Brew pressure, boiler insulate, preheat HX coil for Isomac

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cannonfodder
Team HB

#1: Post by cannonfodder »

Well, I decided I wanted to put a pressure gauge on my millennium. I thought about getting a portafilter mounted gauge but decided I would like to have it available during my brewing session. While I was at it, I decided to add a preheat HX loop around the boiler and then insulate most of the boiler

It is not finished yet, but I was so excited that it all works that I just had to post a couple of quick photos.

This is the back of the machine, I added a T on the HX input. Then I ran a line from the T to the back of the boiler and looped it under and then back along the top. That line then hits an elbow and feeds into the HX. The line off the top of the T runs to a fluid filled 160psi/11bar gauge. Right now the gauge is floating in the air, first mockup just to make sure everything works and does not leak (I had to solder weld the original HX fittings onto a new piece of 1/4" copper tube, more on that at a later date). No leaks and the fluid gauge dampens the needle flutter to only about 5psi. To my surprise, I am getting 10bar on OPV, I will have to adjust that later.

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The gauge will be going just under the boiler gauge. The hard part is going to be cutting that 1 ½ inch hole in that stainless steel. I have a plan but I am too tired to mess with it any more tonight.

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More to come on the process, now off to bed.
Dave Stephens

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HB
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#2: Post by HB »

cannonfodder wrote:No leaks and the fluid gauge dampens the needle flutter to only about 5psi.
All the machines I've seen have dry gauges and eliminate flutter by coiling very thin 1/8" OD tubing several times to act as dampeners. Manufacturers install the tee further downstream to reduce the effects of the vibration pump's pulses and the thin tubing dissipates heat that would otherwise be transmitted to the gauge. I bet replacing the 1/4" OD tubing pictured above with a generous coil of 1/8" OD tubing would give you a rock solid reading.

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Brew pressure gauge tee on the Andreja Premium at the heat exchanger exit
Dan Kehn

lennoncs

#3: Post by lennoncs »

cannonfodder wrote:The hard part is going to be cutting that 1 ½ inch hole in that stainless steel.
The 400 series stainless that seems to be the favorite choice of the manufacturers is nasty stuff to work with, it dulls cutters fast and leaves little magnetic flecks of the stuff everywhere. good luck


Cheers,
Sean


I have found that a 12 gauge with slugs is very fast and effective for the 1.5 inch gauges but I do recommend making sure things are cleared out from behind the panel :wink:

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cannonfodder
Team HB

#4: Post by cannonfodder »

lennoncs wrote: I have found that a 12 gauge with slugs is very fast and effective for the 1.5 inch gauges but I do recommend making sure things are cleared out from behind the panel :wink:
The 12 gauge slug was tempting, but my experience has taught me that when a moderate velocity hunk of soft led hits a very dense and thick metal, you are typically left with a dent and a lot of lead spatter. Now a few steel core copper jacket rounds from my Kolishnakov would sure punch some holes.

After I spun the tip on three drill bits, I was tempted to shoot it, but on further reflection, I decided that would not be a wise decision.

I did, however, go to the hardware store and get a set of dedicated steel drill bits instead of the general purpose bits I was using. Bingo, they cut through that stainless with no problem.

I have to download and edit my photos, then I will put up several photographs and document the process later today. I will say that it works very well, I had one of my best shots ever this morning thanks to the preheat coil and insulation, thermal stability is a wonderful thing.
Dave Stephens

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cannonfodder
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#5: Post by cannonfodder »

I had to cut the HX line to insert a T so I have a place to tap my pressure gauge. The machine fittings are metric so I had to make use of the OEM fittings. After getting the gauge, mount, pipe and fittings I cut the HX line. To my surprise, a standard ¼" pipe fitting does not fit the factory pipe, it must be metric as well. To fix the problem I had to use the OEM fittings and sweat a ¼" pipe into them. Not what I had planned on but thankfully I got everything together and sealed.

I installed my T and ran my pressure gauge line over the top of the boiler and pre-existing lines. From the 'out' side of the T, I ran a line along the side of the boiler to about 1" from the end. Then I looped it under the boiler and back to top. Then I ran it back the full length of the boiler again. This is my preheat line for the HX. Then I ran this into an elbow and down to the original HX input. The parts are labeled in the photo.
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I decided to rearrange the original gauge placement. The new pressure gauge was too deep to mount it where I wanted, and the existing boiler gauge has a nice ring around it which would conceal any irregularities in my hole. So I remove the OEM boiler gauge and mounted my new pressure gauge in that hole. Then I marked the outer circumference of my newly relocated boiler gauge onto the face of the machine.

Now for the hardest part of the entire project, cutting a 1.5" hole in that thick stainless steel. I decided to drill smaller holes just inside the mark and then use a carbide cutter in my rotary tool to connect the dots. I was using general purpose drill bits in a hand drill, trust me, if you decide to drill into this stainless steel, don't use a general purpose bit. I spun out (sheared off the cutting edge) on three drill bits and had not made one hole. So off to the hardware store, I purchased a set of dedicated cobalt bits designed for drilling stainless. The right tool for the job makes all the difference, these cut through that SS with no problem.
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After drilling around the perimeter, I connected the dots with my carbide cutter, now I had a roughed out hole. Make note of the wood behind the hole. If you drill a hole in anything, you should have an appropriate backstop to prevent damaging anything behind your work surface. These bits would cut a copper line in seconds (or drill into your boiler) safety first.
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Once I had the hole, I rounded it out with my cutter, and then ground it out to smooth the edges and shape the hole. Then I mounted my boiler gauge in my newly cut opening and hooked it up. Power the machine up and pressure test everything with a blind basket, then let it heat up and check for leaks again. I repeated this process several times just to make sure there were no leaks.
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Now I wrapped the boiler in foil backed pipe insulation. I insulated the HX preheat line but left the T exposed. While my gauge is rated for quite a bit of heat, why tempt fate. So the T is isolated from the boiler heat to reduce the heat transferred to the new pressure gauge. I also insulated the hot water line. The entire boiler is not covered, I left both ends exposed and a little of the boiler back (where I could not quite reach). This still allows some heat to escape up through the cup warmer but provides enough insulation to heat the HX preheat line and significantly reduce my boiler cycle time.
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Then I buttoned it up, cleaned it up and reinstalled it and hooked up my water supply line.
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The boiler cycle time is significantly reduced. My cooling flushes are now much longer than before due to the preheat line. However, the extraction temp is now much more stable. Using my E61 mounted thermometer, I was getting around a 1 degree drop over the extraction time, now it is more like .4 of a degree. Now before anyone yells about the inherent inaccuracy and latency of the thermometer, let me say I know. But using it as a general guide, I get a much flatter temp than before. My first shot from the machine was very, very good. One of the best I have pulled, and I attribute that to the preheat loop and boiler insulation. If anyone wants to loan me a data logging TC and a thermofilter PF I would be happy to run some real tests!

My hot water dispenser also gained a few degrees thanks to the boiler insulation and insulating the water dispenser line leading from the boiler. One unexpected bonus, steam power, I have a very noticeable increase in the volume of steam because the boiler holds a higher, steadier temperature

The work was worth the end result. The pressure gauge is nice, but the insulation and HX preheat loop made a big difference. I plan on posting a bit more detail as well as more photos on my blog in a day or two if anyone is interested in more detailed photos and descriptions.

One side note unrelated to the mods, my green ready light has been illuminating sporadically for a couple of months now, works some times, doesn't others. It is not critical since I know when my machine is heating because of the red light and I can hear the boiler heating. Anyone else have this problem? Anyone from WLL reading this, I am pretty sure it is still in warranty.
Dave Stephens

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HB
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#6: Post by HB »

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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External front view

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Probe exit above dispersion screen

BTW, did you you notice a drop in the grouphead's idle temperature? I would expect the thermosyphon loop to slow down due to less of a temperature differential.
cannonfodder wrote:One side note unrelated to the mods, my green ready light has been illuminating sporadically for a couple of months now, works some times, doesn't others. It is not critical since I know when my machine is heating because of the red light and I can hear the boiler heating. Anyone else have this problem? Anyone from WLL reading this, I am pretty sure it is still in warranty.
Sounds like flakey wiring. If it's the bulb, Chris' Coffee sells replacement power lights if it really bugs you.
Dan Kehn

tsquared

#7: Post by tsquared »

Do you have some numbers on the post-mod boiler cycle time? My uninsulated Mondiale is cycling 6 seconds on, 60 seconds off and I'm wondering how much of an improvement I'll see if I insulate the boiler.

Also, now that you have a brew pressure gauge, how fast is it hitting 9 bars during the shot?

-T

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cannonfodder
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#8: Post by cannonfodder »

HB wrote: Are you ready to tap the grouphead for a Scace-mounted thermocouple so we can answer the question authoritatively?
Funny you mention that. I have two omegalock fittings in an envelope. I thought about drilling and mounting one in GH, but this was enough work for now. I was thinking more of the Scace portafilter device for now.
HB wrote:BTW, did you you notice a drop in the grouphead's idle temperature? I would expect the thermosyphon loop to slow down due to less of a temperature differential.
I honestly have not had time to do any true testing. I have only pulled three shots since I made the changes. I believe my initial GH temp was about the same prior to my first cooling flush. You can see the temp on the thermometer in the photo. That was after an approximate 45min untouched preheat. I believe that is slightly lower but not enough to call my attention to it.

I noticed that the temp dropped more this morning than it did Sunday during my morning shot. I think that may be a timing issue. I would imagine the cooling flushes will have to be timed a little different. I believe the key will be flushing enough to keep the HX from flash boiling while not running so much water through the preheat loop that I drastically cool the preheat line. i.e. more flushes but of lower volume.

I can say without reservation, that my shots are better. Les harsh, smoother, sweeter, dare I say better cup clarity thanks to the flatter temp? It is almost like having a new machine.
Dave Stephens

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cannonfodder
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#9: Post by cannonfodder »

tsquared wrote:Do you have some numbers on the post-mod boiler cycle time? My uninsulated Mondiale is cycling 6 seconds on, 60 seconds off and I'm wondering how much of an improvement I'll see if I insulate the boiler.

Also, now that you have a brew pressure gauge, how fast is it hitting 9 bars during the shot?

-T
I knew this was going to bite me in the butt after I made the mods. I thought to myself, I should have made some measurements prior to the changes. Unfortunately, I did not, so I only have my observations or rely on, and those can be incorrect on occasion. I will time the cycle times this evening. Your 6 second on cycle sounds about right but the off time sounds longer than my stock config. I do not believe my Isomac was getting 60 seconds between cycles, intuition tells me it was a little shorter than that, maybe in the 40-50 second range.

I know a fellow CG'r that has a millennium, I will have to email him and have him make some observations on his stock machines cycle time, provided we are running the boiler at the same point (my unit is hitting 1.3 at top of cycle and 1.1 at bottom). Any other HB'ers have the same setup? If so, power it up, let it heat for a half hour, do a flush then time the cycles and post them.
Dave Stephens

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cannonfodder
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#10: Post by cannonfodder »

tsquared wrote: Also, now that you have a brew pressure gauge, how fast is it hitting 9 bars during the shot?

-T
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.
Dave Stephens