# Gaggia Classic PID wiring diagram - DIY PID



## GiovaD (Jan 18, 2021)

Hello everyone

First of all I wanted to say that I have already done quite a lot of research about how to mount a PID on a Gaggia Classic and I am aware that it has already been spoken many times on this forum, for that I am sorry for bringing up a new thread.

I was now doing quite some in depth research about how to mod my Gaggia Classic 2002 with a PID, and I wanted to do it DIY because my budget is limited and also because I love the challenge of having to set it up myself and to learn new things.

I have now looked into the mechanics of this machine, I basically have studied every component of it and I want to figure out exactly how to mount the PID before actually going ahead and mounting it. That's why I have made a Diagram of the electronics of the machine on Illustrator, to figure out what to do.

Here is a pdf of the original wiring diagram and the modified one with the PID, I am planning to use the Rex C100 and 2 SSRs both for steam and brew. I would like to ask you if I'm doing anything wrong, it looks to me as something is wrong, especially with the heating element on the right side of the boiler..

Please could anyone point out to me if it's more or less correct? (I uploaded an image and a pdf file for you to check it out)

P.S. you can also refer to the original wiring diagram from Gaggia to understand how it works and how it's drawn
View attachment Gaggia PID_scheme_pdf.pdf


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## Steve_M (May 26, 2018)

Why would you need 2 SSRs when there's only 1 boiler?

The temperature probe would feed the PID, the SSR controls the boiler and if you tie into the steam switch, that should trigger the PID to use a higher setpoint.


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## AndyDClements (Aug 29, 2016)

The PID actually only attempts to achieve one temperature (brew temp), the second SSR bastardises a secondary output in order to achieve the second temperature (steam temp). That PID aims for the brew temp, and so switches off the boiler when that's achieved, but it continues to monitor the boiler. When the second SSR is in use, we then use the steam switch to re-route power and so continues to heat the boiler until the PID raises an alarm that the boiler is over the set warning point, and that output is used as the way to control the second SSR.

The need for two SSRs is the equivalent of needing two switches in the original system.


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## GiovaD (Jan 18, 2021)

AndyDClements said:


> The PID actually only attempts to achieve one temperature (brew temp), the second SSR bastardises a secondary output in order to achieve the second temperature (steam temp). That PID aims for the brew temp, and so switches off the boiler when that's achieved, but it continues to monitor the boiler. When the second SSR is in use, we then use the steam switch to re-route power and so continues to heat the boiler until the PID raises an alarm that the boiler is over the set warning point, and that output is used as the way to control the second SSR.
> 
> The need for two SSRs is the equivalent of needing two switches in the original system.


 That's a fantastic explanation! thank you about that. I myself was not sure as to why I would need two, but this explains it quite good.

So would you say this kind of scheme I put together would work? I am not sure about a few things: the bottom pin at the brew switch connects directly with the heating element, without going thru the stock 130°C thermal switch.. I don't know if that's the correct way to do that.

I have modified this drawing to show you what I mean:


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## Muratozt (Mar 27, 2021)

Hello, I have a double SSR diagramm for Gaggia Classic which I can share with you. (SSR DA for brew, AA for steam alarm function). I just could not make sure how to connect the brew SSR's one end to heating element physically. Maybe we can share each other about knowledge and experience.

In summary we need to wire steam and brew SSR circuits in parallel to each other instead of series. If you want to control only brew side with PID, connecting brew thermostat ends to SSR output does the job simply. However if you add SSR circuit to steam side as well, one end of brew thermostat has to be removed and connected directly to heating element because there is no more ability in the system to bypass steam circuit which will be closed until steam button is powered.


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## thinkertinkering (Oct 1, 2021)

Muratozt said:


> Hello, I have a double SSR diagramm for Gaggia Classic which I can share with you. (SSR DA for brew, AA for steam alarm function). I just could not make sure how to connect the brew SSR's one end to heating element physically. Maybe we can share each other about knowledge and experience.
> 
> In summary we need to wire steam and brew SSR circuits in parallel to each other instead of series. If you want to control only brew side with PID, connecting brew thermostat ends to SSR output does the job simply. However if you add SSR circuit to steam side as well, one end of brew thermostat has to be removed and connected directly to heating element because there is no more ability in the system to bypass steam circuit which will be closed until steam button is powered.


 @Muratozt you may refer to this reference i've compiled :

https://www.coffeeforums.co.uk/topic/18238-diy-pid-steam-and-brew/?do=embed&comment=863413&embedComment=863413&embedDo=findComment


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## newdent (Feb 20, 2021)

Also, to anyone PIDing soon (as I intend to), I saw this post of a chap that uses a dual SSR unit from Aliexpress that is basically two SSRs built into a unit the size of one standard SSR. Looks great for saving space inside the machine and cheap too. He also has details on many other mods on his blog, I found the blog when looking for details on the steam valve modification:

https://gaggiaclassicmods.blogspot.com/2020/10/podwojny-przekaznik-ssr-25a.html?m=1

In Polish but chrome auto translate does a good enough job to get the gist.


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## groundpilot (10 mo ago)

GiovaD said:


> Hello everyone
> 
> First of all I wanted to say that I have already done quite a lot of research about how to mount a PID on a Gaggia Classic and I am aware that it has already been spoken many times on this forum, for that I am sorry for bringing up a new thread.
> 
> ...


My temp probe has 3 wires..? 1 red 2 white..? Any idea which colours go where on the Rex?


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## TomHughes (Dec 16, 2019)

I still can't get my PID to do the steam/alarm function. 

What settings are people using on the rex?

I fear there may be something up with my wiring, I've followed the instructions above.

I also think it could be my PID that's the issue as I bought the _MAN_ model, so had to remove one of the internal relays. I ended up removing both, then putting on the one for the Alarm back in, which I think is where the problem lies. 

I'm thinking of getting an XMT7100 but I can't find a source for one?


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## Bhodgson (11 mo ago)

The XMY7100 isn’t sold in the U.K. though I believe you can order from China. You’ll pay 20%vat on top of the sale price.


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## groundpilot (10 mo ago)

TomHughes said:


> I still can't get my PID to do the steam/alarm function.
> 
> What settings are people using on the rex?
> 
> ...


I’ve just finished my diy PID using the Inkbird 106VH bought via eBay, it seems to work well and quite easy to set up although I only have brewside wired at the moment


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## Bhodgson (11 mo ago)

+1 from me for @groundpilot suggestion. They’re only a fraction more costly then the REX. But are so simple to set up, and use.
I’ve installed both, and much prefer the Inkbird.


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## groundpilot (10 mo ago)

Bhodgson said:


> +1 from me for @groundpilot suggestion. They’re only a fraction more costly then the REX. But are so simple to set up, and use.
> I’ve installed both, and much prefer the Inkbird.


I still haven’t worked out how to wire a second SSR to the steam side and into Inkbird yet…


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## Bhodgson (11 mo ago)

Just connect an AA SSR inputs to the pids alarm connectors. Then plug the output side into the flag spades from the steam thermostats. all thats left is to set the temp you want, I’d suggest 150-5c.


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## groundpilot (10 mo ago)

Bhodgson said:


> Just connect an AA SSR inputs to the pids alarm connectors. Then plug the output side into the flag spades from the steam thermostats. all thats left is to set the temp you want, I’d suggest 150-5c.


Any idea which menu on Inkbird to set temp? Is there an upper and lower limit I need to set?


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## TomHughes (Dec 16, 2019)

Bhodgson said:


> +1 from me for @groundpilot suggestion. They’re only a fraction more costly then the REX. But are so simple to set up, and use.
> I’ve installed both, and much prefer the Inkbird.


Thanks
I think I'll get one.

I'm not sure I understand how it works with the setup you described. 

Does the AA not need to be set up in parallel to the DA like above??

Does the steam switch still initiate moving into the steam circuit/higher temp?


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## TomHughes (Dec 16, 2019)

This one?









Inkbird ITC-100RH 240V Digital Pid Temperature Controller k sensor pt100 | eBay


Find many great new & used options and get the best deals for Inkbird ITC-100RH 240V Digital Pid Temperature Controller k sensor pt100 at the best online prices at eBay! Free delivery for many products.



www.ebay.co.uk


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## TomHughes (Dec 16, 2019)

TomHughes said:


> This one?
> 
> 
> 
> ...


Annoyingly these are all the wrong type!
R type - internal relay
V type - SSR output. 

I may get one and remove the internal relay, I did this with the REX and the brew on that is working. 

Anyone got a REX to run from the alarm side, can you share you settings in the COD screen??


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## TomHughes (Dec 16, 2019)

To go back to the Rex, when I have it linked up as above when I flick the steam switch there is a 240v output from the 'alarm' contacts. 
But nothing else happens. 

I bench tested the AA SSR and it appears to work properly. No idea!


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## TomHughes (Dec 16, 2019)

Actually this might be the one.
VL version









Inkbird ITC-100VL Dual Digital PID Temperature Controller heater cool 12V 24V | eBay


Find many great new & used options and get the best deals for Inkbird ITC-100VL Dual Digital PID Temperature Controller heater cool 12V 24V at the best online prices at eBay! Free delivery for many products.



www.ebay.co.uk


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## Bhodgson (11 mo ago)

TomHughes said:


> To go back to the Rex, when I have it linked up as above when I flick the steam switch there is a 240v output from the 'alarm' contacts.
> But nothing else happens.
> 
> I bench tested the AA SSR and it appears to work properly. No idea!


You have to connect the AA SSR outputs to the connectors unplugged from the steam thermostat.

No there is no need to connect the SSRs in paral.


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## Bhodgson (11 mo ago)

TomHughes said:


> Actually this might be the one.
> VL version
> 
> https://www.ebay.co.uk/itm/32246191...ash=item4b143a4e0c:g:eek:OYAAOSwLF1X33-h#rwid


VL is 24v VH is 240v.


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## TomHughes (Dec 16, 2019)

Bhodgson said:


> VL is 24v VH is 240v.


Which one do I want?

Which numbers on the AA SSR are the outputs? as It's not as clear as on the DA?

Are the inputs just from the Inkbird? 

So, when I flick the steam switch this should then switch into the alarm function on the inkbird? How is the inkbird connected to the steam switch?


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## TomHughes (Dec 16, 2019)

Also, presumably I could wire the REX up in the same way and it should work?


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## groundpilot (10 mo ago)

Bhodgson said:


> VL is 24v VH is 240v.


This is my one, but had to buy a separate PT100…INKBIRD ITC-106VH Digital Pid Temperature Controller 220V heater sensor pt100 | eBay


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## Bhodgson (11 mo ago)

TomHughes said:


> Which one do I want?
> 
> Which numbers on the AA SSR are the outputs? as It's not as clear as on the DA?
> 
> ...


3 and 4. Connect 1and 2 to to steam thermostat spades.


TomHughes said:


> Also, presumably I could wire the REX up in the same way and it should work?


Yes, exactly the same.


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## TomHughes (Dec 16, 2019)

Bhodgson said:


> 3 and 4. Connect 1and 2 to to steam thermostat spades.
> 
> Yes, exactly the same.


Thanks!


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## TomHughes (Dec 16, 2019)

groundpilot said:


> This is my one, but had to buy a separate PT100…INKBIRD ITC-106VH Digital Pid Temperature Controller 220V heater sensor pt100 | eBay


Thanks,
did you get yours from China?


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## groundpilot (10 mo ago)

TomHughes said:


> Thanks!


Any idea the menu setting on Inkbird for steam alarm? Is there an upper/lower temp setting?


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## TomHughes (Dec 16, 2019)

Bhodgson said:


> 3 and 4. Connect 1and 2 to to steam thermostat spades.
> 
> Yes, exactly the same.


For some reason that didn't work. 

And when I disconnected the spades and connect them as you say the brew side didn't even work either. 
I think there is something up with the wiring in mine though as when used the steam switch earlier the boiler temp rose and kept on rising and didn't stop.


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## TomHughes (Dec 16, 2019)

And to add to that, when the PID switched into alarm mode and the temp climbed the light didn't come on on the AA SSR. And when the alarm flashed up (which should have told it to stop heating it just kept on going. I wonder if there is a connection issue somewhere?

There was an electrical incident where I was trying to set this up in the beginning and the connection blew off the back of the switch module, maybe there is an issue in there somewhere?

Doesn't seem to affect the brew side of things though.


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## TomHughes (Dec 16, 2019)

Bhodgson said:


> 3 and 4. Connect 1and 2 to to steam thermostat spades.
> 
> Yes, exactly the same.


I'm wondering if my issue is my gaggia wiring.

It doesn't resemble the wiring diagram posted above. 

Mine is like this. 

There is only one wire coming out of the bottom part of the brew switch (unlike 2 above) and my elements appear to be connected in series. 

I think the steam thermostat has blown, and is closed, so provides a connection across it. This is connecting the circuit coming from the bottom of the brew switch to the wiring that would go through the brew thermostat. 

When I try and use brew only I have to keep the steam thermostat plugged in. Does that indicate something is up?


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## TomHughes (Dec 16, 2019)

Sorry @Bhodgson to batter you with questions, but I have one more!

If I have the settings correct on the PID, should the alarm contacts be putting out 240v all the time, UNTIL the alarm light comes on? Then they cut the voltage?

As currently mine aren't putting any voltage out and I suspect either the internal relay is naffed, or the settings are wrong (as I have it set to high deviation alarm. 

Thanks!


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