Post By Dimal
Adjusting pressurestat: how to tell when it's correct without a pressure gauge?
It's been clear for quite a while that my Bezzera BZ-99 pressure is too low. Steam is truly anaemic; takes 30+ seconds to steam 200ml of milk and it's impossible to get proper microfoam. The temp at the group head is also lower than it should be based on a non-scientific comparison with my other machine (Silvia).
I cracked the seal on the pressurestat and made some small incremental adjustments, but in the absence of a pressure gauge I'm not sure when I should stop. Is there any way to know just from other symptoms when I've gone too high?
Thanks in advance.
Well, without any instruments to verify the outcome of any adjustments, I'd adjust the P/stat about 90° clockwise at a time. Wait at least 30-45 minutes for the machine to stabilise and then flush some water through the group. If it doesn't flash off to steam immediately, try another 90° and wait another 30-45 minutes, and so on...
When you get to a point where you do get water from the group flashing off to steam immediately, it's time to reverse your adjustment a little, say 45° anti-clockwise, wait and try again. When you get to a point where there is no flashing off to steam, you can either leave it there or increase the setting by 22.5° clockwise, wait and try again. If you now just notice a little steam flashing off for a second or two, that's where I'd leave it. The steaming ability will look after itself...
Out of interest, have you ever touched the Maximum Water Level Probe at all? This should always be left at the factory setting to ensure that the correct volume above the water level is maintained to ensure adequate steam production.
Thanks v. much Mal - I only adjusted it about 45 degrees when playing with it yesterday because I wasn't sure how sensitive the mechanism was. In some googling on the subject I found one guide recommending only adjusting 20 degrees at a time, but this may have been for a specific p/stat model because even after I incremented mine up to 45 degrees it didn't significantly change the outcome.
I'll have another go today with your recommended approach.
I have pulled and cleaned the water level probes before, but I made sure to put them back at the same position they were originally. I guess it's possible this original position was wrong, since I bought the machine second-hand. Any way of finding out what the factory position is?
I guess if anyone has a couple of photos "under the bonnet" that they could post up of untouched Probe Heights, or perhaps the measurement of the probe remaining above the boiler fitting. It will be different for all machines so you'd need to get this info for your particular make/model/year to be confident of reasonable accuracy...