Rocket Appartamento - OPV Adjustment Caused Temperature Spike?

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coolguy121
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#1: Post by coolguy121 »

Just got Rocket Appartamento 6 weeks ago, and kept it factory (~14 bar pressure). Amazing machine!
This morning adjusted OPV by a full turn (now sitting at around 11 bar) and shots from Natural Ethiopian Light Roast tasted much better.

However, from Eric's group thermometer, the idle temp goes higher.
Here is temperature after 30 minute machine idle:
@stock 14 bar: 211 F
@OPV Mod 11 bar: 223 F (over 10 F higher)

This caused a longer flush (with long boiling gurgle) before shot pulls.

Is this normal? Does this damage machine in any ways?

Thanks much for helping out! :D

JRising
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#2: Post by JRising »

I have to assume it's coincidental. Lowering the spring pressure on the pump's OPV to lower the max brew pressure really shouldn't be able to cause a raise in head temperature. I don't doubt your observation, but I think your pressostat may be increasing its deadband and getting a little hesitant to shut off. Does the pressure gauge seem to maintain the same range as always? 1.1 to 1.4 Bar or whatever it usually is for your machine?

Shuka
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#3: Post by Shuka »

Perhaps not useful, but on my (old) Andreja premium, an opv leak lead to killing the thermosyphon action, and reduced brew head temperature. Then, also on that machine, the opv releases the preheated water in the heat exchange during the shot, so a lower opv setting leads to faster reductions in temperature during the shot...
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JRising
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#4: Post by JRising »

Yes. I agree with Shuka.
Making the OPV more likely to relieve could cause a "brew head too cool" issue, but I can't imagine it being the cause of "Brew head too hot".

coolguy121 (original poster)
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#5: Post by coolguy121 (original poster) »

Appreciate the feedback John & Shuka. Seems like this is quite opposite from what usually happens from OPV adjustment.
In regards to boiler pressure, it always stayed at 1.1 - 1.2 bar throughout the idle time and still at 1.1 when pulling shot.

There is one other mod I did, adjusting Brew Switch (behind lever) further back to avoid early pump engagement. Before this, pump engaged on half stop lever, now it has to be fully raised for pump to engage.

From my limited knowledge, I doubt switch adjustment has anything to do with thermosiphon, but I could easily be wrong on this.

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homeburrero
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#6: Post by homeburrero »

Shuka wrote:Perhaps not useful, but on my (old) Andreja premium, an opv leak lead to killing the thermosyphon action, and reduced brew head temperature. Then, also on that machine, the opv releases the preheated water in the heat exchange during the shot, so a lower opv setting leads to faster reductions in temperature during the shot...
Normally an OPV leak creates a vapor bubble that stalls the thermosyphon and causes the group head to idle way too cool. But if it were to leak a whole lot of water you could get in a situation where much of the HX is vapor, and the group is in a steam condensation loop where steam is vaporizing in the HX and then condensing in the group. I've had this mysteriously happen on my Rocket EVO and can easily demonstrate it by draining water from the group with the lever in the midway position and the pump not yet engaged. My machine that normally idles at 203F can go above 220F when I do that.
coolguy121 wrote:There is one other mod I did, adjusting Brew Switch (behind lever) further back to avoid early pump engagement. Before this, pump engaged on half stop lever, now it has to be fully raised for pump to engage.
That, and the way you use the lever, may be causing this issue and not the OPV. Flush a good stream of water and drop the lever quickly and fully, then wait and see if it idles at a normal temp after you do that.
Pat
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coolguy121 (original poster)
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#7: Post by coolguy121 (original poster) »

homeburrero wrote:I've had this mysteriously happen on my Rocket EVO and can easily demonstrate it by draining water from the group with the lever in the midway position and the pump not yet engaged. My machine that normally idles at 203F can go above 220F when I do that.

That, and the way you use the lever, may be causing this issue and not the OPV. Flush a good stream of water and drop the lever quickly and fully, then wait and see if it idles at a normal temp after you do that.
Pat, this makes complete sense now. I did flush fully (with pump on) and quickly drop the lever and 3 way solenoid relieve pressure. After leaving the machine for 10 minutes or so, idle is at normal temperature again (~211F). Thanks for the pointer!

On prior condition where temp >220, I just did a long "pre-infusion" after adjusting the brew switch. It kept running for 15 seconds or so, then I dropped the lever. After leaving for a while, temp spiked to 220 which scared me a bit. Exactly like how you described above.

Just out of curiosity, if this happened a couple times unintentionally, do you know if it harm the thermosyphon or boiler? I just imagine it's not normal to have 220+ F in the circulating in the thermosyphon.

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homeburrero
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#8: Post by homeburrero »

coolguy121 wrote:Just out of curiosity, if this happened a couple times unintentionally, do you know if it harm the thermosyphon or boiler? I just imagine it's not normal to have 220+ F in the circulating in the thermosyphon.
That's not normal, but not enough to damage the machine. You will notice a a noisy and steamy flush. If you pull a shot with it that hot you'll notice an explosion of steam when you drop the lever, and you'll get a chance to learn what espresso tastes like when brewed too hot.
Pat
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