Control Panel for 3ph Heaters

[jparker86]

Hello,
I am new to the forum and would be most grateful if anyone here could help me with a project I am working on.

I have a control panel which I have made that controls 2 x heaters and 1 x pump.

Both heaters are 6kW (three phase) and the pump is single phase.

It all works, and I have on/off push buttons to operate the heaters and pump all run via the emergency stop button.

Where I am stuck is that my three phase heaters have a built in thermostat, which switches the contactor from on to off when the heat exceeds x degrees. My problem is that with my current design, unless someone presses the start button again it wont switch back on!

Under my current design, the thermostat isn't installed I left this until last (I underestimated how easy it would be).

Currently, all that happens is the device will turn on and off.

What I want is for the thermostat to cut in and cut off the power to the heater when temperature gets too high.

In my head I am thinking the best idea would be to have a contactor which is controlled via the on/off buttons, and that powers another contactor that is controlled by the thermostat?... or am I missing something that could help me?

I below attach the wiring diagram for both the heater in question and the control circuit diagram.

Any help would be gratefuly rec'd.

 

[plugsandsparks]

Cannot make out the line drawing but why not use a simple on/off selector switch instead of a PB

 

[Marvo]

Maybe you just need a rotary type on/off switch rather than one that momentary makes when pressed. I also can't really make out your hand drawing, did you use the aux contact on the heater contactor as a self hold? Maybe that could be the problem.

 

[Knobhead]

Drawing unreadable and not enough information.

 

[Darkwood]

After you've sorted out you wiring issues then you'll find long term operational issues may be you next problem.
More info as others have asked, nature of the job, temperature control (critical to maintain or flexible)
Last thing you want is hunting where the contactor is pulling in and out rrepeatedly as the temp goes over and under the stat setting.
If the heaters are trying maintain a specific temperature which is critical to the job in hand you should looking into P.I.D. controls possibly with solid state switching relays which in turn will require ultra-fast fuse protection (semiconductor fuses) to protect the relays if elements short.

You need to get a detailed list of the nature of the job in hand as its alright us correcting your wiring issue but without knowing more it might not be the correct design for job in hand.

Trying to answer your query you use you start heater buttons to pull in a relay with retaining link that controls feed to the stat, use the stat switch wire to pull in the heater contactor(non retaining)which will pull in and out on demand, the heater stop button will drop out the stat supply relay subsequently dropping control of the heater contactor out.

 

[Knobhead]

Based on guess work, try this.

View attachment 13963

 

[jparker86]

Hello,
Thanks for all your replies.

I looked at the drawing but am I correct in saying their is no "start/stop" buttons for the heaters?

The idea is that the control panel can turn the heaters and/or pump on and/or off, but while heaters are on they maintain a set given temperature.

Do we think the best thing is to remove the start/stop buttons and replace with selector switches?

Jase

 

[plugsandsparks]

Maybe you just need a rotary type on/off switch rather than one that momentary makes when pressed. I also can't really make out your hand drawing, did you use the aux contact on the heater contactor as a self hold? Maybe that could be the problem.

Thats what i said

 

[plugsandsparks]

Again cannot really work out your control strategy but FWIW, i did a 5 heater thermostatically controlled panel, very simple. One thermostat and heaters selected for need. I used 5 contactors (one for each heater) 5 selector switches, one for each heater. On the control side , the thermostat supplied or not control voltage to all heaters selector switches and other side of switch to relevant contactor.

 

[jparker86]

Thats what i said

Just in my head trying to figure out how it would work :s

 

[plugsandsparks]

I understand you want to bring in a heater by thermostat but thats it. You say the heater has a built in stat but its cutting out and not resetting the contactor.

So this implies, i think, that you have L1,L2L3 to each heater plus a couple of wires from the stat to the control panel where the contactors are ?

Its hard to make out exactly what is where.

Tonys drawing gives you a proper working solution for push button to start the lot and lets each heater be controlled by thermostat.

If you want additional control of heaters, i.e. selector switch, wire them between th1 and k2 and th2 and k3.

 

[jparker86]

Hello,

At the moment the stat is not controlling anything. Presently I press start and stop and the heater or pump will turn on. I can have anything on and off at once. For example two heaters on without the pump, and then I want the pump on so I turn that on.

Problem is that I want the thermostat to cut off the heater when the temperature set is exceeded. This is where I am coming unstuck.

From Tony's drawing I see how this works but won't be able to turn the heaters on and off without hitting the e/stop?

For example in this application we might want to just operate a pump without the heaters on at all.

 

[Knobhead]

For Christ's sake it's not rocket science

 

[Darkwood]

For Christ's sake it's not rocket science

View attachment 13969

You forget to put Sw1 and Sw2 in the 'Key' ...... im lost now... what could they be :rolleyes2:

 

[Sparkattack]

Just use the stats to switch the contactor coils in and out