I have a Expobar office lever that i've been using successfully for 6 months or so. paired with my HG-one, its been a lovely combo.

i just performed my second descale last week. after the descale, i noticed the group doesn't come up to the temperature it used to previously. it idles now at a very low temp that doesn't even register on my orphanespresso temp strips.

once i flush some water thru the group, then it works as before, gets back up to correct temp after some period of time, and will stay idling at the correct temp. i also observe on this first flush that it takes longer than normal before water comes out of the group. subsequent flushes appear to work normally.

it appears from reading this site that i might have a thermosyphon stall of some kind that occurs whenever my machine first turns on. my boiler pressure and temp appear fine.

my question is what part or valve i affected with the descale that has caused this? i have my machine on a timer so its nice to not have to flush and wait for the group to come to correct temp.

Since you report that your TS doesn't seem to work after a descale, the first thing that comes to mind is some grit has loosened and ended up in your TS loop. However you also mention there is more lag before water exits the group. It might be that your OPV is leaking hot water from the HX back to the tank while the machine is idling. I had that very issue and I experienced such delay as well, although my machine doesn' t havd a TS. But if there is constant leaking, pressure cannot build in the HX, the HX water is evaporating, accumulates in the grouphead and is likely to stall the TS circulation. I would dissassemble the OPV and check it for grit.