Burnham MST396 - Manual (Page 36)

36
BOILER SEQUENCE OF OPERATION WITH PROBE LWCO (See Figure 18)
When the thermostat calls for heat, it energizes the R8285C Control Center relay which in turn energizes the cad cell
primary control, bringing on the burner. The burner will operate in the following sequence: Prepurge for the first 10
seconds; fire until the thermostat is satisfied or the limit setting on the high limit is reached; post-purge for the last 10
seconds. When the pressure limit control restores the circuit on a drop in pressure, the burner will start if the thermo-
stat is still calling for heat.
The probe low water cut-off will shut down the burner after a 10-15 second delay, if the water level in the boiler drops
below the probe level.
The Hydrolevel CG450 low water cut-off will shut down the burner for 90 seconds every 10 minutes of firing time to
allow water level to stabilize. If the water level is too low the burner will not be allowed to restart.
The probe low water cut-off will reset and restart the burner with a call for heat a few seconds after the water is re-
turned to its normal level.
On burner start, if the cad cell does not see flame within approximately 15 seconds, primary control will shut burner
down and enter into a recycle mode, after 60 seconds burner will restart and repeat trial for ignition. If after three
(3) trials for ignition, flame is not detected, control will enter into restricted mode and must be reset manually before
burner can be restarted.
When there is no demand for heat, the operating control will maintain the boiler water temperature at the selected
setting for proper operation of the domestic water heater, if equipped with optional tankless heater.
BOILER SEQUENCE OF OPERATION WITH PROBE LWCO (See Figure 19)
When the thermostat calls for heat, it energizes the R8285C Control center relay, which in
turn energizes the cad cell primary control, bringing on the burner. The burner will
operate in the following sequence: Prepurge for the first 10 seconds; fire until the
thermostat is satisfied or the limit setting on the high limit is reached; post-purge
for the last 10 seconds. When the pressure limit control restores the circuit on a
drop in pressure, the burner will start if the thermostat is still calling for heat.
The probe low water cut-off will shut down the burner after a 10-15 second delay, if
the water level in the boiler drops below the probe level.
The probe low water cut-off will reset and restart the burner with a call for heat a
few seconds after the water is returned to its normal level.
On burner start, if the cad cell does not see flame within approximately 15 sec-
onds, primary control will shut burner down and enter into a recycle mode, after 60
seconds burner will restart and repeat trial ignition. If after three (3) trials for igni-
tion, flame is not detected, control will enter into restricted mode and must be reset
manually before burner can be restarted.
When there is no demand for heat, the operating control will maintain the boiler
water temperature at the selected setting for proper operation of the domestic
water heater, if equipped with optional tankless heater.
BOILER SEQUENCE OF OPERATION WITH FLOAT LWCO (See Figure 0)
When the thermostat calls for heat, it energizes the R8285C Control center relay, which in turn energizes the cad cell
primary control, bringing on the burner. The burner will operate in the following sequence: Prepurge for the first 10
seconds; fire until the thermostat is satisfied or the limit setting on the high limit is reached; post-purge for the last 10
seconds. When the pressure limit control restores the circuit on a drop in pressure, the burner will start if the thermo-
stat is still calling for heat. The low water cut-off will shut down the burner if the water level in the boiler drops too low.
The control resets and restarts the burner with a call for heat a few seconds after the water is returned to its normal
level.
On burner start, if the cad cell does not see flame within approximately 15 seconds, primary control will shut burner
down and enter into a recycle mode, after 60 seconds burner will restart and repeat trial for ignition. If after three
(3) trials for ignition, flame is not detected, control will enter into restricted mode and must be reset manually before
burner can be restarted.
When there is no demand for heat, the operating control will maintain the boiler water temperature at the selected set-
ting for proper operation of the domestic water heater, if equipped with optional tankless heater.
McDonnell & Miller PS-801
Terminals May be Lettered or
Numbered as Follows:
Wire
Color
Numbered
Terminals
Lettered
Terminals
RD 5 B
BK 1 H
WH 2 N
Jumper 1-3 H-C