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Captain_Crema wrote:Steam from the grouphead? If it's not coming out under pressure I think it's likely to be water vapour (the two aren't quite the same). If the grouphead's over 100 degrees C the water will come out boiling.
Captain_Crema wrote:Modifying the thermocouple is fairly straightforward if you're careful, but I need to take pictures to explain.
Captain_Crema wrote:Suffice to say that once done it's easy to attach to the boiler. You don't need to take the old thermostat off, either. All will be revealed presently, when I have taken some pictures. I'm proposing to have the PID in a separate case with its own mains lead and only low voltage wires going into the Classic. (thermocouple and SSR control). This is the safest way.
Captain_Crema wrote:The SSR would therfore be mounted inside, using the stainless case as a heatsink. In order to avoid drilling holes I will mount it using the grille at the back although it might need to be relocated if the heater wires don't reach. It may be necessary to insulate the boiler (there is a thread about this) in order to keep the case cool so the SSR can lose excess heat, but right now I don't know about the heatsink requirements of the device.
Captain_Crema wrote:
The thermocouple can be attached to the boiler body by trapping it between the boiler and the earth tag, which is screwed in. This is how I measured the threshold temperatures. An alternative would be to unscrew the thermostat (it's the one on the left hand side of the boiler, not the top) and insert the thermocouple into the screwhole. It may be necessary to use some heat transfer compound here (there's some on the mating surface of the thermostat - it's like a white cream).
Captain_Crema wrote:
Note that the thermostat body does not make contact with the water, it measures the boiler body temperature. In other words, the screw hole doesn't penetrate the boiler so there is no chance of leakage if you get it wrong.
Captain_Crema wrote:The most important thing for me (apart from safety, of course) is to ensure that the operation is reversable if I find it doesn't work well enough or I want to sell the machine. I think if I can get one of those Gaggia plinths (with a drawer for a knock box) I could butcher it and fit the PID in there. It would look neat and be electrically safe, but it's a way off for me. I need to test it out first.
The temperature cycle is between 94 at its coldest and 113 at the hottest (and I can see it is overshooting quite a bit, as the heater turns off way before the temperature stops rising).
ben_edwards wrote:Yes I agree... if the boiler is above 100 deg C steam / water vapour will be produced. I have never seen any differentiation between these two terms: As far as I was aware the vapour (definition: gaseous state of a substance) of water is steam. Could you clarify/provide a source if I'm mistaken.
Now thats bad luck. You did read the specs prior to purchasing, did you?
...PID outputs 12V DC...
I was asked before about the control voltage range on these, and as I have no data on them I had to conduct an experiment.
My test rig used a 30V dc 3A current-limit supply as the load, using the relay to short out the supply.
I then tried a variety of control voltages and found that 5V dc was no good, but 9V derived from a rechargeable PP3 battery (!) worked every time.
This is of course a bit empirical, but hopefully indicates that not all is lost.
ben_edwards wrote:...PID outputs 12V DC...
its 10V DC according to the manual. Have you measured with a multimeter or was this a mistake?
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