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?

 

[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