A company I work for have Installed a 3ph supply to a Distribution board on a Jetty. The Board feeds 2 415 Commando Sockets through C20 MCBs protected by a 4 Pole 100ma FP RCCBs The Sockets feed Inverters for some kind of Zip wire water activity. Anyhow, there seems to be some nuicence tripping. 10mm earth wires were installed for any earth leakage, this however has nor worked. They are now proposing to chang the RCCBs to 300ma Does this comply as I can't find a minimum rating in the regs in section 709 -Marinas and similar locations etc.
nuicence tripping on 100ma 3ph rcd
- Thread starter zenpirate
- Start date
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709.531.2 states that all socket outlets shall be protected individually by an all-pole and refers to 415.1.1 which states 30mA.
Fitting a less sensitive device to avoid a fault is not the answer.
Fitting a less sensitive device to avoid a fault is not the answer.
The sockets are individually protected. The RCCBs have only tripped few times in 4 months. Could this not be nuisance tripping? Also I'm sure 100ma RCCBs were recommended by the equipment Installers. I wasn't on the job so I'm just going on what I've been told. So this was wrong already?
Your problem here is that inverter drives do leak a small current to earth due to the filters on the front end. If you consult the manufacturers instructions you will probably find that they either recommend that an RCD is NOT used or they will suggest a particular type of RCD is used. I would also suggest that you use an RCD per inverter, trying to share one device across two drives will only make the problem worse.
Adding a decent earth bond will not solve the problem, if anything it will make it slightly worse. I don't think what you are seeing is a 'fault' ....more poor design and not reading the inverter drive manual.
If you hard-wire the inverters to the supply (hence removing the plug/sockets) then you may be able to dispense with the RCDs altogether (they are only going to protect up to the input of the inverter anyway - they will not be able to 'see' the output side nor the motor).
Adding a decent earth bond will not solve the problem, if anything it will make it slightly worse. I don't think what you are seeing is a 'fault' ....more poor design and not reading the inverter drive manual.
If you hard-wire the inverters to the supply (hence removing the plug/sockets) then you may be able to dispense with the RCDs altogether (they are only going to protect up to the input of the inverter anyway - they will not be able to 'see' the output side nor the motor).
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So each point has a local normal 30mA RCD?
If so then a time delayed RCD may be used to protect the distribution system and help achieve discrimination.
Then at least the nuisance tripping should only occur on the problematic part of the system.
I'm assuming this is a TT system? TN-CS is a definite no-no.
If so then a time delayed RCD may be used to protect the distribution system and help achieve discrimination.
Then at least the nuisance tripping should only occur on the problematic part of the system.
I'm assuming this is a TT system? TN-CS is a definite no-no.
Even when fixed in a secure concrete pillbox on the jetty? (I know this might be a stupid question and I apologies, but I'm not qualified and I'm going in tomorrow to tell guys that are what I found out so I need to be 100% to tell an engineer he doesn't know what hes on about 
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They are wrong.
Yes.
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411.3.3 Additional protection
In a.c. systems, additional protection by means of an RCD in accordance with Regulation 415.1 shall be provided for:
(i) socket-outlets with a rated current not exceeding 20 A that are for use by ordinary persons and are intended for general use, and
(ii) mobile equipment with a current rating not exceeding 32 A for use outdoors.
An exception to (i) is permitted for:
(a) socket-outlets for use under the supervision of skilled or instructed persons, e.g. in some commercial or industrial locations, or
(b) a specific labelled or otherwise suitably identified socket-outlet provided for connection of a particular item of equipment.
This is general for all items but:-
709.531.2 RCDs
Socket Outlets shall be protected individually by an RCD having the characteristics specified in Regulation 415.1.1. Devices selected shall disconnect all poles. including the neutral.
Final circuits intended for fixed connection for the supply to houseboats shall be protected individually by an RCD having the characteristics specified in Regulation 415.1.1. The device selected shall disconnect all poles, including the neutral.
Is for MARINAS AND SIMILAR LOCATIONS I would assume the guy in NIC who said as long as the commando skt is clearly labelled as for
Specific use ONLY then its fine???? did not know it was for a Marina.
There are special RCD's that auto reset and also special rules where loss of supply could cause danger, but the reams of paperwork required and HSE involvement mean it really is last resort. With a batching plant I worked on we had monitors rather than trips because of the drastic results from power loss but it required the unit to be always manned and "The RCCBs have only tripped few times in 4 months." does not really warrant that sort of approach.
Whether he didn't know, or knew but didn't know what the regulations say about marinas is irrelevant - he was wrong.
What worries me more is "A company I work for have Installed a 3ph supply to a Distribution board on a Jetty. The Board feeds 2 415 Commando Sockets through C20 MCBs protected by a 4 Pole 100ma FP RCCBs".
Dangerously ignorant and incompetent idiots at work there.
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