Vulcan-Hart MHB24E Electric Steamer User Manual


 
VHX SERIES STEAMER - ELECTRICAL OPERATION
F25154 (February 2004) Page 34 of 48
1) K4(1) N.O. contacts close and K4(1)
N.C. contacts open.
2) High pressure light goes out.
3) K4(2) N.O. contacts close.
a. AUX contactors A & C energized,
heating elements powered.
NOTE: As boiler heats up and builds
pressure, some by-pass water/steam
is produced which runs into the steam
drain box. This causes the cold water
condenser (CWC) solenoid to cycle,
cooling the drain water and
condensing any steam vapors before
exiting the drain. The CWC solenoid is
powered through the CWC cycling
thermostat.
7. Boiler steam pressure reaches upper limit set
point of 12 PSI (Approx. 15 minutes).
A. Cycling pressure switch opens.
1) Cycling contactors B & D de-
energized and power is removed from
heating elements.
8. Boiler steam pressure drops below lower limit
set point of 10 PSI and the cycling pressure
switch closes.
A. Cycling pressure switch continues to cycle
between the upper and lower set point
limits. This energizes and de-energizes the
heating elements to maintain pressure in
the boiler.
This sequence continues until one of the
following occurs:
1) Power switch is turned off.
2) Boiler water level drops below the
LLCO probe for the main water level
control and the AUX LLCO probe for
the auxiliary water level control.
3) Boiler pressurizes to 15 PSI, causing
the high limit pressure switch to open.
Water Refill (After Initial Fill)
1. Water level drops below low level probe (LL).
A. HL relay is energized.
1) HL-3 (N.O.) contacts close.
2) Boiler fill valve is energized.
3) HL LED comes on.
2. Water reaches LL (low level) probe.
3. Water reaches high level probe.
A. HL relay is de-energized.
1) HL-3 (N.O.) contacts open.
2) Boiler fill valve is de-energized.
3) HL LED goes out.
4. The water refill cycle will occur whenever the
water level is below the low level probe and will
not affect the operation of either the preheat or
cook cycle.
Boiler Blowdown/drain
1. Power switch turned off.
A. Automatic blowdown valve (N.O.) is de-
energized and valve opens to drain the
boiler.
B. Power is removed from all components
except cold water condenser (CWC)
thermostat and solenoid valve. The CWC
thermostat cycles as necessary to lower
the discharge temperature of the water and
condense steam going into the drain.
COOKING COMPARTMENT CONTROLS
1. Conditions.
A. Doors shut (closes the N.O. door switch
contacts).
B. Cooking timers off.
C. Compartment pressure switch contacts
open.
2. With boiler at operating pressure.
A. Cooking compartment pressure switch
closes (approx. 3 PSI).
1) Cooking compartment ready light
(green) comes on.
3. Start a cook cycle.
A. Insert product into steamer and close door.
B. Set a cook time.
NOTE: On initial startup, if a cooking timer is set
immediately after the ready light comes on,
steam solenoid chattering will be heard (oil
canning) and the ready lights will flash for
several seconds. This condition is caused by
the manifold steam pressure being on the fringe
of the pressure switch set point. When a cook
timer is set, the compartment steam solenoid
valve opens causing the manifold steam
pressure to drop, slightly below the pressure
switch set point. At the same time, steam
pressure is still increasing in the boiler. This
opposing condition causes a pressure bounce
to occur. After the steam pressure passes
approximately 4 psi this condition subsides.
During normal operation, this condition will not
be seen.
C. Contacts 1/3 of cook timer close and timer
motor is energized.