MCE - replace pressurestat with PID

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#1: Post by Bibib »

Hello, everybody! I have a mecoffee PID and I'm trying to figure how to machine it's an older (one group, one boiler) MCE espresso. The boiler have 3 separate heating resistances (1 resistance-1 wire) and other 3 (coupled together - 3 resistances- one wire). All the wires are going in the Sirai pressurestat. Maybe somebody have an idea about the way to go ( I'm thinking to put all wires together maybe in a separate socket and go with 1 wire to the PID for temperature control). Of course next steps are a challenge to...Any help? Thanks!

Bibib (original poster)

#2: Post by Bibib (original poster) »

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#3: Post by Nunas »

This can definitely be done. But, I don't understand the problem. The MeCoffee is a complete conversion package, including everything you need.

For a PID to replace a pressurestat, you need a temperature sensor, the PID and a relay (usually solid-state these days). The MeCoffee PID conversion contains all of these. As for the heater wiring, nothing needs to change; the heater is currently switched by the SIRAI, and it will now be switched by the MeCoffee. The only possible problem I foresee is that perhaps the heaters of your machine exceed the capability of the MeCoffee module. If so, this is easily remedied by adding a relay. The output of the MeCoffee is wired to the coil on the relay (which draws very little current) and the switched contacts of the relay are used to activate the heater, just as the SIRAI does now.

What am I missing?

Bibib (original poster)

#4: Post by Bibib (original poster) »

I didn't know it's possible to wire the mecoffee directly in the relay on the switched contacts. Do I need to completely disconnect the pressurestat? Can I connect the power supply to in the relay? What about the pump - valve control? How to wire to control steaming? Thanks!

Bibib (original poster)

#5: Post by Bibib (original poster) »

My relay...

Team HB

#6: Post by JRising »

If you want to keep the elements 3 phase, you'd probably have to replace the pressostat with a 3 pole contactor and have the PID controlling that.
Wouldn't you?

Bibib (original poster)

#7: Post by Bibib (original poster) »

Hmmm...really don't know which is better...

Bibib (original poster)

#8: Post by Bibib (original poster) »

...about what contactor type are you thinking? NO, NC?

Team HB

#9: Post by JRising »

Well, if the PID's going to be giving an ON signal for heat, then it would make sense to use a NO contactor, but I suppose you could make either work. Since you're weirding the machine up pretty thoroughly, there's really no longer a "the only way" to do it once you're changing things to this degree.

Although, I may be wrong about it all after re-glancing at your Control Box picture. I'm not sure the element is wired three phase, now.
Making the assumption that the yellow wires jumped together at the box are 2 of those element wires(to p-stat currently of course), it seems to me that maybe it's been rewired single phase and uses only 2 elements in parallel. Sorry if I have said anything misleading, I don't have the machine in front of me.

Bibib (original poster)

#10: Post by Bibib (original poster) »

At the P-stat...