controlling heaters with contactors.

[cjclem]

Hi Everyone,

I need some advice on heating control circuits please.

I have 6 single phase 2kw infrared heaters which are fed from 6 individual 15A circuits on a 3 phase distribution board. Each circuit then goes to a local switch next to each heater and then on to the heater itself, and is currently controlled using the local switches.

I now need to be able to control all 6 heaters using 1x 7 day thermostatic timer. I am assuming that the best way to do this is to install contactors next to the distribution board, run each circuit from the distribution broad, through the contactors and then onto the local switch (which I will be retaining in case local switching is needed) and then onto the heater itself. With the contactors controlled using the

My question is: Do I need to switch both live and neutral in each circuit (3x 4 pole contactors) or can I just switch the live in each circuit? (2x 3 pole contactors.)

 

[Pete999]

7 day timer Control the D/B with 1 suitably sized 4 pole contacter controlled via a 7 day timer through a fused single phase supply

 

[cjclem]

That won't workfor me because the D/B supplies the power to the rest of the building, so if I switch the whole D/B I would loose power to the lights and sockets as well as the power supply to the control circuit.

 

[D Skelton]

I'm assuming that the 3P DB isn't specifically for the 6 heater circuits? If this is the case then you just need a small enclosure with 3 DP 20A contactors switching the line conductor of each circuit.

 

[Knobhead]

2 X 3 pole contactors, job done.

 

[SPARTYKUS]

I'd make it twice the size and fit a blank either side of contactors. They get warm.