Standalone Photocells keep breaking

[Andiwoo]

Hi all I was hoping someone may have some good ideas for a problem I'm having. I'm just finishing my level 3 now so I'm still learning.

I was sent to a barn that has 2 rows of twin fluorescent lights 5 in each row. Built in to 2 of these fluorescent lights are night lights that switch on from a standalone photocell outside of the barn. There's also a lower part of the barn that also has 5 twin fluorescent lights with 2 of them with built in night lights with its own standalone photocell on the outside of the barn, this is a separate circuit. Both on the same fuseboard mind.

Now the problem is both photocells were staying closed so the night lights were constantly ON. So I changed both photocells and tried them both out 3 times and both circuits worked fine. The next day they were both broke, they wouldn't stay ON. I covered the photocell over and I could hear them click ON and OFF very fast, this was on BOTH circuits.
I took the photocells off and connected Live and switch live together and the lights came on fine no problem. The wiring is correct as it has been up for 10 years and we've checked it over.

As we had more photocells we replaced them both again, same thing happened during the night.

Checked voltage, 232V
Night lights are only 7W each.
RCD isn't blowing.
The 6A MCBS aren't tripping.
The installation is on surge protection.
I tested the neutral for a high voltage.

The chances of the light fitting causing the problem is unlikely as there's 2 circuits and it's happening on both. Plus they're all working fine.

Anyone had similar problems?

 

[linfield-sparky]

Might sound silly but have you made sure the heads are definitely clicked in right?

 

[Andiwoo]

Haha my supervisor said the same thing. Yes I definitely checked that quite a few times, it was definitely clicked in right

 

[linfield-sparky]

U said you touched sw L and L together and it worked but is it connected right at the photocell?

 

[Andiwoo]

Yes I checked the wiring in the terminals first, it's clearly marked on the fitting for L, SW and N. The photocell its self will only go on one way too. Infact on the first time I only changed the PHOTOCELL I used the old fittings as they were fine. I only changed them after they blew the new photocells, but it just happened again :/

 

[Jimsparky]

Are the night lights fluros aswell ?

 

[linfield-sparky]

It's a head scratcher, is the photocell controlled through a time clock or hand off auto switch?

 

[Andiwoo]

Yes they're 7w fluorescent 2 pin. I've been up to these lights and they look fine, no apparent damage. As the problem is happening on 2 separate circuits it's odd, if it was happening on 1 circuit i'd try just replacing the fittings

 

[Andiwoo]

Nope the circuits go to separate rotary switches and then up to the photocells, this just enables them to switch the night lights off or isolate them if they're not needed. These switches are obviously on.

It definitely is a headscratcher linfield

 

[Andiwoo]

I should also mention that there's 5 other barns with exactly the same setup. I also changed 4 photocells over 3 of these barns and they're all working fine. It's just this one barn that's having the problems

 

[Brightspark2]

Is there a minimum inductive load on the photocell?...

 

[telectrix]

i'd put it down to incompatibility between the photocells and the fluorescent lights.

 

[Andiwoo]

I'm not sure on a minimum but the photocell is a 5A inductive load 60MFD. I'm waiting on more information from the manufacturer, whom seemed stumped on the problem. I know inductive loads can have a blow back voltage but surely the diodes in place will stop that damaging the photocell?!

Could be a compatibility issue, the only problem with that is all the barns have these photocells and never had any problem with them.

1 of them was changed again today and left on for 2+ hours and nothing happened to it. Also after 2 + hours it was then switched on and off a few times and again no problems. So that one has been left on ready for tonight so we'll see if this one goes during the night.

What is strange is the old ones that had been up for many years both suddenly and at the same time started staying ON, they wouldn't turn off. These new ones are the opposite, they seem to stay open.

Probably end up being something simples

Thanks for all the suggestions sparkys

 

[Fast&Rough]

I allways use the photocells to bring in a contactor , one dodgy fitting will fry the photocell, probably because we used to use crap photocells but wouldn't have flourys straigt off the cell just a nice wee 230v coil in the contactor

 

[Andiwoo]

We did think a fitting would be causing the problem but not only did we check all the night light fittings, but both photocells are on separate circuits and they're both breaking around the same time, it's almost like the neutral is getting a high voltage in the installation but we've tested for this and it's fine

Hopefully this one we changed survives tonight and it was all a very odd coincidence (unlikely)

 

[Jimsparky]

Same as telectrix I've had this before on an incompatibility between a digital ballast and a photocell. Use a contactor, problem solved.

 

[Andiwoo]

Quick update: I mentioned the contactor but as we had to change the Night lights at some point anyway they opted for that. So we changed all the Night lights for 9W Bulkheads and even changed the Photocells to a different make, same problem happened on both circuits.

This again is just the Photocells breaking, NO MCB OR RCD TRIP. Shorted out the photocells and left the Night lights on for 8 hours, no problem. Next job will be the contactors which should sort this problem unless it's somehow a neutral fault

 

[chrish_1977]

Just a quick one, are they meant to point a certain direction, ones I have fitted have a point on them that must be pointing north, either that or switch it for a known good one from one of the other barns

 

[Andiwoo]

Yeah i've checked for that in the instructions but all they say is to keep it out of direct sunlight which they are. I also tried changing them from one off another barn, it blew that one too. The same photocells are on all the barns and never had a problem, this barn is just being unreasonable. But like I said we tried a different brand too which can take up to 10A and that blew

 

[Scornio]

Can I just ask why if they keep blowing, why would you keep installing them? Surely the compatibility between photocells and any type of inductive load would be the first thought and easily solved through the use of contractor.

 

[telectrix]

think he's probably fixed it by now , the thread's 6 months old.

 

[Scornio]

Lol more of an after thought... Interested to know what they did.

 

[Andiwoo]

Because if you'd read the thread this installation had been up for 10 years with photocells installed with no problems and there's 5 other barns with the same set up which didn't have ANY problems what so ever, so the cause of this one didn't seem obvious as each photocell is only operating 2 7w fluorescents. These barns are obviously all off the same main incoming supply. I had already thought of Contactor but I didn't want to start chucking things in for no reason when this has been fine for 10 years but if it didn't get solved then I would have put in a contactor. The night lights had to be changed anyway so that was done first. The photocells were changed because the supplier said they'd had a couple of problems with them so they swapped them for us.
The problem was from a blood machine in the path lab that self cleaned itself at 5-6pm everyday, the load was only small but somehow causing a problem on the main incoming supply, the mains is also on surge protection. No idea why it didn't blow the other photocells on the other barns as well and I don't even know the end final result as I was on another job when the investigation started.

 

[Scornio]

A blood machine...lol