Voltage OPerated ELCB

[Piratepete]

HI Guys
Quick question.
Does the RCD test also test VOELCBs? Guess the answer is No! How do you test them?
Cheers
Pete

 

[SPARTYKUS]

You don't theyre obsolete. Needs replacing dude.

 

[Piratepete]

You don't theyre obsolete. Needs replacing dude.

Hi Spartykus
I'm aware of that. But it feeds 2 domestic boards, one local the other remote. It trips every few hours so I'm trying to find the cause of the trip. Just wondered if there's a way to test if it's faulty. No time to test every cct b4 Christmas! Left customer the job of eliminating one board or the other. Will go back later to test the boards.
Can I just replace the VOELCB with an RCD in a box? Does it count as like for like? Or do I have to upgrade the boards to 17th Ed?
Pete

 

[Richard Burns]

I would just change it out for a normal RCD as maintenance replacement. You may still have a circuit fault you need to find but if you don't then the VOELCB was faulty!

You are making it safer at least.

 

[Specialist]

As Richard said: Just swap it out for a good quality RCD, also check the main Earth size.

 

[NMc]

Before anything do an IR test on the wiring there may be leakage which will trip the new RCD.

 

[Engineer54]

There used to be a specialised test kit to test these VOELCB's, i haven't personally seen one for nearly 30 years!! You basically don't have a choice in this matter, the old ELCB unit you have has been discontinued and you have no-means of testing it's values or it's efficiency. So the only course open to you, is to replace to present unit with a modern day equivalent, a RCD device. Not only will a RCD be a suitable replacement, it's protection level will be a vast improvement over the existing unit.

There is no reason, why at this time, you can't provide an RCD device for each of the supplies you talk about, which will further improve the protection afforded to this installation. As the VOELCB's were never known to be reliable, ....RCD's also, are not ''totally'' reliable, but compared to those old voltage operated units there isn't any comparison, an RCD outclasses them hands down.

 

[IQ Electrical]

There used to be a specialised test kit to test these VOELCB's, i haven't personally seen one for nearly 30 years!! You basically don't have a choice in this matter, the old ELCB unit you have has been discontinued and you have no-means of testing it's values or it's efficiency. So the only course open to you, is to replace to present unit with a modern day equivalent, a RCD device. Not only will a RCD be a suitable replacement, it's protection level will be a vast improvement over the existing unit.

There is no reason, why at this time, you can't provide an RCD device for each of the supplies you talk about, which will further improve the protection afforded to this installation. As the VOELCB's were never known to be reliable, ....RCD's also, are not ''totally'' reliable, but compared to those old voltage operated units there isn't any comparison, an RCD outclasses them hands down.

Agreed, the main problem with the VOELCB was that it didn't 'see' leakage from any parallel paths-if the earth fault did not travel back to the unit, it didn't trip!

The test used a double wound transformer connected to the supply, output voltage not to exceed 45 Volts and connected between 'neutral' and 'frame' terminals.

Adequate tripping was defined as 'instantaneous'.

 

[trebor]

as everyone says they obsolete, however even when we were fitting them as new equipment there were serious issues
1. the elcb needs a low impedance electrode value, not relevant to your problem
2. They can operate via transient voltaes travelling in reverse from via the electrode to a better earth path within the installation, it was common to have tripping caused by a cooker for example in an adjacent or nearby property, may be relevant in this case

 

[hermetic]

You saved me a lot of typing Trebor, Trips every couple of hours? I would be looking for a faulty immersion heater perhaps? I have installed hundreds of the "chiltern" type, (175 in one council contract!) in the seventies, and I must admit we had a zero failure rate. Most of those will be on PME by now, but believe me, it aint universal in East Yorkshire by any means, and I came across one( one of the old old style black horrors, not a chiltern) last year still installed after the PME had been put in! If anything we found them a mite too sensetive, often exposing faulty appliances that had been leaking to earth unknown for years, and a boiled over pan was an instant trip. No doubt a properly installed RCD is better, but you still need an earth/cp path BEFORE someone touches the faulty appliance!
Phil.

 

[hermetic]

Sorry, missed out, we used to test them with a 40w incandescent test lamp from live to earth at a socket, should trip instantaneously. As has been said above you DO need a good earth, although nowhere near as good as you would need for a rewirable fuse, one of the reasons they were specified was because our area is very thin topsoil over chalk, and a good earth loop test in wet soil in winter could dissapear in hot dry summers!

 

[Engineer54]

Can't remember who actually made the test kit for those VOELB's, but i believe there were two of them going around. The one i remember had an indicator light that came on when the test complied time wise. Had some sort of time measurement, that didn't actually display, just indicated a pass!!

Instantaneous, after all is anyone's guess when talking in milliseconds. I remember the first RCD testers didn't actually display a trip time, just indicated a pass or fail...

 

[hermetic]

What I mean by instantaneous is that there should be no discernable delay between the apllication of the test and the click of the trip. The timings quoted today for RCD tripping are the maximum times allowable. In other words , on the application of a standardised test, a trip rated at 3mS passes if it trips at 2mS, but fails if it trips at anything over 4 mS. Wether testing at this level is repeatable over a temperature differential is questionable, but the line in the sand has been drawn. A VOELCB should trip "clean" there should be no buzz or other noise associated, and if the trip has a constant low level buzzing, there is usually an earth fault of very low voltage leaking to earth or a poor/loose earth spike which should be corrected. Whilst these C/B's are obsolete and should be changed if there is any doubt at all about safety, there are probably thousands still in sevice in the more remote areas of the country providing good earth protection where no other is available. The firm where I served my apprenticeship is still using the same bench test board with the same "Chiltern" ELCB, in fact I cannot remember ever having changed a faulty Chiltern, although almost all of the earlier type (all black with red test button, maker I can't recall) are inoperative when tested. I checked an installation recently and found that the installation had been largely rewired quite recently, PME was present, but no external N/E block had been installed so not connected, and the older type ELCB was inoperative, trip coil burnt out as usuall, and had no earth spike connected to it anyway. The entire installation had only some cursory 2.5mm bonding to provide an earth. luckily there was no fault present. I fitted a s/h ELCB and called YE, who came on the hurry up and fitted the PME block, but could offer no explanation as to why this wasn't done when the undergrounding/upgrading was done. The above comments about tripping caused by surface currents from faults at adjacent properties I have had personal experience of. We used to install a polythene insert in the incoming (metal) water supply which cured the problem in most cases.