Brew pressure, boiler insulate, preheat HX coil for Isomac - Page 2

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Bubble_Boy

#11: Post by Bubble_Boy »

cannonfodder wrote: Once again it will have to time them, but one initial observation, the pressure slowly ramps up to a point, then appears to pause for a second, then continue up to 9 bar.

One side note, with no PF or a PF with a blind basket, it produces a more even rampup with very little needle flutter. With coffee in the basket, I get much more needle flutter. I was going to run a 1/8 inch line as Dan suggested. That would not only dampen the pulsing but make running the line much easier. When I showed the factory boiler pressure gauge to my local plumbing supply stores, they thought that was pretty neat but had nothing to reproduce the connections. Tubing I can get with no problem, the fitting to put on the end of the tubing was the problem.

I will be installing a snubber in the future to dampen the effect more. It is not unusable, but very disappointing.

WOW !!!

good job.

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cannonfodder (original poster)
Team HB

#12: Post by cannonfodder (original poster) »

Incase anyone is wondering, the KPa markings on the gauge are the bar indicators. 200KPa is 2 bar, 800KPa is 8 bar etc... that is a 160psi/11bar gauge. Purchased it from Grainger with the gauge mount kit, it set me back a whopping $11. The drill bits I used to cut the SS were 3x that.
Dave Stephens

lennoncs

#13: Post by lennoncs »

HB wrote:Interesting modification, thanks for sharing the details.

I'm thinking over insulated / preheated HXs as you've done and wondering how much it would flatten the tail end of the temperature profile. Intuitively, I wouldn't expect much of a difference since the flush should still be purging the entire line, essentially meaning the modification is an added foot of hot copper tubing to preheat the water. Are you ready to tap the grouphead for a Scace-mounted thermocouple so we can answer the question authoritatively?

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Dan,

Those 1/8" bored-thru compression fittings are HUGE!
The 1/16" ones are perfect and you could almost get away with no machining on the group, just a drill and tap.

Sean

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cannonfodder (original poster)
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#14: Post by cannonfodder (original poster) »

After trick-or-treat, I powered up my machine and let it heat for about one hour, then ran some tests.

My boiler heats for 4-5 seconds and averages 45 seconds between cycles. Prior to the insulation, the heat kicked on (guessing from prior observations here) around every 30 seconds. You have to take into consideration that I am running my boiler at 1.3 bar, drops to 1.15 bar then heats up so my pressure stat is running a relatively narrow dead band (.15 bar).

If I open the steam valve, my pressure drops to 1.0 then recovers to 1.1 bar in about 5 seconds. It will hold 1.1 bar forever (or at least the two minutes I let it blow steam everywhere). I took a frozen bell pitcher, put a measured 6oz of 43 degree milk in it and opened up the valve. I hit 150 in 36 seconds and it carries over to 154 in another couple of seconds. Normally I stop steaming at 140. Then I took a similar pitcher, filled it with a measured 8oz of 45 degree water. I hit 150 in 45 seconds, carry over to 154 (I am too cheap to waste milk so I used water for the second test).

I also played with my flush timing. There is a sweet spot, now I just have to modify my routine to keep me in that zone. As I surmised, if I run more lower volume flushes, the HX preheat helps me hold a much flatter temperature. If I run two large flushes, then I get a minimal change from the stock to modified temp stability. Using the shorter flushes, I get a much flatter temperature. My recovery time is quicker from shot to shot as well.

I will time the pressure increase tomorrow morning when I pull my shots.
Dave Stephens

rudedog

#15: Post by rudedog »

My Tea is set to 1.1 top end
and the cycle seems to be about 49 seconds.

Man there is some good stuff here on this site.
All these informative posts are great.

I'm really trying.
Been measuring flush temps myself.
It's crazy.

One day I hope to be get this nailed down.

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cannonfodder (original poster)
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#16: Post by cannonfodder (original poster) »

rudedog wrote:One day I hope to be get this nailed down.
Me to.

I may try another type of insulation one day. That pipe insulation is thin and only rated at R2.
Dave Stephens

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cannonfodder (original poster)
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#17: Post by cannonfodder (original poster) »

If anyone wants to see more, I just finished a three part blog post with a more detailed description of the process and lots of photos. I also have a couple of mpg's I want to post as soon as I figure how to reduce the file size. One is a naked shot, the other is all steam but they are 15 and 10 MB respectively, and only 30 and 20 seconds long.
Dave Stephens

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cannonfodder (original poster)
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#18: Post by cannonfodder (original poster) »

I made a few more alterations to my Isomac Millennium.

Even with the oil dampened pressure gauge, I was getting way too much flutter. This not only renders the gauge nearly useless, but will lead to a speedy demise of the gauge. The constant pulsing will blow the diaphragm out of the gauge. I also wanted to reinsulate the boiler. The pipe insulation I had original used had a very low R value and does not provide adequate insulation.

I managed to find the adaptors to convert my ¼ inch T fitting to a 1/8 inch OD pipe, and from the 1/8 inch OD pipe back to the 1/8 inch NPT fitting on the gauge. I purchased 4 feet of soft copper tube and wrapped it around the handle of a screwdriver to create the coil. The smaller tubing, longer length and coils eliminated the entire pump pulsing. The gauge now operates without any flutter.

I pulled the pipe insulation off of the boiler. I used some ceramic foil backed insulation I had left over from a wood burning stove installation. I wrapped the insulation around the boiler and end caps. It does not look pretty, but works very, very, good. With the machine heated and running at 1.3 bar, I can put my hand on the foil backing. It is no hotter than a heating pad.

While I was in there I decided to play with the Pstat setting. I have one of the older pstats with the deadband adjustment screw. I gave it a very small turn to tighten the deadband, and made a very slight increase in boiler pressure. I am getting a .05 deadband now. The boiler cycles from 1.25 to 1.3. I found that to be quite shocking. I did not expect any change.

Unfortunately, with the added insulation, the boiler is now too hot. It steams like a champ, 8 seconds to stretch and about 15 to heat, 15-20 seconds to steam total. I have to run an absurd cooling flush and the HX is overheated in just a few seconds (15-20) so I am constantly pulling 8 oz (or more) flushes to cool the unit before extraction. I am almost afraid to touch the Pstat fearing that my nice tight deadband will go away, but it has to be adjusted down.

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Dave Stephens

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Kristi

#19: Post by Kristi »

I was thinking of just going around the boiler 6 or 8 times (having given no thought whatsoever as to just exactly I would do this without removing the entire boiler!) But taking softwall tube and bending it back and forth on itself a bunch of times, the length of the boiler, and then using a couple of large hose clamps to encourage it in close proximity (BELOW THE STEAM LEVEL), and then putting the insulation over that, would certainly give enough to preheat about a shot's worth. V E R Y interesting idea!!! I would also put the T and the capillary to the pressure gauge just where it goes into the head and HX.

Now I wonder if all that crimping would affect the brew pressure. certainly would help provide a preinfusion ramp-up.....



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cannonfodder (original poster)
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#20: Post by cannonfodder (original poster) »

I cut the HX line, installed a T and ran the HX preheat line down one side of the boiler, looped under the boiler, then back down the top of the far side of the boiler. Then a right angle adapter and a straight shot down to the HX input. I formed the tube very tightly against the boiler and insulated over the entire works forgoing the clamp to hold it to the boiler. I used ¼ soft copper tube and the gentle curves had no impact that I noticed on ramp up pressure timing.

I also wrapped the thermosyphon supply line but left the return line open. I also insulated the hot water tap line to keep the hot water hotter. I was getting 210F out the water tap until the boiler refill kicks in. But if I need more than a few oz of water I just tap it from the 11 liter machine.

Off the T, I ran a 1/16 line with several loops to kill the vibe pump pulsing (hint, wrap it around the handle of a screwdriver to make the nice loops). Then used an above average quality liquid filled gauge with a 1/8 NPT fitting. Most OEM machine gauges are not too precise.

It was a lot of work, but I have an uber flat temperature profile.



But before you start hacking, learn the basics. Spend some time getting to know you new box before you start hacking. The best machine in the world is no substitute for an experienced Barista.
Dave Stephens