Bard WPV48D, Руководство по установке

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Manual 2100-250
Page 19
1. COOLING WITH OR WITHOUT DUCT HEATERS
Whenever the system lever is moved to COOL, thermostat system switch completes a circuit R to O,
energizing the reversing valve solenoid. On a call for cooling, the cooling bulb completes a circuit from
R to G, energizing the blower relay coil. The blower relay contacts complete a 230 volt circuit to the
blower motor and the blower operates. R to Y circuit is completed at the same time as the fan circuit
and current flows from Y to terminal 4 at the lockout relay. Terminal 4 of the lockout relay provides two
paths for current flow.
A. Through the lockout relay coil which offers the resistance of the lockout relay coil.
B. Through the normally closed contacts of the lockout relay to terminal 5 of the lockout relay and then
through the high and low pressure switches to the compressor contactor coil.
If the high pressure and low temperature switches remain closed (refrigerant pressure and temperature
remains normal), the path of least resistance is through these safety controls to the compressor
contactor coil. The contacts of the compressor contactor complete a 230 volt circuit to the compressor
and the compressor runs. If discharge pressure reaches the set point of the high pressure control, the
normally closed contacts of the high pressure control open and current no longer flows to the
compressor contact coil--the coil drops out. Current now can take the path of least resistance through
the lockout relay coil, energizing the lockout relay coil and opening terminals 4 and 5 of the lockout
relay. The lockout relay will remain energized as long as a circuit is completed between R and Y at the
thermostat. In the meantime, since the compressor is operating, refrigerant pressure will equalize and
the high pressure switch will automatically reset. However, the circuit to the compressor contact will not
be complete until the lockout relay is de-energized by moving the thermostat system switch to OFF,
breaking the circuit from R to Y dropping out the lockout relay coil and permitting terminals 4 and 5 to
make. When the high pressure switch closes, a circuit is complete to L at the thermostat, energizing
the signal light to indicate a malfunction. When the system switch is moved from OFF to COOL, the
cycle is repeated.
2. SINGLE STAGE HEAT WITHOUT DUCT HEATERS
Compressor circuit R to Y including lockout relay and pressure controls is the same as cooling. Blower
circuit R to G is the same as cooling. With system switch set to HEAT, no circuit is completed between
R and O and reversing valve solenoid is not energized.
3. TWO STAGE HEAT WITH DUCT HEATERS
First stage heat is the same as single heating without duct heater. When the second stage thermostat
bulb makes, a circuit is completed from C to W2, energizing the duct heater heat contactor, through the
heating element and manual reset limit. C to W2 also simultaneously energizes the 24 volt coil on the
interlock relay, closing the contacts, which in turn energize the low voltage coil on the blower relay to
close the high voltage contacts and power the blower motor. The elements and blower remain energized
as long as C to W2 are made.
4. EMERGENCY HEAT
When the system switch is moved to EMER, the compressor circuit R to Y is disconnected. Control of
the electric heaters is from C to W2 and W3 through the thermostat second stage heating bulb. Blower
operation is controlled by the second stage heating bulb. Operation is the same as above, "Two Stage
Heat with Duct Heaters."
SEQUENCE OF OPERATION