Post By noidle22
Calibrating a HX machine
I recently got my dad a 2nd hand diadema unico splendor, I think it's about 10 years old. It's great but seems to run quite hot, it needs substantial cooling flushes (well I think so, I've only used a DB, not HX, it steams/splutters for a good 10-20 seconds before calming down). This isn't too much of a problem but does mean it goes through the water in the tank much faster than if it didn't.
From what I've read, HX machines here are "calibrated" so as to not require cooling flushes. Is this possible to do on a machine like this, is it something I can do myself? It was recently serviced at jetblack so I don't think there's anything actually wrong with it, I'm just guessing it's an older model that was sold before this calibration became a thing.
Last edited by Agrajag; 14th May 2018 at 07:32 AM.
Reason: update link
What's it running at by the gauge? It may need turning down if it's clicking off over 1 bar. Though these machines do have a reputation as heat monsters..
You will need to fit a restrictor in the thermosyphon to bring the temperature down. To obtain the correct group temperature by only adjusting boiler pressure will be difficult and will reduce the steaming power considerably.
In my BFC Junior (same boiler/HX setup) I installed a 4mm restrictor with the pressurestat cutoff at just over 1 bar. I think it still may be a little hot though.
I would suggest trying a few sizes between 3.5mm-4.5mm and trialing them out to see which performs the best.
I'm not sure if there is anyone who makes or sells these restrictors but you can get them made or make them yourself if you have the equipment. You will need 1.5mm thick or therabouts copper sheet in which you punch out discs that fit between the top HX pipe and the group head inlet. I don't remember the disc size but you can measure the inlet to the group with a set of calipers and use that measurement.
You drill the appropriate sized hole through the disc them install it between the HX pipe and the group head and tighten down.
You will need a fast response K type or similar thermocouple to measure the water temp, or, install the E61 group head thermometer which can be found online.
Have a chat withJetblack about the machine. I asume they would have noticed if the machine is running too hot.
I'll double check what the gauge is reading, from memory it's about 1 bar but will check.
@noidle22 that's some fantastic information, thanks heaps for that, I understand what the restrictor actually does now. Making one ourselves is probably a bit beyond our ability so we'll probably just make do with long cooling flushes for now and when it's up for its next service we'll see what jetblack can do.
Thanks for the replies all
So in tuning the restrictors...
Does this mean the flow to the group becomes a mix.
Generally the flow through the thermosyphon is from the hx to the group and return. With restrictors, does it mean some water comes through the hx and some from the reversed flow of the thermosyphon and then cool water.
My musica has 2 restrictors, 1 is slightly bigger than the other. I assume this is to balance the flow and get the correct mix of hotter and cooler water.
Tuning this would do my head in. Maybe use needle valves in the first place or go with the musica sizes as a start point.
My understanding is that it just restricts the flow of water to the group, lessening the thermosiphon so the flow through the group is slower so it has more time to cool down = lower temp.
Ok it's up to 1.15. We'll try turning that down to ~1 and see how steam pressure is affected (he mostly drinks espressos anyway)
Originally Posted by Agrajag