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Master-slave unit chilled water pump control
For Master-Slave unit, the Master section and Slave section UC800 systems offer 2 relay contacts of chilled water
pump control separately, total 2 control schemes are provided.
Scheme 1, when the chilled water pump are corresponding with specific unit and controlled by this unit, the relay
contact J2-4 and J2-6 of Master section module 1A20 controls the chilled water pump running and stop, when the
unit receives the running command, this relay contact will close. In most cases of the unit fault diagnostics
appear, this contact will open to shut the chilled water pump, to avoid the pump overheat. The relay contact J2-1
and J2-3 of Slave section module 1A20 need to be connected to chilled water pump control circuit with Master
section water pump control relay 1A20-J2-4 and 1A20-J2-6 in parallel, as part of the evaporator antifreeze
protection, or when entering the oil return protection, the contact needs to close to activate the pump.
Scheme 2, when the chilled water pump is controlled by customer, the relay contacts J2-1 and J2-3 of Master
and Slave section module 1A20 need to be connected to customer's chilled water pump control circuit in parallel,
as part of the evaporator antifreeze protection, or when entering the oil return protection, the contact needs to
close to activate the pump.
Chilled Water Flow (Pump) Interlock
water flow
The UC800 system offers the binary input port for the contact of flow detection device (chilled
switch).
For single unit, when the chilled water pump is corresponding with specific unit and controlled by this unit, the
customer shall connect the water flow switch and the dry contact of the chilled water pump running feedback in
series, then connect to terminal 1X5-39 and 1A6-J3-2. When the chilled water pump is controlled by customer,
the water flow switch needs to be connect to terminal 1X5-39 and 1A6-J3-2.
For Master-Slave unit, when the chilled water pump is corresponding with specific unit and controlled by this unit,
the customer shall connect the water flow switch and the dry contact of the chilled water pump running feedback
in series, then connect to Master section terminal 1X5-39 and 1A6-J3-2. And connect the water flow switch to
slave section terminal 1X539 and 1A6-J3-2. When the chilled water pump is controlled by customer, the water
flow switch needs to be connect to Master section and Slave section terminal 1X5-39 and 1A6-J3-2 separately.
NOTICE - Important!
Do not start/stop the unit by activating/deactivate the chilled water pump, this will lead the compressor(s)
to full load then shut. Utilize the External Auto/Stop input for unit start/stop operation.
Partial Heat Recovery Power Supply
The partial heat recovery heat exchanger and water piping are insulated from ambient air and protected from
freezing temperatures by an electrical heater. It is required to provide an independent power source to the heater.
Note: The heater should only be powered on when the heat recovery heat exchanger has water in it. If partial
heat recovery heat exchanger is drained, the heater must be turned off to avoid heater burnout.
Alarm and Status Relay Outputs (Programmable Relays) - Optional
The UC800 system provides a programmable relay concept for enunciation of certain events or states of the unit.
Total four relays are provided (generally with a Quad Relay Output LLID) as part of the Alarm Relay Output
Option.
The list of events/states that can be assigned to the programmable relay LLID 121 can be found in below table.
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