Possible Quickmill Anita temperature problem

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GC7

Postby GC7 » Jun 05, 2009, 10:56 pm

I'd really appreciate some advice on the performance of my 9 month old Quickmill Anita HX machine.

Background: The machine has a PID'ed boiler that is set on 250* and that results in about 1.1-1.15 bar pressure. This has been and is constant. I get nice overheated water from the HX and steam with no problem. The NY reservoir water I use has 30-35 ppm solids and much of the early 9 months of use I've Brita filtered it resulting in about 20-25 ppm solids. I've stopped using Brita filtered water the past couple of months. Therefore, I doubt I have problematic scale buildup after 9 months BUT who knows.

The Problem: My grouphead temperature using Eric's probe had always been 213.5 to 214* This was pretty darn constant and my flushes and recoveries had been calibrated on this and all was working well with my drinks. Lately however, the grouphead temperature is down to 210.5 and has even been as low as 209. The boiler temperature is still 250 and the pressure remains 1.1-1.15 bar. I get good overheated water when I initiate a flush and good steaming. My recovery time between drinks is affected and the grouphead temperature measured by the probe seems to get significantly lower after pulling a shot then it did before.

Something seems amiss and it is affecting my espresso. I would not think I need to descale but I really don't know. The ambient temperature in the room is not affected and if anything its warmer now in spring then it was in winter. The only other recent "symptom" I've had was after taking some (250-300 ml) hot water from the tap. The pump continued longer then I expected so I shut the machine down and started it up after a minute of so. It continued pumping and I noticed as much hot water returning to the reservoir as being drained. The boiler therefore was not filling. After shutting down again the pump worked properly and filled the boiler but I do note that the water reservoir does get warm from returning water and I can't say I've seen that much previously.

Can anyone think of what might be lowering my grouphead temperatures and how I can fix it? Could I have a problem with the thermosyphon loop in a QM Anita? Many thanks.

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TimEggers

Postby TimEggers » Jun 06, 2009, 1:38 am

When was the last time you chemically backflushed? My guess would be a coating of coffee oils on the probe...

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GC7

Postby GC7 » Jun 06, 2009, 9:37 am

Tim

Thanks or responding. I religiously backflush with Cafiza every three to (at most) four weeks. I last did it on 4/30. I can check the probe for residue.

In a way your theory might be interesting as I thought it very difficult to believe that the mass of the grouphead could get cooled as easily as it seemed from my temperature readings after flushes. They are not nearly as "off" as in cases I've read here of thermosyphon stall on other brand machines (VBM ?) therefore I don't think that air bubbles or such is my problem.

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erics

Postby erics » Jun 06, 2009, 12:22 pm

Geoffrey -

I would check the water level in the boiler immediately after it goes through its "cold fill" - like in the morning. I just measured the boiler and probe dimensions and the numbers work out such that "design" water level is 4.40" in the boiler. This info contradicts some numbers I provided in a previous post but keep in mind that actual water levels will typically be a little higher than the 4.40" depending upon electrical circuit sensitivity. You can measure water level with a 1/16" wooden dowel, lightly sanded to enable the wood to show the water better.
Image
A water level higher than normal, as would be encountered with some corrosion buildup on the level probe, will reduce grouphead temperatures.

edit - drawing dimensions changed slightly
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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GC7

Postby GC7 » Jun 06, 2009, 8:21 pm

Eric

Thanks for going to the trouble to post that diagram. I'm away from home this weekend with the machine off. I'll get to it when I'm back. I assume I need to remove the water level sensor and use the dowel in its place to do this?

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erics

Postby erics » Jun 06, 2009, 9:12 pm

No, the water level sensor can be a toughie because of access. Of course it can be done but . . .

I would undress the machine a little and turn it on from cold. The fill should come on for about 3 to 4 seconds. Now shut her down and unplug and loosen/disconnect the hot water spigot tubing. You don't need to remove the tube that extends into the boiler. Now simply stick a wooden dowel into the hole and let it go to the bottom of the boiler. Remove & measure. Repeat for good luck.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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GC7

Postby GC7 » Jun 07, 2009, 11:22 am

Hi Eric

Still not home by my machine. I assume the hot spigot outlet with hoses is on top of the boiler where I can get a probe down into the boiler.

If there is corrosion on the sensor probe might that have caused my temporary problem with refill (described above) where hot water continued to flow into the reservoir at the same rate as fresh water was being pumped into the boiler?

Thanks

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erics

Postby erics » Jun 07, 2009, 11:58 am

Yes, the hot water outlet is on top of the boiler. A 6" long, 8 mm tube extends into the boiler to draw water from the bottom. This tube does not need to be removed as your homemade dipstick (1/16" dowel) will be inserted into the above tube till it touches bottom. Once you check the water level this way, you will be amazed as to how simple it really is.

When you use the expression "hot water", is that water you could not hold your finger under? If so, that is water getting past a malfunctioning OPV and NO WATER should get past the OPV under simple flushing or boiler filling conditions. Water does flow from the pump priming valve at all times (except brewing) but this water is at reservoir temperature, i.e., not hot. Anita's water reservoir can reach ABOUT 100 F after being on for, say 8 hours.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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GC7

Postby GC7 » Jun 07, 2009, 2:55 pm

Eric

My impression was that the water returning to the reservoir was VERY hot and quickly made the temperature of the reservoir well above 100*. After shutting down and turning on the machine again it seemed to reurn to "normal" with short bursts of refilling and shut off.

Could an OPV problem affect boiler fill levels and might that be the source of my grouphead temperature fluctuation?

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erics

Postby erics » Jun 07, 2009, 3:45 pm

Could an OPV problem affect boiler fill levels and might that be the source of my grouphead temperature fluctuation?


No, OPV and boiler fill are unrelated, sorta.

HOWEVER, it certainly appears as though you have a leaking or intermittently leaking OPV and that would, in fact, flow water through the hx and out the OPV back to the reservoir even during a boiler fill - see schematic below.
Image
The now cooler hx would remove some heat from the group and lower its temp. So, time to remove the OPV. But before you do, order some replacement parts from CC (new OPV "rubber" insert, new o-ring, food-safe grease).
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com