Should all the sockets be wired to ring circuit

Discussion in 'Electricians' Talk' started by mfizz, Jul 29, 2021.

  1. mfizz

    mfizz New Member

    I live in a new build and the other day I had someone round to install some security lights.

    He turned off the sockets from downstairs and all the sockets in the house turned off, or so it appeared.

    When he went to look at the socket that would be used to supply power to the security light, it was still powered up. It had 3 live wires going into and we discovered eventually that this particular socket was powered off the boiler circuit!

    My question is, is there anything in the regulation preventing electricians from doing this or am I just getting fussed over nothing...
  2. spirits are real 2016

    spirits are real 2016 Screwfix Select

    Ideally there should be three circuits one down, one up and separate ring for the kitchen with the boiler sometimes on it's own circuit.. and when we had immersion heaters they should of been on a dedicated circuit.. and electric shower and cooker on their own circuits.. plus lights..
  3. The Happy Builder

    The Happy Builder Screwfix Select

    You actually discovered that the boiler is supplied from a socket circuit ;)
  4. sparky steve

    sparky steve Screwfix Select

    To answer your question,

    “Should all the sockets be wired to ring circuit”?

    Answer, No!

    Sockets are also wired via the radial method.

    Is your boiler connected to the supply simply by plugging into a socket?

    Usually the boiler would be connected to the electrical supply via a FCU, via the ring final. Or alternatively on its own circuit. (Radial)

    How did your “someone” finally connect the security lights?
    Last edited: Jul 30, 2021
  5. CeSparky1

    CeSparky1 Active Member

    Not really a problem, on a recent rewire I put a bathroom heater and pull cord extractor fan on the boiler circuit.. Cause they wanted the isolators for the fan and heater in the boiler cupboard right next to the bathroom. If doing something like that though I think its important to label up which is often missed especially on new builds where they just have to throw things in because of the cost restraints.
  6. MGW

    MGW Screwfix Select

    There are many ways to wire sockets, what we want is to reduce inconvenience and danger as much as possible within a budget. So we are told
    And Appendix 15 gives examples.
    So each electrician likely has a slightly different idea as how this is best achieved. In the main we tend to go for three ring finals, one for kitchen, and one for each side of the house, better than up/down as it means if one fails then no extension leads on the stairs, and also in the main a lower loop impedance, and also more even load. However with the twin RCD consumer unit there is a problem, lights are easier to split up/down, and we don't want some one should the get a shock from a socket circuit to also be plunged into darkness, so we want the lights and sockets in every room from different RCD's.

    If we were to follow BS7671 to the letter then there would be a host of dedicated circuits, and item not normally unplugged and over 2 kW would have a dedicated circuit, so oven, dish washer, washing machine, tumble drier, and immersion heater, but in real terms only items using 2 kW for an extended time are give dedicated circuits, like the immersion heater, the oven often has a dedicated circuit because some ovens over 3 kW and really the drier or washer drier should have a dedicated circuit, but normally it causes no problem being in the ring final.

    Before all RCD protection was asked for, dedicated circuits were also used for freezers, so less likely to trip and have defrosted food. Once all RCD was required, having the freezer on its own RCBO was due edged, as less likely to trip, but also less likely to notice it had tripped (RCBO = RCD and MCB combined).

    Some boilers need special RCD's, I have seen Bosch manual ask for Type A, where many homes fitted with all type AC, and we don't want the boiler to be unplugged before it has gone through its shut down cycle, so the FCU (fused connection unit) is preferred by many for boilers. However although one can put a lock through the fuse holder or use special clamps to lock off a FCU it is hard to ensure the neutral is isolated with TT supply, but there are devices [​IMG]that can lock off any plug, so some prefer a plug and socket arrangement.

    Many boiler manufacturers say all items connected with the boiler should come from the same supply, and many heating guys read supply as being circuit, so want thermostat, pumps, fans, etc, all to switch off with one switch, breaker or isolator, my house 10 independent supplies, one FCU and 9 pairs of AA batteries. And before I worked on the central heating there were 4 FCU's and one came from a fuse box and rest from a consumer unit, but ideally having one device to switch off when working on the boiler is good. So the supply to Myson fan assisted radiator should be same as boiler, as to why never really worked out, the Myson will not switch on unless water is hot, but it seems they do as they are told, and don't think it through.

    So there is a likely hood of multi points powered from same MCB/RCBO which were designed to be connected to central heating in some way.

    So each house is likely a little different which does not mean right or wrong, just different, with commercial it was common to used red, yellow and blue circles with things like DB1/5 written on them, to show distribution unit 1 way 5 and colour showed which phase, but in domestic this is rarely done, but there should be some writing on the consumer unit to give you a clue.

    With outside lights we have to expect as some time water may get in, so we always include a method to isolate both line and neutral today, in the past before the RCD only the line was switched, but a neutral to earth fault can really cause problems with a RCD so today always duel pole switching so both live wires are switched. So if there is a fault one can isolate the fault. Although neutral not switched with my house, when outside lights fitted there were no RCD's.

    I could not be sure what every breaker does in my house, I know I have 14 type AC 30 mA RCBO's and left hand side is for main house and right hand side is the old garage turned into a flat, so I always use the correct method to prove dead, and have locking off devices with the CU so circuits can be locked off. I never rely on what is marked on the consumer unit.
    mfizz likes this.
  7. mfizz

    mfizz New Member

    thank you all for your detailed responses. I was just wondering if I had something to go back to with the new build.

    No the boiler isn't just connected to a socket. The central heating thermostats and boiler are on one circuit, as well as what appears to be this socket.

    They connected another socket to fused spur which is connected to a junction box outside into which the wire fro the security light is fed...
  8. Shaun Mitchell

    Shaun Mitchell New Member

    Sometimes in new builds they don't put in ground floor and first floor ringmains they will do front of house and rear of house or left of house and right of house and the boiler being spured off the sockets is not an issue
    mfizz likes this.
  9. MGW

    MGW Screwfix Select

    Glad to hear that, far better method, one the cable run is shorter so better loop impedance, two the load is more even, and three should a circuit fail no need for temporary extension leads up/down stairs to maintain freezer etc.

    The problem arises where the installer tries to get away with two RCD's, as in the main lights are wired upper and lower floor, so to comply with.

    Presents a problem, it refers to RCD's and currents so it would seem the RCD does form a circuit. We are allowed for a 30 mA RCD a non fault current of 9 mA, so the designer must be satisfied that in normal use the leakage to earth will not exceed 9 mA. Now with a socket we are allowed before we need to take special precautions up to 3.5 mA, clearly not all items plugged in will take that, in fact it will likely be a lot less, however a 3 watt LED bulb in spite of having a small leak resistor can often flash when connected to a two way lighting circuit due to capacitive and inductive linking within the cable. And also many items have filters built in, which cause again a small drain to earth.

    So in a small flat having two RCD's may be OK, but as the property gets bigger we reach a point where two are no longer enough, however there is no laid down demarcation point, we had the "take account of" and when the designer does the design for a house he has no idea of what "equipment in normal operation" will be, it is guess work. Personally I want to play safe and use all RCBO, but even that has a problem, in the main solar panels and EV charging points, and DC leakage caused by them, which may require better than a type A RCD/RCBO, and you can't get a single modular width RCBO which is type B (note type not curve, and some manufacturers still call curve B type B).

    But in the grand scheme of things does it really matter? I have not had an LED fail in this house with a surge protection device (SPD) fitted, but I have no idea if due to having a SPD, and with all type AC RCBO's what is the chance that a DC current will freeze the unit at the same time as there is an earth fault? I think that must be very slim.

    I have had a roof leak which did cause RCBO's to trip, and I was able to leave the circuits dead as with 14 RCBO's in the board I could work around it, but the regulations say "normal operation" so roof leaks are not normal, so no requirement to fit all RCBO's to cover that. The reason for spending an extra £200 for all RCBO was last house the RCD tripped while away and we lost two freezers full of food, which was well in excess of £200, and previous to that I had a freezer go down, I heard it go, so know when it failed, and by chance had a spare in the garage, so switched it on and allowed to cool for an hour before transferring food, however clearly the faulty one had just finished the defrost cycle when it failed, and food at top had de-frosted within the hour. So this 8 hours may be true with a chest freezer or upright without frost free, but not frost free models, it just depends where it was in the cycle.

    When we get a new consumer unit the electrician can measure the leakage before changing, so he can make a reasonable judgement as to if two RCD's will be OK, but with a new build it is pure guess work, so I would say need at least three RCD's one would be in the form of a RCBO, and likely would want outside lights on their own RCBO and the sockets as the designer has no control over what is plugged in, so three socket circuits, and outside lights, so 4 RCBO's at which point one has to ask why not all RCBO?

    No one has said designing an electrical installation is easy, but adding to an existing installation you have to work with what is already there, and I see no real problem as long as a two pole switch is used for outside lights so if there is water ingress it can be isolated, you would not want water in outside lights to stop the boiler working.
  10. The Happy Builder

    The Happy Builder Screwfix Select

    So are you saying when you turn the SFCU off the socket doesn’t work?

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