Quickmill Andreja Premium - slowing temperature rebound

[tellicherry]

Hi,

I've had my Andreja Premium for about a year now and I've run into an annoying problem related to temperature control. I've got one of Eric's temperature adapters installed and I've used it religiously.

This brings me to my problem, my observation that the rebound time after flush has lengthened to the point that seems to be taking me far too long to get through my morning ritual of making cappas.

My idle temp is 214 after a 1 hour warm up. I flush the usual 6-8 oz to bring the temperature down to 190 and then allow the machine to start the rebound. The temperature rises a few degrees then drifts down a few degrees and then very very slowly starts to come back up. It takes nearly 5 minutes for the temp to come back up to 198 at which point I'm ready to pull my shot. Subsequent shots are even worse with re-equilibration times reaching 6 minutes.

This is much different behavior than when the machine was brand new. Based on my early records, the shot rebound time was about 2-2.5 minutes so I know that something has changed.

I've descaled, pulled the mushroom and cleaned the particulates off of the gicleur screen. When that didn't help, I raised the boiler pressure (up to 1.3 bar from 1.0 bar). No difference other than making it more difficult to steam small volumes of milk.

My guess is that something is interrupting the thermosyphon from establishing properly but I can't seen any obvious blockage and don't have any ideas as to what to try next.

I'd love to hear any suggestions you folks might have for me.

Thanks,

Cory

[erics]

I suspect that your grouphead temperature (with that pstat setting) might continue to rise past an indicated 214 although it may take another hour or so.

Normal pstat cycling on a fully warmed up Anita, Andreja, or Vetrano is 35-40 seconds or about 3 cycles in two minutes, 6 cycles in four minutes, etc., etc. What does your's do? I suspect it is in the neighborhood of 60-65 seconds or longer. This is indicative of, as you say, a reduced thermosyphon flow, likely caused by scale still remaining on the hx surfaces.

What was the performance prior to descaling? Did you notice that the degradation occurred over a period of time?

[tellicherry]

Hi,

Thanks for the reply and your thoughts. I actually undertook a complete HX and boiler descale when the rebound time from completion of flush to 198 degrees had stretched out to almost 4 minutes. I expected this would solve the problem but found no improvement. This led me to disassemble the gliceur and look for partially or fully plugged orfices but didn't find this either. I'm using bottled water with less than 3 grains of hardness and the machine is just one year old and it had its full descaling at 9 months. When I pulled the mushroom, I found that much of the chrome was pitted and the brass had a distinct blue green corrosion. There was a collection of chrome flake as well, but none large enough to block anything.

In comparison to the graphs you've posted here, my original characterization of the machine was that I was getting rebound times of about 2.5 minutes (188-187 degree flush temp rebounding to 198). This slowly extended to 3.5 minutes when I started to find it annoying and then to 4 minutes when I decided to clean and descale. In the subsequent four months, the problem has continued to worsen with 5-6 minute rebounds.

With respect to your question about boiler cycle time, I'm finding times that hover just over two minutes - much different than what it sounds like you would expect. From looking at the gauge closely, I think it is more accurate to say that the pstat is keeping the boiler closer to 1.15 bar rather than the 1.3 bar that I originally reported. It seems that the boiler pressure cycle is also wider than it used to be running between 1.0 at the start of the boiler heating cycle and reaching 1.3 when the p-stat trips off.

I can descale the HX again if you guess that it will help. I'm also wondering if I've got a huge bubble that has "locked" the thermosyphon. It seems the only possibility that I can think of right now.

I'll be interested to see what you think!

Cory

[quar]

I see similar performance from my Anita, a sister machine of your Andreja. Eric's graphs show a much faster resposne time that I'm seeing. My numbers are in line with yours. I've also descaled, pulled the mushroom, cleaned the gicleur screen, etc. as well.

I'm wondering if there's been a change in the diameter of the gicleur. My machine is one of the first batch of Anita's back from 2005. IIRC, Eric's machine is around a year old. Wonder if there was a design change shortly after you bought your Andreja. Guess it depends when Eric bought his...

Mike

[erics]

The size of the gicleur in Anita, Andreja, & Vetrano (and lots of other machines) is 0.70 mm. While it will affect the flush rate (and thus the time it takes to cool the grouphead to temperature "x", it is NOT in the thermosyphon loop and thus has NO effect on recovery.

My Anita was purchased (new) in December 2006. It has never been descaled but has been inspected (yanked heating element). The disassembled mushroom assembly has been vinegar soaked but, again, this does not effect the thermosyphon. I use Brita pitcher water which does reduce the hardness but not what you might think - Jim Shulman's "Insanely Long Water FAQ": http://www.big-rick.com/coffee/waterfaq.html gives a better explanation of what Brita (and similar) can do and cannot do.

I am not 100% convinced that in-place descaling works as well as a lot of folks think and I also believe it can take a toll on that little Ulka pump. Seeing before & after pics and a reasonable description of the method employed would sway me but that can be one PITA. I've read a lot of procedures and BELIEVE it works well with a situation involving "light" scaling but once you hit a certain level . . .

Unfortunately, the only way to get a feel for how well the descaling procedure worked would be before & after recovery time numbers or a visual inspection of the hx surfaces. A boiler (pstat) cycle time of two minutes is way too long. The pstat cycles because the steam is continually condensing and reforming on the hx surface as the thermosyphon flow takes place.

[quar]

We do have reasonably hard water here, but I've been using bottled water and mixing it with my filtered water for a resulting TDS of 80ppm. While I did have some scale issues (autofill probe) when my machine was younger, they seem to have been resolved via descaling. There was nothing but the smallest trace of scale on my mushroom when I pulled it. Visual inspection of my hx (what I could see in with the mushroom removed didn't seem to have any evidence of scale. My p-stat takes a much shorter time to cycle than the OPs, but I still take at least 90 to 120 seconds longer to reach 198 than does your Anita. Honestly, I'm stumped. She seems to be performing well in all aspects, just a longer recovery time than reported.

I wonder what the OP and I have in common....

Mike

[Nickel]

I have a Vetrano and the duty cycle of the heater is as always about 10 seconds and the p-stat cycles at about 1.5 minutes. I never see 214 on on the meter but 210. When I do flush I see 214-216 during the flush.

I am confused as to why a longer p-stat cycle indicates a scaled hx. Is it that a longer p-stat cycle is due to boiler scaling and as such indicates the hx is scaled? I was under the assumption that the p-stat cycle was only related to the pressure inside the boiler, and has nothing to do with the hx circuit.

I would also like to know if the teflon gasket at the top of the mushroom was replaced or if it was reused after removal for inspection.

Nick

[erics]

You really need to time around three "cycles" on a fully warmed up machine and then, of course, divide by three - I realize it is a PITA. A cycle is usually defined as the time from the beginning of an event (heater coming on)to the beginning of that same event. You could also "start" your cycle clock when the heater shuts off - just be consistent.

Everytime the heater comes on, you're putting heat into the boiler which causes additional steam to form, replacing that which was condensed on the hx surfaces exposed to the steam. The steam condenses because the water flowing through the thermosyphon loop (inside the hx) is cooler than both the steam and boiler water on the outside of the hx.

The amount of heat per unit time (Btu's per minute) that can be transferred though a scaled hx is less as compared to "new" or recently cleaned machine.

[Nickel]

If I am understanding this, you are talking about the outside of the hx not the inside. Then the boiler is also scaled. A good descaling is in order. This would account for the lengthened p-stat cycle. Is this correct?

Nick

[erics]

Yes, the steam, which occupies anywhere from 1/3 to 1/4 of the boiler volume, continually condenses on the outside surfaces of the hx which are not surrounded by boiler water. However, the cleanliness of both the inside and outside surfaces of the hx are important from the standpoint of heat transfer and both are subject to scale formation.

By ITSELF, boiler surface scaling is actually beneficial as it acts as an insulator. The only drawback to this that comes to mind is the reaction time of the safety thermostat to an overheat condition.

[Nickel]

Thanks Eric. I guess its time to descale. As always, you have the answer for us new to hx machines.

Nick

[erics]

Nick -

Do an HB forum search on "Vetrano & descale".

I believe it may very well be worthwhile to buy an inexpensive pump from Home Depot (or wherever), rig up a small holding tank (1 gallon tupperware or similar) and have at it with some flex hose and hose clamps.

This is probably better in a separate post or as an addition to an existing Vetrano descale thread.

[Nickel]

Eric,
I have read just about every thread that involved descaling as well as all information available on the Vetrano.
It would be helpful to have a new view on the subject of descaling that was machine specific. The Vetrano is a popular machine and a discussion of this machine lends well to other machines of the same design. I know there is other information on this site as to the proper way to descale these machines, but a different point of view as to the whys and hows would be helpful.

Nick

[cafeIKE]

When you descale the boiler, do you over fill boiler so the HX is completely submerged?
If not, then descaling may have reduced effect as the exposed part may still be covered.

See Simplified HX Descale [PourOver] for a method to overfill the boiler.

When I had a pStat in the Vibiemme, idle cycle time was 10 on / 140 off. Never varied.

[erics]

I concur with your numbers Ian. I have a Vibiemme on loan and at a max pstat setting of 0.85 bar, the element is "on" for 13 seconds, and "off" for 133 seconds (based on the measurement of a single cycle with a fully warmed up machine, 67 F ambient).

[tellicherry]

Hi,

I'm back with info and a call for more info.

I've descaled my machine again and not found that it has improved things at all for me. I was a bit skeptical that I've got any serious scale since when I pulled the mushroom during my first descaling adventure, I didn't see even a hint of scale.

Anyway, the problem that I described continues to get worse and I had a 6.75 minute rebound for my shots this morning. I've come to the conclusion that I'm going to have to have to try something else.

I'm thinking that perhaps I've got something that is blocking the thermosyphon in some way and it seems that understanding this problem is going to require a disassembly of the boiler. My question is whether this is a job for mere mortals or if I should just bite the bullet and send it to Chris Coffee for service. I'm handy with tools and don't mind minor repair, but would hate to undertake this project only to find that I can't solve it myself.

Recommendations?

Thanks everyone!

Cory

[cafeIKE]

You may want to pull out the water sensor and check the boiler water depth. If the water level is too low, it may be possible that the thermosyphon is stalling. Normal water level should be 60 to 75% of the boiler depth.

[HB]

Recommendations?

In addition to Ian's suggestion, it may be worth calling Roger at Chris' Coffee. They've seen every problem under the sun and pride themselves on customer service. Do you have a thermocouple to measure temperature? If you stuff a basket with a sponge and gently lock in the portafilter, I believe the measured temperature against the dispersion screen will be around 195F when idle.

[erics]

Earlier in this thread, I said this:

Normal pstat cycling on a fully warmed up Anita, Andreja, or Vetrano is 35-40 seconds or about 3 cycles in two minutes, . . .

I was wrong - as I was basing it on what my Anita did and not fully taking into consideration a minor leak at the vacuum breaker valve. That said, what is your pstat cycle time like on a FULLY WARMED UP machine?

Get out a stopwatch and measure the average "on time" for the heating element over about three cycles, i.e., red light on to green light on. What is your average time? _______. Now, how long does it take for a complete cycle? Fill in the blanks - red light on to red light on _______.

A higher than normal boiler water level would also increase recovery time BUT NOT, I believe, to the extent you are seeing.