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General => Wiki and forum discussion => Topic started by: greasemonkey on June 13, 2013, 08:41:23 PM
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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?
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Is this what you are looking for
http://www.graham-laming.com/bd/thermostat/thermostat.htm
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Aye, cheers. Sure I saw it around here somewhere as well, but that is basically what I want.
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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.
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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.
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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.
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I am with you on that Jim everything should be designed to be fail safe
where ever possible
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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.
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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.
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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.
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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.
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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.
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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"
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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).
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Don't think you have ... it'll be limited to quite a low max temp.
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Seems I've overthunk and and over complicated things (again).
Not really, remember LOTS of peeps read these posts so a cautious approach is best, ask the question.
New thermostats are set at a relatively low temperature, a blob of silicon on most, I wind the stat up to max remove the cap and knob, spin the knob back 90deg and rebuild.
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Do they not have a high temperature trip now-a-days?
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Do they not have a high temperature trip now-a-days?
Yes they do, that's why it's best NOT to remove the thermostat form an immersion.
If any or all things fail the power is cut at the 95C mark.
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Just done it. Basically, there are two terminals in the box on the end of the thermostat. The live goes into one terminal. There is a set of points. The one side of the points is on a bi-metal strip. The adjuster controls the pressure on the bi-metal strip, and thus the temperature before it cuts out. As far as I can tell, undoing the adjuster, and releasing the pressure on the strip will give the highest temp.
The other terminal is power out to the one side of the element, there is another set of points on a bi-metal strip. These are not adjustable, so I guess that is the max temp cutout.
Now the Mig has run out of gas. Grrrrr.........
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Now the Mig has run out of gas. Grrrrr.........
I got loooooaaaaaaads o'gas thank you.
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The other terminal is power out to the one side of the element, there is another set of points on a bi-metal strip. These are not adjustable, so I guess that is the max temp cutout.
Is it too late to get photos of what you've done? We could put a wiki page together with a strong rider I guess.
It'll be interesting to know at what temperature the additional cut out operates. If you can ascertain that it would be good info for the page.
Similarly if you have any info or photos, Jim we could include those.
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I can take some photos of the inside of the stat. No trouble.
I guess once its up and running, I might be able to tell where the cutout operates. No problem.
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I can take some photos of the inside of the stat. No trouble.
I guess once its up and running, I might be able to tell where the cutout operates. No problem.
Depending on the make of stat the cutout could be between 85 and 95. I can get my reactor up to 95 without a problem.
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It's woth adding that not all immersion heaters have the cutout built into the stat,
some have a seperet cutout mounted on the heater backplate.
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Roger that. I'm hoping to write a wiki article. Remind me to include that. Sometime around Christmas..............
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Roger that. I'm hoping to write a wiki article. Remind me to include that. Sometime around Christmas..............
2014 or 2015 ?
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Just every Christmas, till it gets done.