Hands up!
How many Techs out there would assume 4 bar (approx 60psi).
Was a satisfactory differential between a systems H.P Cut-out setting and The HP PRV setting?

Basically we had a situation recently where a system condenser fan speed inverter received a electrical spike.
Causing the fans to stop and the H.P pressure to rise to-wards it's H.P. cut-out setting of 20.0 bar.
(H.P. PRV set at 24.0 bar)
3 comps on a common circuit with individual mechanical HP cut-outs.
Comp 1 trips on H.P. comps 2 and 3 do not.
The PRV lifts and then resets!
When the above was re-simulated.
Comp 1 H.P. cut-out at approx 20 bar whereas the other 2 stayed shut until the Technician shut the system down at 21/21.5 bar for fear of lifting the PRV again.

This system is periodically tested for H.P. cut-out operation.
Yet because of the inaccuracy of Mechanical HP switches and a possibly slightly low 24bar set PRV.
A reasonable 4bar diff was proved to be un-suffice!

Obviously we have recommended their replacement.
And I suspect these will be wired in series not parallel as before.
Can anyone think of a reason why they are individually wired?
A long story I know but maybe someone will benefit
Moral.... Periodic reset using nitrogen of the pressure switches is recommended!
Cheers Grizzly