coffee-forum.net
Promoting coffee discussion.

Main
Date: 24 Jul 2007 00:24:24
From: Robert Harmon
Subject: Should air be purged from boiler before pulling a shot?

The link below shows a drawing of a simplified boiler similar to that used
in most home machines. As shown, water must at least reach the top of the
stand pipe before it can flow through the group.


If there is air trapped above the stand pipe is it compressed or is forced
through the group as the boiler is completely filled before pulling the
shot? If the air is being forced through the group couldn't that negatively
affect the puck as aerated water seeks a path through it? If the air is
trapped & compressed could this have an impact on group pressure?


Would group performance be better regulated by bleeding off any air by
opening the steam valve to let it escape before inserting the filled
portafilter & starting the shot?


Robert (curious minds want to know) Harmon
http://tinyurl.com/2sk9yu - simplified boiler




 
Date: 29 Jul 2007 14:07:32
From: hbuchtel
Subject: Re: Should air be purged from boiler before pulling a shot?
On Jul 23, 6:24 pm, Robert Harmon <r_h_har...@Zhotmail.com > wrote:

> Would group performance be better regulated by bleeding off any air by
> opening the steam valve to let it escape before inserting the filled
> portafilter & starting the shot?
>
> Robert Harmon

I *think* that you are right that bleeding off any trapped air would
result in there being more water in the boiler.

Are you hoping that this will help keep the temperature in a good
range? It seems like it ought to help at any rate!

I don't think that air will ever come out the group during a shot
because the pressure in the boiler will compress the air at the top of
the boiler, keeping it away from the tip of the standpipe.

Henry



 
Date: 29 Jul 2007 13:16:52
From: hbuchtel
Subject: Re: Should air be purged from boiler before pulling a shot?
Sorry, the link I meant to post was this one, also about the air
pocket and releasing air before the shot-

http://www.home-barista.com/forums/filling-boiler-for-better-temperature-stability-t3197.html

Henry

On Jul 27, 10:44 am, hbuchtel <henry.buch...@gmail.com > wrote:
> Funny, I was wondering the same thing...
>
> I'm thinking that there is always air inside the boiler, but that it
> is always compressed (the spring to the group can hold about 3 bar of
> pressure).
>
> For more questions ->
>
> http://www.home-barista.com/forums/single-boiler-full-of-water-how-do...
>
> Henry
>
> On Jul 23, 6:24 pm, Robert Harmon <r_h_har...@Zhotmail.com> wrote:
>
> > The link below shows a drawing of a simplified boiler similar to that used
> > in most home machines. As shown, water must at least reach the top of the
> > stand pipe before it can flow through the group.
>
> > If there is air trapped above the stand pipe is it compressed or is forced
> > through the group as the boiler is completely filled before pulling the
> > shot? If the air is being forced through the group couldn't that negatively
> > affect the puck as aerated water seeks a path through it? If the air is
> > trapped & compressed could this have an impact on group pressure?
>
> > Would group performance be better regulated by bleeding off any air by
> > opening the steam valve to let it escape before inserting the filled
> > portafilter & starting the shot?
>
> > Robert (curious minds want to know) Harmonhttp://tinyurl.com/2sk9yu-simplified boiler




 
Date: 27 Jul 2007 17:10:07
From: Flasherly
Subject: Re: Should air be purged from boiler before pulling a shot?
On Jul 27, 1:15 pm, yuvali...@gmail.com wrote:
> On 27 Temmuz, 17:44, hbuchtel <henry.buch...@gmail.com> wrote:
>
> > Funny, I was wondering the same thing...
>
> > I'm thinking that there is always air inside the boiler, but that it
> > is always compressed (the spring to the group can hold about 3 bar of
> > pressure).
>
> > For more questions ->
>
> > http://www.home-barista.com/forums/single-boiler-full-of-water-how-do...
>
> Bingo! For all the fools considering the group not air tight
> (solenoid, puck, valve whatever).
>
> David

Appears always tight. Tight when holding water potential for
extraction. Tight when releasing water that flashes into steam. -Not
tight- as an interaction with the standpipe and/or OPV sensor, to
release pressure/water level back into the reservoir (if lacking for a
needle gicleur valve to fill the same function as a different design
implementation?). How else could it be bubbling back into the
reservoir during the steaming, as does mine (a few gurgles before
reaching temp when it quiets down)... Water mineral deposits also
affect the interaction, which turns into a noisier bubbling affair
from the reservoir during steam heating, dripping water from the group
(steam wand and screen), etc, until I clean it up with lemon juice
concentrate every few weeks. That quiets everything down, stops the
leaks, with time and efficiency improved. Lasts a week or more until
symptoms return.



 
Date: 27 Jul 2007 10:15:17
From:
Subject: Re: Should air be purged from boiler before pulling a shot?
On 27 Temmuz, 17:44, hbuchtel <henry.buch...@gmail.com > wrote:
> Funny, I was wondering the same thing...
>
> I'm thinking that there is always air inside the boiler, but that it
> is always compressed (the spring to the group can hold about 3 bar of
> pressure).
>
> For more questions ->
>
> http://www.home-barista.com/forums/single-boiler-full-of-water-how-do...

Bingo! For all the fools considering the group not air tight
(solenoid, puck, valve whatever).

David




 
Date: 27 Jul 2007 14:44:14
From: hbuchtel
Subject: Re: Should air be purged from boiler before pulling a shot?
Funny, I was wondering the same thing...

I'm thinking that there is always air inside the boiler, but that it
is always compressed (the spring to the group can hold about 3 bar of
pressure).

For more questions - >

http://www.home-barista.com/forums/single-boiler-full-of-water-how-does-it-steam-t3158.html

Henry


On Jul 23, 6:24 pm, Robert Harmon <r_h_har...@Zhotmail.com > wrote:
> The link below shows a drawing of a simplified boiler similar to that used
> in most home machines. As shown, water must at least reach the top of the
> stand pipe before it can flow through the group.
>
> If there is air trapped above the stand pipe is it compressed or is forced
> through the group as the boiler is completely filled before pulling the
> shot? If the air is being forced through the group couldn't that negatively
> affect the puck as aerated water seeks a path through it? If the air is
> trapped & compressed could this have an impact on group pressure?
>
> Would group performance be better regulated by bleeding off any air by
> opening the steam valve to let it escape before inserting the filled
> portafilter & starting the shot?
>
> Robert (curious minds want to know) Harmonhttp://tinyurl.com/2sk9yu- simplified boiler




 
Date: 25 Jul 2007 14:35:54
From: Flasherly
Subject: Re: Should air be purged from boiler before pulling a shot?
On Jul 23, 6:24 pm, Robert Harmon <r_h_har...@Zhotmail.com > wrote:
> The link below shows a drawing of a simplified boiler similar to that used
> in most home machines. As shown, water must at least reach the top of the
> stand pipe before it can flow through the group.
>
> If there is air trapped above the stand pipe is it compressed or is forced
> through the group as the boiler is completely filled before pulling the
> shot? If the air is being forced through the group couldn't that negatively
> affect the puck as aerated water seeks a path through it? If the air is
> trapped & compressed could this have an impact on group pressure?
>
> Would group performance be better regulated by bleeding off any air by
> opening the steam valve to let it escape before inserting the filled
> portafilter & starting the shot?
>
> Robert (curious minds want to know) Harmonhttp://tinyurl.com/2sk9yu- simplified boiler

Simple enough to remove the PF and see if compressed air in the water
when turning on the pump. I haven't, although I'd want a steady flow
of water. Being "opposite" I steam first then extract, but before I
do, after steaming, I run near a full cup (6 oz. sniffer) of water
through the hot boiler to cool things down. Stream water at that
point, hopefully, and quickly enough back up to temperature, even if
tending to need a little "surf tapping" on the dedicated steam
thermostat to keep it subsequently within extraction ranges. Steaming
on the other hand can get noisy, bubbling back-flow releases into the
reservoir, plastic molding groans and creaks, occasional exploding PF
improperly seated, and etc. Though none of that when extracting -
nice sort-of-low hum to it is all.



 
Date: 25 Jul 2007 10:44:16
From: Jack Denver
Subject: Re: Should air be purged from boiler before pulling a shot?
The puck is not even close to "air tight", especially before it is wetted
and expands - whatever air gets sent thru the puck blows right thru and I
doubt is enough to disturb the cake.

It looks like the air above the level of the top of the stand pipe should
remain and be compressed (and it would if the head space was large enough
and the flow of the pump was slow enough - this is how home well systems
achieve their pressure), in reality I think the most of the air gets sent
down the pipe in the turbulent flow because the headspace involved is tiny.


"Robert Harmon" <r_h_harmon@Zhotmail.com > wrote in message
news:Xns9976B120E9F24rhharmonZhotmailcom@194.177.96.26...
>
> The link below shows a drawing of a simplified boiler similar to that used
> in most home machines. As shown, water must at least reach the top of the
> stand pipe before it can flow through the group.
>
>
> If there is air trapped above the stand pipe is it compressed or is forced
> through the group as the boiler is completely filled before pulling the
> shot? If the air is being forced through the group couldn't that
> negatively
> affect the puck as aerated water seeks a path through it? If the air is
> trapped & compressed could this have an impact on group pressure?
>
>
> Would group performance be better regulated by bleeding off any air by
> opening the steam valve to let it escape before inserting the filled
> portafilter & starting the shot?
>
>
> Robert (curious minds want to know) Harmon
> http://tinyurl.com/2sk9yu - simplified boiler




 
Date: 24 Jul 2007 08:00:30
From: SJM
Subject: Re: Should air be purged from boiler before pulling a shot?
On Jul 23, 3:24 pm, Robert Harmon <r_h_har...@Zhotmail.com > wrote:
> The link below shows a drawing of a simplified boiler similar to that used
> in most home machines. As shown, water must at least reach the top of the
> stand pipe before it can flow through the group.
>
> If there is air trapped above the stand pipe is it compressed or is forced
> through the group as the boiler is completely filled before pulling the
> shot? If the air is being forced through the group couldn't that negatively
> affect the puck as aerated water seeks a path through it? If the air is
> trapped & compressed could this have an impact on group pressure?
>
> Would group performance be better regulated by bleeding off any air by
> opening the steam valve to let it escape before inserting the filled
> portafilter & starting the shot?
>
> Robert (curious minds want to know) Harmonhttp://tinyurl.com/2sk9yu- simplified boiler

So, how's 'bout doing a side-by-side test for taste and posting your
results for us, eh???