Mini Digital Temperature Controller

[norstar]

Hi guys.

I've been coveting everyones temperature controllers and have bought an STC-1000 and two plugs, but as an accountant, not a Sparks, I'm confused about the wiring and electical components and hope someone can help.

Wiring: RS Electrical sell 3 core in .75mm, 1mm and 1.5mm widths. Do people just buy the thickest, remove the sheath and use that to wire the plugs and controller together, and use the rest to connect the box to the mains? Or would this do it: http://www.maplin.co.uk/3-core-13a-main ... code=XR10L

The cable connectors: they're all in different ratings. 30A, 15A.... Which one do I need for the internal connections? Will a 15A one like this do: http://www.maplin.co.uk/terminal-blocks-42654

Think the rest makes sense but we'll see!

Thanks...

[46philh]

Mine is only for the fridge and 60 watt tube heater so just used some thick 3 core cut from the roll at wilko the stripped off the white out shield.

[troublebrewing]

Hi guys.

I've been coveting everyones temperature controllers and have bought an STC-1000 and two plugs, but as an accountant, not a Sparks, I'm confused about the wiring and electical components and hope someone can help.

Wiring: RS Electrical sell 3 core in .75mm, 1mm and 1.5mm widths. Do people just buy the thickest, remove the sheath and use that to wire the plugs and controller together, and use the rest to connect the box to the mains? Or would this do it: http://www.maplin.co.uk/3-core-13a-main ... code=XR10L

The cable connectors: they're all in different ratings. 30A, 15A.... Which one do I need for the internal connections? Will a 15A one like this do: http://www.maplin.co.uk/terminal-blocks-42654

Think the rest makes sense but we'll see!

Thanks...

Not trying to be patronising, but sounds like you should consult an electrician. If you are confused now, what about a bit further down the line? That said, yes, you can use the 3183, as long as it is stranded; don't, for heaven's sake use solid core for ring mains. As for your connectors, use the one appropriate for your cable. If you have 18AWG wire powering your STC, then use 1A fuse for supply, but other connectors use 15A. What enclosure are you planning to use? How much room do you think you'll have to play with to fit in your wiring?

[Kev888]

I've been coveting everyones temperature controllers and have bought an STC-1000 and two plugs, but as an accountant, not a Sparks, I'm confused about the wiring and electical components and hope someone can help.Wiring: RS Electrical sell 3 core in .75mm, 1mm and 1.5mm widths. Do people just buy the thickest, remove the sheath and use that to wire the plugs and controller together, and use the rest to connect the box to the mains? Or would this do it: http://www.maplin.co.uk/3-core-13a-main ... code=XR10L
The cable connectors: they're all in different ratings. 30A, 15A.... Which one do I need for the internal connections? Will a 15A one like this do: http://www.maplin.co.uk/terminal-blocks-42654

Hi,
Yes, take care of yourself and don't do anything if you're not sure how to do it safely.

The ratings you 'need' depend on what you're building this for, but I'd suggest that you may as well go with cable and connectors which will let the controller be used to its full rating - it won't cost much more and allows for maximum flexibility.

The STC-1000 has a max contact rating of 10Amps or 2.4kw (if you were wanting to control more than this - say 3kw immersion element - or awkward inductive loads like big motors then some sort of external relay would be needed but thats a bit more advanced). The size of cable you will need to carry 10Amps has conductors equivalent to at least 1 square mm; I'd personally go with 1.25 square mm or 1.5 square mm, especially if there are longer cable runs involved or if the cable may be covered by stuff. You can use the same cable for wiring inside the controller's box - as you say the external sheathing can be stripped off for that. That maplins cable would be fine, but if you need a few meters you can find it quite a bit cheaper in small coils - e.g. from DIY sheds (like here)

The connectors should also be rated to 'at least' 10A, so that 15A one will be fine. You may want to also use some with higher ratings if you have a few wires to connect into the same connector simply because they're made to take bigger wires, but don't use massive ones for small wires as the wire can escape through the larger gap around the screw.

Again, take care of yourself with this and post lots of questions if you're unsure.

Cheers
kev

[norstar]

Sorry - should have said shouldn't I? I'm using the junction box that most other people seem to use - IP56 I think. The unit is to switch a standard undercounter fridge on and off, and power a tube heater - sounds like 60w is ample.

Don't get me wrong, I've wired things up before and can follow a wiring diagram, but the finer points such as the specific loads and ratings escape me.

If it's okay with you then, I'll post the results after I've put the stuff together and perhaps someone can run their eye over it to comment if I've done anything drastically wrong before I flip the switch and knock out Croydon's grid...

[troublebrewing]

It's ok with me

Posting of pictures is definitely a plus point too, btw.

Take your time and make everything as neat a possible.

[norstar]

Confused. Got my components and I'm happy with most aspects of this and have started my build, but the different examples on this thread appear to be wired differently in the "power in" socket of the STC1000:

This was someone elses posted example - the Neutral wire is furthest left, then live and STC1000 switches live wires into the sockets:


This is pdntc's build from his blogspot - Live furthest left, then neutral and STC1000 switches live wires into the sockets (altho Pdntc did say he ran out of brown wire for the appliance switches!):


This diagram suggests that the first pic is correct but pdtnc is still posting so he can't have blown up:


Is the power supply into the STC1000 reversible or is one way correct?

[troublebrewing]

Correct. It doesn't make any difference which one goes where.

[norstar]

Right then!

Is there any chance someone in the know could run an eye over this? Basically I've run both socket neutrals and both lives from the STC-1000 into a 30a connector before taking a wire from those connectors to the main one on the left where the mains will come in. In the end, I used wire stripped from the flex cable from my old washing machine plug lead - looks a little thinner than the wire I bought so may be 1mm as opposed to 1.5mm. Assume if it powered a washing machine it'll be good for a fridge/60w tube heater tho?



And while there's electrical gurus looking, anyone have any idea how to bypass this fridge thermostat?



The unit nearest the pic on the right is the door switch for the light, the unit on the left is the thermostat temperature controller. The white cable in the background goes to what appears to be a sensor in the freezer box, and the grey cable goes into the compressor at the back. Slightly confused what that black cable does!

[Kev888]

Hi,

the STC setup looks correct to me - though I'm more of an ATC user myself so please chip in anyone if you can see anything I missed. (I'm assuming the senor will be added later..) Yes I'm sure a cable suitable for a washing machine will power a 60w tube heater okay. Good stuff!!

That thermostat isn't quite like mine and i can't make the wires out too clearly, but i'd imagine the black wire may go to the fridge's motor (as well as a blue one and an earth)?

BTW, unless you're using temperatures at or below normal fridge temperatures you don't really need to bypass the sensor - set it to its coolest and (because the fridge will always be warmer than the thermostat wants) it will automatically try to cool whenever the STC switches power to the fridge.

Cheers
kev

[AnthonyUK]

I used wire stripped from the flex cable from my old washing machine plug lead - looks a little thinner than the wire I bought so may be 1mm as opposed to 1.5mm. Assume if it powered a washing machine it'll be good for a fridge/60w tube heater tho?

I only used 1.5mm cable in case it was ever needed to control something upto its 10A rating.
If you'll only ever use it for that fridge and heater then it will be fine.

As mentioned but worth reiterating - NO NEED TO MODIFY THE FRIDGE
These temperature controllers work by switching the fridges power (and the heater, through the mains supply) on and off when the set temperatures are reached.
Bypassing the fridges thermostat in this instance is achieved by controlling the power supplied to the fridge via the temperature sensor connected to the external unit.

[Aleman]

And while there's electrical gurus looking, anyone have any idea how to bypass this fridge thermostat?

OK The Live comes in via the Brown Wire, and goes to the thermostat, which 'switches' the power to the compressor. 'Switched Live' will be taken to the compressor via the Black Wire. To bypass the thermostat simply connect the Brown wire from the stat to the black wire from the stat . . . Job Done

Disclamer: You are playing with mains voltage here, make sure you do so safely, ensure all terminals are not exposed, and are water tight. If you do not know what you are doing get a competent person to do it for you.

[Kev888]

Excellent - thats what I was expecting too; just didn't like to say for definate from the photo - mine looked quite different and had black and white wires; the joys of standardisation!

Cheers
Kev

[norstar]

Super! Thats what I thought. I would leave the thermostat alone but it's gone wrong, hence why I acquired the fridge!

Right, shall have a go and switch on with a broom handle. Thanks for the advice guys...

[Samahon]

I had made a couple of these a few months ago for some friends. Friends abroad wanted a simple looking wiring layout so I done this for them...

[img]http://i753.photobucket.com/albums/xx18 ... ngDiag.jpg[/img]

Great site you have here...