# Maintaining temperature stability



## DonRJ (Apr 3, 2010)

Ok some geekyness going on here.

Having headed down the path of adding some electronic geewhizzery to my new Espresso purchase, I started thinking about other steps to achieving / maintaining ideal temperatures for extraction.

Really serious 7L boiler and loadsa massive brass grouphead machines do it by their sheer thermal mass (if thats a correct term), so with a little espresso machine a big issue is temperature drop when you pump cold water in from the reservoir to the boiler. I will be adding electronics to control water temperature more accurately in the boiler but could I give it a helping hand by reducing the differential between the reservoir water temp and boiler water temp I thought.

The short answer is yes, if I added a little water heater/stat to the reservoir eg an aquarium one, I can heat the reservoir to 30c as part of the warm up process. Used the aquarium example because you can just go out and buy one and some come with a protective cage so they don`t come in contact with the reservoir body. I would have to ensure that the water intake pipe for the pump was raised to leave some water at the bottom of the reservoir for the heater to sit in.

Anyway did the maths for a Silvia and assuming (worst case) that the reservoir water was normally 5c, by heating it to 30c I would reduce the drop in water temperature by 5c in the boiler during a typical 3 oz triple extraction, the drop would be less with a double of course. This of course does not take into account any other variables such as the heater kicking in to raise temp as the extraction takes place.

My figures were, water in boiler at 105c before extraction and I got a drop to 85c if water was 5c in the reservoir and a drop to 90c if reservoir water was at 30c, a 25% improvement for about £10-15.

Makes you think, well me anyway.

Don (currently in mad professor mode)


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## DonRJ (Apr 3, 2010)

Brain still working and I came up with a rather neat outcome, if I could heat the Silvia reservoir assumed to be full with a 300w aquarium heater to 50c (assumes I have hot rodded the thermostat), I would do this in just under 30 minutes which is a reasonable time estimate to fully warm up the machine from power up. The temperature drop of the water in the boiler assuming no other factors is now 105c to 94c when drawing in the 3oz the shot would need which is right in the middle of the extraction temperature range. Add in the heater in the boiler kicking plus the heat in the metal parts of the system, this could be a pretty temperature consistent setup for extraction.

Hmm I could wire the reservoir heater to come on when I power up the machine, Mr BlackAdder sir, I have a cunning plan.

Don ---> Imagines future conversation in th RJ household ---> Don, yes love, nice coffee that, cool, but theres a problem, whats that love, kitchens on fire!!!!!


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## sandykt (Dec 3, 2009)

I have a headache now!!!


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## BanishInstant (Oct 12, 2009)

You have too much time on your hands


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## DonRJ (Apr 3, 2010)

BanishInstant said:


> You have too much time on your hands


Don`t I know it. LOL


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## Glenn (Jun 14, 2008)

Not sure that I would want to start with hot water going into a boiler

Maintaining a clean water reservoir would become an issue as the bacteral growth would be accelerated with the heat

There has to be a taste differential as well one would assume


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## DonRJ (Apr 3, 2010)

You have a point there Glenn, if I ever explore this idea keeping the reservoir clean would be an issue. I was purely having a brainiac moment to myself and got plenty messing about in prospect anyway.

Don


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## Glenn (Jun 14, 2008)

Thinking about this further there may be pressure / vacuum issues as well which may affect filling the boiler


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## DonRJ (Apr 3, 2010)

The water in the reservoir would only be somewhere between 30 and 50c so not at a temperature too far away from a very hot Italian summers day if the water was at the ambient temperature of the theoretical Italian kitchen, aquarium thermometers (unless fiddled with) only heat to 34c anyway. So I will make a sweeping assumption that it would work without some form of thermodynamic mayhem ensuing.

Sadie would no doubt stop me in my Heath Robinsonian tracks anyway before I got too far, either that or cunningly suggest I continue my efforts in the comfort of the shed.

Don


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## DonRJ (Apr 3, 2010)

Further discoveries on the reservoir temp theme, I had the machine for a very extended period today and realised that the water reservoir temperature had reached 30c due to the heat conduction from the boiler and of course the water being returned to the tank, so no need for any reservoir preheating. Just leave it on all morning with a full reservoir at startup so I don`t have to add any cold water when making drinks.

Don


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