PID switch advice

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SteveElder

SteveElder

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Evenin all!!

A few months ago I built a PID controller from various bits of info on here and the rest of the net. I’ve used it a couple of times but each time after about an hour the switch (purchased from EBay) has melted and shorted.

I think the wiring is O.K but maybe the switch is faulty... it’s supposed to be rated to 40 amp but given its origin maybe not.

It’s a 4 pole 2 throw switch with an LED light so I can see when the thing is on or off. Does anyone know where I can get a decent one.... assuming of course that is the problem???

Any thoughts,
Steve
 
What size of load is it your switching as it is rated for 9.5kw,but being a PID it would normally be switching a solid state relay with AC/AC switching.
Can you post a link or photo of the switch?
 
Thanks for the response. Pic of the switch below. The PID is running a 3kw kettle via an SSR.
 

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SteveElder said:
Thanks for the response. Pic of the switch below. The PID is running a 3kw kettle via an SSR.
Click to expand...
Those are certainly not rated at 40amp with spade connector's.They are a double pole switch which will isolate both Live and Neutral simultaneously but are designed for switching contactors/relays etc and not for switching high current loads.take a look here
 
Cheers Gerryjo, would this one work?
 

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Hey @SteveElder , just to help. And because i am a little concerned that the switch you are talking about is melting when the element is on for a while makes me wonder if you have it on the wrong side of your circuit?

You should, which means your on/off switch is not having some serious current pass through it look like the below.
Simple SSR and Switch Circuit.jpg

Excuse the noddy drawing but i did it quick on power point before leaving work. This way you are not switching the load when you turn on/off and you will also be turning off your PID and not confusing it and allowing it to try and control when it cannot. Your PID controller may prefer switching the L or the N but that is just down to the model variant.

Make sense?
 
Cheers GerryJo, Hods,

Much appreciated guys! I’ve got the uprated switch on order and check the wiring.

To be honest I think the box the whole thing is in is too small and may also be not helping with overheating so probably needs a complete rewire. Any specific box / box sizes recommended for these things when used as a stand-alone PID rather than a full electric brewing system??

Steve
 
If your switch is melting it's current overload capacity which is the cause.If your gear is current and voltage rated you should have no issues as there should be little heat but ventilation is good....
 
Cheers Gerryjo, gonna have a look tonight and fit the new switch. Will leave the box it’s for now.
 
Hoddy said:
Hey @SteveElder , just to help. And because i am a little concerned that the switch you are talking about is melting when the element is on for a while makes me wonder if you have it on the wrong side of your circuit?

You should, which means your on/off switch is not having some serious current pass through it look like the below.
View attachment 19721
Excuse the noddy drawing but i did it quick on power point before leaving work. This way you are not switching the load when you turn on/off and you will also be turning off your PID and not confusing it and allowing it to try and control when it cannot. Your PID controller may prefer switching the L or the N but that is just down to the model variant.

Make sense?
Click to expand...

So are you saying the on/off switch goes before the PID and not on the output to negate the heat build up and melting the switch? I wanted to bypass mine but perhaps its not advisable. Apologies if i have asked this before.
 
BeerCat said:
So are you saying the on/off switch goes before the PID and not on the output to negate the heat build up and melting the switch? I wanted to bypass mine but perhaps its not advisable. Apologies if i have asked this before.
Click to expand...

Yes because in this configuration the "power" side of the SSR is not being switched by the mechanical contacts that have been burning out. The switch here means you can turn the PID circuit on/off by taking power away form the PID controller. And then you can disconnect the actual element "power side" by using a normal MCB rated to the element as you would normally.

That's where the issue is, these small switches are not designed to have a constant 13+ amps going through them hence why they melt as they get hot.
 
Hoddy said:
Yes because in this configuration the "power" side of the SSR is not being switched by the mechanical contacts that have been burning out. The switch here means you can turn the PID circuit on/off by taking power away form the PID controller. And then you can disconnect the actual element "power side" by using a normal MCB rated to the element as you would normally.

That's where the issue is, these small switches are not designed to have a constant 13+ amps going through them hence why they melt as they get hot.
Click to expand...

That makes perfect sense now. When you have a moment could you put up a link for a suitable MCB please. I am running 2.6kw.
 
BeerCat said:
That makes perfect sense now. When you have a moment could you put up a link for a suitable MCB please. I am running 2.6kw.
Click to expand...

I would say that you should be using 2.5mm cable (diameter per L and N cable) with a 16amp MCB on the live (https://www.screwfix.com/p/british-general-16a-sp-type-b-mcb/35253) i assume you are using this in a panel you have built? So the one in the link is DIN rail mounting.

Your 2.6KW single phase element is pull 11.5amps at full load so you need to go up to a 16amp MCB.

I am also assuming that you have an RCB protected supply and that the kettle that the element is fitted to is earthed back to protect you and the equipment form any short to earth?

Hopefully that helps.
 
I've used one of these rotary switches in the past. Big, clonky, fiarly waterproof and designed for panels.
16A rated too and as many contacts as you want.
https://www.ebay.co.uk/itm/CA10-AC-...307167?hash=item2ac7c696df:g:pAsAAOSwwptdVdvK
s-l1600.jpg


I've just built my first kettle using similar switches to the ones you've shown, but they are switching individual elements of 1kW each and are rated at 16A 250V. plus have waterproof covers if needed.
https://www.ebay.co.uk/itm/09029-Mains-Snap-In-Illuminated-Rocker-Switch-15A-250V-4PIN-DPST-OFF-ON-I-O-Sign/273782297956?ssPageName=STRK:MEBIDX:IT&var=573433496865&_trksid=p2057872.m2749.l2649

My SS Relay got a bit hot even with mounting it to the stainless outer of the kettle on it's heatsink and wouldn't trust it in a small plastic box without a fan. It really needs a larger heatsink and a metal case just to help thermal dissipation.
 
Last edited:
Hoddy said:
I would say that you should be using 2.5mm cable (diameter per L and N cable) with a 16amp MCB on the live (https://www.screwfix.com/p/british-general-16a-sp-type-b-mcb/35253) i assume you are using this in a panel you have built? So the one in the link is DIN rail mounting.

Your 2.6KW single phase element is pull 11.5amps at full load so you need to go up to a 16amp MCB.

I am also assuming that you have an RCB protected supply and that the kettle that the element is fitted to is earthed back to protect you and the equipment form any short to earth?

Hopefully that helps.
Click to expand...

That looks good. I don't use a DIN rail at the moment as i didn't know about them when i built this. I used heavy duty terminal blocks. Going to redo the wiring at some point though so will switch to one of them.

My fuse board has a master RCB and one for each circuit. Are you saying i should have one on the plug as well? The earth on the kettle goes directly to the plug if that is what you meant? Cheers
 
Last edited:
Richie_asg1 said:
My SS Relay got a bit hot even with mounting it to the stainless outer of the kettle on it's heatsink and wouldn't trust it in a small plastic box without a fan. It really needs a larger heatsink and a metal case just to help thermal dissipation.
Click to expand...

I just bought a 12v ac to dc converter and small fan for mine. I have ran it successfully though for many many brews without but i like the idea of adding it as a precaution.

I am using one of the switches you linked for my pump. Feels nice and solid.
 

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