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.

 

[jparker86]

Finally think I have worked out my issue... I have now got four contactors, two for each heater.
One switches the main coil on and off, and the other switches the 3ph electric on and off to the heater.
I think my issue is that the contactor controlling the main contactor is not latched, and thus when power to A1 is lost the whole cirucit remains dead.

 

[oldtimer]

First of all the thermostat in the heater I take it is a control stat ? then there should be a high limit cut out safety stat Yes Ok if so these need to be left in the circuitry.

So Me think you need to fit a timeclock for occupancy times and a area or room stat but if the stat on the heater is on the return side then thats fine other than that have an override switch for not occupancy times.

If the stat on the heater is on the return side then you can control the area temp with this but if it is on the discharge side then you will need a area wall stat

 

[Knobhead]

Here's one last ditch attempt

View attachment 13986

 

[jparker86]

Here's one last ditch attempt

View attachment 13986

Thanks Tony I think I have figured it from Spark's drawing.

Here is what I have done. I hope this will work.
J

 

[Knobhead]

The control relay will still drop out when the thermostat operates. The stop is in the wrong place and there's no need for the Aux on the contactor.

 

[jparker86]

The control relay will still drop out when the thermostat operates. The stop is in the wrong place and there's no need for the Aux on the contactor.

Yeah sorry I just realised that I wont need that Auxillary anymore because their will be a constant supply to A1.
Why will the control relay still drop out when the thermostat operates? How can i change it?

 

[jparker86]

How does this look

 

[Knobhead]

I give up!

Follow the last drawing I've given you. It will work with no problems.

 

[jparker86]

I give up!

Follow the last drawing I've given you. It will work with no problems.

Tony I don't mean to offend you but your drawing makes no sense to me. I'm here because I need help. Again something that seems relatively straight forward to you is in actual fact very difficult to me.

 

[Darkwood]

I think you are struggling because you cant interpret tony's wiring diagram because you dont understand what the R1/1 etc means ....
R1 relates to relay 1
R1/1 relates to relay 1 and the first pole/way so looking at the diagram when you press the start button R1 will close.... this will close R1/1(pole no1) and because its in parallel with the start button it holds R1 closed.
R1/2 is the second pole of R1 so when R1 closes R1/2 becomes energised supplying the next part of the control circuit.

Try reading the wiring plans now with this info..... my worry is you will need to supply a wiring schematic with your control panel yet you can't initially read them yet alone draft one up.

 

[jparker86]

I think you are struggling because you cant interpret tony's wiring diagram because you dont understand what the R1/1 etc means ....
R1 relates to relay 1
R1/1 relates to relay 1 and the first pole/way so looking at the diagram when you press the start button R1 will close.... this will close R1/1(pole no1) and because its in parallel with the start button it holds R1 closed.
R1/2 is the second pole of R1 so when R1 closes R1/2 becomes energised supplying the next part of the control circuit.

Try reading the wiring plans now with this info..... my worry is you will need to supply a wiring schematic with your control panel yet you can't initially read them yet alone draft one up.

Hi Darkwood, I am confused because Spark's drawing doesn't mention a relay. This one does? I have loads of contactors, but no relays in my stock and wanted to make it this week? So are we saying Sparks drawing will not work?

 

[Darkwood]

Tony has supplemented relays to do the control side as they are cheaper, less room etc, the contactors are just larger versions of relays for the heavier loads.... take the both as meaning the same if you have all contactors.

 

[jparker86]

Tony has supplemented relays to do the control side as they are cheaper, less room etc, the contactors are just larger versions of relays for the heavier loads.... take the both as meaning the same if you have all contactors.

Thanks,I apprechiate that but just want to work it with contactors.
8 don't want to confuse myself any more lol.

What wwould I need to do to get my current drawing work? I thought I did it just like spark said?

 

[spark 68]

You have shown a diagram with 2 contactors on, K1 is you initial latching contactor (k1/1), k2 is your first heater control and using the common connection K1/2 to supply you 2nd heater would be fine, less expensive and leave more room as it removes the need for the extra contactor. (excluding E-stop and pump controls)

Hi DW,
K1 could easily be a relay instead of a contactor (cheaper) as the control element in my drawing, K 1-1 and K1-2, are 2 pairs of contacts on the K1 relay, K2 is a 3 or 4 pole contactor which has the stat or cutout in series with the control coil.

I had cut this drawing down to it's most basic skeleton, the OP could have used extra contacts on the start/stop relay for status indicators and the like.

I had initialy assumed the OP was controlling both heaters from one stop/start circuit, but then he wanted to control both heaters seperately, hence the mention of three contactors initially, revised to four, to give independent control to each.

Half the trouble I had was the actual drawing with the software package (Tinycad), as Iam not used to drawing in software.

This was the circuit for one heater, as I said he would need to duplicate this circuit (apart from the E-stop) for additional heaters.

 

[jparker86]

Hi DW,
K1 could easily be a relay instead of a contactor (cheaper) as the control element in my drawing, K 1-1 and K1-2, are 2 pairs of contacts on the K1 relay, K2 is a 3 or 4 pole contactor which has the stat or cutout in series with the control coil.

I had cut this drawing down to it's most basic skeleton, the OP could have used extra contacts on the start/stop relay for status indicators and the like.

I had initialy assumed the OP was controlling both heaters from one stop/start circuit, but then he wanted to control both heaters seperately, hence the mention of three contactors initially, revised to four, to give independent control to each.

Half the trouble I had was the actual drawing with the software package (Tinycad), as Iam not used to drawing in software.

This was the circuit for one heater, as I said he would need to duplicate this circuit (apart from the E-stop) for additional heaters.

Spark what you say is exactly what I want.
What I did on the paper above is what I think your drawing is telling me to do.
My drawing will be replicated for the 2nd heater as per your post, except for emergency stop which kills all three (2 pumps and heater)
What I'm asking is what's wrong with how I've drawn it out?