HydroTherm VGAB Series Installation, Operation And Maintenance Manual page 15

OPERATING SEQUENCE FOR STEAM BOILERS
EQUIPPED WITH STANDING PILOT, VENT
DAMPER, HI-LINIT_ E,C,O & 67 LWCO
I, MOTOR DRIVES VENT DAMPER TO C_IqSE]3 PBSITTJ3N AN]3
REMAINS CLOSED DURING
STANDBY,
STANDING PILOT REMAINS L_,
3, SENS_G
CIRCUIT
IS CONT]]_.E]USLY NBN_TBRED,
4, THERMOSTAT (J3R OPERATING CONTRI]L) CAU_S FOR HEAT,
5,
DAMPER BLADE
DP_S.
6, DAMPER E31"DSWITCH CLOSES G°PJ3XFIJIGVEN-_ DAMPER
OPEN)
7, MAIN
VALVE IS E-NERB-LZ£-D
8. UNIT OPERATES UNTIL THERMOSTAT _R OPERATING
CDNTRD_ IS SATISFIED,
9,
SYSTEN R£-FUPJIS TD STANDBY WITH DAMPER CLOSE-D,
FIELD WIRING
FACTORY WIRING-
PRESSURE 67
CDN_PJ]L LWCD THERMDSTAT
OR DP ER_ T_NG
BLK I
_PEPzJ 13o I t IF
I/S
I
I GAS VALVE
[ -J
U5/24V
TRANSF, U
GAS
--E_ VALVE
SECI2NDARY PRESSURE
CONTROL
IT ANY BE- THE DRIGLNAL W'_P-Z AS SUPPI_ WITH THE APPLIANCE
MUST BE REPLACE-D, ['T MUST BE REPLACED _TN TYPE MT_/ (I05°C)
WIRE DR ITS EQUI_/ALENT,
LI LB
i-_ l15V AC q
tAAA22222J
I15/24V
PFTTT]
42-5745 REV 1
PRESSURE SPILL T'STAT OR
°
RDLLDLrT
S_/,TCH
GAS VALVE
VALVE
-------_SECON'BARY PRESSURE
CQNTEBL
SPILL AND R£]LLDUT S_/ITCHES USED _ INPUT
IS LESS THAN 300,000 BTUH
FIGURE 2.17: WIRING DIAGRAM & OPERATION
SEQUENCE FOR BOILERS EQUIPPED WITH
STANDING PILOT, MCDONNELL-MILLER LOW
WATER CUT-OFF & SECOND PRESSURE
CONTROL (FOR VGA-350 & VGA-400 N.G.)
OPERATING SEQUENCE FOR SREAM BOILERS
EQUIPPED WITH STANDING PILOT, VENT DAMPER,
HI-LIMIT, ECO & CG-400 SERIES LWCO
1, MOTOR DRIVES VENT DAMPER TO CLOSED POSITION AND
REMAINS CLOSED DURING STANDBY,
2, STANDING PILOT REMAINS LIT,
3, SENSING CIRCUIT IS CONTINUOUSLY MONITORED,
4, THERMOSTAT (OR OPERATING CONTROL) CALLS FOR HEAT,
5, DAMPER BLADE OPENS,
6, DAMPER END SWITCH CLOSES (PROVING DAMPER OPEN),
7, MAIN VALVE IS ENERGIZED,
8, UNIT OPERATES UNTIL THERMOSTAT (OR OPERATING
CONTROL) IS SATISFIED,
9, SYSTEM RETURNS TO STANDBY WITH DAMPER CLOSED,
FIELD WIRING
FACTORY WIRING ? THERMOSTAToR OPER
LOW WATER CONTROL
CUTOFF PRESSURE
(N) (H) (B) BUR CONTROL F_
2 l P1 P2 A NER
I
IT F° T ° T I TI _.s,=4v
' / ' 0LOEI k
BLK
GAS VALVE
OAMPRR I_ol I IREO / i_EO I o,,_,I
CONTROL SVALVE
IF ANY OF THE ORIGINAL WIRE AS SUPPLIED WITH THE BOILER
MUST BE REPLACED,USE A SIMILAR WIRE OF 105_ C RATING.
H
t-- 115VAC
LWCO
(H) (B)
L.LU,_.LU..i.,U
115V/24V
Ctq'q'qq
-1
VENT
GAS VALVE
_o
................. I
CONTROL _ o GAS VALVE
N
=i
FIGURE 2.18: WIRING DIAGRAM & OPERATION
SEQUENCE FOR BOILERS EQUIPPED WITH
STANDING PILOT, CG-400 SERIES LWCO &
SECOND PRESSURE CONTROL (FOR VGA-350
& VGA-400 N.G.)
15