My F/F is on a non-RCD socket.
17th Edition
- Thread starter jimblev
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It is a problem working out what trips an RCD. The 17th Edition states:-
So for example if some one swapped the original 100ma S type RCD for a 30ma within 40ms RCD protecting the whole house then it would not comply with 314.1 and that is about the only fault which could be blamed on the consumer unit.
It has been a question of debate as to if two RCD's for whole house is enough with many going down the RCBO route so every circuit has it's own RCD however the UK consumer unit does not use double pole RCBO's which means with a TT system our hands are tied and it's double RCD no real option for anything else.
However once a 30ma RCD has been fitted then to revert back to a 100ma RCD is not really an option as one would be making the premises less safe. Only option is then to split the RCD protection into two or more or use special cable for the fridge supply.
Onto the fridge/freezer now. Many today have a auto de-frost or frost free function and this often means every so many hours the motors either run in reverse or a heater is used to melt and drain away any water. A fault with this could cause it to trip every so many hours each time it goes into the auto defrost cycle and this is the most likely cause.
However to test this one would need to monitor the leakage over some 10 hours or do some dismantling to test the heater so really not easy to test. Only real way is a non RCD protected supply to an RCD socket so the fridge/freezer is only item plugged in.
One of the problems with multi-items fed from one RCD is a neutral - earth fault on a low power item can trip the supply when another high powered item is used. So for example a fault on the toaster can trip the RCD when the kettle is used. This could be the case when the fridge/freezer goes onto defrost cycle the extra power could trip the supply due to another item being faulty. However I think that is very unlikely as would not think the elements are that big.
So you can try telling us what the report says. It will say the earth system TT, TN-S or TN-C-S that will help us work out likely problems. Also clearly why it says it's not 17th Edition complainant.
This means that unless some special way of connecting is used like with a cooker the earth leakage of an appliance like a fridge is limited to 3.5 mA but a standard RCD with trip between 15 mA and 30 mA so 5 items all with maximum leakage could trip the RCD without there being a fault. Some special RCD's like the X-Pole are set to trip at 90 - 100% rather than 50 - 100% so will not trip as much with multi-leakage paths. It also has an indicator to warn when approaching the trip point.
IT equipment is a problem as the filters used to stop spikes also cause leakage and although people may unplug the computer they often don't unplug TV, Video and filtered extension leads.
I know you will not understand all I have said but trying to put a few pointers as to a cure. And if you think what I have said may contain answers then you can ask more questions.
I did myself consider a non RCD supply to fridge/freezer this is permitted but would need special cable or surface cable. Much would depend on the way the CU is configured as to how easy this would be.
If the fridge is faulty this is not normal operation but if it is just tipping the balance then it could be said that it's normal operation and the installation is faulty.
So for example if some one swapped the original 100ma S type RCD for a 30ma within 40ms RCD protecting the whole house then it would not comply with 314.1 and that is about the only fault which could be blamed on the consumer unit.
It has been a question of debate as to if two RCD's for whole house is enough with many going down the RCBO route so every circuit has it's own RCD however the UK consumer unit does not use double pole RCBO's which means with a TT system our hands are tied and it's double RCD no real option for anything else.
However once a 30ma RCD has been fitted then to revert back to a 100ma RCD is not really an option as one would be making the premises less safe. Only option is then to split the RCD protection into two or more or use special cable for the fridge supply.
Onto the fridge/freezer now. Many today have a auto de-frost or frost free function and this often means every so many hours the motors either run in reverse or a heater is used to melt and drain away any water. A fault with this could cause it to trip every so many hours each time it goes into the auto defrost cycle and this is the most likely cause.
However to test this one would need to monitor the leakage over some 10 hours or do some dismantling to test the heater so really not easy to test. Only real way is a non RCD protected supply to an RCD socket so the fridge/freezer is only item plugged in.
One of the problems with multi-items fed from one RCD is a neutral - earth fault on a low power item can trip the supply when another high powered item is used. So for example a fault on the toaster can trip the RCD when the kettle is used. This could be the case when the fridge/freezer goes onto defrost cycle the extra power could trip the supply due to another item being faulty. However I think that is very unlikely as would not think the elements are that big.
So you can try telling us what the report says. It will say the earth system TT, TN-S or TN-C-S that will help us work out likely problems. Also clearly why it says it's not 17th Edition complainant.
This means that unless some special way of connecting is used like with a cooker the earth leakage of an appliance like a fridge is limited to 3.5 mA but a standard RCD with trip between 15 mA and 30 mA so 5 items all with maximum leakage could trip the RCD without there being a fault. Some special RCD's like the X-Pole are set to trip at 90 - 100% rather than 50 - 100% so will not trip as much with multi-leakage paths. It also has an indicator to warn when approaching the trip point.
IT equipment is a problem as the filters used to stop spikes also cause leakage and although people may unplug the computer they often don't unplug TV, Video and filtered extension leads.
I know you will not understand all I have said but trying to put a few pointers as to a cure. And if you think what I have said may contain answers then you can ask more questions.
I did myself consider a non RCD supply to fridge/freezer this is permitted but would need special cable or surface cable. Much would depend on the way the CU is configured as to how easy this would be.
Any thoughts on why that is? Although I've never experienced it myself, it seems to be a pretty common complaint.
The only specific theory I can recall having heard is that overflow from an auto-defrost reservoir (if it doesn't evaporate quickly enough) can sometimes run onto elecrical connections. If that's true in some cases, it's surely a design fault that could easily be rectified.
Beyond that, I can't see why a fridge/freezer should be any more likely than anything else to result in L-E or N-E faults - or is it being suggested that something about F/Fs is 'exploiting' the susceptibility of RCDs to something other than L-E or N-E faults? A motor switching on and off should not trip an RCD (although it obvioulsy might trip and OPD).
Could it perhaps just be that fridges and fridge freezers are the commonest and most ubiquitous domestic loads/appliances which run 24/7. Even if they didn't result in any more " 'faults per 'on hour' " than anything else, that would mean that they would probably end up as the most common culprit, simply because they are 'always on'.
Kind Regards, John
Nice words Eric and I take it they are for the wider audience. No doubt this will now invite another contributor and/or their American friend to pontificate on the values, aims truths of something or other.
Because if it aimed at the OP then by their question and answers/non answers they don't really have a clue about the problem they think they have. If they have an electrical problem at all!!
Knowing the difference between an RCD and MCB or the ability to put a photograph of the 'offending' CU on line would help. But that appears beyond the OP.
The OP is confused and their replies or lack of them make their predicament even more confusing to those trying to help.
Unless the OP is able or willing to supply answers to questions raised then it is very difficult to give an electrical answer.
Furthermore Hotpoint engineers will have given the OP a worksheet that will have various meter readings taken either at the installation time or the re-inspection time including Earth Leakage test. They will be using those readings to stipulate their machinery is working fine and pass the buck back to the OP.
Hotpoint raising the 17th edition CU as an excuse to counter the Sale of Goods Act is questionable and clearly a legal issue rather than an electrical issue. Perhaps that is the OP's best route rather than trying to getting the impossible from this forum.
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It is possible that manufacturers are aware that the high start up current when a compressor in a fridge or freezer starts can, because of an earth leakage fault elsewhere in the house, cause the RCD to trip.
The fridge or freezer is not in itself defective but in connection with something else it is a major contribution to the tripping of the RCD.
17th edition installations are assumed to have been tested for earth leakage and therefore there is ( should be ) no earth leakage to divert some of the compressor's start up current on the neutral past the the RCD via the CPC.
The fridge or freezer is not in itself defective but in connection with something else it is a major contribution to the tripping of the RCD.
17th edition installations are assumed to have been tested for earth leakage and therefore there is ( should be ) no earth leakage to divert some of the compressor's start up current on the neutral past the the RCD via the CPC.
If you want any of that, you'll have to rely on transatlantic contributions, since, as you say, there's probably nothing more that any of us could currently say which would help the OP. The OP has already been told that non-compliance with the current regs cannot, per se, explain RCD tripping - and unless/until we are told more about what the report(s) said, there is no more help that can be given. What eric has just written is, indeed, all very reasonable, but I don't think it will help the OP.
Given the extent of difficulties (and time consumed) seemingly often involved in detecting the source of nuisance RCD trips, I'm rather surprised that we do not see (or do not see being used) 'leakage' monitors - or, at least, detectors. I'm sure, for example, that it would be easy enough to produce a relatively cheap plug-in device with a few LEDs which indicated whether L-N imbalance has exceeded certain levels (say 1, 5, 10, 20, 30, 50mA) during the period it had been in circuit. If the OP's electrician had such a device, a definitive answer about the appliance concerned could be achieved very easily. Do any such devices exist?
Kind Regards, John
Interesting idea, but I'm still not sure how '17th edition compliance' would come into it ...
IR testing would detect any 'leaks' in the fixed wiring, but I would have thought that by far the majority of 'leaks' (L-E or L-N) are due to equipment/appliances (the testing of which ahs nothing to do with any edition of the Wiring Regs), not fixed wiring. In any event, IR testing was around long before the '17th Edition'.
Kind Regards, John
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I would agree a residual current monitor (RCM) with recording would be a good tool but I also see some problems. First it would need to be on a non protected circuit and second would need a chart recorder not an every x seconds and join dots like used with current and voltage.
The three level warning given would show where the back ground earth leakage is too high. Using items with filters can easy raise the back ground level so instead of a 15 - 30 mA earth leakage tripping the RCD a mere couple of milliamp can tip the balance.
Washing machines, dish washers, as well as freezers have items which are switched in well after the device is switched on. So a faulty pump, de-frost element or any other timed item can cause it to trip well past the point where any PAT tester will detect.
I have had that problem at home and I use an extension lead and swap items from one RCD supply to another and monitor if the fault trips the other RCD. It may take some time to work out what is causing the trip to operate but in the end one gets a reasonably good idea which item it is.
Where we had a real problem was in the narrow boat where the whole boat was supplied through two RCD's in series. Same problem with a caravan but this should not be a problem with a house.
I will guess this guy has a whole house through one RCD as one would with a caravan or boat and this is the problem. But as many have stated he has not returned with any details.
The three level warning given would show where the back ground earth leakage is too high. Using items with filters can easy raise the back ground level so instead of a 15 - 30 mA earth leakage tripping the RCD a mere couple of milliamp can tip the balance.
Washing machines, dish washers, as well as freezers have items which are switched in well after the device is switched on. So a faulty pump, de-frost element or any other timed item can cause it to trip well past the point where any PAT tester will detect.
I have had that problem at home and I use an extension lead and swap items from one RCD supply to another and monitor if the fault trips the other RCD. It may take some time to work out what is causing the trip to operate but in the end one gets a reasonably good idea which item it is.
Where we had a real problem was in the narrow boat where the whole boat was supplied through two RCD's in series. Same problem with a caravan but this should not be a problem with a house.
I will guess this guy has a whole house through one RCD as one would with a caravan or boat and this is the problem. But as many have stated he has not returned with any details.
It's a cop-out.
Because their equipment is producing excessive leakage currents and is therefore tripping an RCD they are saying that the installation is therefore not compliant with 314.1 (iv).
I more-or-less agree. However, I suppose that, at least for some types of equipment (probably not including F/Fs), there is an 'acceptable' (and probably largely unavoidable) low level of leakage which the manufacturer can't really be 'blamed' for. For example, if a PC results in (and is known to result in) a 5mA leakage, I don't think one could take the manufacturer to task because it caused an RCD trip when, say, something else was already resulting in a 27mA leak in the installation.
Kind Regards, John
It may well be a Hotpoint 'cop out' but on the information provided it is difficult to see why you have automatically assumed its their equipment that has caused an RCD problem?
Firstly the OP hasn't confirmed what type of CU he has, other than Hotpoint states he has a non 17th edition CU, whatever todays interpretation of that is.
So we could have an:
All MCB CU.
A single RCD controlling all of the MCB's.
A single RCD controlling some of the MCB's
For all we know he could have semi rewireable fuses etc.
And secondly even if it is an Earth leakage problem, jumping to the assumption that the FF is the cause of the problem seems a bit judgemental.
As you know full well and as others have stated All electrical equipment will have some earth leakage - it could well be that all the other electrical equipment on the circuit(s) has earth leakage and the FF has simply taken it over the limit.
If Hotpoint are stating that their equipment is sound, their engineer will have conducted an earth leakage test, then the OP has only two options either get a solicitor involved or get an electrician around.
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