Posted Sun Jan 22, 2012, 11:14am Subject: Re: Gaggia Classic PID Preinfusion + temp
I don't have a PID - but I have a thermomter/thermocouple mounted on my Classic boiler. I find that 215F is about the temp I settle at but this is a matter of taste and your particular coffee. It will also depend on where and how the thermocouple is mounted on your boiler and may even vary slightly from one boiler to the next - so you will need to use your tastebuds to guide you in the exact setting.
Here is something I found with lots of test equipment to measure the brew temp with a PID on a Gaggia: Click Here (www.afonic.org)
I've often wanted to try a PID - I feel like I can get the same (maybe better) results manually with my thermometer and my surfing technique (I've added a switch so I can control the heater during the pull - and also a preinfuse switch) - but I have to be on top of it to do it manually and a PID would certainly be nice to let me focus on other things.
One thing I notice with my surf technique - I know that when I start the shot, a lot of cold water will rush in right at first as the coffee puck gets soaked until the pressure builds up - that cools the boiler right off the bat. SO I always get the temp stabilized and then hit the heater for 3-4 seconds just before I start the shot and this helps the shot temp stay stable throughout the entire pull. During the shot, I am cycling the heater (probably about the same as a PID would be doing) -- but I don't think the PID has any way to anticipate when you are going to start the shot so it has to catch up by turning on the heater after it has already started to cool.
If I had a PID, I would probably experiment by hitting the steam switch for 3 seconds just before I start the shot - perhaps you could try that and report the results using your new PID.
I don't have a PID - but I have a thermomter/thermocouple mounted on my Classic boiler. I find that 215F is about the temp I settle at but this is a matter of taste and your particular coffee. It will also depend on where and how the thermocouple is mounted on your boiler and may even vary slightly from one boiler to the next - so you will need to use your tastebuds to guide you in the exact setting.
Here is something I found with lots of test equipment to measure the brew temp with a PID on a Gaggia: Click Here (www.afonic.org)
I've often wanted to try a PID - I feel like I can get the same (maybe better) results manually with my thermometer and my surfing technique (I've added a switch so I can control the heater during the pull - and also a preinfuse switch) - but I have to be on top of it to do it manually and a PID would certainly be nice to let me focus on other things.
One thing I notice with my surf technique - I know that when I start the shot, a lot of cold water will rush in right at first as the coffee puck gets soaked until the pressure builds up - that cools the boiler right off the bat. SO I always get the temp stabilized and then hit the heater for 3-4 seconds just before I start the shot and this helps the shot temp stay stable throughout the entire pull. During the shot, I am cycling the heater (probably about the same as a PID would be doing) -- but I don't think the PID has any way to anticipate when you are going to start the shot so it has to catch up by turning on the heater after it has already started to cool.
If I had a PID, I would probably experiment by hitting the steam switch for 3 seconds just before I start the shot - perhaps you could try that and report the results using your new PID.
The PID should theoretically stop the need for temperature surfing as you should be able to set the temperature. What I'll do is set the PID to have a temp between 99c and 107c (as per the link). Currently my Gaggia Classic has a 107c thermostat for brew, but obviously suffers from -+>10c difference (which would explain why in a 2oz shot I get about 85c, and in a 3oz shot I get about 90c or so).
I don't think the PID will stop the need for flushing the machine prior to a shot (from my basic, non-scientific experiment with the polystyrene cup), but it will definitely speed up the boiler kicking in after a flush.
My current theory is if I set the pre-infuse time for about 3-4 seconds, wait 1-2 seconds, the heater SHOULD theoretically start before the shot itself. I'll let you know though!
Well my theory (though I don't have a PID) is that once the shot is underway, the PID will keep the temp stable. But I have found (especially with the Gaggia where the heater is on the outside of the boiler) that it takes about 4 seconds of having the heater turned on before it starts to affect the temp of the water inside the boiler. So to me, that means that when you first start the shot (and the heater is off) and that first large amount of cold water is pumped into the boiler to wet the puck - the PID will see the temp drop and turn the heater on - but it will be about 4 seconds until that electricity heats up the heater coil and conducts to the water inside the boiler.
Once the puck is saturated, then the rest of the pull goes at a pretty consistent flow - so I think the PID will keep everything right. It's just that first blast that is flowing cold water into the boiler at a much faster rate.
That's why I like to get the shot started when the heater is cycled in the on position - just so the heater is already on the upward ramp before that initial blast of cool water hits it.
With a PID you could just watch it and start you shot just after you see the PID turn the heat on.
Anyway ... this is all speculation on my part as I haven't got one. I'd be very interested to hear your reports after you get it all setup.
Well my theory (though I don't have a PID) is that once the shot is underway, the PID will keep the temp stable. But I have found (especially with the Gaggia where the heater is on the outside of the boiler) that it takes about 4 seconds of having the heater turned on before it starts to affect the temp of the water inside the boiler. So to me, that means that when you first start the shot (and the heater is off) and that first large amount of cold water is pumped into the boiler to wet the puck - the PID will see the temp drop and turn the heater on - but it will be about 4 seconds until that electricity heats up the heater coil and conducts to the water inside the boiler.
Once the puck is saturated, then the rest of the pull goes at a pretty consistent flow - so I think the PID will keep everything right. It's just that first blast that is flowing cold water into the boiler at a much faster rate.
That's why I like to get the shot started when the heater is cycled in the on position - just so the heater is already on the upward ramp before that initial blast of cool water hits it.
With a PID you could just watch it and start you shot just after you see the PID turn the heat on.
Anyway ... this is all speculation on my part as I haven't got one. I'd be very interested to hear your reports after you get it all setup.
Ah, now that I didn't know (re: ~4 secs). What I'll try is when I get it and install it, I'll play with the time and temps.
If it's about 4 seconds, I think I may be able to tweak it (theoretically of course), so that the pre infusion starts the cold water coming in, and then the shot is at a stable temp throughout afterwards (auberins PID does auto pre-infusion, then xx second pull).
Gaggias are not designed to want/need/accommodate pre-infusion. Same goes for "cooling flushes" which are for HX machines.
If you start and then stop the pull all it means is you have to wait for the cold water that got pulled into the tiny little boiler to be brought back up to temperature.
And, no, a PID doesn't do anything for intra-shot temperature. All it does is make sure the temp is what you want it to be before you start to pull the shot.
More questions? Bring them over to the Gaggia Group.
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