Is VAF cable in conduit and buried allowed?

[Crocbait]

I recently had some lights installed on my fence and the contractor ran 2 x 1.5 VAF cable in PVC conduit buried in the ground for approx 15mtrs. Is this allowed here as I thought VAF cable shouldn't be installed in PVC, let alone buried in the ground?

[Crossy]

Official answer.

No problem with VAF in conduit although it may need de-rating slightly, but no way it should go anywhere it may end up in standing water.

You should use NYY for this application http://www.bangkokcable.com/product/backoffice/file_upload/131007_34-450!750V 70C NYY-2C.pdf

 

Pragmatic answer.

If the circuit is protected by an RCD/RCBO it will be fine for many years. If/when it fails replace with NYY.

If there is no RCD/RCBO, install one

[Crocbait]

Many thanks Crossy.

We have a Safe T Cut consumer unit installed and the RCBO unit failed, though It is approx 5 years old. This happened not long after the lights were installed and I was wondering if the use of this cable contributed to the problem. After a couple of months (after a big storm) when the lights were switched on the breaker tripped. The circuit was run from existing lights (and on the same switch) and worked fine at first. So not sure what the problem is. As usual trying to get them to fix the problem or getting another competent electrician in the boonies is nigh near impossible. I have disconnected the circuit at the light switch until I can get it resolved on my next trip back.

 

My first thought was to replace all the cable, but I fear it will be difficult to remove as the cable is in conduit inside the concrete gate posts with quite a few elbows, with the section between the two gate posts buried in concrete. Do you know any tricks to pull the cable out?

 

Thanks for your help, it is much appreciated.

[Wirejerker]

RCBO s are very reliable piece of electrical apparatus.. A faulty circuit will not cause the RCBO to fail but it will make it trip. When a RCBO trips and cannot be reset it usually means the fault is still there and the RCBO is working fine.. When u replaced the RCBO did you do same for same or go to a lower sensitivity?
Let get over the fact you don't have the top of the range wiring but we are just running a couple of piddling lights so short of someone driving a nail through the conduit it should be ok. So what's left after the switch . Any junction boxes out there where water/insects can get in. The lights themselves


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[Crocbait]

Thanks Wirejerker,

When the RCBO unit failed...tripped on any sensitivity and every circuit, could not source a replacement locally so local electrician wired in some other breaker to get it working. Last trip I got my wife to ring Safe T Cut in Bangkok and they said that the model I have can't be repaired/replaced and gave us some names of repair centers in Khon Kaen, which is a three hour drive away. I can't see why the whole RCBO Unit with breakers in the unit can't be replaced, but the usual Thai run around, so nothing has been done to replace it yet. I have been thinking of ripping out the whole box and replacing it with Schneider or Square D, but haven't found an electrician to do it yet.

There is a junction box in the carport roof and probably another taped connection, but shouldn't be any water able to get in, but the geckos and other insects probably can.. Difficult to access, so will have to drop the ceiling sheets to have a look. I had an electrical guy who came to install new water heater  to check water ingress at the lights, said they were fine, but didn't want to find the problem.

 

Agree, there's only 4 x 8w CF on the circuit so I wasn't too fussed about the cable problem until it started tripping.

[Wirejerker]

Hi croc, I am having trouble following you as you are all over the place. I believe you were thinking a dodgy light circuit caused premature failure of your safe T Cut but a Safe T Cut is designed to detect dodgy circuits and trip. It then can be reset after fixing or isolating the fault.

So now we have a failed RCBO unit that can't be repaired or replaced and your electrician wired in " some other breaker"  

Question:1 Was the failed breaker a RCD or a RCBO

Question:2 Was it replaced with a RCBO or a RCD or a CD or "some other breaker"

please don't go ripping sheets off your ceiling to look at that connection as that will be a pretty low risk connection. I would be looking outside where the cabling loops from light to light. I hope your electrician didn't do a running connection in the conduit cause u won't find that.

Summing up I don't think you conduit circuit caused a failure in the safe t Cut but it still may have tripped it. 

[johng]

2 hours ago, Wirejerker said:

RCBO s are very reliable piece of electrical apparatus..

Yes until the ants arrive     they seem to be very attracted to any electric field  so far for me they killed 2 hard drives

I computer monitor/TV  a keyboard  numerous light switches,sockets and breakers  when they short out and make the magic smoke their bodies form an extremely good insulator that stops the contacts conducting if you take the switch (or whatever) apart and clean up they will often work again.

 

this one from a water heater

 

 

 

[Wirejerker]

There u go Johng no pics there of RCBO s . Reliable huh. Told ya


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[johng]

Oh ok yes my bad  its an ELCB    

 

I'm sure the little buggers would cause much the same chaos nesting inside this one

 

[bankruatsteve]

FYI:  An "ELCB" is same thing as "RCD".  "RCBO" is RCD + MCB.

 

Ants and other critters don't usually bother these things but it wouldn't surprise me.

 

As to the OP, since the Safe-T-Cut can't be repaired or the RCBO replaced, was it set to "Direct" to allow function without tripping?  Not easy to imagine how another breaker could be wired in.  

[Wirejerker]

FYI:  An "ELCB" is same thing as "RCD".  "RCBO" is RCD + MCB.
 
Ants and other critters don't usually bother these things but it wouldn't surprise me.
 
As to the OP, since the Safe-T-Cut can't be repaired or the RCBO replaced, was it set to "Direct" to allow function without tripping?  Not easy to imagine how another breaker could be wired in.  

Just diagnostics Steve. Know what we started with, know what we got now and what caused the last trip. Getting my ducks in a row


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[Crocbait]

Hi Wirejerker,

Sorry if I seem to be jumping all over the place, I will try to give concise sequence of events:

1. Lights installed on gate posts, circuit hooked into existing lights circuit in carport roof using VAF cable in conduit.

2. Worked fine for a few weeks, then that circuit breaker started tripping every time light switch was activated. RCBO I don't think was tripped.

3. Safe T Cut RCBO started tripping on all sensitivities and all breakers. I wasn't there and wife got some electrician to look at it.

4. Electrician took out Safe T Cut RCBO Unit and replaced with 1 RCD breaker so power could be supplied. Light circuit deactivated at switch.

 

So I want to get some competent electrician to replace the RCBO or whole unit and check the wiring for the fence lights. Initially I was wondering if the incorrect cable started the problem, which from what you said shouldn't be a problem.

I know the circuit was hooked into other light circuit in the roof, so I wondered if there is a faulty connection there, because the only other join in the cable is the lights on the fence posts.

Thanks.

[Led Lolly Yellow Lolly]

On 03/03/2017 at 3:24 PM, bankruatsteve said:

Ants and other critters don't usually bother these things but it wouldn't surprise me.

 

I had a single pole Schneider RCBO fail on me just a couple of weeks ago. The ants got into the device in sufficient numbers to set fire to themselves. The RCBO tripped, but not due to L/N imbalance, I think it was short current. After replacing I gave the failed RCBO a few hard taps on the table and out came all the cooked ants. The RCBO now works again, but I'll probably bin it anyway.

 

On 02/03/2017 at 6:42 PM, Crossy said:

Official answer.

No problem with VAF in conduit although it may need de-rating slightly, but no way it should go anywhere it may end up in standing water.

VAF cable, particularly cheap brands that are everywhere here, quickly become hygroscopic, to the point it doesn't need to be submersed. I had a real headache tracing an earth leakage on an air conditioner a couple of years back. Turned out to be VAF cable running alongside the condensation drain leaking current to the grounded coolant pipe. Personally I wouldn't advise anyone to leave VAF cable in the ground, it's just a matter of time before it gives you problems. Buried cables need to be NYY, >60 centimetres below the surface in high density polyurethane pipe and covered in concrete. This will last for a hundred years. I'm working on a project right now where gardeners are digging through live THW cables just 2 inches below the surface. Their spades just slice straight through the conduit (wooden handles, fortunately). Waste of time if it's not deep, and concreted. As this company is finding out to their cost, they all need replacing.

Edited March 24, 2017 by NilSS

[Crocbait]

Thanks NilSS. Next trip back I am going to pull it out and use correct NYY cable.

[johng]

Here is last nights failed breaker

looks like old ants nest caused it to trip then stupid tiny fragile plastic

latching linkage broke so it couldn't be turned on and locked in the on position.

 

[Led Lolly Yellow Lolly]

On 03/03/2017 at 3:24 PM, bankruatsteve said:

FYI:  An "ELCB" is same thing as "RCD".  "RCBO" is RCD + MCB.

 

I hate to be the horse's ass here but I'm a self confessed pedant. They are not the same thing. An ELCB detects actual earth leakage directly and MUST therefore have an earth connection to function as intended. An RCD/RCBO detects imbalance between Live and Neutral and assumes this to be an earth leakage, and will therefore operate even without a CPC. . . and in Thailand, the advantage of the latter should be obvious.

Edited April 27, 2017 by NilSS

[Crossy]

Whilst NilSS is technically correct, in the world outside the industry the terms ELCB and RCD (along with GFI, etc etc) are used interchangeably.

 

If you see an item labelled "ELCB" outside a commercial installation it's going to be an RCD.

[kamalabob2]

I would advise the OP to consider NYY. I had a small fire inside my home a few years ago directly related to improper electrical cable being installed in gate lights. Water crept into the yellow conduit, buried in concrete. I had good home insurance, and complete replacement with NYY in HDPE proper black conduit too place by a licensed electrical contractor. The warning signs were the breaker tripping. The door bell wire also was the wrong type and it went bad. The door bell would go off by itself.  The fire was minor, and the insurance company paid for 100% repairs with no delay.