Voltage Trips

[huntos33]

Just wondering how sensitive the old crabtree voltage trips are compaired to a RCD ?

 

[telectrix]

dunno about sensitive...useless is a more appropriate description.

 

[huntos33]

A customer has one up front of DB and needs some work done, told them this needs changing before i can continue but i always have that worry of tripping curcuits after. Just curious to see how effective the old Voltage trip was but i guess you've answered that !!. I'll cover myself in my quote first and see if i can run a few tests first also. Silly questions i know but im new to SE and advice is always good.

 

[hermetic]

The old VO trips such as the chilton or crabtree worked on a voltage of 50V to earth. RCD's otoh work on imbalance in the current flowing in the live and neutral conductors. RCD's are much more sensitive, but can be problematic because of this. as far as I know all VO ELCB's are obsolete, but in my area (east Yorkshire) they are almost universal in village installations, and work very well. when these were installed we used to put a polythene insert in the incoming water supply to prevent parralell earth paths, and also make sure that all bonding went back to the CU earth terminal(and thus through the elcb operating coil). the most vunerable part of the installation is the connection to the earth spike, and the fact that in prolonged periods of dry weather the earth loop impedance may rise considerably. Although I have never seen a trip that, when tested, failed to operate in dry weather, cases of nuisance tripping caused by localised fault currents from other earth spikes do rise. There are probably hundreds of thousands of the Crabtree "Chilton" pattern still in use, and although they are now obsolete, the reports I hear that they are dangerous are mainly excuses which generate work and profit, and sometimes may leave a householder with less protection than they had before. I have had absolutely no problems with Crabtree trips of the early (black with red button) or later (grey with yellow button) types. There os however an older model made by Tenby (I think) that almost always has a burnt out trip coil (you can smell them from yards away!) they also emit a slight buzzing indicating that current is flowing to earth but because of shorted windings, it can't trip. These are dangerous and should be changed! checking online I find many types of ELCB are still available, so they must still have a place in some installations. see Earth leakage circuit breaker - Wikipedia, the free encyclopedia for more info.

 

[Knobhead]

I’m amazed that someone would still regard a voltage operated ELCB as still suitable and fit for continued service.
I’m sorry but we’ll have to agree to disagree.

 

[hermetic]

I would like to know the reasons you think they are not "still suitable and fit for continued service". whenever I see one, I test it, both at its test button, and also by applying a test fault to a remote part of the installation, as I have said, apart from the now rare Tenby elcb, they still operate perfectly well, and although the protection may be "coarser" than an RCD they are still better than a fuse. They were after all, approved by the IEE regs, and when installed in compliance with the regs, they work perfectly well. I wonder how many of the RCD's being installed today will still be providing adequate protection in forty years time, I suspect not very many.

 

[StuSpiers]

If they operate no they are not c1.
but they are definatly c2 'potetially dangerous' and will result in an unsatisfactory result on an eicr.

the danger is and has always been parallel paths.

 

[Knobhead]

As Stu has pointed out “parallel paths”, all to easy to create in these days of DIY.

The company I served my time with had a large estate with 100’s of farms and cottages, all originally fitted with VO ELCB’s. After a rather nasty accident* they were systematically replaced with RCCD’s throughout the entire estate.

*Ironically it was one of our electrician’s wife that was put in hospital by a faulty unit. His house was even fed off our own distribution system, so basically we had full responsibility for our tenant’s safety. The company even tried to haul the estate electrician over the coals for it until he produced a memo he’d written warning against them.
I was a second year apprentice then, I’ve never liked them ever since. Got us a lot of overtime and free breakfasts and dinners when we were sent out at the weekends to help with the change over. Every house visited would insist on feeding you, by the end of a day I was awash with tea.
A group of us would be dropped off at a row of cottages armed with Crabtree 300mA RCCD’s and a load of earth clamps plus 7/.064 to bridge all the plastic bits of pipe the estate plumbers had put in.

 

[Engineer54]

As far as i can remember you needed to test those old VOELCB's with a dedicated tester, to get any meaningful result, as to there operating efficiency!! Haven't see one of those test kit's for years now, not even on Ebay!! ...lol!! To be honest, they have passed there sell by date, current balance breakers are by far the better arrangement. If variants of the voltage operated type are still being sold, it would i think be for specialised installations, you certainly wouldn't replace an existing unit with a new one!! lol!!

 

[spark 68]

As others have said, parallel earth paths effectively render these useless, the touch voltage cannot rise enough to trip them, so by ensuring that the main bonding is up to date reg 132.16 (again) they are effectively useless.

At least this is my understanding of the situation, I would happily stand to be corrected if anyone can clarify this point.

 

[Knobhead]

As far as i can remember you needed to test those old VOELCB's with a dedicated tester, to get any meaningful result, as to there operating efficiency!! Haven't see one of those test kit's for years now, not even on Ebay!! ...lol!! To be honest, they have passed there sell by date, current balance breakers are by far the better arrangement. If variants of the voltage operated type are still being sold, it would i think be for specialised installations, you certainly wouldn't replace an existing unit with a new one!! lol!!

I remember our estates electrician had one. That’s going back 40 years.

 

[spark 68]

checking online I find many types of ELCB are still available, so they must still have a place in some installations.

Would these still have a use in say an IT system ?

 

[GLENNSPARK]

The old VO trips such as the chilton or crabtree worked on a voltage of 50V to earth. RCD's otoh work on imbalance in the current flowing in the live and neutral conductors. RCD's are much more sensitive, but can be problematic because of this. as far as I know all VO ELCB's are obsolete, but in my area (east Yorkshire) they are almost universal in village installations, and work very well. when these were installed we used to put a polythene insert in the incoming water supply to prevent parralell earth paths, and also make sure that all bonding went back to the CU earth terminal(and thus through the elcb operating coil). the most vunerable part of the installation is the connection to the earth spike, and the fact that in prolonged periods of dry weather the earth loop impedance may rise considerably. Although I have never seen a trip that, when tested, failed to operate in dry weather, cases of nuisance tripping caused by localised fault currents from other earth spikes do rise. There are probably hundreds of thousands of the Crabtree "Chilton" pattern still in use, and although they are now obsolete, the reports I hear that they are dangerous are mainly excuses which generate work and profit, and sometimes may leave a householder with less protection than they had before. I have had absolutely no problems with Crabtree trips of the early (black with red button) or later (grey with yellow button) types. There os however an older model made by Tenby (I think) that almost always has a burnt out trip coil (you can smell them from yards away!) they also emit a slight buzzing indicating that current is flowing to earth but because of shorted windings, it can't trip. These are dangerous and should be changed! checking online I find many types of ELCB are still available, so they must still have a place in some installations. see Earth leakage circuit breaker - Wikipedia, the free encyclopedia for more info.

yep...been out filey today....BS3036-6 way...TT=87.6 ohms.... crabtree VO ELCB....were gonna do away with the voelcb on second fix=test and put a stand alone RCD for the 3036 as its good for continued service .....

 

[Deleted member 9648]

Removed one in a farmhouse last week....unit inoperative,L-E fault on the D/S ring....Ra of 700 ohms.....everything connected to the 'earthing system' in the house live and giving shocks.

 

[Shaun1987]

Ive come across quite a few, some of them can be a real pain to reset.

 

[richy3333]

yep...been out filey today....BS3036-6 way...TT=87.6 ohms.... crabtree VO ELCB....were gonna do away with the voelcb on second fix=test and put a stand alone RCD for the 3036 as its good for continued service .....

What, you're gonna keep a 3036 board in use, no forced RCD board change, you'll have the Electrical Trainee's foaming at the mouths

 

[GLENNSPARK]

What, you're gonna keep a 3036 board in use, no forced RCD board change, you'll have the Electrical Trainee's foaming at the mouths

yes...but you do what needs to be done to ensure compliancy...nowt less.....and nowt more unless the person ordering the work asks for it....i have IR`d all final circuits being fed from that C/U...so i know when we introduce an earth leakage device into the mix there should be no nasty surprises.....:38:

 

[Guest123]

If you come across one of these VO ELCB units to BS 842 1965, when conducting an EICR, industry guidance suggests a minimum of a code 3 be attributed even if the device is found to be operating correctly.

If the install is old enough to still have one of these present, chances are the earth path may be still be via a metallic service pipe which would warrant a minimum of a code 2.


IMHO, even functioning units of this type are unfit for contiuned service and should be removed & replaced as a matter of course.


Early versions of the newer grey Chilton units were also VO ELCB's but soon changed to become ELCB's BS 4293 1968, these were early versions of the humble RCD. Care should betaken when identifying these, the simplest indicator is the rating of the unit, VO ELCB's will have 50V written on them ELCB's will have a mA rating.

 

[hermetic]

As I said, If you test with the units test button, AND by simulating a fault at the remote end of the installation ( which rules out parralell earth paths), they provide protection which is better than fuses alone. there are 1001 things a DIYer can do to render an installation dangerous. Someone mentioned touch voltage, they are irellevant in this case as as soon as the earthed metal starts to conduct a fault current, it trips the ELCB. Actually it is the same with an RCD as long as the metalwork is earthed, it will also trip.As I also said, the earth spike/connection needs to be maintained (as does all parts of any electrical system, remember "This installation should be periodically checked and tested" etc etc) You can mark anything down as "potentially dangerous" just as any human being is a potential murderer! I have seen many modern installations that I consider to be "potentially dangerous" not becuase they are badly installed or incorrectly specified, but because some of the modern equipment is so poorly made with exposed live parts, poorly fttting clamping screws,and dubious looking cable clamps that hardly look able to carry their rated current etc etc. Only time will tell if the RCD will be as reliable, and safe (and "fail safe") as everyone seems to believe it will be. whilst typing this, a thought occurs to me, it seems ok to subject a householder to a "touch voltage" to operate an RCD under certain circumstances, and yet there now seems to be an embargo on neon screwdrivers on HSE grounds...............just a thought. I have used a neon all my working life, and still do, the only time I ever got a belt of it was when one of my "mates" fitted a slightly smaller resistor............but I got my revenge on the B*****D
Phil

 

[GLENNSPARK]

As I said, If you test with the units test button, AND by simulating a fault at the remote end of the installation ( which rules out parralell earth paths), they provide protection which is better than fuses alone. there are 1001 things a DIYer can do to render an installation dangerous. Someone mentioned touch voltage, they are irellevant in this case as as soon as the earthed metal starts to conduct a fault current, it trips the ELCB. Actually it is the same with an RCD as long as the metalwork is earthed, it will also trip.As I also said, the earth spike/connection needs to be maintained (as does all parts of any electrical system, remember "This installation should be periodically checked and tested" etc etc) You can mark anything down as "potentially dangerous" just as any human being is a potential murderer! I have seen many modern installations that I consider to be "potentially dangerous" not becuase they are badly installed or incorrectly specified, but because some of the modern equipment is so poorly made with exposed live parts, poorly fttting clamping screws,and dubious looking cable clamps that hardly look able to carry their rated current etc etc. Only time will tell if the RCD will be as reliable, and safe (and "fail safe") as everyone seems to believe it will be. whilst typing this, a thought occurs to me, it seems ok to subject a householder to a "touch voltage" to operate an RCD under certain circumstances, and yet there now seems to be an embargo on neon screwdrivers on HSE grounds...............just a thought. I have used a neon all my working life, and still do, the only time I ever got a belt of it was when one of my "mates" fitted a slightly smaller resistor............but I got my revenge on the B*****D
Phil

and this is why i aint a believer in the `magic` 1667 ohms rule as a way of getting round high Zs....