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Date: 20 Sep 2006 00:54:53
From: I->Ian
Subject: ThermoSyphon Stall
About a week or two ago I started getting a sour third or fourth shot.
At that point, the machine has been on for at least an hour to an hour
and a half.

Prior to this, I could not recall a sour shot. The machine is about 3
months old. I pull 3 or 4 doubles every morning but Sunday. Occasional
frothing for the missus and occasional hot water for what have you.

The machine has a boiler pressure gauge and it was in the normal 0.9
to 1.1 range. Logs of the external boiler temp vary by not more than
2F @ 240F, so the pStat and boiler pressure gauge are spot on.

I had noticed that cooling flushes were very short, so I placed
thermocouples on the upper and lower thermosyphon tubes where they
connect to the group.

The image at
http://www.ielogical.com/coffee/ThermoSyphon.gif
shows what is happening with this e61 HX machine.

After much head scratching and data logging, I came to the conclusion
that the thermosyphon tube becomes insulated by gas from the boiler
water as it is heated.

Steaming the boiler down from 1.1 to 0.5 bar has no effect.

Flushing ~200mL from the boiler appears to clear the air blanket from
the thermosyphon and serenity is restored.

I attribute the changed behavior to the fact that I'd recently
switched to Crystal Geyser from Arrowhead Mountain Spring bottled
water.

To test this hypothesis, I put 100mL each of CG, AH MS and LA DWP
water in three [nearly] identical [5g] glasses and set them in the
center of a large pan of water on the stove. I placed a metal skewer
in each of the glasses to act as a 'precipitator' for the gas and
slowly heated the pan on a gas flame.

Sure enough, the gas in the Crystal Geyser water formed a blanket of
very tiny bubbles that are much more immune to perturbation than the
larger ones formed by Arrowhead or LA DWP water.

Comments? Suggestions?




 
Date: 23 Sep 2006 00:52:42
From: CrackAddict
Subject: Re: ThermoSyphon Stall
Thanks Dan - I suspect you are right. It's not a big deal, so I can
live with it. It has yet to appear on the second machine (in our
cottage so not used as much).


Dan Bollinger wrote:
> One of my two Expobar Office machines exhibits an intermittent
> thermosiphon failure. <snip>

> CA,
> I've had this problem, too. It was a faulty check valve allowing HX water to
> escape back into the tank in the form of steam until the HX was dry. However, it
> sounds like this is not the case with you since you've replaced both check
> valves in your system (one in the pump, the other in the OPV). Changing the
> vacuum breaker will have no effect on your symptoms since you say the boiler is
> always hot.
>
> Here is what I think is happening. It happens to some extent on every HX
> machine that is turned on from a cold state. The pressurstat reads 1.2 bar, but
> the temperature is low. 'Burping', by releasing some steam allows excess
> trapped air to be release, which then permits the heater to come on, heat the
> water, and thermosiphon to begin. The proof would be if you could measure the
> boiler temperature.
>
> Dan



 
Date: 21 Sep 2006 02:08:38
From: CrackAddict
Subject: Re: ThermoSyphon Stall
One of my two Expobar Office machines exhibits an intermittent
thermosiphon failure. It's on a timer and the group will be hot most
mornings, but about one in five, it stalls and needs to have water
pumped through the group to restart it. When this happens, it takes
about 20 seconds for water to appear, so it seems that the pump has
lost prime.

I replaced the vacuum breaker, Ulka pump and water diverting valve
(HX/boiler) with no effect. I can say that on mornings where I hear it
run the pump immediately when the timer comes on, I do not have the
problem. So perhaps it is a sticky/insensitive boiler refill switch?

There is plenty of steam when this happens, so the boiler is hot but
the group is only warm. Running off some steam or hot water always
triggers the refill action, which then restarts the thermosiphon.


I- >Ian wrote:
> About a week or two ago I started getting a sour third or fourth shot.
> At that point, the machine has been on for at least an hour to an hour
> and a half.
>
> Prior to this, I could not recall a sour shot. The machine is about 3
> months old. I pull 3 or 4 doubles every morning but Sunday. Occasional
> frothing for the missus and occasional hot water for what have you.
>
> The machine has a boiler pressure gauge and it was in the normal 0.9
> to 1.1 range. Logs of the external boiler temp vary by not more than
> =B12=B0F @ 240=B0F, so the pStat and boiler pressure gauge are spot on.
>
> I had noticed that cooling flushes were very short, so I placed
> thermocouples on the upper and lower thermosyphon tubes where they
> connect to the group.
>
> The image at
> http://www.ielogical.com/coffee/ThermoSyphon.gif
> shows what is happening with this e61 HX machine.
>
> After much head scratching and data logging, I came to the conclusion
> that the thermosyphon tube becomes insulated by gas from the boiler
> water as it is heated.
>
> Steaming the boiler down from 1.1 to 0.5 bar has no effect.
>
> Flushing ~200mL from the boiler appears to clear the air blanket from
> the thermosyphon and serenity is restored.
>
> I attribute the changed behavior to the fact that I'd recently
> switched to Crystal Geyser from Arrowhead Mountain Spring bottled
> water.
>
> To test this hypothesis, I put 100mL each of CG, AH MS and LA DWP
> water in three [nearly] identical [=B15g] glasses and set them in the
> center of a large pan of water on the stove. I placed a metal skewer
> in each of the glasses to act as a 'precipitator' for the gas and
> slowly heated the pan on a gas flame.
>
> Sure enough, the gas in the Crystal Geyser water formed a blanket of
> very tiny bubbles that are much more immune to perturbation than the
> larger ones formed by Arrowhead or LA DWP water.
>=20
> Comments? Suggestions?



  
Date: 21 Sep 2006 11:30:31
From: Dan Bollinger
Subject: Re: ThermoSyphon Stall
One of my two Expobar Office machines exhibits an intermittent
thermosiphon failure. It's on a timer and the group will be hot most
mornings, but about one in five, it stalls and needs to have water
pumped through the group to restart it. When this happens, it takes
about 20 seconds for water to appear, so it seems that the pump has
lost prime.

I replaced the vacuum breaker, Ulka pump and water diverting valve
(HX/boiler) with no effect. I can say that on mornings where I hear it
run the pump immediately when the timer comes on, I do not have the
problem. So perhaps it is a sticky/insensitive boiler refill switch?

There is plenty of steam when this happens, so the boiler is hot but
the group is only warm. Running off some steam or hot water always
triggers the refill action, which then restarts the thermosiphon.

CA,
I've had this problem, too. It was a faulty check valve allowing HX water to
escape back into the tank in the form of steam until the HX was dry. However, it
sounds like this is not the case with you since you've replaced both check
valves in your system (one in the pump, the other in the OPV). Changing the
vacuum breaker will have no effect on your symptoms since you say the boiler is
always hot.

Here is what I think is happening. It happens to some extent on every HX
machine that is turned on from a cold state. The pressurstat reads 1.2 bar, but
the temperature is low. 'Burping', by releasing some steam allows excess
trapped air to be release, which then permits the heater to come on, heat the
water, and thermosiphon to begin. The proof would be if you could measure the
boiler temperature.

Dan



   
Date: 24 Sep 2006 01:52:42
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Thu, 21 Sep 2006 11:30:31 -0400, "Dan Bollinger"
<danNObollinger@insightSPAMbb.com > wrote:

>Here is what I think is happening. It happens to some extent on every HX
>machine that is turned on from a cold state. The pressurstat reads 1.2 bar, but
>the temperature is low. 'Burping', by releasing some steam allows excess
>trapped air to be release, which then permits the heater to come on, heat the
>water, and thermosiphon to begin. The proof would be if you could measure the
>boiler temperature.
>
>Dan

I pulled the water fill and o/p hose and put them in separate
containers to see water was being forced back, but only a drop or two.

If I pull water from the group, all I get is coolish water. No gas,
air, steam.

I looked at the filter in the top of the group and there is ZERO
scale.

I also pulled the thermosyphon apart. There is only a black coating on
the copper. I can still see copper in places.

I can flow water through the group and thermosyphon pipes when
disconnected from the boiler.

The pressurestat reads 0.9 to 1.1bar. Temperature logged with K-TC at
water fill boss reads 238-242 all day long, even when the problem is
happening.

Today I left the unit alone for an hour after the problem appeared. It
oscillated around 185. Image at
http://www.ielogical.com/coffee/TS060923.gif

I then disconnected the water fill prove wire for about 5 seconds,
allowing the pump to run for about 3 seconds. As you can see the
temperature shot back up immediately. NO water was removed from the
boiler.


    
Date: 24 Sep 2006 10:39:14
From: Dan Bollinger
Subject: Re: ThermoSyphon Stall
> Today I left the unit alone for an hour after the problem appeared. It
> oscillated around 185. Image at
> http://www.ielogical.com/coffee/TS060923.gif

Ya know, its OK to add titles to replace the 'Series 1' and 'Series 2' labels.
I have no idea what these curves are showing.



     
Date: 24 Sep 2006 18:56:01
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Sun, 24 Sep 2006 10:39:14 -0400, "Dan Bollinger"
<danNObollinger@insightSPAMbb.com > wrote:

>> Today I left the unit alone for an hour after the problem appeared. It
>> oscillated around 185. Image at
>> http://www.ielogical.com/coffee/TS060923.gif
>
>Ya know, its OK to add titles to replace the 'Series 1' and 'Series 2' labels.
>I have no idea what these curves are showing.

Series 1 is the thermosyphon entrance to the top of the group.
Series 2 is the thermosyphon exit from the bottom of the group.
Two K thermocouples, slid into the space between the pipe and the
compression nut, held in place with a tie wrap.

Data log interval is 10 seconds. My apologies for not assigning it to
the X axis.


    
Date: 24 Sep 2006 00:41:58
From: jim schulman
Subject: Re: ThermoSyphon Stall
On Sun, 24 Sep 2006 01:52:42 GMT, "I- >Ian" <someone@nowhere.com>
wrote:

>
>I then disconnected the water fill prove wire for about 5 seconds,
>allowing the pump to run for about 3 seconds. As you can see the
>temperature shot back up immediately. NO water was removed from the
>boiler.

It could be you are losing water out of the thermosyphon via the OPV
back to the tank because of a bad check valve:


Normal:

Pump-- >-->OPV-->-->checkvalve-->-->Tsyphon loop



Bad Checkvalve:

Pump-- >-->OPV<--<--checkvalve<--<--Tsyphon loop


     
Date: 24 Sep 2006 10:44:44
From: Dan Bollinger
Subject: Re: ThermoSyphon Stall
>>I then disconnected the water fill prove wire for about 5 seconds,
>>allowing the pump to run for about 3 seconds. As you can see the
>>temperature shot back up immediately. NO water was removed from the
>>boiler.
>
> It could be you are losing water out of the thermosyphon via the OPV
> back to the tank because of a bad check valve:
>
>
> Normal:
>
> Pump-->-->OPV-->-->checkvalve-->-->Tsyphon loop
>
>
>
> Bad Checkvalve:
>
> Pump-->-->OPV<--<--checkvalve<--<--Tsyphon loop
>


      
Date: 24 Sep 2006 16:46:20
From: jim schulman
Subject: Re: ThermoSyphon Stall
On Sun, 24 Sep 2006 10:44:44 -0400, "Dan Bollinger"
<danNObollinger@insightSPAMbb.com > wrote:

>The water level in the boiler is too low. The HX is not
>immersed. The solution is to raise the autofill probe in the boiler.

If it's low, it's low -- how could the loop get up to proper
temperature before it drops. Something has to be slowly changing.

In some of these machines, the loop is tuned to allow for some water
to flow through the return part to the head when the pump is engaged,
bypassing the HX and tempering the overheated water. I have no idea
how this works, Micheal Teahan says it's something tweakable on the
E61 innards. In any case, that could make up for the missing water.


       
Date: 24 Sep 2006 18:47:11
From: Dan Bollinger
Subject: Re: ThermoSyphon Stall
>>The water level in the boiler is too low. The HX is not
>>immersed. The solution is to raise the autofill probe in the boiler.
>
> If it's low, it's low -- how could the loop get up to proper
> temperature before it drops.

Jim, I'm thinking partially submerged HX. It would explain subsequent shots
being cooler, but shots after the machine is idle being normal temps. It would
be an easy thing to check. Ian, when the machine acts up again, but before the
autofill operates, measure the height of the water in the boiler. You'd have to
let it cool, though.

> In some of these machines, the loop is tuned to allow for some water
> to flow through the return part to the head when the pump is engaged,
> bypassing the HX and tempering the overheated water. I have no idea
> how this works, Micheal Teahan says it's something tweakable on the
> E61 innards. In any case, that could make up for the missing water.

I'm unclear on the internal plumbing of the E61 even though I've torn mine apart
and rebuilt it. I do know the cold replacement water from the pump enters the
loop's return line at a tee near the boiler. I believe the loop is shutoff when
the lever is raised. That way, when the pump is turned on, the water is forced
to travel into the HX and the onto the grouphead and PF. If the E61 valve was
faulty, it means that cold water could enter into the grouphead, bypassing the
HX (meaning it would not pick up additional heat). And, when the lever was
returned to normal position it would return to a functioning thermosiphon. This
explains some, but not all, of Ian's symptoms. Without having the machine in
front of me I'm at a loss. Dan



        
Date: 25 Sep 2006 02:07:54
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Sun, 24 Sep 2006 18:47:11 -0400, "Dan Bollinger"
<danNObollinger@insightSPAMbb.com > wrote:

>>>The water level in the boiler is too low. The HX is not
>>>immersed. The solution is to raise the autofill probe in the boiler.
>>
>> If it's low, it's low -- how could the loop get up to proper
>> temperature before it drops.
>
>Jim, I'm thinking partially submerged HX. It would explain subsequent shots
>being cooler, but shots after the machine is idle being normal temps. It would
>be an easy thing to check. Ian, when the machine acts up again, but before the
>autofill operates, measure the height of the water in the boiler. You'd have to
>let it cool, though.

Prior to your reply I removed the autofill probe and the water level
is as I estimated. I raised the level 1cm, but shant pull a shot until
the morrow.

I took a couple of photos to show what's what:
http://www.ielogical.com/coffee/TCLoc.JPG shows the location of the
TCs

http://www.ielogical.com/coffee/TSLayout.JPG show the layout of the
boiler and the thermosyphon.

When the machine is acting up I can't pull shots as they are sour. The
grouphead is about 160F above the PF measured with a IR thermometer at
the center of the head. Only adding water to the boiler restores the
thermosyphon operation and group temperature. FWIW, the water inject
is the lower thin pipe in the TSLayout.jpg and it looks like it shoots
directly at the base of the thermosyphon.

>
>> In some of these machines, the loop is tuned to allow for some water
>> to flow through the return part to the head when the pump is engaged,
>> bypassing the HX and tempering the overheated water. I have no idea
>> how this works, Micheal Teahan says it's something tweakable on the
>> E61 innards. In any case, that could make up for the missing water.
>
>I'm unclear on the internal plumbing of the E61 even though I've torn mine apart
>and rebuilt it. I do know the cold replacement water from the pump enters the
>loop's return line at a tee near the boiler. I believe the loop is shutoff when
>the lever is raised. That way, when the pump is turned on, the water is forced
>to travel into the HX and the onto the grouphead and PF. If the E61 valve was
>faulty, it means that cold water could enter into the grouphead, bypassing the
>HX (meaning it would not pick up additional heat). And, when the lever was
>returned to normal position it would return to a functioning thermosiphon. This
>explains some, but not all, of Ian's symptoms. Without having the machine in
>front of me I'm at a loss. Dan

FWIW with the boiler level higher, the upper group temperature still
hovers at ~225F. I moved the lower TC to the bottom of the boiler
inlet to see what is happening there and it is ~20F lower, the same as
the lower group outlet.

The thermosyphon has the cold water from the pump injected in the
middle of the tube in the boiler, so the water from the inlet and
outlet is mixed to brew.

From the images at H-B of the e61, it looks like the thermosyphon is
open and the water is forced up through the filter screen at the top
of the group and then down the center.

It's definitely pulling a shot that stops the flow as today's single
double shows.

I'm thinking that perhaps there is a critical point that is a
combination of boiler temp, scale, inlet water temp, the moon that
will stall any thermosyphon and I'm there. Or at least I'm guessing /
hoping that!

[ I could no scale see through the autofill port. FWIW this machine
had been on less than 100 hours when the problem first appeared ]





         
Date: 25 Sep 2006 16:42:56
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Mon, 25 Sep 2006 02:07:54 GMT, "I- >Ian" <someone@nowhere.com>
wrote:

> I raised the level 1cm

NO stall. Brilliant!


          
Date: 25 Sep 2006 19:42:56
From: Dan Bollinger
Subject: Re: ThermoSyphon Stall
>> I raised the level 1cm
>
> NO stall. Brilliant!

Woo Hoo! Ian, I'm not sure which I like better. You having your problem fixed,
or me figuring out the solution. :) Enjoy. Dan



      
Date: 24 Sep 2006 18:50:29
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Sun, 24 Sep 2006 10:44:44 -0400, "Dan Bollinger"
<danNObollinger@insightSPAMbb.com > wrote:

> The water level in the boiler is too low. The HX is not
>immersed.

The HX passes from the bottom through the top of the boiler.

If the HX were not immersed, the element would be long melted, no?

If the HX were not immersed, the group would never heat, which is not
the case. The problem is the group cools after as few as one shot.
Here the machine has been on for more than 24hours. The TS temp is
225. One 85mL cooling flush and one 75mL shot causes this.
http://www.ielogical.com/coffee/TS060924a.gif
75mL water drawn from the boiler caused the temp to return to normal


I can turn off the machine and draw 450mL from the boiler with steam
pressure alone. There is still plenty of steam pressure in the tank
when the hot water stops. The hot water exit is about 6cm from the
bottom edge of the tank and above the top of the heater flange.

I estimate that 450mL is about 2.5cm, so the water level is about 8 or
9 cm. The internal diameter of the tank is about 13cm.


       
Date: 24 Sep 2006 16:04:27
From: Dan Bollinger
Subject: Re: ThermoSyphon Stall
>> The water level in the boiler is too low. The HX is not
>>immersed.
>
> The HX passes from the bottom through the top of the boiler.

If you say so, you never have said what machine this is. I don't know the
internal configuration of your boiler. I do know from experience that an
autofill sensor set too low wil interfere with heat transfer to the HX.

> If the HX were not immersed, the element would be long melted, no?

Again, I don't know your internal configuration, and don't know where your
heating element is located. I wish I did, but I'm just going on what I know and
what information you've provided.

> If the HX were not immersed, the group would never heat, which is not
> the case.

Not! It would heat much more slowly. It may be partially submerged, plus the
heated air will transfer heat, too, but at a slower rate. It is conceivable that
it would return to full temp given time.

> The problem is the group cools after as few as one shot.
> I can turn off the machine and draw 450mL from the boiler with steam
> pressure alone. There is still plenty of steam pressure in the tank
> when the hot water stops. The hot water exit is about 6cm from the
> bottom edge of the tank and above the top of the heater flange.

Plenty of hot water in the boiler, but none in the HX after emptying it once? I
think we agree that heat is not being transferred to the HX. You say it is
bubbles. I say low boiler height. Maybe we are both wrong/right. :)

> I estimate that 450mL is about 2.5cm, so the water level is about 8 or
> 9 cm. The internal diameter of the tank is about 13cm.

Sounds a tad low, but not by much. I figure a depth of 75% to be about right.

Dan



  
Date: 21 Sep 2006 10:26:45
From: Neal Reid
Subject: Re: ThermoSyphon Stall
In article <1158829718.600598.97690@e3g2000cwe.googlegroups.com >,
"CrackAddict" <smppix@gmail.com > wrote:

> One of my two Expobar Office machines exhibits an intermittent
> thermosiphon failure. It's on a timer and the group will be hot most
> mornings, but about one in five, it stalls and needs to have water
> pumped through the group to restart it. When this happens, it takes
> about 20 seconds for water to appear, so it seems that the pump has
> lost prime.

With my machine, that symptom is invariably the seal in (what I
believe is) the overpressure valve - the valve in the loop that
returns water to the tank. It consists f a spring pressing a
rubber gasket onto a brass pipe. Particularly as the gasket ages,
bits get stuck in the seat and, rather than the thermosyphon
heating the group, it heats the tank (slowly).

Until recently, I couldn't find a replacement gasket so I just
regularly (every 3 months or so) took the valve apart, cleaned up
the gasket and polished the seat. A couple months ago, I got feed
up, cut a piece of rubber to size and - so far so good...

--
M for N in address to mail reply


 
Date: 20 Sep 2006 15:42:17
From: jim schulman
Subject: Re: ThermoSyphon Stall
On Wed, 20 Sep 2006 00:54:53 GMT, "I- >Ian" <someone@nowhere.com>
wrote:

>About a week or two ago I started getting a sour third or fourth shot.
>At that point, the machine has been on for at least an hour to an hour
>and a half.
>
>Prior to this, I could not recall a sour shot. The machine is about 3
>months old. I pull 3 or 4 doubles every morning but Sunday. Occasional
>frothing for the missus and occasional hot water for what have you.

The thermosyphon on all machines that have one shuts down ater pulling
a shot (since all the temperatures are equal), and only statrs working
again after the HX has heated up. Semi-commercial E61s usually require
a 30 second to 1 minute rest between shots (90 id one has just
steamed) to maintain temperature. Any flushing when shots are done
this fast will drop the temperature like a stone. It takes about 4 to
5 minutes for the thermosyphon to get going again, and one should only
to quick flushes if the gap between shots is 2 to 5 minutes.

So the least exotic reason why you observed what you did is that you
made these shots in rapid sequence, whereas on the prior occasions you
did not.

Hot water radiator systems (the original thermosyphon) can get locked
up by steam, so lots of bubbles might shut down yours. The problem
with the explanation is that once the water has been in the tank for
an hour, all the dissolved gasses are gone, even if, due to some
glitch at the bottlers, they were there in the bottles. This makes
bubbly water unlikely. You can try using a bottle of seltzer; somehow
I doubt even the bubbles in that would survive lonmg enough to shut
down your thermosyphon.


  
Date: 21 Sep 2006 11:22:12
From: Dan Bollinger
Subject: Re: ThermoSyphon Stall
> So the least exotic reason why you observed what you did is that you
> made these shots in rapid sequence, whereas on the prior occasions you
> did not.

Jim, You said it better than I did in a former post. He's noticing a cooling
effect. Removing hot water and replacing it with cold has a cooling effect until
heat is added back in. Dan




   
Date: 21 Sep 2006 22:51:12
From: jim schulman
Subject: Re: ThermoSyphon Stall
On Thu, 21 Sep 2006 11:22:12 -0400, "Dan Bollinger"
<danNObollinger@insightSPAMbb.com > wrote:

>> So the least exotic reason why you observed what you did is that you
>> made these shots in rapid sequence, whereas on the prior occasions you
>> did not.
>
>Jim, You said it better than I did in a former post. He's noticing a cooling
>effect. Removing hot water and replacing it with cold has a cooling effect until
>heat is added back in. Dan
>

Sorry for repeating what you said; I replied to the top of the thread
without reading the other responses. Very poor netiquette on my part.


  
Date: 20 Sep 2006 22:11:32
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Wed, 20 Sep 2006 15:42:17 -0500, jim schulman
<jim_schulman@ameritech.net > wrote:

>
>So the least exotic reason why you observed what you did is that you
>made these shots in rapid sequence, whereas on the prior occasions you
>did not.

Hi Jim,

Thanks for the input.

If one views the 10s interval time scale, in Min:Sec, at the bottom of
the graph, the first cooling flush is 10:20, the first shot at 13:00

The temperature is heading for the basement when at 22:30 I drew water
from the boiler and the temp immediately climbed back to the normal
level.

At 26:40, I made a small cooling flush and the temperature had
recovered by 30:00 when I made the second shot.

By 33:30 the temp was back to 225

I drew a cooling flush at 34:40 and a shot at 38:30 at which time the
temperature was heading to the bottom.

NO shots or water were drawn until 1:15:40 when I drew water from the
boiler. The temp went up to 200ish for 35 minutes and then up to
225ish where it remained for the rest of the day and night.

FWIW, in the H-B Tamper Road Show, I pulled several kilos of shots
over three days almost non-stop with no problem what so ever.

I'm also a creature of habit, so unless I suddenly compressed my
morning routine by a factor of 5 or so, I don't think I'm any where
close to exceeding the HX when it's functioning normally.

Puzzling, eh, wot


   
Date: 20 Sep 2006 17:32:48
From: jim schulman
Subject: Re: ThermoSyphon Stall
On Wed, 20 Sep 2006 22:11:32 GMT, "I- >Ian" <someone@nowhere.com>
wrote:

>
>If one views the 10s interval time scale, in Min:Sec, at the bottom of
>the graph, the first cooling flush is 10:20, the first shot at 13:00
>
>The temperature is heading for the basement when at 22:30 I drew water
>from the boiler and the temp immediately climbed back to the normal
>level.

D'oh, I didn't see the graph; btw, very cool how one can see the
boiler cycle on the supply but not the return. More significantly, one
can see the boiler cycle creating a much more dramatic temperature
change in the valley period; enough to transmit through to the return.
This indicates that for 25 minutes, the flow was very reduced, but
didn't quite stop.

I'd say a bit of crud in the group is the likliest cause. Short out
the boiler autofill (so it doesn't kick in), and descale the HX and
group with citric acid or a home descaler. Flush 6 ounces or so every
20 minutes or so, and let it circulate in between. If that does it, it
was a bit of calcium. If it doesn't, work on something more exotic.


    
Date: 20 Sep 2006 22:55:13
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Wed, 20 Sep 2006 17:32:48 -0500, jim schulman
<jim_schulman@ameritech.net > wrote:

>
>I'd say a bit of crud in the group is the likliest cause.

That was my first thought, but could not explain the HX restart by
running water from the boiler. Running the pump on a cooling flush for
the same interval as required to refill the boiler does not clear the
problem. Of course the water flow could be keeping the crud in
position.

I have your HX descale post from H-B. If I'm going to descale any
reason not to do the whole enchilada at the same time?

And if it still happens after descale, I guess it's a tear-down?


     
Date: 20 Sep 2006 19:36:41
From: jim schulman
Subject: Re: ThermoSyphon Stall
On Wed, 20 Sep 2006 22:55:13 GMT, "I- >Ian" <someone@nowhere.com>
wrote:

>That was my first thought, but could not explain the HX restart by
>running water from the boiler. Running the pump on a cooling flush for
>the same interval as required to refill the boiler does not clear the
>problem. Of course the water flow could be keeping the crud in
>position.

It could be blocked in the return side of the thermosyphon, then
flushing wouldn't help, but descaling might.

No problem descaling the whole machine, but it (hopefully) shouldn't
affect this problem.

The graph showing the boiler cycle reflected in the thermosyphon
temperatures proves it's not a glitch in the heat transmitting to the
HX. So I can't figure why a boiler flush would affect the low flow. I
think it may be coinicidence.


 
Date: 19 Sep 2006 22:18:17
From: Dan Bollinger
Subject: Re: ThermoSyphon Stall
> Comments? Suggestions?

I don't see how bubbles could 'insulate' the interior of the tubing, and even if
they did, isn't this a good thing? An airlock is more likely to stop the slight
flow of a thermosiphon, but we are talking about a short length of 3/8" tubing.
Not likely. And, you say the effect disappears after awhile. So where are you
mystery bubbles going to?

To me, it is more likely that heat isn't getting into your HX water. That would
explain why later shots and not early ones are effected. Time to descale,
perhaps?

Dan



  
Date: 20 Sep 2006 05:24:45
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Tue, 19 Sep 2006 22:18:17 -0400, "Dan Bollinger"
<danNObollinger@insightSPAMbb.com > wrote:

>> Comments? Suggestions?
>
>I don't see how bubbles could 'insulate' the interior of the tubing, and even if
>they did, isn't this a good thing? An airlock is more likely to stop the slight
>flow of a thermosiphon, but we are talking about a short length of 3/8" tubing.
>Not likely. And, you say the effect disappears after awhile. So where are you
>mystery bubbles going to?
>
>To me, it is more likely that heat isn't getting into your HX water. That would
>explain why later shots and not early ones are effected. Time to descale,
>perhaps?
>
>Dan

Thanks for the ideas, but:

Wouldn't bubbles on either side of the pipe act in the same manner? A
contiguous layer of bubbles on either side would isolate and therefore
insulate one of the water / pipe interfaces, robbing the HX of heat.

It's quite possible bubbles are formed on the HX side, but why then
doesn't the cooling flush shift them?

It's my belief the bubbles are on the boiler side of the HX pipe,
because the cooling flush / pulling shots would presumably move
bubbles on the group side. Drawing water from the boiler clears the
problem. It also stands to reason, I think, that bubbles are likely to
be produced at the heating element / water interface in some quantity.
Whether these are rising and sticking to the HX tube or the bubbles
are 'precipitating out' is anybody's guess.

I thought about scale, but the machine is 'new' and the Arrowhead is
not THAT bad. If it was scale, I don't see how drawing water from the
boiler would cause the effect to stop, do you? Also it's unlikely that
the effect would begin just when I switched water, no?.

Is it possible the scale from Arrowhead is 'reacting' with the
minerals in the CG? Jim?

If heat isn't getting to the HX water how would you explain the step
rise in the HX temperatures. It looks like a switch was flipped, but
the boiler temp is rock solid. Scale would presumably prevent such a
step.

I thought about an air lock, but again, how would drawing water from
the boiler immediately clear the problem.

Any opinion on what effect raising / lowering the pStat pressure might
have, if any? The 1bar setting seems ideal for my use: Gobs of steam
and moderate cooling flush volumes.

Once the effect is gone, I can pull shots at will.


   
Date: 20 Sep 2006 12:39:35
From: Dan Bollinger
Subject: Re: ThermoSyphon Stall
> It's my belief the bubbles are on the boiler side of the HX pipe,
> because the cooling flush / pulling shots would presumably move
> bubbles on the group side.

This doesn't cut it. The amount of new water added to the boiler is only what
is consumed by steaming and that amounts to teaspoon fulls. And, if that was the
culprit, you'd be seeing temperature loss after the boiler automatically
refilled, not after a few shots.

>Drawing water from the boiler clears the
> problem.

Which is then replaced by new, more oxygenated water, which, if your hypothesis
is correct, would exacerbate the problem, not clear it. Right?


> It also stands to reason, I think, that bubbles are likely to
> be produced at the heating element / water interface in some quantity.

Again, only for the meager amount of 'new' water added after an autofill.

I'm not saying that bubbles aren't the culprit. I am saying that it is unlikely,
and perhaps you are trying to make the problem more exotic than it is.

Dan




    
Date: 20 Sep 2006 17:58:17
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Wed, 20 Sep 2006 12:39:35 -0400, "Dan Bollinger"
<danNObollinger@insightSPAMbb.com > wrote:


> Which is then replaced by new, more oxygenated water, which,
> if your hypothesis is correct, would exacerbate the problem, not clear it. Right?

Except the fresh water added to the boiler is heated almost instantly,
rather than 'slowly' as the machine heats up. Presumably, any disolved
gas does not have the opportunity to make bubbles.

>perhaps you are trying to make the problem more exotic than it is

You may be correct, but I can't think of any mundane solution that
would exhibit all the symptoms and results

I'd considered that the bubbles should be forming on the inside of the
pipe as that is where the fresh water goes, but then why would
removing water from the boiler clear the symptom when removing water
from the HX does not.

I'd also considered that the cleaning flush after removing the PF that
drops the HX pressure from ~9.5 to ~0.5 bar could be causing a
spontaneous bubble formation, but leaving the pressure up did not
prevent the issue.

I'd considered that a gas lock could be preventing the HX flow, but
when the problem is absent, there is loads of steam present in a
cooling shot. When the condition is occurring, the cooling shot is
just 'cool' water and no steam.

I'd be thrilled for someone to come up with an alternate theory that
could explain all the mechanisms.


 
Date: 19 Sep 2006 20:14:45
From: Ken Fox
Subject: Re: ThermoSyphon Stall
"I- >Ian" <someone@nowhere.com> wrote in message
news:6021h2hn43a94q3ddv6ptfidm4aqh57qp1@4ax.com...
> About a week or two ago I started getting a sour third or fourth shot.
> At that point, the machine has been on for at least an hour to an hour
> and a half.
>
> Prior to this, I could not recall a sour shot. The machine is about 3
> months old. I pull 3 or 4 doubles every morning but Sunday. Occasional
> frothing for the missus and occasional hot water for what have you.
>
> The machine has a boiler pressure gauge and it was in the normal 0.9
> to 1.1 range. Logs of the external boiler temp vary by not more than
> 2F @ 240F, so the pStat and boiler pressure gauge are spot on.
>
> I had noticed that cooling flushes were very short, so I placed
> thermocouples on the upper and lower thermosyphon tubes where they
> connect to the group.
>
> The image at
> http://www.ielogical.com/coffee/ThermoSyphon.gif
> shows what is happening with this e61 HX machine.
>
> After much head scratching and data logging, I came to the conclusion
> that the thermosyphon tube becomes insulated by gas from the boiler
> water as it is heated.
>
> Steaming the boiler down from 1.1 to 0.5 bar has no effect.
>
> Flushing ~200mL from the boiler appears to clear the air blanket from
> the thermosyphon and serenity is restored.
>
> I attribute the changed behavior to the fact that I'd recently
> switched to Crystal Geyser from Arrowhead Mountain Spring bottled
> water.
>
> To test this hypothesis, I put 100mL each of CG, AH MS and LA DWP
> water in three [nearly] identical [5g] glasses and set them in the
> center of a large pan of water on the stove. I placed a metal skewer
> in each of the glasses to act as a 'precipitator' for the gas and
> slowly heated the pan on a gas flame.
>
> Sure enough, the gas in the Crystal Geyser water formed a blanket of
> very tiny bubbles that are much more immune to perturbation than the
> larger ones formed by Arrowhead or LA DWP water.
>
> Comments? Suggestions?

Switch back to Arrowhead?

ken
;-)




  
Date: 20 Sep 2006 04:26:00
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Tue, 19 Sep 2006 20:14:45 -0600, "Ken Fox"
<morceaudemerdeThisMerdeGoes@hotmail.com > wrote:

>Switch back to Arrowhead?

Wanna job descaling?


   
Date: 19 Sep 2006 22:37:58
From: Ken Fox
Subject: Re: ThermoSyphon Stall
"I- >Ian" <someone@nowhere.com> wrote in message
news:slg1h25a7h5vemsso8c57se1ebh24m3ubk@4ax.com...
> On Tue, 19 Sep 2006 20:14:45 -0600, "Ken Fox"
> <morceaudemerdeThisMerdeGoes@hotmail.com> wrote:
>
>>Switch back to Arrowhead?
>
> Wanna job descaling?

Actually, Ian, I'd move on to cation softened water, which if you can deal
with whatever foul tasting elements may be present in your SoCal water, will
produce very decent shots and eliminate any likelihood of significant
scaling if you will just replace your boiler water every month or so.

ken




  
Date: 20 Sep 2006 03:21:44
From: Marshall
Subject: Re: ThermoSyphon Stall
>"I->Ian" <someone@nowhere.com> wrote in message
>news:6021h2hn43a94q3ddv6ptfidm4aqh57qp1@4ax.com...

>> I attribute the changed behavior to the fact that I'd recently
>> switched to Crystal Geyser from Arrowhead Mountain Spring bottled
>> water.
>>
>> To test this hypothesis, I put 100mL each of CG, AH MS and LA DWP
>> water in three [nearly] identical [5g] glasses and set them in the
>> center of a large pan of water on the stove. I placed a metal skewer
>> in each of the glasses to act as a 'precipitator' for the gas and
>> slowly heated the pan on a gas flame.
>>
>> Sure enough, the gas in the Crystal Geyser water formed a blanket of
>> very tiny bubbles that are much more immune to perturbation than the
>> larger ones formed by Arrowhead or LA DWP water.
>>
>> Comments? Suggestions?

That's very odd. The Crystal Geyser specs are near perfect. I would be
using it now, if they had 5-gallon dispenser bottles and home delivery
(largest size is 1 gal. stand-up bottles, and, as far as I know, you
have to lug them home from the ket yourself).

shall


   
Date: 20 Sep 2006 04:26:34
From: I->Ian
Subject: Re: ThermoSyphon Stall
On Wed, 20 Sep 2006 03:21:44 GMT, shall
<mrfuss@ihatespamearthlink.net > wrote:

>as far as I know, you
>have to lug them home from the ket yourself).

Tell me about it!