Blodgett SB-E Series - Manual (Page 14)

12 OM-E-SB
Sequence of Operation
When electrical power is turned on to the unit, the following happens:
• The drain valve closes
• The water valve opens
• The unit fills with water
As the boiler fills, the water is detected by two probes. The first of these is the “mid”
probe, which activates the RESET light. The second (“hi” probe) is reached when the
boiler is full, and shuts off the water supply. As the water supply drops below this
probe, the water supply opens until it is again reached.
A thermostatically-controlled air vent remains open while the boiler fills. As steam
begins to develop, this vent will close. Some steam may escape from this vent before
it is fully closed (at approximately 200ºF).
Once the pressure has reached 12 PSI (kPa), the operating pressure switch will open
the heater element contactors. As pressure decreases, the heater element contactors
close to maintain the pressure at 12 PSI (83 kPa).
If something causes the pressure to pass 14½ PSI, (100 kPa), a high-limit safety
switch will electrically shut down the boiler. If this happens, the unit should not be re-
started until the problem which caused the shut-down has been corrected.
As an additional safety measure, the unit is equipped with an A.S.M.E.-certified safety
valve which will open to relieve excess pressure at 15 PSI. The ability of this valve to
discharge steam pressure is greater than the boiler’s ability to generate steam.
When the “ON/OFF” switch is turned “OFF,” a thermostatic switch mounted on
the boiler shell will keep the drain valve closed until the temperature drops to
approximately 130°F (77°C). Then the switch opens, and water drains from the boiler.
A vacuum breaker allows air to enter the boiler.
CAUTION
ESCAPING STEAM MAY CAUSE SEVER
BURNS. STAY AWAY FROM THERMOSTATIC
AIR VENT AND PRESSURE RELIEF VALVES.