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

 

[plugsandsparks]

Well - its pretty much on a plate, still dont understand how the built in thermostats are dropping out the contactors in the panel.... but hey, had a miserable day fitting an extractor fan - would have loved to wire up a panel today

 

[Darkwood]

Reading the OP hes has wired the stat control to pull in and drop out the contactor, because it dosn't pull the contactor in auto the i assume hes wired the stats in series with the stop circuit hence once stat opens the OP needs to use the start button again.

 

[plugsandsparks]

Reading the OP hes has wired the stat control to pull in and drop out the contactor, because it dosn't pull the contactor in auto the i assume hes wired the stats in series with the stop circuit hence once stat opens the OP needs to use the start button again.

makes sense - oh dear

 

[Darkwood]

Its all a learning curve we were all their at some point, remember opening and trying to fault my first all in one start/stop contactor in enclosure..... it took an hour to just figure it out, nowadays i find myself following idiots who have connected them up all wrong and strip and wire in 5mins to their annoyance but hey! thats not my fault as they are site sparkies for the companies ..... my experience is the majority of the wing their jobs talking the talk unable to back it up, i got loads that ring me for advice ..... makes me wonder what exactly they are paid for.

 

[jparker86]

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

Hi people,
I apprechiate each and every reply but I am not familiar with how to read electrical drawings. Something that is simple to you isn't really that easy for me.

The circuit works but just when my thermostat cuts off the contractor, it won't work again once my thermostat asks for more heat unless someone presses the start button.

As I say I can make the thermostat control my contactor but I don't always want my heaters on.

 

[Darkwood]

If you dont get sorted b4 weekend il draft you up a simplified wiring format that you can follow, dont worry about not understanding them yet you pick it up along the way but if its an interest you'd be good to get a beginners guide to control wiring and schematics just understanding the schematics helps you plan your own wiring better as you are constantly looking at examples.

 

[jparker86]

If you dont get sorted b4 weekend il draft you up a simplified wiring format that you can follow, dont worry about not understanding them yet you pick it up along the way but if its an interest you'd be good to get a beginners guide to control wiring and schematics just understanding the schematics helps you plan your own wiring better as you are constantly looking at examples.

That would be a great help. I have today gone and got another contactor but still problem is once stop circuit is interrupted the thing won't work again. Shall I have a go at doing another drawing for you ?

 

[plugsandsparks]

OK, try this way, have you numbered the panel wires ?
if so simply list each wire you have in the panel. If not have a go at listing all the wires but its easier to explain what to change if they are numbered

So example

wire 1 - from emergency stop to 110V rail
wire 2 emergency stop to push button (start)

ect ect

include the power wiring and all control wiring.

Maybe we can then say " move wire 3 from a to b... etc

sorry for assumptions - no offence meant

 

[Darkwood]

Have the start stop button pulling in a main contactor then from one of its poles send the supply out to a switch (on/off) which in turn goes to the stat then the switch wire from the stat to the contactor coil for the heater..... this is pretty much what Tony's diagram shows then repeat for 2nd heater.
I assume your problem is your controlling the same contactor with both a start/stop button and stat control and you stat control is acting as a stop command dropping out the retained contactor, this is why you need a independant contactor just for the start/stop command so it remains energised until either Estop or stop is pressed.

 

[jparker86]

Have the start stop button pulling in a main contactor then from one of its poles send the supply out to a switch (on/off) which in turn goes to the stat then the switch wire from the stat to the contactor coil for the heater..... this is pretty much what Tony's diagram shows then repeat for 2nd heater.
I assume your problem is your controlling the same contactor with both a start/stop button and stat control and you stat control is acting as a stop command dropping out the retained contactor, this is why you need a independant contactor just for the start/stop command so it remains energised until either Estop or stop is pressed.

Thanks gents for sticking with me on this one. I know it's annoying talking to someone like me who aint got the first clue but I am not going to let this beat me!
Here is my new drawing which hopfully you can see a bit better. This is just one button, the last drawing had all three but they are all identical in how they work.

 

[jparker86]

Have the start stop button pulling in a main contactor then from one of its poles send the supply out to a switch (on/off) which in turn goes to the stat then the switch wire from the stat to the contactor coil for the heater..... this is pretty much what Tony's diagram shows then repeat for 2nd heater.
I assume your problem is your controlling the same contactor with both a start/stop button and stat control and you stat control is acting as a stop command dropping out the retained contactor, this is why you need a independant contactor just for the start/stop command so it remains energised until either Estop or stop is pressed.

Darkwood, yes this is exactly what I need to do. I have this here which I think will do what you are saying, is this what I need?

 

[Darkwood]

its beer time for me, il also explain about E-stops as yours wouldn't comply il see how far youve got by weekend.

 

[jparker86]

Darkwood would what I took a picture of do the job?

 

[Alot Isaiah]

i think you have a great idea there. why not try it perhaps it will work.using a thermostat to control another contactor is possible since the thermostat is a sensor.

 

[Swicade]

jparker 86....refer back to post #13 kindly donated by Tony as that is spot on. Only thing i'll add is afew more bits to the key offered:-

K1/1 = N/O contact on pump contactor (K1)
Sw1 = Rotary on/off switch for Heater bank 1 contactor (K2)
Sw2 = Rotary on/off switch for Heater bank 2 contactor (K3)
Th1 = Thermostat on Heater bank 1
Th2 = Thermostat on Heater bank 2

Definitely rotary switches on heater bank circuits instead of push buttons.

It may help if you copy/draw out Tony's donation on paper to help you understand the circuit better.