Multiplex MB-8-1, Technician'S Handbook

Page: 144 / 178

144 Part Number STH034 3/12
X4 Gear Motor Protect Relay
– This relay coil
energizes when there is current flow through the gear
motor windings. If there is no current flow i.e. open
protector, open windings, no power, the GMPR will not
energize and close contacts 4 and 6 which tie to timer
board terminals 10 and 11 which is the gear motor
proofing circuit. (The timer board will not start the
compressor unless terminals 10 and 11 are closed.)
X5 Water Control Relay
– This relay coil is tied to the
top float switch. At start-up, the inlet water valve
energizes through contacts 1 and 5 to fill the reservoir.
When the reservoir fills and closes the top float switch,
this relay energizes.
•
Contacts 4 and 6 close to make the circuit to
terminals 3 and 4 on the timer board (low water
protection circuit).
• Contacts 3 and 5 close to put the bottom float in
charge of the relay coil (holding circuit).
• Contact 1 is no longer energized to supply voltage
to the inlet water valve.
As ice is made, the water level lowers. When the
bottom float switch (holding circuit) opens:
•
The coil is de-energized opening contacts 3 and 5
and 4 and 6. This opens the low water protection
circuit terminals 3 and 4 and closes contacts 1 and
5 to energize the inlet water valve.
• The incoming water raises the floats and the
operation repeats A above.
• As long as terminals 3 and 4 close within 90
seconds, the unit continues to operate.
Low Water shutdown:
•
If terminals 3 and 4 remain open longer than 90
seconds (no water flow), the timer board cycles the
compressor off and then de-energized the gear
motor relay to stop the gear motor.
• When water flow is restored, the operation reverts
back to A.