Control Panel for 3ph Heaters

jparker86 · Aug 8, 2012

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.

[ElectriciansForums.net] Control Panel for 3ph Heaters

jparker86 · Aug 10, 2012

Tony said:
Out of curiosity what do you normally sell?

I sell industrial equipment that filtrates liquid into a 5 micron level ensuring particle free liquids. Mainly aimed at oil people who buy and or collect used vegetable oil and want it filtering down to remove solids.

spark 68 · Aug 10, 2012

Hi JP,

Try this

jparker86 · Aug 10, 2012

spark 68 said:
Hi JP,

Try this

Thanks Spark, I was following the drawing cause it says on the drawing to have the stop button interrupt the live into l1? Is this not correct?

spark 68 · Aug 10, 2012

jparker86 said:
Thanks Spark, I was following the drawing cause it says on the drawing to have the stop button interrupt the live into l1? Is this not correct?

On the drawing I did, the stop is above the start button, it is just conventionally done this way, as it interrupts both the coil and the contact.

In fact the drawing I gave you is more like this:

Edit: Drawing corrected after Richard pointed out my mistake

jparker86 · Aug 10, 2012

I think part of my trouble was understanding how the start button stays closed when it's normally open. Am I correct in saying that the moment the start button is pressed it is feeding in a loop and as a result stays retained

spark 68 · Aug 10, 2012

jparker86 said:
I think part of my trouble was understanding how the start button stays closed when it's normally open. Am I correct in saying that the moment the start button is pressed it is feeding in a loop and as a result stays retained

Your start button is N/O , it closes temporarily (when you press it), this energises the coil pulling in the contacts, one of the contacts then keeps the coil energised even after the start button has opened again (finger off), ie. it is self sustaining, until you break the circuit again with the stop button.

Richard Burns · Aug 10, 2012

The "switch" 1-2 is supplying the coil in parallel with the start supply. Once the contactor is energised using the start button it closes 1-2 which then supplies the coil and so keeps the contactor actuated.

To stop the contactor you need to interrupt the supply going to 2 to deactivate the contactor, the two mods above would leave the contactor actuated, as they are disconnecting the start button supply to A1, perhaps try this.
Edit talking rubbish here, this would not work, you could never start!

Edit2 the stop button is NC so it would work, what an idiot, think before posting!!!

spark 68 · Aug 10, 2012

You are of course 100% correct Richard, my mistake LOL, Iam in the middle of filling in an EIC and not paying attention.

I will edit the above drawings.

Edit: I did make a mistake on my drawing too though Richard, it's that time of night on a Friday lol.

jparker86 · Aug 10, 2012

Ok so the above drawing would work?

Richard Burns · Aug 10, 2012

Sorry Jp all gets a bit vague at this point.

My drawing in post 97 would work and would disconnect the contactor when you press the stop button, however this would not disconnect the supply to terminal 3 in the drawing (although the contactor being off would stop the supply to the stat). Spark68 has edited his picture in post 94 so that all the supplies to all the terminals in the contactor (bar the neutral) will be disconnected by the stop button and will also work and be more secure (in case of the contactor welding closed, etc.)

spark 68 · Aug 10, 2012

jparker86 said:
Ok so the above drawing would work?

My last corrected/Edited drawing (in response to Richard kindly pointing out my mistake earlier) in Post #94 is electrically almost the same as Richards and should work (it follows the drawings I did earlier).

Richard has got the Stop button as N/O when it should be N/C, which he has already pointed out.

It's been a long week! lol

jparker86 · Aug 10, 2012

Lol.
Beautiful! Well a huge thank you ladies and gentlemen and I'll post ttomorrow and see how I get on. I'm wondering if I should buy a stc-1000 off eBay to give digi temp reading

jparker86 · Aug 10, 2012

jparker86 said:
Lol.
Beautiful! Well a huge thank you ladies and gentlemen and I'll post ttomorrow and see how I get on. I'm wondering if I should buy a stc-1000 off eBay to give digi temp reading

Have I finally cracked it?

Richard Burns · Aug 10, 2012

Yes I believe so, good luck.

jparker86 · Aug 10, 2012

Whooooo!!

Control Panel for 3ph Heaters

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