38
103536-08 - 4/18
BOILER SEQUENCE OF OPERATION WITH PROBE LWCO (See Figure 20)
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 60 seconds every 15 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 21)
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 McDonnell & Miller PSE-801 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
seconds, 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 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.
McDonnell & Miller PSE-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
Section VI: Electrical (continued)
Summary of Contents for MegaSteam MST288
Page 54: ...54 103536 08 4 18 Bare Boiler Assembly Section XII Repair Parts continued...
Page 56: ...56 103536 08 4 18 Bare Boiler Assembly Section XII Repair Parts continued...
Page 58: ...58 103536 08 4 18 Jacket Assembly Section XII Repair Parts continued...
Page 62: ...62 103536 08 4 18 Beckett AFG Burner Section XII Repair Parts continued...
Page 65: ...65 103536 08 4 18...
Page 66: ...66 103536 08 4 18...
Page 67: ...67 103536 08 4 18...
