Hi, my new extension has its own consumer unit. All has been fine for about a year. I recently installed an exterior IP56 Masterseal 13 amp socket by taking a spur from an internal socket straight through the wall. I also sealed all round the joint between socket and brickwork with silicon. Now, whenever there is a hint of moisture in the air, the whole consumer unit trips, not the individual ring circuit. Any suggestions as to how to overcome this please? Thanks + regards Richard
exterior socket causes tripping
- Thread starter richardcooper
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What is it that "trips".
Is the main switch an RCD?
Is the inside of the socket damp?
What were the insulation resistance test measurements of the additional spur, when you installed it?
Is the main switch an RCD?
Is the inside of the socket damp?
What were the insulation resistance test measurements of the additional spur, when you installed it?
Certainly sounds like a water/moisture issue, but 'a mere hint of moisture in the air' shouldn't trip an RCD (which is what I presume you're talking about). Did you drill the drain hole in the bottom of the Masterseal socket?
Kind Regards, John.
many thanks for the replies -
The Consumer unit has a 2 pole RCD, and each individual circuit is protected by an RCBO.
Maybe 'hint' was a little exaggerated, sorry but certainly it will trip when the atmosphere is still damp after rain.
There is no obvious moisture or wetness inside the socket unit, and the drain hole is open.
I haven't tested the spur, so I don't know the insulation resistance measurement.
Regards Richard
The Consumer unit has a 2 pole RCD, and each individual circuit is protected by an RCBO.
Maybe 'hint' was a little exaggerated, sorry but certainly it will trip when the atmosphere is still damp after rain.
There is no obvious moisture or wetness inside the socket unit, and the drain hole is open.
I haven't tested the spur, so I don't know the insulation resistance measurement.
Regards Richard
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You should have an electrician change the RCD for a regular switch - no point in having RCBOs on each circuit and an overall RCD, as you are discovering.
Well it sounds as though something is getting wet.
Are you sure that your silicone sealing is 100% effective?
Did you drill the hole for the cable sloping downwards from inside to out?
Have you looked inside the house socket for signs of water?
Seems to me that there is a bit of jumping to a conclusion by suspecting the new socket.
As the RCD is tripping you cannot know which of the circuits the fault is on so I would suggest that a bit more investigation may be required particularly to confirm which circuit the fault is actually on
As the RCD is tripping you cannot know which of the circuits the fault is on so I would suggest that a bit more investigation may be required particularly to confirm which circuit the fault is actually on
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Where a RCD feeds a RCD there should be a factor of around 3 times between them so for example a 500ma will feed a 300ma which will feed a 100ma which will feed a 30ma which will feed 10ma. This will not guarantee they trip is sequence but it is likely to result in the individual RCD tripping first. A RCBO is still an RCD.
There are a number of reasons for fitting RCD's 300ma is considered ample for removing power in the case of a fire for example where 30ma is considered as minimum to protect people.
Some RCD's have a delay normally referred to as S type. But in the domestic there are limitations as to types used as some require access by only skilled personal.
Where the installation is TT then it would be common to have a 100 or 300ma as main switch with likely a delay (S type) then 30ma as RCBO's. The selecting of a RCD with a TT supply would be dependent on the earth loop impedance so step one is to look at the installation certificate or minor works certificate issued when the work was done and to see what the ELI is and supply type.
Of course if some one doing the work has broken the rules and not tested and made out the certificates then one would need an inspection and test to get these results. No one can advise as to what is wrong without these figures as it would be all too easy to assume and assume wrong.
I would guess the best would be to get an electrician to test and advise as even to hire a test set will cost around £75. Likely the main RCD needs to be changed for a higher ratting but you will only know this once you have test results.
There are a number of reasons for fitting RCD's 300ma is considered ample for removing power in the case of a fire for example where 30ma is considered as minimum to protect people.
Some RCD's have a delay normally referred to as S type. But in the domestic there are limitations as to types used as some require access by only skilled personal.
Where the installation is TT then it would be common to have a 100 or 300ma as main switch with likely a delay (S type) then 30ma as RCBO's. The selecting of a RCD with a TT supply would be dependent on the earth loop impedance so step one is to look at the installation certificate or minor works certificate issued when the work was done and to see what the ELI is and supply type.
Of course if some one doing the work has broken the rules and not tested and made out the certificates then one would need an inspection and test to get these results. No one can advise as to what is wrong without these figures as it would be all too easy to assume and assume wrong.
I would guess the best would be to get an electrician to test and advise as even to hire a test set will cost around £75. Likely the main RCD needs to be changed for a higher ratting but you will only know this once you have test results.
Why ever not? It's so simple to do.
As a matter of (perhaps pedantic) detail, that's actually only a factor of 1.67, and I doubt would provide discrimimation .....
I must say that I'm pretty sceptical about discrimination of RCDs, except when some are time-delayed. If a L-E fault current (hence a L-N imbalance) of, say, 2000 mA were to suddenly appear, I would not put no money on which (out of 500, 300, 100, 30 and 10mA ones in series) would operate first, nor on how many of them would trip. As with the 'misconceptions' thread, people tend to think of gradually increasing fault currents, so that an RCD will trip immediately the fault current 'rises' to its trip threshold - but that's not really the real world. Fault current usually arises 'instantaneously', at the full level determined by Ohm's law, so that a fault current considerably higher than the 'rating' of an RCD can flow until the disconnection occurs.
Kind Regards, John.
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I did say it would not guarantee the lowest ratted one will go first and even with time delay I have seen the 30ma in site hut, the 100ma in dis-box, the 500ma at 1/2 second in WMDU in ours and the 1A at 1 second in suppliers WMDU all trip when a guy knocked in a nail to hang his coat on.
I have also seen how a test button on a 10ma socket can take out the 100ma trip in dis-box which should not happen in theory.
However if one looks at how often they do go in order and how often they don't one does find it often does reduce the number of times the main RCD opens.
There are RCD's which also monitor and even those which will auto reset. The list gets longer with passive and active and A, AC types etc.
But in the case in question a 10ma feeding outside socket where dampness is the problems should trip before the 30ma in the CU.
However I would not automatically blame the outside socket. In many cases it is a build up of many leakage paths which causes the RCD to open and the most effective method is to split the circuits.
But then one looks at the nitty gritty and it's money. To have a all pole RCD feeding a collection of single pole switching RCD's is asking for problems and with a TT system with an all pole RCD as main incomer and RCBO's single pole switching in the consumer unit we are really asking for problems. I think we should select the highest milliamp RCD which can be used with the electrode fitted rather than just fit a 100ma as we have done that for years.
I would like to see a reasonable priced consumer unit able to take all pole switching RCBO's but at the moment to do that we have to use a distribution unit rather than a type tested consumer unit.
I have also seen how a test button on a 10ma socket can take out the 100ma trip in dis-box which should not happen in theory.
However if one looks at how often they do go in order and how often they don't one does find it often does reduce the number of times the main RCD opens.
There are RCD's which also monitor and even those which will auto reset. The list gets longer with passive and active and A, AC types etc.
But in the case in question a 10ma feeding outside socket where dampness is the problems should trip before the 30ma in the CU.
However I would not automatically blame the outside socket. In many cases it is a build up of many leakage paths which causes the RCD to open and the most effective method is to split the circuits.
But then one looks at the nitty gritty and it's money. To have a all pole RCD feeding a collection of single pole switching RCD's is asking for problems and with a TT system with an all pole RCD as main incomer and RCBO's single pole switching in the consumer unit we are really asking for problems. I think we should select the highest milliamp RCD which can be used with the electrode fitted rather than just fit a 100ma as we have done that for years.
I would like to see a reasonable priced consumer unit able to take all pole switching RCBO's but at the moment to do that we have to use a distribution unit rather than a type tested consumer unit.
Many thanks for all the replies. I did not realise it would become quite so technical! I did the complete installation myself, and I don't possess any testing equipment.
I used the council-approved inspector to undertake the Part P certification. Originally, I did not have RCBO on each circuit, just an RCD covering the main CU switch. The inspector instructed that each circuit had to be covered (a bit OTT and expensive I thought - but rules are rules.), and the installation was then certified.
Anyway, I reconnected the exterior spur, checked all the connections, re-sealed the installation, and directed the garden sprinkler onto the socket - no tripping, so hopefully now all OK.
Thanks for all the interest, and I'll be back if the tripping re-starts when the rain arrives. Regards Richard
I used the council-approved inspector to undertake the Part P certification. Originally, I did not have RCBO on each circuit, just an RCD covering the main CU switch. The inspector instructed that each circuit had to be covered (a bit OTT and expensive I thought - but rules are rules.), and the installation was then certified.
Anyway, I reconnected the exterior spur, checked all the connections, re-sealed the installation, and directed the garden sprinkler onto the socket - no tripping, so hopefully now all OK.
Thanks for all the interest, and I'll be back if the tripping re-starts when the rain arrives. Regards Richard
You know what they say about a little knowledge...
No way should you have done a rewire or CU install if you're at the stage where the above seems quite technical and you don't have test equipment.
Did he carry out full testing?
Did you wait until that had been done before energising?
So you embarked on doing the complete installation without knowing what the regulations required?
Hmm., Thanks for your reply. The installation was found to be quite satisfactory apart from not having an RCD covering each individual circuit, this part of the regulations I had misunderstood.
You advised "No point in having RCBOs on each circuit and an RCD" and actually advised me to change this - so who is not clear on the rules?
The inspector has to do a full and thorough test under the Part P regulations, and no, the installation was not energised until passed. Everything I have done has been legal and safe.
Regards Richard
You advised "No point in having RCBOs on each circuit and an RCD" and actually advised me to change this - so who is not clear on the rules?
The inspector has to do a full and thorough test under the Part P regulations, and no, the installation was not energised until passed. Everything I have done has been legal and safe.
Regards Richard
Who tested the outside socket which is part of a "special installation" before it was energised?
As others have said, a main RCD with downstream RCDs of the same size is asking for problems. What size is your main RCD switch? What size are the RCBOs (mA trip rating)?
As others have said, a main RCD with downstream RCDs of the same size is asking for problems. What size is your main RCD switch? What size are the RCBOs (mA trip rating)?
What earthing arrangement do you have
//www.diynot.com/wiki/electrics:earthing_supply_types_and_bonding:earthing_arrangements
//www.diynot.com/wiki/electrics:earthing_supply_types_and_bonding:earthing_arrangements
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