Departures from bs7671, certification.

[odawire]

Hi, I have always made sure my installs have no departures from bs7671 but I'm doing a ccu change next week and have done some preliminary testing and the heating circuit (boiler and heating controls) has low IR readings, had a look in all obvious places and cant find any problems, had trouble breaking the circuit up as its a bit messy, client has just decorated so he doesn't want any damage to the house, seeing as its all fixed equipment (I'm unsure on the cable routes but id guess its buried less than 50mm at some point) is it acceptable to leave this circuit unprotected and note it on the departures section? all the earthing/bonding is mustard. Any experience on this would be appreciated, thanks.

 

[telectrix]

firstly, what was the IR reading for the heating circuit? secondly, the cable buried <50mm deep -- if it's going to be RCD protected, then no problem. don't forget that the IR would need to be under 10KΩ to cause RCD tripping.

 

[odawire]

Hi, should have explained, I have a rig I made up I use sometimes, its basically an rcd adaptor that I wire into and plug into a socket, when I did this it tripped, the IR reading was bouncing around I think it settled around 7Mohms across all points, I remember it was the exact same number. The reason Im asking is, I want to know if its acceptable to leave it off the RCD side if I have to, as I don't think I can leave them with no heating at this time of year, can I note it as a departure as the cable is probably less than 50mm deep

 

[telectrix]

at 7MΩ, i wouldn't worry. BS7671 quotes 2MΩ as a minimum, so just RCD protect the circuit.better still, fit a RCBO in the non RCD section of the CU.

 

[odawire]

thanks for your response but im not worried about the circuit, when I put it on an rcd it was tripping straight way, so I don't want to RCD protect it, I want to put it on an MCB with no rcd protection.

 

[telectrix]

then there's a fault on either the circuit or the heasting system. does it still trip with the boiler out of circuit?

 

[Guitarist]

Personally, I wouldn't just put it on a non-protected side due to a fault. Tell the owner that it will need to be sorted before the CU can be changed.

 

[Richard Burns]

Just as a reminder departures from BS7671 are only cases where the circuit is not designed to BS7671 but is still safely designed, it is not a non compliant situation, which is what you are describing (circuit requiring RCD protection not RCD protected because of a fault on the circuit).

That said if you are changing a CU you only need to ensure that the circuits you are reconnecting are safe for continued use (which may well be dubious in this case) not that they meet current regulations.
I would do as Guitarist says, tell them they need that fault rectified before changing the CU.

 

[DPG]

thanks for your response but im not worried about the circuit, when I put it on an rcd it was tripping straight way, so I don't want to RCD protect it, I want to put it on an MCB with no rcd protection.

So...Would you sleep soundly at night knowing that you had connected this known-faulty circuit to the non-RCD side so that the fault wouldn't show up? Daz

 

[GLENNSPARK]

Hi, I have always made sure my installs have no departures from bs7671 but I'm doing a ccu change next week and have done some preliminary testing and the heating circuit (boiler and heating controls) has low IR readings, had a look in all obvious places and cant find any problems, had trouble breaking the circuit up as its a bit messy, client has just decorated so he doesn't want any damage to the house, seeing as its all fixed equipment (I'm unsure on the cable routes but id guess its buried less than 50mm at some point) is it acceptable to leave this circuit unprotected and note it on the departures section? all the earthing/bonding is mustard. Any experience on this would be appreciated, thanks.

what do you want?...a round of applause?
i had this down as standard...

 

[Guitarist]

So...Would you sleep soundly at night knowing that you had connected this known-faulty circuit to the non-RCD side so that the fault wouldn't show up? Daz

I've known of builders and plumbers doing that when they change a CU and the RCD goes out on the RFC.

 

[DPG]

I've known of builders and plumbers doing that when they change a CU and the RCD goes out on the RFC.

Good point. Odawire, are you a plumber/builder/qualified electrician? Daz

 

[odawire]

Thanks for replies, I am a qualified electrician, I will be fully testing the circuits prior to the change and will try to rectify the fault before. As I said before, I have looked at all circuit connections and cannot see any problems, I will break it down and try to find the fault but I fear part of the circuit will need re-wiring and I don't think they will want this. Because of the fault being the same across all conductors I think that points to cable damage/insulation breakdown, as long as other tests were acceptable then putting it un-rcd protected would only be a C3 recommendation code

- - - Updated - - -

what do you want?...a round of applause?
i had this down as standard...

What's the point of a comment like this?

 

[odawire]

then there's a fault on either the circuit or the heasting system. does it still trip with the boiler out of circuit?

haven't got that far with the testing yet, ill let you know

 

[Jdsparky]

It would only be a c3 if doing a periodic and it was done to old regulations, but u are effectively updating the installation to 17th edition regs by applying Rcd protection, and as u say u think cable is in wall less than 50mm so to 17th obviously needs Rcd protection. But I would explain to customer that it needs sorting before changing Fuseboard, as you have tested circuit and it fails test so further investigation is required.
i also applaud you for testing installation prior as many don't, and has also potentially got you more money out of the job rather than sorting later at your expense/time finding and fixing fault.

 

[Guitarist]

With the greatest respect, don't "try" to rectify the fault, but make it clear that it MUST be sorted before you proceed further. If your test was 7 meg and that was an end to it, then all well and good. A note that IR tests were low would have covered you. However, as it is taking the RCD straight out, then there is something very wrong somewhere.
How would you feel if there's a fire due to this fault, and you'd walked away saying "I had a look, but nothing I could do"?

 

[odawire]

It would only be a c3 if doing a periodic and it was done to old regulations, but u are effectively updating the installation to 17th edition regs by applying Rcd protection, and as u say u think cable is in wall less than 50mm so to 17th obviously needs Rcd protection. But I would explain to customer that it needs sorting before changing Fuseboard, as you have tested circuit and it fails test so further investigation is required.
i also applaud you for testing installation prior as many don't, and has also potentially got you more money out of the job rather than sorting later at your expense/time finding and fixing fault.

Thanks for the reply, BS7671 does not require circuits to be upgraded to current regulations to be connected to a replacement ccu, only for it to be ascertained that they are not an immediate danger (which I would read as no C1's or C2's), GN3 even says there is no obligation to inspect or test any part of the installation!

Also found this : www.niceic.com/Uploads/File1950.pdf Guidance on cu replacement, which also says the same. interesting reading.

 

[odawire]

So...Would you sleep soundly at night knowing that you had connected this known-faulty circuit to the non-RCD side so that the fault wouldn't show up? Daz

Its not necessarily "faulty"

 

[Platinum lad]

Just a thought I would disconnect any zone valves or circulation pump I know from experience they can be a pain

 

[telectrix]

disconnect at the FCU> if it's only single pole, then take the N out of the terminal. then test your circuit. if the fault is on the heating then you need the customer to get it sorted, either by you or a heating " engineer" (that's usually a plumber that can read and write).