What is this black cylinder/tube?

[Cotonwood]

Hi all,



I have an outdoor junction box, cables from which supply an outdoor hanging heater.

When the heater is on, after approx. 2 minutes popping and crackling noises come from the junction box.

Inside the junction box are two small black cylinders with black and earth wires into them. One of which is showing signs of melting. What is this and could it be the cause of the RCD tripping?

Pictures attached show junction box closed, junction box open and zoomed in on black cylinders/tubes.

 

[Avo Mk8]

Hi Cotonwood,
I believe the troublesome black cylinders are supressors, either just capacitors inside, or a combination of capacitors and inductors.
These have been known to fail! If they are 'popping and crackiling' that's likely the cause of your MCB tripping.
You could disconnect the one that's melting as a short term solution. If your heater is a simple resistive element, I'm not clear why the capacitors are even necessary, unless it's to help protect the contactor contacts.

Hopefully someone here can advise whether you can leave them off.

 

[Cotonwood]

Hi Cotonwood,
I believe the troublesome black cylinders are supressors, either just capacitors inside, or a combination of capacitors and inductors.
These have been known to fail! If they are 'popping and crackiling' that's likely the cause of your MCB tripping.
You could disconnect the one that's melting as a short term solution. If your heater is a simple resistive element, I'm not clear why the capacitors are even necessary, unless it's to help protect the contactor contacts.

Hopefully someone here can advise whether you can leave them off.

Thanks for the response, really appreciate it.

There are 4 plug sockets and 8 spotlights running through that junction box too. But it's only the heater that causes the cracking and popping in the junction box.

 

[Avo Mk8]

Thanks for the response, really appreciate it.

There are 4 plug sockets and 8 spotlights running through that junction box too. But it's only the heater that causes the cracking and popping in the junction box.

If that's the case, maybe they are in the heater circuit only. Are you able to trace the wiring to establish exactly how they are connected (after turning off the power to the whole box obviously), otherwise I suggest getting an electrician in.

Do you have a temperature control, thermostat, or even just a separate switch for the heater somewhere?

There appears to be something like a regulator or solid state relay at the back in the middle of the cabinet, with thermal paste to the box to act as a heat sink? It's possible the black things form more of a functional part of the circuit than I first assumed.

Is there any more you can tell us about what the box is there for, other than as a connection unit?

 

[Cotonwood]

If that's the case, maybe they are in the heater circuit only. Are you able to trace the wiring to establish exactly how they are connected (after turning off the power to the whole box obviously), otherwise I suggest getting an electrician in.

Do you have a temperature control, thermostat, or even just a separate switch for the heater somewhere?

There appears to be something like a regulator or solid state relay at the back in the middle of the cabinet, with thermal paste to the box to act as a heat sink? It's possible the black things form more of a functional part of the circuit than I first assumed.

Is there any more you can tell us about what the box is there for, other than as a connection unit?

There is temperature control which is like a light dimmer switch.

The box would usually be closed and not easily opened, beyond being a junction box I've no idea specifically what it is for.

Strangely changing the position of where the black tube sits within the box (previously resting near a ground point as per picture) it is now not tripping. I'm not sure why it's now working correctly but I'll probably get an electrician just to give it a once over and make sure everything ok.

 

[Cotonwood]

There is temperature control which is like a light dimmer switch.

The box would usually be closed and not easily opened, beyond being a junction box I've no idea specifically what it is for.

Strangely changing the position of where the black tube sits within the box (previously resting near a ground point as per picture) it is now not tripping. I'm not sure why it's now working correctly but I'll probably get an electrician just to give it a once over and make sure everything ok.

Thanks again for your help and advice.

 

[Avo Mk8]

Thanks for the further info.
The metal box seems to hold the components that give temperature control - it's purely for the heater.
The temperature control knob is connected via the centre red/yel/blu 3 core cable, via the white connector, to the control module fixed on the back in the middle. That controls the heater power, the heater connected to the grey terminal block at the bottom. The supressors are probably there to protect the electronics in the temperature controller module. So on that basis it would be good to replace the faulty one, not just disconnect it. There might be some writing on the black tube things that would help identify exactly what they are. A good idea to get someone to fix it!
Best wishes.

 

[Lucien Nunes]

They look like delta capacitors, typically connected to line, neutral and earth. They would serve as interference suppression / snubbing for a solid-state relay or triac controlling the heaters. Inside each canister are normally three capacitors, two small class-Y types connected L-E and N-E and a larger class-X-between L-N. When Y-caps fail they are supposed to go open-circuit so that they don't create an earth fault, but if the whole thing cooks then it is indeed a likely culprit for your leakage trip events.

Post pictures of the data printed on the side of the caps so we can locate suitable replacements. They are widely available but you should replace with the correct values.

 

[Cotonwood]

They look like delta capacitors, typically connected to line, neutral and earth. They would serve as interference suppression / snubbing for a solid-state relay or triac controlling the heaters. Inside each canister are normally three capacitors, two small class-Y types connected L-E and N-E and a larger class-X-between L-N. When Y-caps fail they are supposed to go open-circuit so that they don't create an earth fault, but if the whole thing cooks then it is indeed a likely culprit for your leakage trip events.

Post pictures of the data printed on the side of the caps so we can locate suitable replacements. They are widely available but you should replace with the correct values.

There isn't any date on the side unfortunately just plain black all the way around and no raised lettering etc.

The only information is a label inside the box, however the company doesn't seem to exist anymore.

Pictures of label and black tubes, one showing some melting at the end

 

[Dan]

There isn't any date on the side unfortunately just plain black all the way around and no raised lettering etc.

The only information is a label inside the box, however the company doesn't seem to exist anymore.

Pictures of label and black tubes, one showing some melting at the end
View attachment 61942View attachment 61943View attachment 61944

I've added the pictures to your post for you. In future just do that yourself please. Those external photo hosting sites are useless in the future when you erase the pictures and it renders the thread incomplete.

Thanks for understanding.

 

[Lucien Nunes]

I've never seen a delta cap with no info on at all. Odd. Perhaps the printing is just very faint. Look at the good one under the light of an LED torch - that often shows up otherwise invisible or rubbed-off printing on components.