PID problem.

Elcarajillo

Whilst awaiting a capacitor for my Verona (still waiting) I started using my faithful old Classic with Mr Shades PID.

Coffee coming out very tasty, then coffee temp started declining 93 - 88 as pour progressed.

Checked parameter settings all OK. Checked PT 100 OK, reseated with fresh compound.

Tried M/ch again temp slow to reach 88, tried steam, very rapid rise to boiling/ kettling sound. switch off. This with RO water. Conclusion PID kaput ?? Any electronic experts have other thoughts ? Moka pot not so tasty😝

Petre

So it did not do this before? As you pour, it’s normal to get some temp drop on the PID probe but the water at the brew head should be at the right temp.

DavecUK

@Elcarajillo I would expect exactly that behaviour due to the very small boiler of the classic as cold tank water rushes in…I don’t believe there is anything wrong. As @Petre said, the effect on brew temp won’t be as large…although there will be some effect.

Elcarajillo

This is far from normal, the usual drop at pour would be one max two degrees and has always been consistent before recovering. When switching to steam mode it would rise steadily up to 137 /140 deg and stabilise at that.

Thanks for thoughts.

mobius

PID on an ECM Classika (and I suspect other similar) will also drop around 6 degrees, in my own experience, across a shot. That isn’t the drop at the pour, just the boiler.

I don’t know anything about the Gaggia PID MOD, but looking online, it seems that the same behaviour should be expected 🤷🏻

DavecUK

mobius I don’t know anything about the Gaggia PID MOD, but looking online, it seems that the same behaviour should be expected 🤷🏻

It would be hard to explain why the same behaviour wouldn’t happen in such a small boiler, unless PID placement did not allow it to correctly measure brew boiler water temperature OR, the PID doesn’t react as we expect it to. For it not to show a temperature drop breaks the laws of physics.

Dusk

Perhaps worth getting in touch with Mr Shades as he should know if that behaviour is to be expected or not

Elcarajillo

Dusk Thanks for that, I had thought that would be my next step.

Petre

the drop you see in the boiler (and pid read) also is higher if the machine is cold. you heat up the machine pretty good and should not drop that much.

Elcarajillo

AN UPDATE. Doing various checks found that the PID supply to the brew boiler SSR is only 2 volts input says 3 32volts DC.

Steam boiler SSR supply says 80 -250 volts AC. output reads 6 volts ?

Any thoughts ?

DavecUK

Elcarajillo Either the SSR switches or it doesn’t, so that’s probably a red herring. Output of the SSR is only really realised when there is a load.

Petre

Elcarajillo did you measured that when the heating is supposed to be fully on (ie cold machine)? on input you need to measure DC

Output behaves like a switch so in AC you should have 0v when ssr is ON and 240AC when is off.