# Gaggia Classic Pro 19 PID wiring for steaming



## Muratozt (Mar 27, 2021)

Hello, I am new to Gaggia world with my Classic Pro 2019 model and on the way of installing DIY PID for both brew and steam functions. I managed to succeed on brewing side with DA SSR however I could not find an appropriate diagramm for adding my AA SSR for steaming alarm function. I found a manual in this forum which seems to have been created by a Rex C100 supplier however the Gaggia described there is an old model and the manual explains only the connections but not the logic. Therefore I can't adapt it to my system. My PID unit is XMT-7100 which has single SSR and a single alarm function. Alarm is just a switch that turns on and off and has no signal output unless a voltage is given. It is on until the High alarm point. Can anyone help me with a diagram or at least explain the logic how to do the wiring?


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## PACMAN (Feb 11, 2021)

Wiring diagram (not sure if it is the same for 2019 models though) is here: https://coffeeforums.co.uk/topic/18238-diy-pid-steam-and-brew/page/17/?tab=comments#comment-579068

It took me some time to understand how it all works and I'm not totally sure I can explain it without going round in circles. The PID allows, via the pt100, the temp to be controlled. When the steam switch is turned on, I think it 'bypasses' the PID pt100 control aspect until it reaches the AL1 temp. At this point, it 'alarms' and turns off the power to the brew SSR. Once the temp drops to the AH1 temp, it allows the brew SSR to switch back on again, thus keeping the steam temp up. One of Mr Shades posts, gives: https://coffeeforums.co.uk/topic/51214-ah1-and-al1-on-mr-shades-pid/?do=findComment&comment=733856



> Mr Shades post said: As was said before, just use two values 0.1c apart : so AH1 of 136.9 and AL1 of 137.0
> If you want more steam power then increase both by the same amount, so go to 144.9 and 145.0 for example.


 or something like that...


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## Muratozt (Mar 27, 2021)

Hello, thanks for help. I have checked the diagramm, it looks right. However I still have some concerns and questions not answered:

My settings for PID unit are already done. AH 144, AL 145 Celcius are OK to keep the steam temp in required position for me. Already checked and alarm is working correctly. Shutting of (switch open) at 145 Celcius and turning on back on (switch closed) 144 Celcius. My problem is making sure about connection and wiring:

I have seen Rancilio Sylvia's diagram. Same as the one for Gaggia, it shows a modification for brew and steam circuits from series to parallel connection. Normally they are in series, between them there is live power coming from steam switch to create a bypass over brew circuit. When you modify Sylvia (http://www.skenedesign.com/Silvia/) the way is little different than for Gaggia above, because there is a direct connection to heating element. Direct connection to heating element is required for brew circuit to bypass steam circuit while brewing (during brewing, steam circuit is closed because SSR AA is not powered). But Gaggia has no direct connection to heating element and wirings need to be done in a different way. This is where I was stuck.

Until now I have seen two different options:

A-Mr Shades option which shows SSR DC output to brew thermostat cable ends and SSR AA output to steam thermostat cable ends. I have seen this in a video but I don't know what he does for the rest, maybe his XMT 7100 unit is modified to give AC voltage to alarm output making AA SSR always on. Thus brew and steam circuits can preserve their position in series connection. But as I am not sure, it is a point of confusion for me. (Is keeping AA SSR always on not a problem of over heating?)

B-Your diagramm that shows complete parallel connection between steam and brew circuits. What I understand is, both SSR output's are connected in parallel from beginning side of heating circuit (one side of brew thermostat cable end coming from on-off switch) to the end side of heating circuit (one side of steam thermostat cable end going to heating element). Steam switch live which normally creates bypass for steaming is connected to the AA SSR's input. According to a user in Gaggiausersgroup (http://www.gaggiausersgroup.com/index.php/topic,724.msg7025.html#msg7025) this connection can be done using the free cables left from brew or steam thermostats. However in the REX C100 manual (thanks to *NJD1977* for sending me https://docs.google.com/document/d/1YKahCYmW8_O8aR2HE877M7nzGrYzTuF3Lse6WfiQsog/edit) three different connections are made to the brew and steam switches which don't mention this option and confuse me. I also can't copy the connection there because my unit is different than the one described there (Classic Pro 2019)

I am not an electrical engineer and don't want to burn my unit.Therefore I need someone to tell me which way to go in terms of connection logic. My questions as below for forum user's kind help:

1- Why does Mr Shades use a different option than connecting SSR's (therefore brew and steam circuits) in series? What happens when both brew and steam switches are in close position? Any chance for short circuit?

2-In Rex C100 manual, are the extra connections to brew and steam switches for giving neutral and live to alarm section? Why is there a need for a third connection to switches if steaming bypass cable that was previously connected to thermostats is already free?

Both questions are important for me because I feel the need to make sure I understand every detail clearly. Only then I can move safely.

I know it looks a bit complicated but I hope there will be someone to read this title until the end and will be kind to answer me.


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## PACMAN (Feb 11, 2021)

I can't help much more as I don't know the specifics of the 219 model, but the pre 2105 model power switch details are in this post: https://www.reox.at/gaggia/hacking/ You might be able to cross check with your switch and see if anything on that page helps you.


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