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the micro sees the temperature dropping at an exces-
sive rate anticipating temperature will soon fall into the
CONTROL RANGE.
When temperatures are in the temperature range
ABOVE THE RATE CONTROL RANGE, the micro will
load the chiller in intervals of 30 sec. to bring the tem-
perature down as quickly as possible. The micro is ca-
pable of providing 20 steps of loading / unloading.
NOTE: The micro’s control loading and unloading re-
sponses on a 20 step scale regardless of the
number of stages present. Therefore, loading
and unloading responses on chillers with less
than 10 steps per module may appear delayed
(time between steps increased) when miss-
ing steps are activated or de-activated by the
micro.
The sequence of loading will always cause the lead
system of the Master Module to start and load first, fol-
lowed by the lad system of the Master Module. As load-
ing continues, the lead system of the Slave Module will
start, followed by the lag system of the Slave Module.
This sequence will always be followed unless for some
reason a refrigerant system safety causes the respec-
tive system to shut down or if a system switch is placed
in the OFF position.
The Master and Slave Microprocessor Boards will indi-
vidually control loading and unloading of their associ-
ated systems. However, the Master Microprocessor will
command the Slave that a correction is necessary and
allow the Slave to implement loading / unloading. The
Master will continue to ask for correction until mixed
leaving water deviation from setpoint is satisfactory. As
mentioned before, loading / unloading timers as well
as rate control software must be satisfied before load-
ing loading / unloading will occur. This reduces the pos-
sibilities of cycling.
Fig. 28 shows the sequence of loading and unloading.
TEMPERATURE
RISE LOAD UNLOAD
20. SLAVE LEAD COMP +3 STEPS, LAG COMP +3 STEPS_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
19. SLAVE LEAD COMP +3 STEPS, LAG COMP +2 STEPS_ _ _ SLAVE LEAD COMP +3 STEPS, LAG COMP +2 STEPS
18. SLAVE LEAD COMP +2 STEPS, LAG COMP +2 STEPS_ _ _ SLAVE LEAD COMP +2 STEPS, LAG COMP +2 STEPS
17. SLAVE LEAD COMP +2 STEPS, LAG COMP +1 STEP_ _ _ _ SLAVE LEAD COMP +2 STEPS, LAG COMP +1 STEP
16. SLAVE LEAD COMP +1 STEP, LAG COMP +1 STEP_ _ _ _ SLAVE LEAD COMP +1 STEP, LAG COMP +1 STEP
15. SLAVE LEAD COMP +1 STEP, LAG COMP UNLOADED_ _ SLAVE LEAD COMP +1 STEP, LAG COMP UNLOADED
14. SLAVE LEAD COMP +3 STEPS, LAG COMP OFF_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ *
13. SLAVE LEAD COMP +2 STEPS, LAG COMP OFF_ _ _ _ _ _ SLAVE LEAD COMP +2 STEPS, LAG COMP OFF
12. SLAVE LEAD COMP +1 STEP, LAG COMP OFF_ _ _ _ _ _ SLAVE LEAD COMP +1 STEP, LAG COMP OFF
11. SLAVE LEAD COMP UNLOADED LAG COMP OFF_ _ _ _ _ _ SLAVE LEAD COMP UNLOADED LAG COMP OFF
10. MASTER LEAD COMP +3 STEPS, LAG COMP +3 STEPS_ _ _ MASTER LEAD COMP OFF, LAG COMP OFF
9. MASTER LEAD COMP +3 STEPS, LAG COMP +2 STEPS_ _ _ MASTER LEAD COMP +3 STEPS, LAG COMP +2 STEPS
8. MASTER LEAD COMP +2 STEPS, LAG COMP +2 STEPS_ _ _ MASTER LEAD COMP +2 STEPS, LAG COMP +2 STEPS
7. MASTER LEAD COMP +2 STEPS, LAG COMP +1 STEP_ _ _ _ MASTER LEAD COMP +2 STEPS, LAG COMP +1 STEP
6. MASTER LEAD COMP +1 STEP, LAG COMP +1 STEP_ _ _ _ MASTER LEAD COMP +1 STEP, LAG COMP +1 STEP
5. MASTER LEAD COMP +1 STEP, LAG COMP UNLOADED_ _ MASTER LEAD COMP +1 STEP, LAG COMP UNLOADED
4. MASTER LEAD COMP +3 STEPS, LAG COMP OFF_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ *
3. MASTER LEAD COMP +3 STEPS, LAG COMP OFF_ _ _ _ _ _ MASTER LEAD COMP +2 STEPS, LAG COMP OFF
2. MASTER LEAD COMP +1 STEP, LAG COMP OFF_ _ _ _ _ _ MASTER LEAD COMP +1 STEP, LAG COMP OFF
1. MASTER LEAD COMP UNLOADED, LAG COMP OFF_ _ _ _ _ _ MASTER LEAD COMP UNLOADED LAG COMP OFF
MASTER LEAD COMP OFF, LAG COMP OFF_ _ _ _ _ _ MASTER LEAD COMP OFF, LAG COMP OFF
TEMPERATURE
FALL
* This step is skipped on a temperature drop.
FIG. 28 – 20 STEP LEAVING WATER CONTROL LOADING / UNLOADING