Fridgewatch 2100 Controller Mk4
Publication 3-58
Section 3
Page 110 of 152
Issue 1.1 : 01/08
Enter configuration mode. Make changes, if required, to Configuration
Settings S41 to S74, i.e. other than S75 to S81 which update the
date/time. Last of all, step through S75 to S80 updating the date and/or
time as required. IMMEDIATELY after altering the minutes value (S80),
step to S81, change the setting to 1 (to update the clock) and return the
Supervisor Key to the Locked position.
Display date and time from the Information Page
→
Date-Time to check
that the current date and time has been input correctly.
S82 Energise outputs 243 and 343 on start-up (units: seconds)
These outputs are normally used for:
243 'on' = 2 or more compressors running.
343 'on' = 3 compressors running.
For special applications, typically multi-circuit direct expansion shell and
tube evaporators, these digital outputs may be used (via a low
consumption relay with reverse bias diode) to energise (open) solenoid
valves in the liquid lines feeding the evaporator circuits.
S82 is normally set to 0 (the default), but for the special application
described above, S82 may be set as described in the example below to
prevent nuisance tripping of the LP cut-out.
Example
This type of evaporator contains two or more refrigerant circuits
with refrigerant metered into each circuit through a thermostatic
expansion valve and liquid line solenoid valve. The solenoid valve
of one circuit is energised (opened) when the compressor starts.
Other circuits are brought into operation as the demand for
refrigeration increases, when the compressor loads to 50 % (say),
or for a multi-compressor application, when the second or third
compressors start or reach a particular load condition.
When the plant starts, one compressor running and only one
evaporator circuit operating, there may be very little condenser
head pressure available to force liquid through the expansion valve
and into the evaporator. This can lead to a rapid fall in suction
pressure, sufficient to trip the LP cut--out and stop the compressor.
If S82 is assigned a value other than 0, the default, on starting the
compressor the evaporator is supplied with extra refrigerant by
energising (opening) the liquid line solenoid valves for all
refrigerant circuits for S82 seconds. The extra refrigerant gas
evolved in the evaporator maintains the suction pressure above the
LP cut-out setting. When S82 seconds expire, all the liquid line
solenoid valves, except one, de-energise (close).
S83 Independent oil level trip for each compressor
Set S83 to 0 for applications using one, two or three compressors
operating on one oil separator/reservoir. The volt-free contacts of the
separator/reservoir oil level switch or opto-sensor conditioning relay are
connected across terminals 119/120 on the 3M101 card (refer to Fig 24)
for compressor 1. A break in the contacts across 119/120 causes all
running compressors to stop.
To avoid spurious trips on applications using two or three compressors
on one oil separator/reservoir, link terminals 219 and 220 and link
terminals 319 and 320 on the 3MIO2 card(s); refer to Fig 26.
