Contactor issues on ceiling heater circuits

[Dengar]

Hi

I looked at a contactor schneider ict 4 pole 400v 25a. The fault was a loud knocking noise coming from the electricial riser cupboard.

I suspected one of the contactors was pulling in and out rapidly (this known as chattering?)

I am hoping you can point me in a direction as I'm not massively contactor experienced.

The contactor is for 4x 16a ceiling heater circuits. There is a control circuit with timeclock bringing on all contactors for a shop. There is a Sunvic Tlm2453 Room Thermostat controling the heaters.

My question is which is more likely to to be the fault, the contactor or thermostat. The chattering is happening when the thermostat is reading near the set temp. When I set thermostat up to about 28°c the contactor stopped chattering completely. But when its set around 20-21°c (near room temp) it will happen.

Is there a component in the thermostat that could cause this. Simular to like faulty pir sensor relay clicking and causing lighting to flash constantly?

Many thanks

 

[SparkyChick]

Hi Dengar,

Welcome to the forums.

Does the chattering happen if the required temperature is much higher than say room temperature? Or just as the temperature approaches the required?

 

[SparkyChick]

And I should add... has the issue started recently or has it been doing it for a long time?

 

[telectrix]

it's a female contactor. they's always chattering, never stop.

 

[Dengar]

Hello

Thanks for replies. It's when it's very close to required temperature.

I believe the boards were upgraded by a 3rd party around 4-5 months ago. The issue is apparently 1 month old.

Cheers

 

[suffolkspark]

Thermostat

 

[westward10]

If you set the stat full on and it doesn't chatter it is likely to be the stat.

 

[DieselShunter]

Sounds like a cheap mechanical stat with no hysteresis. Either use a good quality mechanical stat with good hysteresis or fit a decent digital jobbie.

 

[Dengar]

Thanks for replies, much appreciated.

I was leaning towards faulty thermostat.

Cheers.

 

[littlespark]

Thermostat.

It’s sitting on the edge of the required temperature and is clicking on and off repeatedly.
It’s happens a lot, but more noticeable with contractors because of the noise.

 

[Pete999]

Thermostat.

It’s sitting on the edge of the required temperature and is clicking on and off repeatedly.
It’s happens a lot, but more noticeable with contractors because of the noise.

Yep looks like the stat is going U/S

 

[Rocboni]

Is the stat mechanical? Has the stat got a neutral wired to it, the neutral is used for the return for the anticipator. This is a small thermistor type device that kind of pre-heats the bi-metal strip, reducing 'hunting' and making the stat more efficient. I may not have explained it completely correctly but it's along those lines!

 

[Dave OCD]

Good post Robconi, I think this particular stat is 16 amp resistive rated, they require a neutral for small current loads and that could be part of the issue as it's just pulling in a coil with next to no loading on it.

 

[Lucien Nunes]

The stat mentioned (TLM2453) is a simple mechanical stat that is probably not snapping over smartly due to contact wear or a weakened spring, and is arcing near the set point.

The neutral is required for any level of load. Its purpose as Rocboni describes is to power the accelerator heater, which warms the stat slightly when the room heaters are on, so that its temperature does not lag so far behind the rising room temperature. If the accelerator neutral is not connected, the symptom will be longer cycles with more overshoot above the set temp, because the stat will still be warming up when it is due to go off. It wouldn't cause this faulty switching behaviour.

 

[Darkwood]

I would also agree with the above and add that the positioning of the stat can make it prone to chasing IE rapid repeated on/off signals, can we assume this is not located over or near the heating source?