York YCAQ10 - RWT CONTROL LOADING; UNLOADING (DUAL CIRCUIT UNITS); TYPICAL EXAMPLE (4 STAGES); OPTIONAL 6, 7, OR 8 STAGES LOADING;UNLOADING

62 YORK INTERNATIONAL
Loading/Unloading of cylinders is accomplished in re-
sponse to return chilled water temperature as sensed
by the Micro Logic Board and Cooling Range selection.
A typical example is illustrated below (4 stages).
DUAL CIRCUIT UNITS
STANDARD RETURN WATER TEMPERATURE (RWT) CONTROL
LOADING/UNLOADING
*10°F (5.6°C) ¸ 8 stages = 1.25°F (.7°C) between stages of loading.
**If optional 6 or 7 stage loading/unloading is included, Stage 3 loading and unloading is not included on one or both compressor. Therefore, in
the example above, no system response will take place on loading at 50°F (10.0°C) and/or 55°F (12.8°C) and no system response will take
place on unloading at 53.75°F (12.1°C) and 48.75°F (9.3°C).
If optional 6, 7 or 8 stages of unloading is included, typical load-
ing and unloading is illustrated below.
RWT Setpoint = 55°F (12.8°C)
Cooling Range = 10°F (5.6°C)
System Switches = Both ON
SYS 1 = LEAD
Sw. 5 on Micro = ON (Optional 6 or 8 stages of unloading)
Sw. 3 on Micro = OFF (RWT Control)
RWT Setpoint = 55°F (12.8°C)
Cooling Range = 10°F (–12.2°C)
System Switches = Both ON
SYS 1 = LEAD
Sw. 5 on Micro = OFF
(Typical 4 stages of unloading)
Sw. 3 on Micro = OFF (RWT Control)
Return Water
Temp. °F (°C)
55 (12.8) ----------- --------- Lag Compressor Loads Stage 2------- ---------------------------------------
Cooling 52.5 (11.4) --------- --------- Lag Compressor Starts (Unloaded) -- – Lag Compr. Unloads Stage 2
Range 50.0 (10.00) ------- --------- Lead Compressor Loads Stage 2 ----- – Lag Compressor OFF
*10°F (5.6°C) 47.5 (8.6) ---------- --------- Lead Compressor Starts (Unloaded) - – Lead Compr. Unloads Stage 2
45 (7.2) ------------- --------- Both Compressor OFF ------------------- – Lead Compressor OFF
*10°F (5.6°C) ¸ 4 stages = 2.5°F (1.4°C) between stages of loading.
Temperature
Fall
Temperature
Rise
Return Water
Temp. °F (°C)
55 (12.8) ----------- --------- Lag Compressor Loads Stage 4** ---- -------------------------------------
53.75 (12.1) ------- --------- Lag Compressor Loads Stage 3 ------- – Lag Compr. Unloads Stage 4**
52.5 (11.4) --------- --------- Lag Compressor Loads Stage 2------- – Lag Compr. Unloads Stage 3
Cooling 51.25 (10.7) ------- --------- Lag Compr. Starts (Unloaded) Stage 1 – Lag Compr. Unloads Stage 2
Range 50.0 (10.00) ------- --------- Lead Compressor Loads Stage 4**--- – Lag Compr. OFF (Stage 1)
*10°F (5.6°C) 48.75 (9.3) --------- --------- Lead Compressor Loads Stage 3 ----- – Lead Compr. Unloads Stage 4**
47.5 (8.6) ---------- --------- Lead Compressor Loads Stage 2 ----- – Lead Compr. Unloads Stage 3
46.25 (7.9) --------- --------- Lead Compr. Starts (Unloaded) Stage 1 – Lead Compr. Unloaded Stage 2
45.0 (7.2) ---------- --------- Both Compressors OFF ----------------- – Lead Compr. OFF (Stage 1)
Temperature
Fall
Temperature
Rise