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14 | Sequence of Operation
SEQUENCE OF OPERATION
Cooling Mode
Energizing the "O" terminal energizes the unit reversing
valve in the cooling mode. The fan motor starts when the
"G" terminal is energized.
A fault condition initiating a lockout will de-energize
the compressor irrespective of which stage is
engaged.
Heating Mode
The heating (Y) operates in the same manner as cooling,
but with the reversing valve de-energized. Once the
thermostat is satisfied, the compressor shuts down and
the fan ramps down either fan only mode or off.
COOLING TOWER/BOILER SYSTEMS
The cooling tower and boiler water loop temperature is
usually maintained between 50° F to 100 ° F to assure
adequate cooling and heating performance.
In cooling mode, heat is rejected from the unit into the
water loop. A cooling tower provides evaporative cooling
to the loop water thus maintaining a constant supply
temperature to the unit.
When utilizing open cooling towers, chemical water
treatment is mandatory to ensure the water is free from
corrosive elements. A secondary heat exchanger (plate
frame) between the unit and the open cooling tower may
also be used. It is imperative that all air be eliminated
from the closed loop side of the heat exchanger to
ensure against fouling.
In heating mode, heat is absorbed from the water loop.
A boiler can be utilized to maintain the loop at the
desired temperature.
NOTICE: Water piping exposed to extreme
low ambient temperatures is subject to
freezing.
Consult the specification sheets for piping sizes. Teflon
tape sealer should be used when connecting to the unit
to ensure against leaks and possible heat exchanger
fouling. Do not overtighten the connections. Flexible
hoses should be used between the unit and the rigid
system to avoid possible vibration. Ball valves should be
installed in the supply and return lines for unit isolation
and unit water flow balancing. Pressure/temperature
ports are recommended in both supply and return lines
for system flow balancing. Water flow can be accurately
set by measuring the water-to-refrigerant heat
exchangers water side pressure drop. See specification
sheets for water flow vs. pressure drop information.
8733942456 (2016/04)
NOTICE: No unit should be connected to
the supply or return piping until the water
system has been completely cleaned and
flushed to remove any dirt, piping chips or
other foreign material.
Supply and return hoses should be connected together
during this process to ensure the entire system is
properly flushed. After the cleaning and flushing has
taken place the unit may be connected to the water loop
and should have all valves wide open.
Geothermal (Earth-Coupled) Systems
Closed loop and pond applications require specialized
design knowledge. No attempt at these installations
should be made unless the dealer has received
specialized training. Utilizing the Ground Loop Pumping
Package (GLP), makes the
installation easy. Anti-freeze solutions are utilized when
low evaporating conditions are expected to occur. Refer
to the GLP installation manuals for more specific
instructions.
SYSTEM CHECKOUT
After completing the installation, and before energizing
the unit, the following system checks should be made:
•
Verify that the supply voltage to the heat pump is in
accordance with the nameplate ratings.
•
Make sure that all electrical connections are tight
and secure.
•
Check the electrical fusing and wiring for the correct
size.
WARNING: Ensure cabinet and Electrical
Box are properly grounded.
•
Verify that the low voltage wiring between the
thermostat and the unit is correct.
•
Verify that the water piping is complete and correct.
•
Check that the water flow is correct, and adjust if
necessary.
•
Check the blower for free rotation, and that it is
secured to the shaft.
•
Verify that vibration isolation has been provided.
•
Unit is serviceable. Be certain that all access panels
are secured in place.
Considerations:
WARNING: Always check incoming line
voltage power supply and secondary control
voltage for adequacy
1.
Transformer primaries are dual tapped for 208 and
230 volts. Connect the appropriate tap to ensure a
minimum of 18 volts secondary control voltage. 24
volts is ideal for best operation.
Subject to change without prior notice
CA Model
CA Model
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