earth leakage

[sid]

hi all,
was just wondering if you could help me out, i got a call on thursday where units, keep taking out the rcd.the problem is that there is 3 units,fujutsi,one 1 circut.if i turn them on 1 at a time, its all ok,even if there is 2 at a time,its ok, only when i turn power on too all 3 off them,it takes the rcd out.

can anybody help me out there

[stuartwking]

Hi sid, Is it a triple split with 3 indoor units?,Do they trip when you turn the power on or when you start the units?, The breakers not under sized is it?

[Jus1]

hi Sid,
When you say it happens when you turn all three on, does it happen only when you turn the third one on. I mean do you alternate which will be the third one you switch on. Could mean there is a problem with that one, but if you alternate them then the problem lies else where.
Have you checked that each outdoor and indoor unit is earthed correctly.
Are they new units?

[sid]

thanks for getting back,
the rcd trips as soon as you turn a 3rd on at the power supply, it dosent matter which order you turn them on, it will still trip the rcd,
it is 3 single splits, they have been in for around two years, and only last week the house was re wired and the mcb board that feeds the a/c has had rcd fitted.the wiring has not been touched on the a/c side off things

[nike123]

Are they are all inverters?
Remove neutral from RCD and wire it directly and then try to switch on all 3 units. If trips again, RCD amperage rating is insufficient, and if it doesn't, than you got insulation problem (or some amount of current leakage).

ANEX!
If you establish that RCD doesn't trips with neutral disconnected from RCD, you (or Electrician) should change the RCD with higher residual current rate or other type (type B by VDE 0160/EN 50178) like this one: http://tinyurl.com/2nmxyv
or you need to have dedicated RCD for every AC separately.

[stuartwking]

Sounds like this new board is the problem,.So when all 3 units get power to them the main breaker for the board trips?,not the actual breakers for the units?.Are the breakers all the correct size?..Have you been into the board and checked how its wired?,whats the rating of the board and main breaker?,

[The Viking]

Shall we take a step back again....


As discussed on this forum on numerous occasions,

RCDs ARE FITTED TO PROTECT LIFE (human and otherwise).
Mechanical plant should not be fed via RCDs.

What your customer need, and should have been supplied by the sparkie, is a "split load" dist board. with sockets and light circuits protected by the RCD. Cooker, fridge/freezer and A/Cs should "bypass" the RCD.

If you search the old threads you will find more detailed explanations of why this is so (or just look it up in any of the IEE "Wiring Regulation" books).

[monkey spanners]

A sparky was telling me the other day that under the new 17th edition wiring regs all loads will need to be run off of rcd's....

Don't know if its true or not.

Jon

[The Viking]

A sparky was telling me the other day that under the new 17th edition wiring regs all loads will need to be run off of rcd's....

Don't know if its true or not.

Jon

Mmm,
Me thinks that's a sparkie that's missed the difference between MCB and RCD....

Unless they also brought out a new type of RCDs that can see a difference between "normal" N-L imbalance and "fault" N-L imbalance.
(As the RCDs doesn't actually see "earth leakage", they are looking at the current going through on the live and comparing it to the current going through on neutral)


But then a gain, I might be wrong, it has happened in the past....

[nike123]

Mmm,
Me thinks that's a sparkie that's missed the difference between MCB and RCD....

Unless they also brought out a new type of RCDs that can see a difference between "normal" N-L imbalance and "fault" N-L imbalance.
(As the RCDs doesn't actually see "earth leakage", they are looking at the current going through on the live and comparing it to the current going through on neutral)


But then a gain, I might be wrong, it has happened in the past....

Please Viking, explain this normal and fault N_L imbalance, because I did not heard for such terms ever.
RCDs in Eurpe in residential should be on all circuits except on lights if it is only one, and if they are more of them, then could be on all circuits.
Here in Croatia they are mandatory for all installations in hotels, restaurants, and similar, and only thing what is working when they act is panic lights. Of course, from main power distribution point to the last circuit they are hierarchically placed according to sensitivity.
This is example:
http://www.mediafire.com/?1d9bvbwbnve

This is good guide for electrical installations:
http://www.mediafire.com/?nmzpslhbmk1

[The Viking]

From the UK's IEE regs (admitingly not from the latest version recently released, things might have changed):

531-02-04

A Residual Current Device shall be so selected and the electrical circuits so subdivided that any protective conductor current which may be expected to occur during normal operation of the load(s) will be unlikely to cause unnecessary tripping of the device

412-06-02(ii)

The Residual Current Device shall have a rated residual operating current of not exceeding 30mA and an operating time not exceeding 40ms at a residual current of 5 x the rated current......

As compressors used in refrigeration/ air condition appliances, either DOL with capacitors or inverter driven, are likely to cause symptoms of a residual current above 30mA 531-02-04 comes in to force.
Here in UK the standard for domestic distribution boards is to have most of the MCBs fed via the RCD whilst others are fed straight from the mains incoming (i.e. the circuits are "subdivided" as described in 531-02-04).

[The Viking]

Especially inverters shoul NEVER be connected via RCD as they ( indoor + outdoor unit)communicate digitally which creates a " leak" .that is why it always trips.
As a matter of fact there is nothing wrong with the a/c or the el .board.

Wish you luck.

Also,
Capacitors fluctuates the balance between Live and Neutral, this will under certain circumstances be enough to trip the RCD. Motors whilst running will also upset this balance and (generally) if the motor is big enough it will trip an RCD.

Worth remembering, the RCDs isn't connected to the Protective Earth, they don't measure PE current. They measures Live current and Neutral current, then if this differs assumes that the difference has gone in to PE.

A Residual Current Device (RCD) is a circuit protection device which disconnects the load ("trips") if the current flowing out in the live wire exceeds the current returning in the neutral by a given amount. (Typically 30mA, 100mA, 300mA, depending on the device). 30mA = 0.03A
This imbalance in the return current (the residual current) is leaking to earth, which could indicate a fault in the circuit or a person receiving an electric shock (to earth).

[The Viking]

Nike,
Here in UK a RCD protecting humans (i.e. feeding sockets) should have a rating of 30mA.

If you instead had a RCD with a higher rating, say 300mA, your "normal" A/C system is less likely to trip it.
What rating you are using in Croatia, I do not know.

As seen in the original question, the RCD will cope with the L-N imbalance of 2 A/C systems but not 3. One option would be to fit a RCD with a higher rating but this would not be complying with the requirements for the socket's circuit....

[frank]

A sparky was telling me the other day that under the new 17th edition wiring regs all loads will need to be run off of rcd's....

Don't know if its true or not.

Jon

My son's a sparky and he visited today with the grandkids - great.

We got around to talking about all the retraining we have to go through soon to stay up to date with current regs.

He was telling me although he is NICEIC registered, that he too must undertake 4 days of retraining to be able to continue to sign certificates now that the 17th edition is due to become in force on the 1st July.

He also mentioned that one of the biggest changes is to socket outlets. All socket outlets installed or amended from 1sy July will have to be rcd protected no matter what they are feeding.

A veritable nightmare of call back caused by nuisance tripping.

[monkey spanners]

Frank, rcd's on sockets makes more sense than everything being on rcd's as i was told.

Cheers Jon

[Refrigerologist]

I rarely install rcd's on A/Cs even though some manufacturers recommend them, even on inverter systems. Here in Guernsey it has been a requirement to install 30ma rcd's on all ring main or socket outlet systems as well as bathroom electrical circuits for many years. Fixed appliances are not required to have an rcd installed, but in many instances a higher rated 100ma or 300ma is installed. Also a combination of earth leakage faults to not add together they become a multiple of the fault. This could be why any two units can be operated, but not three together!

[nike123]

Especially inverters shoul NEVER be connected via RCD as they ( indoor + outdoor unit)communicate digitally which creates a " leak" .that is why it always trips.
As a matter of fact there is nothing wrong with the a/c or the el .board.

Wish you luck.

They communicate thru neutral and dedicated (signal) line and that cannot create "leak". Leak is created in electronic filters which have function to filter all harmonics and el. noise created in inverter power circuit. That noise need to be dumped somewhere and that is earth wire. Because energy for that noise is consumed from phase that feed inverter circuit, and it didn't returned thru neutral line, we have imbalance in RCD and that trips him. Earlier versions of such filters are prone to leaking, but using filters of better quality that is highly reduced.
Tripping of RCDs we could avoid by using dedicated RCD for each circuit separately, and by using special RCDs Type B by VDE 0160/EN 50178 as this one:
http://tinyurl.com/2nmxyv

[declan simmonds]

hello all from my experince i have found out that tripping from rcd is caused by inbalance of live and neutral feed, its true you should supply each unit with a seperate rcd . Are the units inverter type ? as i have been told that you should change the rcd to a
RCD TYPE D instead of a type B as it takes long to trip or maybe it allows for a great inbalance someone tell me if this is true or am i talking rubbish? as i have fitted a RCD D TYPE to my daikin multi inverter in my house, becuase before the compressor used to start up slowly and then ramped up and triped the type B breaker,
now ive fitted the TYPE D it doesnt happen
cheers declan

[nike123]

hello all from my experince i have found out that tripping from rcd is caused by inbalance of live and neutral feed, its true you should supply each unit with a seperate rcd . Are the units inverter type ? as i have been told that you should change the rcd to a
RCD TYPE D instead of a type B as it takes long to trip or maybe it allows for a great inbalance someone tell me if this is true or am i talking rubbish? as i have fitted a RCD D TYPE to my daikin multi inverter in my house, becuase before the compressor used to start up slowly and then ramped up and triped the type B breaker,
now ive fitted the TYPE D it doesnt happen
cheers declan

Here in your statements you are mixing residual current protection device:
http://en.wikipedia.org/wiki/Residual-current_device

Type [AC or A or B]

Standard IEC 60755 (General requirements for residual current operated protective devices) defines three types of RCD depending on the characteristics of the fault current.

Type AC: RCD for which tripping is ensured for residual sinusoidal alternating currents.
Type A: RCD for which tripping is ensured:

• for residual sinusoidal alternating currents,
• for residual pulsating direct currents,
• for residual pulsating direct currents superimposed by a smooth direct current of 0.006 A, with or without phase-angle control, independent of the polarity.

Type B: RCD for which tripping is ensured:

• as for type A,
• for residual sinusoidal currents up to 1000 Hz,
• for residual sinusoidal currents superposed by a pure direct current,
• for pulsating direct currents superposed by apure direct current,
• for residual currents which may result from rectifying circuits, i.e.:
  • three pulse star connection or six pulse bridge connection,
  • two pulse bridge connection line-to-line with or without phase-angle monitoring, independently of the polarity.

and miniature circuit breaker.
http://en.wikipedia.org/wiki/Circuit_braker

Type Instantaneous tripping current
B above 3 In up to and including 5 In
C above 5 In up to and including 10 In
D above 10 In up to and including 20 In
K above 8 In up to and including 12 In For the protection of loads that cause frequent short duration (approximately 400 ms to 2 s) current peaks in normal operation.
Z above 2 In up to and including 3 In for periods in the order of tens of seconds. For the protection of loads such as semiconductor devices or measuring circuits using current transformers.

Miniature circuit breaker should be of B type for inverters and for non inverters of C type
Residual current devices should be of B type for inverters and A type for noninverters

[sid]

thanks everybody for your help,im meeting the sparky on wednesday,and i will pass all this info on...

[declan simmonds]

Well so it looks like i have a mcb connected to my daikin multi inverter type D is that bad or do you recomend that i change it to a type b instead ?
cheers declan

[nike123]

Well so it looks like i have a mcb connected to my daikin multi inverter type D is that bad or do you recomend that i change it to a type b instead ?
cheers declan

You should change it to type B of matching current to your cable cross section which feed your AC, because, MCB are there to protect cables from overheating and not to protect equipment.
If your cable cross section is insufficient, then you need to change cable to one with higher amperage rate and protect it with matching circuit breaker of type B.
If your Inverter AC have fixed speed compressor alongside with inverter one, you need to find inrush current for that AC and divide it with nominal current. If that number is greater then 3 you need type C circuit breaker.
I hope this helps.

[nike123]

Also,
Capacitors fluctuates the balance between Live and Neutral, this will under certain circumstances be enough to trip the RCD. Motors whilst running will also upset this balance and (generally) if the motor is big enough it will trip an RCD.

I think you are mixing here capacitative and inductive current (reactive power) with residual current.
Those two are totally different terms (residual current could be resistive, inductive or capacitative depending on source of leak).
Balance between live and neutral is always maintained if there is no leak of residual current, no matter what type of load (capacitative or inductive) it is.

RCDs and MCBs (for household) have their switching capacity rated for equivalent thermal (resistive current) load and if we have load with high portion of inductive or capacitative current (power factor lower than say 0,8) we then have overload at RCD and MCB, and they are tripping even if their amperage rating is higher than rated amperage of connected equipment. Also, we need to consider here inrush current and tripping curve of MCB or RCD.

Real amount of current thru conductor we get by dividing appliance measured (true RMS) current by power factor of device.

Most of RCDs have type K triping curve and MCB could be type B,C,D,K,Z (for details look at links posted before on replay to declan simmonds).

[ecclesk]

He also mentioned that one of the biggest changes is to socket outlets. All socket outlets installed or amended from 1sy July will have to be rcd protected no matter what they are feeding.

Looks like there are exceptions:

Taken from 17th Edition,

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 20A that are for use by ordinary persons and are intended for general use, and

(ii) mobile equipment with a rated current not exceeding 32A 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 provoded for connection of a particular item of equipment.

[Grizzly]

Can anyone advise.
If you use a switched fuse spur or specific plugged arrangement.
Does this then negate the need for that circuit to be on an rcd??
I other words how specific is the term Sockets (usually interpreted as 13 amp).
Thanks Grizzly

[frank]

In a.c. systems, additional protection by means of an RCD in accordance with Regulation 415.1 shall be provided for:

I haven't yet had sight of the new 17th Edition, but I assume that 'In a.c. systems' means Alternating Current as opposed to Air Conditioning ? ? ?

[nike123]

Can anyone advise.
If you use a switched fuse spur or specific plugged arrangement.
Does this then negate the need for that circuit to be on an rcd??
I other words how specific is the term Sockets (usually interpreted as 13 amp).
Thanks Grizzly

No, switched fuse spur does not provide protection to humans or protection from fire (both of protections is main function of RCDs). It just protect outlet from overload and cable from outlet to device. It is used generally for taking power from ring main circuits usually protected by 32amp MCB and downrating the circuit protection to whatever the new circuit requires.

Term socket usually refers to outlet for portable (that include kitchen appliances with flexible cord and plug) appliance whose power don't exceed 2000W.
Socket rating of 13A (or 16A by VDE) is safe amount of current which ensures no overheating at connection.

P.S. Dont blame me for possible wrong details because I did not updated these data in my head for long time.

[ecclesk]

I haven't yet had sight of the new 17th Edition, but I assume that 'In a.c. systems' means Alternating Current as opposed to Air Conditioning ? ? ?

Frank your right, it's reffering to alternating current.

Can anyone advise.
If you use a switched fuse spur or specific plugged arrangement.
Does this then negate the need for that circuit to be on an rcd??
I other words how specific is the term Sockets (usually interpreted as 13 amp).
Thanks Grizzly

Grizzly, i'm away for a couple of days will look into it when back at work.

i'll be attending the 17th ed course soon, to update from 16th ed, i'll post details when done.

[malcoa]

Can anyone advise.
If you use a switched fuse spur or specific plugged arrangement.
Does this then negate the need for that circuit to be on an rcd??
I other words how specific is the term Sockets (usually interpreted as 13 amp).
Thanks Grizzly

As mentioned by ecclesk

(b) a specific labelled or otherwise suitably identified socket-outlet provoded for connection of a particular item of equipment.

Just put a lable on it saying freezer only or air condioning only and your ok

p.s this is with regard to the 17th ed

[Birds]

My son's a sparky and he visited today with the grandkids - great.

We got around to talking about all the retraining we have to go through soon to stay up to date with current regs.

He was telling me although he is NICEIC registered, that he too must undertake 4 days of retraining to be able to continue to sign certificates now that the 17th edition is due to become in force on the 1st July.

He also mentioned that one of the biggest changes is to socket outlets. All socket outlets installed or amended from 1sy July will have to be rcd protected no matter what they are feeding.
A veritable nightmare of call back caused by nuisance tripping.

The 17th edition will require all circuits where the cables are concealed in walls or partitions less than 50mm deep and not protected by earthed conduit etc, to be protected by a 30ma RCD. This will apply to lighting circuits as well.The adopted method of complying, may be the use of individual RCBO's (combined rcd/mcb)to minimise the inconvenience and dangers of tripping. The use of SWA cable for circuits would not require RCD protection.

Hope this helps

[Birds]

Especially inverters shoul NEVER be connected via RCD as they ( indoor + outdoor unit)communicate digitally which creates a " leak" .that is why it always trips.
As a matter of fact there is nothing wrong with the a/c or the el .board.

Wish you luck.

Mr cooling Magic

I assume by your answer that you have never connected an inverter to an RCD. Try it sometime you will be suprised. I guess you have never installed in an area where the electrical supply is fed overhead i.e. a TT system. If you have any installs that you cannot do because there is an RCD fitted, I can do them for you, without tripping.

Birds

PS nothing much on tv tonight

[Contactor]

Daikin Installation manuals require RCD's for splits.

[nike123]

Mr cooling Magic

I assume by your answer that you have never connected an inverter to an RCD. Try it sometime you will be suprised. I guess you have never installed in an area where the electrical supply is fed overhead i.e. a TT system. If you have any installs that you cannot do because there is an RCD fitted, I can do them for you, without tripping.

Birds

PS nothing much on tv tonight

On this forum we freely exchanging our experience and knowledge. Maybe you should join us and share your.

[Makeit go Right]

Hi, Ecclesk, Back in March/April you were going off to a course to update from 16th to the 17th Edition. I was just wondering if there was a conclusion to it all.

As discussed already, it used to be that the aircon equipment was FIXED EQUIPMENT and was outside the concern of RCDs, which was helpful for inverters that often suffer neusence tripping when provided with RCD protection.

I am not sure a label on a spur/socket makes much of a difference to the intention of the the new 17th Edition, as regards this aspect of protecting hidden cables in walls.

Practically speaking, I would expect that if the feed is in armoured cable, the supply would not need the RCD.

BUT, it is all in the 17th Edition, rather than what is sensible to the man in the street, of course, so I was curious to know how it finished up, when you gave the updated regs a close study.