Elektra D1: One group is much cooler than the other. Why?

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stevescapin
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#1: Post by stevescapin »

Hi,

I noticed something odd and cannot explain the cause of the phenomenon. One group on my two-group machine is much cooler than the other. When I measure the temperature (portafilter fitted with a thermocouple), one group idles at around 90 celsius while the other idles in the low 70. When I activate the hot group, the temperature of the water starts at around 102 celsius and drops to 94 after a few seconds; on the cool group the water creeps to 94 from the low 80 after 10 seconds. I took apart the faulty group and things returned to normal for a few days. I saw nothing wrong when I took the faulty group apart (i.e., scale, etc.). Today, the temperature difference is back. Any idea about the cause of this weird behavior?

Thanks!

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jammin
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#2: Post by jammin »

the first thing that comes to mind is a clogged thermosyphon but it sounds like the jam would have cleared when you took it apart..?

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cafeIKE
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#3: Post by cafeIKE »

Sounds like thermosyphon stall.

If I clean flush for too short a time, say less than about 3 seconds, on the Vibiemmes, the thermosyphon can stall and the group temp drops as described.

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erics
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#4: Post by erics »

It is a thermosyphon stall likely caused by a slight leak in the brew circuit of the cold group. Proving it with a vibe pump machine is pretty easy but in your case (rotary pump), its going to be close. Momentarily flush a couple of seconds worth of water from the "normal" group - the flow should start almost immediately after you push the button. Do the same procedure on the cold group - the flow should hesitate for the time it takes to fill the void (due to the leak) in the hx and then duplicate the other good group.

Yes? If so, the likely culprit is the 3-way solenoid valve.
Skål,

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

stevescapin (original poster)
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#5: Post by stevescapin (original poster) »

Thanks Eric for the thorough answer. Since the coil is working, what I need to change is the pilot on the 3-way solenoid valve, right?

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erics
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#6: Post by erics »

Steve -

Yes, but be careful as to how these parts are sold. Typically it is the whole unit w/ or w/o solenoid coil.

You might also simply unscrew the housing and "pilot" for the valve and let them both soak in some white vinegar for an hour or so. Rinse thoroughly and reinstall.

So . . . the cold group had a little hesitation?
Skål,

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

stevescapin (original poster)
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#7: Post by stevescapin (original poster) »

To be honest, I cannot say that I noticed a significant hesitation. It seemed to be slower to start but not by much. Would this mean that something else could be wrong? I will put the valve in white vinegar just to be sure.

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erics
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#8: Post by erics »

I can think of nothing else that would cause the temperature drop. Injecting only enough water into the hx to cause a flow from the group, you should see a consistent rise in group temp (up to "normal") until the leak rears its ugly head.
Skål,

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

stevescapin (original poster)
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#9: Post by stevescapin (original poster) »

After soaking the pilot in citric acid overnight and doing the same with the interior of the grouphead, I am glad to report that everything is back in order this morning. Let's see if it will last...