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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorRex
    • CommentTimeMay 13th 2018
     
    What ho one and all,

    During the night, we were awoken by the DECT phone beeping to each other. An investigation revealed that there was no power, further revealed that the g/f RCD (which has 6 individual circuits on it) had tripped.

    Reset and all is is good. This morning, when SWMBO came down, again, no power, and again the same RDC at fault. I have reset, boiled the kettle, radio on, etc, etc. and it is not tripping out.

    Nothing new has been plugged in, to the best of my knowledge, nothing has changed. The most likely culprit, which I have yet to investigate, is the submersible rainwater tank pump (pumps water to the loft tank for toilet flushing.) However, that only comes on 10 mins every two hours, and when I have just tested the override switch, the RCD did not trip.

    How do I find which individual circuit is the problem?

    Thanks and toodle pip

    Rex
    • CommentAuthortony
    • CommentTimeMay 13th 2018 edited
     
    Start unplugging things one at a time, plug freezer and fridge into a different circuit via an extension lead

    Biggest suspects are fridge, freezer, cooker and kettle
    • CommentAuthorRex
    • CommentTimeMay 13th 2018
     
    Thanks for your reply.

    Definitely not cooker and unlikely to be the kettle. Cooker was not used yesterday and is always off when not used. Kettle was last used around 21:00 last night but all the kitchen lights were still working then. A few cuppas this morning and nothing has tripped.

    If it had not been for the phone beeping, probably would not have known about the tripping until this morning. However, since resetting twice, all has been hunky dory for the last few hours.

    I will check the submerged pump later.

    May be just a random gremlin!
    • CommentAuthorRex
    • CommentTimeMay 13th 2018
     
    Up-date. Think it is the submerged rainwater pump for the loft tank. It just fired up and within 30 seconds, the circuit tripped out. Reset and it tripped out again.

    Now to get the aqualung out!
    •  
      CommentAuthordjh
    • CommentTimeMay 13th 2018
     
    Glad you found the problem. For the future, remember that as well as a faulty appliance on one circuit it might be the RCD itself that has gone faulty.
    • CommentAuthorRex
    • CommentTimeMay 19th 2018
     
    A further up-date.

    Having retrieved the pump and taken the back off, found there was a bit of condensation inside (apparently that is normal) dried and replaced, everything was fine - for about three days, when it started to trip the RCD again.

    Called the supplier, and the story is that there is probably a very minor seepage from one of the seals. not sufficient to stop the pump work, but as the pump warms up, it evaporates the few drops, increasing the internal humidity and that sets some kind of electrical feed-back that tells the circuit board, something is not correct and that in turn trips the circuit to protect everything.

    It makes a bit of sense as when the circuit is reset, and later the pump turned on again, the internal humidity will have dropped. The pump runs for around one minute and trips out again. He say, that is what happens.

    So have bought a seal replacement kit, will open her up, dry, clean and replace all the seals. Hopefully, good to go for another 6 years of service. Apart from a replacement capacitor, it has not been serviced during that time, so I guess it is due.
    •  
      CommentAuthordjh
    • CommentTimeMay 19th 2018
     
    That's good service in my book :bigsmile:

    What pump is it? Who's the supplier?
    •  
      CommentAuthorSteamyTea
    • CommentTimeMay 21st 2018
     
    Posted By: RexApart from a replacement capacitor, it has not been serviced during that time, so I guess it is due.
    Are you going to change the capacitor this time.
    • CommentAuthorCWatters
    • CommentTimeMay 21st 2018
     
    <blockquote>The most likely culprit, which I have yet to investigate, is the submersible rainwater tank pump (pumps water to the loft tank for toilet flushing.) </blockquote>

    Too late now but having that on the same RCD as a other circuits in the house might be legal but sounds a saving too far in my opinion.

    RCBO are pretty cheap for the extra convenience they provide. I recommend new builder have one per circuit unless funds are exceptionally tight.
    • CommentAuthorgyrogear
    • CommentTimeMay 21st 2018
     
    Posted By: CWattersbut having that on the same RCD as a other circuits in the house might be legal but sounds a saving too far


    +1

    this is an old favourite in France, / especially where external roller blinds or sunshades are wired in to the nearest wall socket (which always happens to be the one with the TV on...). Ask the electrician to run a fresh line to the CU and he looks at U like as if you were a nutcase.

    gg
    • CommentAuthorRex
    • CommentTimeMay 22nd 2018
     
    The pump is supplied by Steelpumps UK (http://steelpumps.co.uk/) and the specific model is X-AJE80PUK. It was in fact, supplied with the rainwater collection tank, along with all the fixtures and fittings.

    As for wiring it separately, there is a specific MCB for the dual, 13a circuit to a single indoor socket with the sole purpose of running the pump. But why it is tripping the RCD for the six circuits rather than the individual MCB for the pump, I don't know.

    All I know is I don't know too much about wiring a house and gave the sparkie the specs and that is what I have. On the plus side, if a bunch of electrical items are not working, I at least know something is not right. If the pump MCB only had tripped, I would probably not have known until the loft tank was empty.
    •  
      CommentAuthordjh
    • CommentTimeMay 22nd 2018
     
    Posted By: RexThe pump is supplied by Steelpumps UK (http://steelpumps.co.uk/) and the specific model is X-AJE80PUK.

    Thanks for the info.

    As for wiring it separately, there is a specific MCB for the dual, 13a circuit to a single indoor socket with the sole purpose of running the pump. But why it is tripping the RCD for the six circuits rather than the individual MCB for the pump, I don't know.

    MCBs and RCDs do different things. An MCB will only trip if the circuit draws too much current, in order to protect the wiring. An RCD measures the difference between the current in the live and neutral wires and trips if there is a difference (a residual current), in order to protect people against shocks.

    So the RCD is tripping because current is leaking out, presumably because of the humidity in the pump.

    An individual RCBO instead of the MCB would avoid other circuits being tripped, but it shouldn't be fed from the RCD. You'll need a Part P electrician to test and certify any change.
    • CommentAuthorCWatters
    • CommentTimeMay 24th 2018
     
    +1

    The most common causes of circuits tripping out are devices that have heating elements (eg toasters, cookers) or mix electricity and water (kettles, immersion heaters, out door lighting).

    Ideally you want any of those things on a separate RCD to sensitive stuff like your computers, lighting, TV recorder, burglar alarm etc

    The cheapest arrangement has one or more RCD feeding a bank of MCB. If the kettle has a power to ground fault it will trip out the RCD causing a loss of power to all the circuits on the RCD.

    A more expensive arrangement has a bank of RCBO one per circuit. RCBO combine the functions of an RCD and MCB into one device. If the kettle fails just the kitchen circuit trips out leaving the other circuits powered.

    I would guess the cost difference for average houses is around £80-100. You might save that later if there is a fault because it can make fault finding a bit easier.
    • CommentAuthorRex
    • CommentTimeJun 1st 2018
     
    I have had the pump on the bench for the last few days, dismantled, cleaned and all O rings renewed.

    Hopefully, will be putting back in the tank tomorrow, when a 'rope thimble' arrives, so that I can improve the lifting out of the tank bits and pieces.

    Will update when I have it back in the tank. There was some water inside the motor section, which I guess would increase the humidity sufficient to trip the circuit. The techie at Steelpump told me that the electrics are pretty simple and robust, so drying out, cleaning and replacing the seals and O rings should solve the problem.

    Time will tell.
    • CommentAuthorRex
    • CommentTimeJun 13th 2018
     
    Had the pump in the tank for two weeks now and it is certainly working as it should. Guess the techie at Steelpump was correct about an increase in internal humidity causing the circuit to trip.
    • CommentAuthorCWatters
    • CommentTimeJun 14th 2018
     
    I've learnt that it's extremely difficult to keep water out of anything electrical.

    For example if the thing contains air pockets then this can expand when hot pushing air out through seals, then when it cools it sucks water in (or rather water is pushed in). Each thermal cycle pumps a little more water in.
    • CommentAuthorRex
    • CommentTimeJul 4th 2018
     
    For the past three weeks, the pump has not been running as the tank is virtually empty! So I took the opportunity to clean all the accumulated sludge out.

    I would agree that the thermal cycle could cause the ingress of water and that may explain why there was some inside the sealed electrical area. I have to admit to being surprised that the back of the pump, that seals the electrics, is a 'hard' push fit / interference fit over the O ring. I would have thought that some kind of bayonet lock would have provided a better seal. Guess that price is a major factor so why design and build something that does not require replacing!

    But what do I know?
    • CommentAuthorCWatters
    • CommentTimeJul 4th 2018
     
    I've just finished fixing some outside lights that water got into. Each light has it's own transformer that is rated for direct burial in the ground, however these had additional silicon sealant applied before being placed into a plastic box filled with so called waterproof cement before being buried. They lasted about 18 months before water got in.
  1.  
    Posted By: CWattersThey lasted about 18 months before water got in.

    Doubtless with a 1 year guarantee.:devil:
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