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.

 

[Richard Burns]

Just make sure you understand why you are doing all this and read again the posts from the much more experienced members who have given some very valuable advice that will make your panel better.

 

[spark 68]

You are getting there JP, lol

That would work, my only preference would be to have the supply to terminal no.3 of the contactor coming from after the the N/C stop button (from the terminal blocks at the top left of your drawing) rather than from the permanent live.

The reason for that is because if you have a latching/locking type stop button this will kill all of the power to the contactor/s.

 

[jparker86]

You are getting there JP, lol

That would work, my only preference would be to have the supply to terminal no.3 of the contactor coming from after the the N/C stop button (from the terminal blocks at the top left of your drawing) rather than from the permanent live.

The reason for that is because if you have a latching/locking type stop button this will kill all of the power to the contactor/s.

The button is a spring loaded stop button.
Mill modify drawing

 

[spark 68]

Your drawing would work as is, it is just my preference.

It just offers slightly more open future options that is all

 

[Knobhead]

If you’re hoping to sell this thing, just think about the legal aspects to it.
With you’re lack of knowledge there is no way this is going to be designed safely or to legislation.

 

[Darkwood]

Im drunk.com but just realised i explained in post 89 how to wire it correctly from OP's diagram and there's a whole page of different wiring configerations before it was corrected to the same suggestion as i did .....no offense meant but made me chuckle

 

[jparker86]

Im drunk.com but just realised i explained in post 89 how to wire it correctly from OP's diagram and there's a whole page of different wiring configerations before it was corrected to the same suggestion as i did .....no offense meant but made me chuckle

Howdy all!
Panel is all working and just installing the lamp holders for the push buttons... What you rekon to the below? Going to link live in from the start button? Good/Bad idea?
J

 

[Swicade]

I normaly take the live feed (run signal) for a light through a N/O contact on the relevant contactor/relay....that way i always know that if the run light is shineing the contactor is definitely engaged.

X1 = live in
X2 = Neutral

 

[jparker86]

Good thinking, and then otherside to neutral

 

[Richard Burns]

Glad the panel is working, hope the modifications go well.
Thanks for letting us know.

 

[Darkwood]

Also not sure how your fusing all this but indication lamps in your set-up would be wise to have own fused feed so a lamp blowing wont take the rest of the control out and shutting the system down as i highlighted in an early post you have a basic circuit set-up and far from the system that would be classed as a marketable, it falls short in many areas and i strongly suggest you get reading up.... although you have a funtional system now which operates correctly its a crude set-up for the job and this will have knock on effects from early failure of contactors if stat control starts hunting to unecessary down time for minor issues. Designing systems isn't just about getting a working model but also about seeing all the senerio's if any part of the system fails and what can be implemented to keep the system going safely, your use of a 240v control circuit limits you as to how you can expand or add if customer asks for additions or changes.
Dont get me wrong here; its good to see enthusiam like yours but be aware of the complexity of control systems goes way beyond what you know at the moment as ive tried highlighting with your system so be cautious not to jump in the deep end before you have learnt to swim.
Id would invest in a control wiring schematic software programme that let you try your circuits on your computer and will let you operate the virtual design to see what happens long before you put it into practice.

Edit .... just to understand what i mean by forseeing all circumstances then tell me what would happen if you had a leak and lost the water or the system was switch on while drained ????? Massive repair bill comes to mind replacing elements maybe even pump if run dry well you get my drift.

 

[spark 68]

Well put DW,

I was going to say, we only gave the basic outline of the functional blocks and nowhere near a final design, as you say there are many other factors to consider.
I believe Tony also mentioned this a few posts back.

OCPD's just being one of them.

 

[Knobhead]

Bet there's still bits missing from this. I hope the OP has taken time to learn how to read a drawing.

View attachment 14083

 

[jparker86]

Bet there's still bits missing from this. I hope the OP has taken time to learn how to read a drawing.

View attachment 14083

Yes understood. I have learned so much in the past week, and thank each and every one of you who took time to write me a reply and do a drawing. This is what forums are all about, and understand that although my present solution is far from prefect, their is room for improvement.

I am looking at your drawing Tony and already in the process of not just putting 1 level switch in, but two (one for min and one for max).

I am just on ebay getting a PID sensor with SSR.

 

[spark 68]

Hi JP,

Glad you got the basics working.

As DW and Tony have said though, this is far from the finished article.

If you noticed on my drawing, and I think Tony's too, we never marked the control circuits with a L or N, this was because generally it is better not to use 230V for the controls (unless all controls are staying inside the panel), as DW pointed out too, it is usually much better to use say 24V DC for these circuits, this would have made it much easier, for example to add your floats or other safety/inhibit sensors which may be remote from the panel.

Using SELV for the controls makes it far easier to comply with electrical regs, where sensors etc. are to be used outside of the control panel, also consider seperate fusing of the controls, as well as the heater side of things, there are other things too to consider, such as earthing the metal work of the panel, a seperate earth strap to any doors and/or any removable covers/gland plates, IP ratings of the panel, safety and voltage labels. As you can see the list just goes on and on, and this is far from easy, if not impossible on an internet forum.

As Tony and Dw also pointed out, it is a massive legal can of worms to design and build an electrical panel which will have to satisfy a number of different statutory regs, and pass mandatory general electrical safety tests too, from a legal point of view, when offering such items for sale.

I do wish you good luck with your project, and Iam also sure different people will have many different views on the best way forward (many ways to skin a cat).