24
SUPPLY
DUAL AQUASTAT
(#1 SET AT 170F,
#2 SET AT 175F)
SINGLE AQUASTAT
(#3 SET AT 180F)
OUTDOOR THERMOSTAT
(SYSTEM STARTER)
H
ELECTRONIC
LOW WATER
CUTOFF
MANUAL RESET
HI-LIMIT
SAFETY
HI-LIMIT
CIRCULATOR
OUTDOOR BULB
(LOCATED ON NORTH WALL)
SUNSHIELD
FIGURE C2: EXAMPLE OF LEVEL I CONTROL FOR SPACE HEATING ONLY
When outdoor temperature falls below setting of outdoor thermostat, the system is energized and circulator is turned on. All modules will fire until
temperature in return header reaches setting of modulating aquastats. Aquastats will then shut off modules until a point is reached where modules
still firing are just able to satisfy heat load. Example (3-module system), as return temperature rises, dual aquastat "steps-out" module #1 (i.e. at
170F), then module #2 (i.e., at 175F). Single aquastat "steps out" module #3 at maximum return temperature (i.e., at 180F).
N
115V
L1
L2
B
B
RETURN
POWER GAS BURNER
SINGLE POLE
RELAY w/ 115V COIL
TO
DISTRIBUTION
PANEL
HI-LIMIT
AQUASTAT
RETURN
TO CONTROL
PANEL
SUPPLY
BURNER CONTROL
GATE VALVE
LOW WATER CUTOFF
HON. RW700 OR EQUIV.
MANUAL RESET
HI-LIMIT
SUPPLY WATER
TEMP. SENSOR
#1
#2
#3
H2A
N
H3A
N
NO C
IN COM COM 24
VAC
AA
HEAT STARTER
240
VAC
COM 120
VAC
Y
TRANSFORMER
AR
RESET
S
STAGE
S
STAGE
240
NC COM NO
NC COM NO
AC
COM 120 NC
C
NO
SENSOR
SUPPLY
SENSOR
D.A.
SENSOR
COM
OUTSIDE AIR SENSOR
SUPPLY WATER SENSOR
OUTSIDE
AIR SENSOR
L1
L2
B
B
#1
DISPLAY
MODULE
(OPTIONAL)
DOUBLE POLE
RELAY WITH
115 COIL
TO CIRCULATOR
CONTACTOR COIL
#2
#3
115V LINES FROM
FUSED DISCONNECTS
POWER DISTRIBUTION
WIRING
D
DISPLAY
PRESS FOR SETPOINT
1
1
8
8
0
0
REQUIRED:
AA HEAT STARTER
OR
EQUIV. AUTOMATIC
CONTROL (T6031A)
OR
MANUAL SWITCH
(TO AVOID BOILERS
FIRING WITHOUT
CIRCULATOR
OPERATION)
H3A
BOILER
ROOM
SWITCH
MANUAL
RESET
HIGH LIMIT
LOW
WATER
CUTOFF
H2A
N H1
H2 H2
FIGURE C3: EXAMPLE OF LEVEL II CONTROL FOR SPACE HEATING ONLY
When outdoor temperature falls below setting of outdoor thermostat, the distribution panel is energized and circulator is turned on. Reset module
regulates supply water temperature in relation to outdoor temperature. Individual stage modules turn on more modules as the outdoor temperature
falls below their settings.