Wiki page on Immersion heater thermostat?

[greasemonkey]

I thought there was a wiki page on by passing the thermostat on an Immersion heater. I can't find it. Anyone know, or was it in the forum?

[oakwoodtv]

Is this what you are looking for
http://www.graham-laming.com/bd/thermostat/thermostat.htm

[greasemonkey]

Aye, cheers. Sure I saw it around here somewhere as well, but that is basically what I want.

[Julian]

That page of Graham's is not really about bypassing the thermostat, but recalibrating it.

The more widly accepted practise is indeed to bypass the thermostat and use an SSR and PID plus a thermocouple to sense the temperature.

I think the wiki could do with more info on electrics and controls, but there is that safety aspect to consider.  I think in these litigious times contributors are wary of committing to putting anything on paper.

I helped a couple of chaps on the VOD put together a PID and SSR combo, but then got criticised for suggesting that 240v be used in a control circuit.

It would be nice to have an electrics/electronics expert as a regular contributor to the wiki, that way we would know the correct way of presenting things.
 

[greasemonkey]

Rodger dodge. I can see the litigation side of it. No worrys anyway, I'll soon work it out. Just wondered why it was not there. I can understand now.

[Jamesrl]

I would never advocate bypassing an immersion thermostat, belt and braces so to speak.

I run a PID via an SSR but still have the thermostat in place, I like to have that over temp. cut out siting in the background.

[oakwoodtv]

I am with you on that Jim everything should be designed to be fail safe
where ever possible     

[Julian]

I would never advocate bypassing an immersion thermostat, belt and braces so to speak.

I run a PID via an SSR but still have the thermostat in place, I like to have that over temp. cut out siting in the background.

If you don't bypass the immersion's thermostat, you are limited to, I think it's around 65°C.  To my way of thinking bypassing it is far safer than trying to reset it.  Most PIDs have a set of alarm contact which can be set up as a high temperature shut down.  That way you get belt and braces, but with a safely adjustable temperature.

[Jamesrl]

If you don't bypass the immersion's thermostat, you are limited to, I think it's around 65°C.  To my way of thinking bypassing it is far safer than trying to reset it.  Most PIDs have a set of alarm contact which can be set up as a high temperature shut down.  That way you get belt and braces, but with a safely adjustable temperature.

The reset safety is set to approx 95C not 65.

[Julian]

If you don't bypass the immersion's thermostat, you are limited to, I think it's around 65°C.  To my way of thinking bypassing it is far safer than trying to reset it.  Most PIDs have a set of alarm contact which can be set up as a high temperature shut down.  That way you get belt and braces, but with a safely adjustable temperature.

The reset safety is set to approx 95C not 65.

It's the resetting bit that would concern me.

[greasemonkey]

I can certainly understand the need for some kind of cut out to avoid over heating, good idea.
So would I be right in thinking that in a heater there is a thermostat, set to around 65c, which is either variable, or needs bypassing, and then there is a cut out at around 95C, which is worth leaving in.

Being as its chucking it down with rain, I will probably go and have a look today.

What about a Wiki page just explaining the internals of the heater, and how they work, with no suggestions of what to do to it to modify it. Anyone keen enough to build a processor, should be able to work it out anyway.

[Julian]

I haven't looked at a recent immersion heater, but I believe you are right.  There's a thermostat with an adjustable setting that won't go too high, probably 65°C (but I'm guessing the figure).  Then I believe as a recent introduction, there's also a cut out that resets with a tiny button which will be a fixed temperature, not sure what that is.

Best bet is to get your hands on one, see what it comprises of and then decide what route you're taking to modify it.

[julianf]

I have a PID and the thermostat in the immersion housing / inline heater.


I calibrated it by turning off the flow, and turning the PID right up (ie out of range) so it was always on.

I then shon my IR thermometer on the housing of the inline, and, when it got close to about 100c ish (i cant recall the exact figure i set it to) i dialed down the stat so it switched off.


This way i know that, if the PID ever fails in an ON state, the system will be limited by the stat in the heater itself (all be it pretty high) rather than just running away.  In normal use, the stat on the element is always "made"

[greasemonkey]

Well i've just had a look and it all seems simple. There is just a dial, exactly as the one on the GL site.
I'll just wind it right up and see what happens.
Seems I've overthunk and and over complicated things (again).

[Julian]

Don't think you have ... it'll be limited to quite a low max temp.