070.750-IOM2 (JUN 22)
Page 15
HPS 273 and 407 Rotary Screw Compressor
Installation
Warning
For high temperature applications, consult factory.
Some of the 3-way thermostatic valves do not work
at high temperatures and damage to thermostatic
mixing valves can occur.
A three-way mixing valve, or one of the alternate methods,
provides warm oil to the compressor quickly, reducing the
pressure drop caused by cold, viscous oil. This ensures
cor-
rect
oil ow and temperature over the full range of operat-
ing conditions. For some applications this valve needs to
be a motor-operated valve controlled by the control panel.
This is necessary for a heat pump where the oil is cooled to
a lower temperature than the condensing temperature.
An ideal oil temperature is the same as the condensing
temperature, for example 80°C (176°F).
In a heat pump application there is a risk the discharge
temperature gets too low at low speed, which means some
hot oil must bypass the oil cooler. Discharge temperature
must be a minimum of 10°C (18°F) above condensing tem-
perature. Consult CoolWare and factory, and refer to PID
diagram examples.
Dehydration/evacuation test
Evacuate the system to 1,500 microns. Valve off the
vacuum pump and hold vacuum for one hour.
Pass: Vacuum cannot rise above the 2,000 micron level
during a one hour hold period.
Fail: Vacuum reading goes above the 2,000 micron
level during a one hour hold period. Identify and
repair any system leaks. Repeat vacuum test until
requirements are met.
Electrical installation
The only electrical connection to make to the compressor
is for the solenoid-operated capacity control valve.
Compressor hydraulic system
Note: The solenoid valves and manifold block are available
as a sales order option.
The compressor hydraulic system actuates the mov-
able slide valve (SV) to load and unload the compressor,
which affects the compressor’s capacity. It also actuates
the moveable slide stop (SS) to increase or decrease the
compressor’s Vi, which determines the compressor’s
compression ratio. The hydraulic cylinder located at the
inlet end of the HPS compressor serves a dual purpose. It
is separated by a xed bulkhead into two sections; the SV
section is to the left of the bulkhead and the SS section is
to the right when you are facing the right side of the com-
pressor. Both operations are controlled by double–acting,
four–way solenoid valves, which are actuated when a sig-
nal from the appropriate microprocessor output energizes
the solenoid valve.
Single acting – (> 10.3 bar [150 psi] pressure differential)
Open valve at SC1
Close valve at SC2
Open valve at BP (bypass)
Compressor loading (single acting): the compressor
loads when SV solenoid YY2 is energized and oil ows
from the unload side of the cylinder out port SC1, through
valve ports A and T to compressor suction. Simultane-
ously, discharge pressure loads the slide valve.
Compressor unloading (single acting): the compres-
sor unloads when SV solenoid YY1 is energized and oil
ows from the oil manifold through valve ports P and A to
cylinder port SC1 and enters the unload side of the cylin-
der. Simultaneously, gas on the load side of the cylinder
is vented through port SC2 and valve BP to compressor
suction.
Notice
To control the rate of loading and unloading, throttle
the needle valve at SC1 port.
Compressor loading or unloading (double acting): the
double-acting capability of the solenoid valves enable for
hydraulic assist in loading or unloading when the pres-
sure differential across the compressor is low, for example
greater than 10.3 bar 150 (psid). HPS compressors are
designed to operate in applications where the differential
pressure is higher than the minimum required and as a re-
sult, double-acting operation is not required or suggested
and doing so without instruction from the factory voids
the compressor warranty.
Warning
Operation of HPS compressors in double-acting
mode may result in severe damage to the internal
cylinder piston and spindle arrangement.
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