Does water tank temperature influence brew temperature?

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Hugonl28
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#1: Post by Hugonl28 »

Sometimes I leave my Strega running all day and then the water in the tank gets pretty warm, never measured it but feels like something around 30-40 degrees C. Other times when I start up the machine and pull a shot after 1 hour, the tank water is cool, I'd say around 20 degrees C. When I fill up the tank, of course the water is even cooler, I'd say around 10 degrees C.

Does this make a difference for the temperature in the shot? Should I replace the water with fresh cold water once it's warmed up that much?

I'm assuming the water just gets heated up in the HX to a high 95+ degrees C or so, then gets cooled down in the grouphead which as I understand has a constant 90 degrees C. But does a 20 degree difference in the water tank not have any effect on the initial temp before it enters the grouphead?

Is this maybe a reason to go plumbed, to have a constant input temp?

Cheers, Hugo

DanoM
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#2: Post by DanoM »

Hugo,

I've read elsewhere that high reservoir temps can greatly influence the temp at the group on an HX. Good or bad. There are many people keeping those Stregas on all day long, so it's likely something that you learn to work with.

Hopefully some Strega owners will chime in here and give you some pointers.
LMWDP #445

cpreston
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#3: Post by cpreston »

I checked that on my Bezzera BZ07 HX and yes, it had a significant effect on temps per my Scace. But the Strega has a much more massive group so this may not apply to you.

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Hugonl28 (original poster)
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#4: Post by Hugonl28 (original poster) replying to cpreston »

Thanks for checking Charles, that's interesting. Do you have to change your flushing routine largely due to this?
Does anybody with a Strega have an idea how big the effect is?

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Carneiro
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#5: Post by Carneiro »

I would guess that for the Strega it makes less difference.

I've done some tests on the Elektra Semiauto I had and the difference was minimal. But normally I used ice on the tank to keep the water cooler so the pump would not suffer...

cpreston
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#6: Post by cpreston »

Sorry, it was a couple of years ago and I don't remember the numbers. I think it was a degree or two. That would be on the order of a a second or two on the flush IIRC.

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another_jim
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#7: Post by another_jim »

The question frequently comes up, and it makes a difference, but not how most people thinks -- the real issue is not the water getting too warm over time, but it being too cold to start out. The difference is in the first hour or so after warm up, when the water in the tank (and everything else on the machine) is cold. Once it and the rest of the machine have warmed, you are at thermal equilibrium, and the machine is running as designed.

Mostly, SOP for semi-commercial machines was to turn the machine on and wait at least an hour. Shots before then would be taste off. But the Strega, and the other Bezzera machines with group head heaters, are oddballs. The separate group heaters mean the groups do not have to wait on the boiler to warm up; and the machine can pull shots in about 10 to 15 minutes. If you do so, it's worth experimenting with no flush shots. These machines are also designed to work for complete amateurs who turn the machine on, wait ten minutes, walk up, make a shot, and turn it off.
Jim Schulman

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Hugonl28 (original poster)
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#8: Post by Hugonl28 (original poster) »

Thank you for the detailed explanation Jim. So I understand that leaving my Strega running all day is actually how it was designed to be used and is not an 'overheated state'. That's great news.
I always wait at least 45 before I pull my first shot, never even tried after 10 minutes, but I'll try that now too.

Cheers, Hugo