All three have a large center screw for adjusting the pressure; the CEME has a smaller off-center deadband screw. To adjust the boiler pressure:
- Verify the direction for increasing or decreasing the pressure by looking for ± arrows. Manufacturers can change among equivalent thermostat models from one run to the next and the adjustment direction may be different.
- Make very small adjustments, equivalent to five minutes on a clock at most (MA-TER and CEME). The adjustment is much larger for Sirai pressurestats (i.e., one half turn = 0.1 bar). Verify the setting has stabilized by activating the pressurestat at least three to four times before making another adjustment.
- The pressurestat "on" setting is the point where the heating element indicator light illuminates. These readings are slightly higher (lower) than the gauge's lowest (highest) point because the pressure continues to drop below the lower setpoint for a moment after the heating element comes on, and momentarily rises past the higher setpoint after it turns off.
The CEME pressurestat has a smaller dead band screw (sometimes it is painted over). Do not adjust it. A common mistake is to turn it too far and break the pressurestat, which will not be covered under warranty. The deadband factory setting is 0.2 bar; if your machine's setting is markedly greater, call your vendor for assistance.