you haven't touched them.
I don't know, does the advice from the IET Chief engineer trump that of the ESC?
Last edited by a moderator:
E
ezzzekiel
However back to the original op, the following extract taken from ESC and Niceic Guidlines
If an existing circuit of a location containing a bath or shower is extended, at least the extended part of the existing circuit must be provided with RCD protection. Supplementary bonding in a bathroom or shower room must be provided unless all the requirements in the 17th Edition for the omission of supplementary bonding are met
If an existing circuit of a location containing a bath or shower is extended, at least the extended part of the existing circuit must be provided with RCD protection. Supplementary bonding in a bathroom or shower room must be provided unless all the requirements in the 17th Edition for the omission of supplementary bonding are met
D
Deleted member 26818
The ESC or NICEIC do not write the Regulations.
However, if you consider that the answer you have quoted, was made in reply to a question asking how to comply with BS7671 when installing an electrical appliance such as a boiler or electric towel rail in a bathroom, the answer seems rather odd.
There is no mention of extending an existing circuit in the question, and I wonder what existing circuit do the ESC suggest be extended to supply the boiler or towel rail, the lighting circuit, or shower circuit perhaps?
Then in answer to the question: "If we reposition a pull switch in a location containing a bath or shower, would the circuit need to be RCD-protected?"
They answer :"Yes, because the work would be more than a like-for-like replacement."
So according to the ESC, if you install an electric towel rail, you can extend an existing circuit, and just provide RCD protection to the extended part of the circuit, but if you re-position an existing pull switch, you have to provide RCD protection for the whole circuit.
Then of course is what I consider their greatest faux pas, in the their best practice guide for PIRs, they do not consider the lack of RCD protection for circuits of locations containing baths and showers to be a non-compliance.
Last edited by a moderator:
E
ezzzekiel
I highly respect your indepth knowledge and read a lot of your posts with great interest, but as a day to day working sparky some of your interpretations of the regulations differ greatly from mine and providing i have guidelines from other official sources then i must agree to disagree on this topic.......
OFFICIAL SPONSORS
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
Advert
Thread Information
Thread Tags
Advert
Advert
TrueNAS JBOD Storage Server
-
-
Understanding TrueNAS JBOD Servers: A Comprehensive Guide- Started by Dan
- Replies: 8
-
