Preheating the incoming water on a Gaggia Classic

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Swemarv
Posts: 11
Joined: Sat Dec 09, 2006 7:43 am
Real Name: Magnus Arvidsson
Equipment: Gaggia Classic with PID control & preheating inc. water
Location: Stockholm, Sweden

Postby Swemarv » Wed Jan 03, 2007 6:19 am

I didn't want to hijack another thread so I will tell my story here

OK heres the story....

During extraction cold water enters the relatively small boiler. This results in a 6-8 C drop in watertemperature during extraction. My idea was to preheat the incoming water to reduce this drop. The easiest would be to preheat the water before the pump, but after testing this by using hot water in the tank, I gave up this idea. The pump sounded strange working with hot water.

The idea was to use the large flat area on the front side of the boiler to attach a chamber that would hold enough water to get a stable temp during extraction. Since this chamber is placed after the pump it must withstand the high pressure and temperature.
The easies I think was to use an aluminum chamber built out of two halves shown below. The chamber holds 70 ml and is hold together with M3 bolts and aquarium silicone.

Image

The chamber is inserted after the pump and before the OPV. Connections are made with PTFE tubings and pneumatic connectors. (quite cheap actually).


See pictures below.


Image
I had to take away the switch in order to be able to place the chamber on the front side of the boiler. Luckily I had a broken switch that I could use as a dummy to keep track of the position of the cables.

Image
On the frontside of the boiler there is a small edge that I removed to get better contact between the boiler and the chamber. I also used heat transfering paste to get better heat transfer.
The chamber is held in place with a hose clamp (is this the right word ??)

Image

The result is shown in the graph below. Temperatures are measured with a probe on the probe on the top of the coffeepuck.

Image

I should also say that I have already installed a PID to get the start temp right.

sonicjason
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Joined: Wed Jan 03, 2007 2:04 am

Postby sonicjason » Wed Jan 03, 2007 9:39 am

It's an amazing job. It looks like a magnified cpu's cooling block. I had thought to add something like heat - exchanger to the boiler. But for me it is difficult to get the preheat chamber like yours. So I rotate the copper pipe around the boiler which length is about 1.8 meters. As is known the boiler is not a cylinder. I think it would only be a little improvement for the temp stability. To shorten the reaction time and heat quickly when brewing I adjust the parameters like 'P' and 'I' at the pid controller and use a thermocouple which is for quickly measure. It is my story above. However I think the chamber is definitely a good idea. Congratulations.

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jesawdy
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Postby jesawdy » Wed Jan 03, 2007 10:39 am

Swemarv wrote:I should also say that I have already installed a PID to get the start temp right.


Swemarv, welcome to HB!

Very nice job and thanks for sharing!

Question - did you fabricate that heating chamber yourself?

Also, installing a PID on a Gaggia is question that comes up here from time to time, can you share any details of your PID installation?
Jeff Sawdy

2xlp
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Real Name: Jonathan
Location: NY

Postby 2xlp » Wed Jan 03, 2007 11:55 am

a) where did you get the connectors for the hose
b) did you consider getting FDA approved silicon instead of aquarium ?

LarsL
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Joined: Fri Dec 15, 2006 9:26 am
Real Name: Lars Laufeld
Location: Malmö, Sweden

Postby LarsL » Thu Jan 04, 2007 5:27 am

Marv,

I've been following your adventures on the swedish forum and I would just like to say that I'm very impressed by what you have accomplished!

Swemarv
Posts: 11
Joined: Sat Dec 09, 2006 7:43 am
Real Name: Magnus Arvidsson
Equipment: Gaggia Classic with PID control & preheating inc. water
Location: Stockholm, Sweden

Postby Swemarv » Thu Jan 04, 2007 7:13 am

jesawdy wrote:Swemarv, welcome to HB!

Very nice job and thanks for sharing!

Question - did you fabricate that heating chamber yourself?

Also, installing a PID on a Gaggia is question that comes up here from time to time, can you share any details of your PID installation?


Yes - I milled the parts myself. It took a while due to the complex shape.

OK, I will try to describe my PIDing of the Classic.

2xlp wrote:
a) where did you get the connectors for the hose
b) did you consider getting FDA approved silicon instead of aquarium ?



I bought the connectors from a swedish supplier of pneumatic equipment called Hydroscand, the manufacturer is Metalwoks i think.
I think you can find other suppliers of these. The only requirements is that they should be able to work at the temperature of the boiler and that they should be capable of handling 15 Bar pressure. This is also why I used PTFE tubing.

I was looking for a silicone that could handle the high temperature that the boiler has when steaming. The only silicone I found that could handle this temperature was silicone for aquarium, and from what I have heard fish are rather sensitive so this silicone should be safe. Also the silicone is only used on the surface where the two pieces are in contact with each other. But of course, if you find a FDA approved silicon that can cope with the high temp that would be preferable.
I should also confess that the use of silicone was an emergency exit, my original idea was to use a gasket to get a tight seal between the two pieces, but I had too little space between the holes and the edge. If I were to do this again this is on of the things I would change.


Maybe I should add that I am very satisfied with the PID and the preheating chamber. 8 to 9 shots out of 10 are good now compared with 1-2 out of 10 with the original classic.

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oofnik
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Postby oofnik » Sun Jan 07, 2007 6:32 pm

Very nice! I think this is an outstanding idea. I actually was planning on doing a very similar modification to my machine. I bought a small copper CPU watercooling block from a computer store. I had planned to run it between the pump and the boiler, and have it actively heated by a power resistor that was controlled through the original 90 C thermostat (which was replaced by a PID). I never got around to it, though. I figured that after the relief valve, pressure gauge, new tubing, splitter, PID and relay it would start getting a little cramped in there. :D
If you could, I would love to see a more hi-res picture of the graphs. It's a little difficult to see what's going on with the tiny one you posted. Thanks!

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welone
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Postby welone » Mon Jan 08, 2007 8:17 am

Thanks a lot for this thread. It has been a wonderful surprise to me that such a temperature stability can be achieved with a gaggia classic.

It's a bit off topic but I would be really happy if anybody could answer my question:

Would it help to stabilize temperature during brewing if I start the pump just before the temperature ready light would switch on again?

I read a dozen times that for a better steaming performance of the classic one has to start steaming just before the light would switch on again. Normally the boiler starts heating again after the first fifteen seconds into the pour, so I wondered if it would help keeping the temperature more stable during brewing if the boiler would heat from the first second of the pour.


greets


marco

Swemarv
Posts: 11
Joined: Sat Dec 09, 2006 7:43 am
Real Name: Magnus Arvidsson
Equipment: Gaggia Classic with PID control & preheating inc. water
Location: Stockholm, Sweden

Postby Swemarv » Tue Jan 09, 2007 11:57 am

Here is a higher res version of the graph

http://img58.imageshack.us/img58/4075/deltatph0.jpg

I was thinking of heating the water with resistors too, but I gave it up because of the high wattage needed.


As for tempsurfing with the classic, I never botherd to learn it. There are two different variabled that need to be controlled. The first is the absolute temperature ot start af extraction, this is best taken care if with a PID in my opinion. The second is the temperature drop during extraction. It could be possible to compensate for this by putting power into the boiler to compensate for the cold water but I just found this to be too tricky and choose to preheat the water instead.

2xlp
Posts: 135
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Real Name: Jonathan
Location: NY

Postby 2xlp » Tue Jan 09, 2007 12:41 pm

i went through the silicon sealants on mcmaster.com

there seems to be a lot of different FDA & NSF certifications:
some are not certified food safe for liquids
some are certified food safe for liquids, but not at high temperatures
some are certified food safe for liquids at high temperatures

your mod is awesome. however, i would strongly suggest finding out the certification of your silicone sealant. i know the EU has its own guidelines -- but I'm sure they will fall roughly into the same categories. if you don't have a high-temp sealent, i'd reseal your line.