Elcb Versus Men

[jombom]

Being from Europe my instinctive view is that ELCB is better. Also I notice many of the electric showers here have built-in ELCB (the test button with reset).

However, the main distribution bard is normally MEN, as is also normal in Oz, I believe.

Views from the experts welcome.

[Crossy]

Neither! They are complementary and provide maximum protection when used together.

Much of the UK is PME (our version of MEN) and we also have RCDs (the modern name for an ELCB which is now reserved for the old voltage-operated units which are no longer permitted) on pretty well all domestic circuits.

In a nutshell, MEN/PME provides protection from L-E faults internal to equipment by causing the over-current device to operate rapidly, MEN will not protect you if you touch a live wire (or an ungrounded Class-1 appliance with a L-E fault).

An RCD provides protection from shock by sensing small differences between the L and N currents and assuming that any difference is going where it's not wanted (through you), touch a live wire on an RCD protected circuit and it should operate before you die (I don't recommend you try this, I can vouch for its accuracy from personal experience). An RCD will protect you if you touch an ungrounded appliance with a L-E fault.

IMPORTANT An RCD is an electronic device which could fail in the event of a surge and then provide zero protection, it should not be relied upon as the primary circuit protection, this would be your ground, be it MEN, TN-S or TT. Test yours regularly using the 'test' button.

[electau]

On a MEN system eg AS3000, RCDs are not installed as a sole means of protection and are used to augment other measures of basic protection, ie earthing and protective devices (MCBs).

RCDs can be electro-mechanical or electronic, they have a very low failure rate but they should be tested at least every 3 months using the test button.

Available in 30mA and 10 mA versions. An RCBO is a combination MCB/RCD.

They are current operated not voltage operated. RCBOs for conection to MEN systems have 1 fixed pole for the neutral, for TT systems the neutral is switched. RCDs for TT systems can be used on MEN installations.

The term ESB or ELCB is slill used as a general term in East Asia and Japan, also known as a GFCI under the North Americian National Electrical Code (NEC).

The Voltage Operated ELCB units were used in the UK but were phased out in the 1970s and are are no longer manufactured, RCDs have replaced them.

RCDs should be installed on all circuits with socket outlets.

RCD is the term for all residual current devices, RCCB is residual current only, an RCBO is residual current, overload and short circuit protection.

[electau]

The main neutral is NOT always earthed in Thailand.

[Crossy]

Could be a little technical for some, but worth a scan anyway it covers the various earthing systems as well as the mechanisms leading to electric shock, The RCD Handbook http://www.beama.org...7188608E386D98D

[jombom]

Thank you for the replies ---- very informative.

A few minor queries remain;

1 --- Does old voltage operated units refer to ''voltage operated'' or the old UK voltage of 240v ?

2 --- Re frequency of testing --- I normally test about every 6 months and always when staying in a hotel etc. As a unit never failed a test, in more than 100 tests, I tend to expect it will operate. Is testing every 3 months a guideline or just good practice ?

3 --- My reason for the opening post was, it strikes me that an Elcb (RCD) includes the live wire, whereas MEN does not. And indeed, like Crossy, I was also that soldier.

[Crossy]

1. The early ELCBs were voltage operated rather than current sensing. They were very easy to accidentally disable by having a parallel earth path hence them no longer being permitted.

2. Up to you how often you test them. If you have a very dusty environment they can stick, those on shower heaters get gummed up with soap residue.

3. The big RCDs (2 units wide) have double pole breakers and open both L & N wires providing positive isolation even if the supply polarity is reversed. The single width RCBOs and MCBs usually only open the Live which could leave you cooking if the supply is reversed.

[electau]

Voltage operated ELCBs were designed to be used on TT systems in the 1920s. They operated at 50VAC and required two electrodes not less than 2 metres apart, The trip coil was connected at the switchboard between the two electrodes. When anearth fault occurred a voltage was developed accross the two electrodes in excess of 50V and the unit would trip.

They were instantanteous in operation but would only operate if the earthing system integrity was maintained. They would be rendered inoperative by if the two earth electrodes where shorted together. They were susceptable to high earth resistance between the electrodes which could cause them to not function.

They could be used on an MEN system and were an option under the Australian wiring rules in the 1930s. They were found to be unreliable and discontinued by the 1940s. They were easy to conect back to a full MEN system. They were rated at 20A and used as a main switch.

The RCD is a current operated device and does not require an earth for it to operate.

Edited February 28, 2012 by electau

[electau]

The RCBOs with one switched pole and one fixed pole are designed for connection to an MEN system. Reversal of polarity will not occur if correct testing polarity procedures are carried out at initial connection or if work has been carried out on the consumers mains.

Eg. replacement of a meter .The neutral should always be clearly identified as such.

The problem is that testing is not always carried out in Thailand. One does not know how often polarity reversal occurs in Thailand due to lack of testing. The main earth will maintain the touch voltage to less than 50VAC if reversal does occur.

[electau]

Could be a little technical for some, but worth a scan anyway it covers the various earthing systems as well as the mechanisms leading to electric shock, The RCD Handbook http://www.beama.org...7188608E386D98D

An excellent source of reference on RCDs, the best one has seen.

Edited February 29, 2012 by electau

[Jayman]

This is an informative post but uses much technical jargon that I'm just not familiar with. I have a background in electronics but not trained as an electrician.

I would like to add an ELCB/RCD to my house. Unfortunately, all the outlets in the house are 2 prong and I'm fairly certain there is no earthed ground. We do have a ground rod put in to the earth close to the washer and have a ground wire from the washer connected to it. That sad thing is that my house is not that many years old and I'm fairly sure that the regs required 3 prong grounded outlets be used (so I've been told) and they just didn't do it correctly.

What do I need to get from the hardware store (homepro/homeworks) in order to give my family more safety from electrocution than we have now? Is an RCD what I need? Can it be wired into the main circuit break box? I do believe we have some spare room in there for it. If not I suppose it could be placed right next to the breaker box. Is it fairly easy to wire up? If I kill all the breakers, would it get wired in after the main breaker and before it goes to the individual breakers?

Any help or info would be greatly appreciated.

[electau]

You require an RCBO, which has RCD protection and overcurrent protection, eg 20A/30ma.

A single RCBO may be installed between the main circuit breaker (MCB) and the line side of the outgoing protective devices ( MCBs) to the circuits.

Alternatively you can install RCBOs on each individual circuit, this is the preferred option.

In Thailand it would be recomended that RCBOs be installed on ALL final subcircuits.

RCD devices should be 10mA or 30mA sensitivity.

You should upgrade your earthing if possible and install 3 pin outlets.

RCDs will operate when the earth resistance is high. There is an automatic disconnection time for a protective device (MCB) of 0.4secs max. An RCD will operate in less than this, typically around 20msecs.

Note:

The earth fault resistance for a 30mA RCD is 230/0,030A=7666 ohms. This figure is impracticable compared to the resistance for voltage drop, but it shows that RCDs are acceptable when the fault loop resistance is high. If an MCB/RCD (RCBO) is fitted then the automatic disconnection requirement will be satisfied..

Most electrical installations in Thailand have 2 pin outlets and if 3 pin oulets are installed they may not be earthed,also many have no compliant earthing or main earth and electrode.

Edited October 3, 2012 by electau

[Jayman]

Thank you for the response. Much more technical than I expected. So you are recommending I install a RCBO on each of the smaller breakers rather on just the main house breaker? What do I ask for in the homeworks? RCBO? Will that be written on the device so I can identify it when I see it?

Note:

The earth fault resistance for a 30mA RCD is 230/0,030A=7666 ohms. This figure is impracticable compared to the resistance for voltage drop, but it shows that RCDs are acceptable when the fault loop resistance is high. If an MCB/RCD (RCBO) is fitted then the automatic disconnection requirement will be satisfied..

What exactly are you saying here? The only part that even makes sense to me I put in bold. Basically are you saying that if I install a RCBO at the breaker box then I am fine? I'm still not clear why 1 RCBO on the main breaker vs one on each smaller breaker is not the way to go. If I put one on each circuit, would thy be smaller in size?

As you can see, I'm just looking for the information needed to go to the HW store and buy what is needed and then to understand where the device needs to be installed. It seems like a big job to wire a 3rd wire ground to all my outlets. Of course I would like to have properly grounded outlets at all power points in the house but not sure if we can jump right on that project right now. I will have to source out a competent electrician to refit all the wiring. In the mean time, I would like to get the RCBO installed and that is a job I feel I could do myself if I know what it is I need and if it's available here in the HW stores.

[electau]

There is a requirement that automatic disconection must occur in less than 0.4secs with an earth fault of negligable resistance. If the resistance is high eg 10ohms operation will occur with an RCD in less than 0.4secs, with a trip current of 30mA.

With a 20A MCB the trip current would be 230/10 = 23A. The MCB would not trip within the required disconnection time.

An RCD will give protection when a protective earth (PE) is broken or there is NO effective earth.

If you use just one RCBO for the whole installation it should be rated at a minimum of 32A/30A, some have a switch to select the trip current in mA.

If you choose to use one on each circuit you replace the existing MCB with an RCBO with a current rating of the MCB that you replace, eg 10A/16A/20A /. 10mA or 30mA

Edited October 3, 2012 by electau

[electau]

They may be known as a GFCI (US terminology) RCBO (IEC terminology) or as an ELCB or ESB , Homepro will know if you go to their electrical department, they will probadly have wiring diagrams available

Edited October 3, 2012 by electau

[Jayman]

Thank you again for the further clarification. I will take a picture of my MCB and bring it with me to the HW store to make sure I get the right rated RCBO. If I go with the single RCBO for the whole house then I should be looking for what size exactly? 20mA.. 20A...30mA..30A.. Larger? I want to make sure it does it's job of tripping within .4 secs. Should I just pick the same size as what my main breaker is rated at which looks to be 45A.

[electau]

Thank you again for the further clarification. I will take a picture of my MCB and bring it with me to the HW store to make sure I get the right rated RCBO. If I go with the single RCBO for the whole house then I should be looking for what size exactly? 20mA.. 20A...30mA..30A.. Larger? I want to make sure it does it's job of tripping within .4 secs. Should I just pick the same size as what my main breaker is rated at which looks to be 45A.

The trip current must not exceed 30mA. The overcurrent protection may be 32/40/50/63A check the size of the main circuit breaker. An RCD/RCBO is designed to trip in less than 0.4secs on an earth fault. They must operate between 50% and 100% of the rated trip current in mA. They must operate on the test button, this is the functional test of an RCD. This test does not check the PE continuity.

Edited October 3, 2012 by electau

[T_Dog]

Thank you for the response. Much more technical than I expected. So you are recommending I install a RCBO on each of the smaller breakers rather on just the main house breaker? What do I ask for in the homeworks? RCBO? Will that be written on the device so I can identify it when I see it?

Note:

The earth fault resistance for a 30mA RCD is 230/0,030A=7666 ohms. This figure is impracticable compared to the resistance for voltage drop, but it shows that RCDs are acceptable when the fault loop resistance is high. If an MCB/RCD (RCBO) is fitted then the automatic disconnection requirement will be satisfied..

What exactly are you saying here? The only part that even makes sense to me I put in bold. Basically are you saying that if I install a RCBO at the breaker box then I am fine? I'm still not clear why 1 RCBO on the main breaker vs one on each smaller breaker is not the way to go. If I put one on each circuit, would thy be smaller in size?

As you can see, I'm just looking for the information needed to go to the HW store and buy what is needed and then to understand where the device needs to be installed. It seems like a big job to wire a 3rd wire ground to all my outlets. Of course I would like to have properly grounded outlets at all power points in the house but not sure if we can jump right on that project right now. I will have to source out a competent electrician to refit all the wiring. In the mean time, I would like to get the RCBO installed and that is a job I feel I could do myself if I know what it is I need and if it's available here in the HW stores.

Jayman..... You are getting good advice on this thread from the experts, but here is a bit more. Be aware that the individual circuit RCBO's that you buy will require that you have a dedicated neutral and load lines to the outlets (loads) that you are protecting. The RCBO's look for a difference in the supply/return (load/neutral) wires of the 10 mA or 30 mA residual current of a particular RCBO. If your house had neutral lines that are daisy-chained in unknown places (common in Thailand) the RCBOs will trip inadvertently from unbalanced currents. So it might not be as easy as taking out a 20 amp breaker and popping in a 20 amp RCBO. A main breaker RCBO can work on an existing house as the load and neutral lines go to one dedicated load, the whole house. Be aware that your refrigerator is likely to be without power if you have a trip with this method.

Regarding grounds, adding entire house grounding is indeed cumbersome and may not have the returns you expect. (How many of your appliances have a 3 prong plug with ground installed? In our house, only the television!) You might be better off adding grounds to your major appliances that have a lot of human contact like your refrigerator, oven, washing machine, etc. Just having a ground in your outlet does not serve much purpose.

[Jayman]

Thank you for the response. Much more technical than I expected. So you are recommending I install a RCBO on each of the smaller breakers rather on just the main house breaker? What do I ask for in the homeworks? RCBO? Will that be written on the device so I can identify it when I see it?

Note:

The earth fault resistance for a 30mA RCD is 230/0,030A=7666 ohms. This figure is impracticable compared to the resistance for voltage drop, but it shows that RCDs are acceptable when the fault loop resistance is high. If an MCB/RCD (RCBO) is fitted then the automatic disconnection requirement will be satisfied..

What exactly are you saying here? The only part that even makes sense to me I put in bold. Basically are you saying that if I install a RCBO at the breaker box then I am fine? I'm still not clear why 1 RCBO on the main breaker vs one on each smaller breaker is not the way to go. If I put one on each circuit, would thy be smaller in size?

As you can see, I'm just looking for the information needed to go to the HW store and buy what is needed and then to understand where the device needs to be installed. It seems like a big job to wire a 3rd wire ground to all my outlets. Of course I would like to have properly grounded outlets at all power points in the house but not sure if we can jump right on that project right now. I will have to source out a competent electrician to refit all the wiring. In the mean time, I would like to get the RCBO installed and that is a job I feel I could do myself if I know what it is I need and if it's available here in the HW stores.

Jayman..... You are getting good advice on this thread from the experts, but here is a bit more. Be aware that the individual circuit RCBO's that you buy will require that you have a dedicated neutral and load lines to the outlets (loads) that you are protecting. The RCBO's look for a difference in the supply/return (load/neutral) wires of the 10 mA or 30 mA residual current of a particular RCBO. If your house had neutral lines that are daisy-chained in unknown places (common in Thailand) the RCBOs will trip inadvertently from unbalanced currents. So it might not be as easy as taking out a 20 amp breaker and popping in a 20 amp RCBO. A main breaker RCBO can work on an existing house as the load and neutral lines go to one dedicated load, the whole house. Be aware that your refrigerator is likely to be without power if you have a trip with this method.

Regarding grounds, adding entire house grounding is indeed cumbersome and may not have the returns you expect. (How many of your appliances have a 3 prong plug with ground installed? In our house, only the television!) You might be better off adding grounds to your major appliances that have a lot of human contact like your refrigerator, oven, washing machine, etc. Just having a ground in your outlet does not serve much purpose.

Thank you for the great advice. Yes, as I have mentioned I wired a ground to the washing machine. That tied to a ground rod. None of the other appliances have 3 prong but the ref came with a wire to connect the case to ground. Also, the only other items I really want ground for is my desktop computer. It seems that the case always has a slight current running through it that should be properly grounded. Maybe I should just have ground wires run to the outlets in my office and change all those outlets to 3 prong. Or maybe easier just to run a ground wire in from the rod outside that the washer is hooked to and tie it to the computer case.

My main house breaker is 45A. If I add the ECBO to that then I should be looking for 45A. If 45A is not available, I want to look for one with a higher rating right? Like 50A. Also, it sounds like I need to look for 2 specs.. the overcurrent rating (ie 45A) and the trip current rating (not to exceed 30mA).. do I have that right?

Edited October 4, 2012 by Jayman

[electau]

A 50A RCBO will be quite OK. This is the continuous rating in amps of the RCBO. The rated trip current on earth fault will not be more than 30mA max.

Make sure that there are no earths on any neutral conductor on the load side of an RCD/RCBO and there are no crossed neutrals between circuits. This will cause tripping of the RCD.

Max standing leakage current should not exceed 30% of the rated trip current in mA to prevent "nuisance tripping".

Edited October 4, 2012 by electau

[T_Dog]

Thank you for the response. Much more technical than I expected. So you are recommending I install a RCBO on each of the smaller breakers rather on just the main house breaker? What do I ask for in the homeworks? RCBO? Will that be written on the device so I can identify it when I see it?

Note:

The earth fault resistance for a 30mA RCD is 230/0,030A=7666 ohms. This figure is impracticable compared to the resistance for voltage drop, but it shows that RCDs are acceptable when the fault loop resistance is high. If an MCB/RCD (RCBO) is fitted then the automatic disconnection requirement will be satisfied..

What exactly are you saying here? The only part that even makes sense to me I put in bold. Basically are you saying that if I install a RCBO at the breaker box then I am fine? I'm still not clear why 1 RCBO on the main breaker vs one on each smaller breaker is not the way to go. If I put one on each circuit, would thy be smaller in size?

As you can see, I'm just looking for the information needed to go to the HW store and buy what is needed and then to understand where the device needs to be installed. It seems like a big job to wire a 3rd wire ground to all my outlets. Of course I would like to have properly grounded outlets at all power points in the house but not sure if we can jump right on that project right now. I will have to source out a competent electrician to refit all the wiring. In the mean time, I would like to get the RCBO installed and that is a job I feel I could do myself if I know what it is I need and if it's available here in the HW stores.

Jayman..... You are getting good advice on this thread from the experts, but here is a bit more. Be aware that the individual circuit RCBO's that you buy will require that you have a dedicated neutral and load lines to the outlets (loads) that you are protecting. The RCBO's look for a difference in the supply/return (load/neutral) wires of the 10 mA or 30 mA residual current of a particular RCBO. If your house had neutral lines that are daisy-chained in unknown places (common in Thailand) the RCBOs will trip inadvertently from unbalanced currents. So it might not be as easy as taking out a 20 amp breaker and popping in a 20 amp RCBO. A main breaker RCBO can work on an existing house as the load and neutral lines go to one dedicated load, the whole house. Be aware that your refrigerator is likely to be without power if you have a trip with this method.

Regarding grounds, adding entire house grounding is indeed cumbersome and may not have the returns you expect. (How many of your appliances have a 3 prong plug with ground installed? In our house, only the television!) You might be better off adding grounds to your major appliances that have a lot of human contact like your refrigerator, oven, washing machine, etc. Just having a ground in your outlet does not serve much purpose.

Thank you for the great advice. Yes, as I have mentioned I wired a ground to the washing machine. That tied to a ground rod. None of the other appliances have 3 prong but the ref came with a wire to connect the case to ground. Also, the only other items I really want ground for is my desktop computer. It seems that the case always has a slight current running through it that should be properly grounded. Maybe I should just have ground wires run to the outlets in my office and change all those outlets to 3 prong. Or maybe easier just to run a ground wire in from the rod outside that the washer is hooked to and tie it to the computer case.

My main house breaker is 45A. If I add the ECBO to that then I should be looking for 45A. If 45A is not available, I want to look for one with a higher rating right? Like 50A. Also, it sounds like I need to look for 2 specs.. the overcurrent rating (ie 45A) and the trip current rating (not to exceed 30mA).. do I have that right?

Yes, those are the two specs to look for, as well as getting one that fits!

Good luck with all that and many of us have been through it a few times here. The tingle you feel on your computer is usually do to the EMI filters on the computer that end up being a voltage divider that "floats" the computer chassis above ground voltage. Ground the case and it should fix it.

[rjhklein]

My water heater has no ELCB nor ELSD in it. I only have the breaker outside my bath room ( 30 AMP).

Honestly I don't feel safe so I am considering getting a unit with either ELCB or ELSD. Can somebody advice on my current situation and recommend a prefered option.

Thanks

[bankruatsteve]

Is that a multi-point water heater? IE: feeds hot water to the shower unit vs. being part of the shower unit?

If so, AND as long as it is properly grounded, you should be OK.

If it's part of the shower unit, then yes, you need RCD protection either in the unit or using RCBO for the breaker.