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stabilizing temps on Gaggia Classic
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Discussions > Espresso > Espresso Mods > stabilizing...  
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wcmocha
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wcmocha
Joined: 26 Dec 2010
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Espresso: Gaggia Classic
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Posted Sun Mar 6, 2011, 2:32pm
Subject: Re: stabilizing temps on Gaggia Classic
 

EricBNC Said:

You could try raising the ambient temps a bit...

Posted March 6, 2011 link

You definitely wouldn't need a heating element there...
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wcmocha
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wcmocha
Joined: 26 Dec 2010
Posts: 218
Location: Colorado
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Espresso: Gaggia Classic
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Posted Sun Mar 6, 2011, 2:38pm
Subject: Re: stabilizing temps on Gaggia Classic
 

I'm trying to minimize the number of connections and make the design as simple as possible so I would like to avoid machining a box.  As soon as I figure out the connections I'm going to start building it.

Anyone know a name for the style of fitting that is on the hose between the pump and boiler?  Is there anything else that uses it or a place to get it in an adapter?  I think it's Gaggia specific.
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randytsuch
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Posted Sun Mar 6, 2011, 4:52pm
Subject: Re: stabilizing temps on Gaggia Classic
 

Well, in case this helps
I used this tubing from mcmaster
http://www.mcmaster.com/#5557k33/=bbk9ni

This coupler works
http://www.mcmaster.com/#5449k193/=bbka11

And this is the adapter that I used to run the pipe into my preheater box
http://www.mcmaster.com/#5508k123/=bbkaj2
They also make a right angle version of this that will work, if you don't have room for this straight one.

I did have to go buy a tap, to tap the hole my box for this adapter.

In this last version, that I am about to try, I used a little hammond box, with an adapter on each end.  Adapter holes are tapped, then I use a lot of food grade RTV to seal the hole when I screw in the adapter.

Inside the box, I have 5 pieces of al, to seperate the box into 6 chambers.  Each piece of al has a hole at one end, with the holes on alternating sides of the box, so the water has to go back and forth through the chambers, within the box.

I also have a Y adapter, which feeds a pressure gauge.  This gauge is between the pump and pre heater in my machine.

Randy
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randytsuch
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Posted Mon Mar 7, 2011, 9:57am
Subject: Re: stabilizing temps on Gaggia Classic
 

To follow up, my new box leaked :(

I think I need to go back to a smaller, square box.  I was trying to use a longer, rectangular box, and I think there is too much distance between screws.
Making something leakproof at 200degrees and over 9 bar is a challenge.

Back on subject
One thing I forgot to mention is to consider the OPV.  Because the OPV in a Classic bolts to the boiler, you have to add the preheater before the OPV.  The problem is then the OPV ends up dumping some preheated water back into the tank, and you lose some of the benefits of the preheater.  Since the volume of the copper tubing is not that great (less then 2 oz, by my calcs), you don't have enough water to dump it back into the tank.

I got around this by adding a fan dimmer to control my pump, and a pressure gauge.  So, I can control the pressure without the OPV.

Randy
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wcmocha
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wcmocha
Joined: 26 Dec 2010
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Espresso: Gaggia Classic
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Posted Mon Mar 7, 2011, 11:25pm
Subject: Re: stabilizing temps on Gaggia Classic
 

Thanks for posting those links.  I think I have an idea figured out and will post up pics. when I have them.

Sorry to hear about the box leaking. There is probably a lot of pressure on that cover as it's likely a few square inches and 130psi plus on each of them.  I don't know if you plan on opening the box again down the road, but once you seal off the edges with something food-safe, you could add some JB weld to bond the two pieces together.  Last I checked it was rated to 500 degrees and is heat conductive.
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ggcadc
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ggcadc
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Posted Tue Mar 8, 2011, 9:39am
Subject: Re: stabilizing temps on Gaggia Classic
 

an FYI for everyone doing this, the OPV will need to be re-calibrated, I lost about 10-15 PSI (about 1/2 BAR).

im anxious to hear how the box turns out, but as of now I am leak free at 135psi, making great shots. however I did make trouble for myself if I should need to do anymore work to the machine(full of copper), a box that's not in the way of anything would be ideal.

also as far as volume, 1/4 copper tube holds 0.00379gal per linear foot, so with ten feet of it around my boiler I have about 4.8oz in there.
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randytsuch
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Posted Tue Mar 8, 2011, 9:51am
Subject: Re: stabilizing temps on Gaggia Classic
 

ggcadc Said:

an FYI for everyone doing this, the OPV will need to be re-calibrated, I lost about 10-15 PSI (about 1/2 BAR).

im anxious to hear how the box turns out, but as of now I am leak free at 135psi, making great shots. however I did make trouble for myself if I should need to do anymore work to the machine(full of copper), a box that's not in the way of anything would be ideal.

Posted March 8, 2011 link

Now that you mention it, wrapping everything in copper tubing was one reason I started working on using a little box for a preheater, it would be a pain if you need to work on it now.

If you use the same adapters I did, here is a tap that works
Click Here (www.drillspot.com)

I had put this project aside for a while, but I really want to make it work now.  The hard part has been getting the box to seal at the lid.

I have used the food safe/hard epoxy method for something similar before, and it worked for a while.  I was trying to seal a hole, and I think I used too much RTV in that case, which is a mistake I think I repeated in my last box.  

I should have new results in a few days, and will post again.

Randy
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wcmocha
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wcmocha
Joined: 26 Dec 2010
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Location: Colorado
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Espresso: Gaggia Classic
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Posted Wed Mar 9, 2011, 6:35pm
Subject: Re: stabilizing temps on Gaggia Classic
 

Looks like it'll be a bit longer until I get the heat exchanger built as I've gotten distracted with a rotary pump conversion.  On the plus side, it will re-circulate the pressurized water as opposed to losing it through the OPV (if I can set the pump to an exact pressure as I'm still experimenting).  This means less volume required for the heat exchanger.  

I did a test shot last night just for calculating.  A double shot pulled in 27 seconds at 8.9 bar bled off 5 oz. of water through the opv valve.  So if I can get the new pump to the exact pressure without the OPV, I only need to hold maybe 2 oz of water in the exchanger, as opposed to 7.  I'll post up here again when I get around to building the exchanger...
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randytsuch
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Posted Wed Mar 9, 2011, 6:53pm
Subject: Re: stabilizing temps on Gaggia Classic
 

So there are a couple of alternatives to adding a rotary pump to the classic.
BTW, I have nothing against adding a rotary to the classic, but I don't think it is a change that most people would do.  However, I'm not sure how many would do the next two things either ;)

You can add a dimmer to the pump voltage to control the pump pressure, which is what I did.  This works with older Eaton pumps, not sure if it would work with the Ulka vib pumps or not.

You can add a different (quickmill izzo) OPV in front of the preheater.  A larger OPV is supposed to work better then the Gaggia OPV.  There's a guide at the gaggia user's group that describes how to add this OPV.

Randy
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wcmocha
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wcmocha
Joined: 26 Dec 2010
Posts: 218
Location: Colorado
Expertise: I love coffee

Espresso: Gaggia Classic
Grinder: Nemox Lux
Drip: Keurig
Posted Wed Mar 9, 2011, 8:57pm
Subject: Re: stabilizing temps on Gaggia Classic
 

You people keep giving me ideas, stop it!!!

I'm just kidding.  I think it's funny though that I first started here looking to get a few tips on dialing in my first espresso machine and now my kitchen looks like I'm building a space ship or something.  It is a fair trade for the kinds of shots I've been pulling lately...

BTW, do you have a link to that OPV Valve?
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