KeepRite K40-CU-IM-13 Installation And Maintenance Instructions Manual - page 19
19
System Accessories
In order to ensure trouble free operation of the refrigeration system it is important that the following system
accessories be reviewed and installed.
(a) A
moisture indicating LIQUID SIGHT GLASS should be installed in the liquid line between the
receiver and as close as possible to the expansion valve on the evaporator. If it is mounted on the
condensing unit, it will be mounted downstream of the receiver outlet service valve and immediately
after the liquid line drier. It will change color if there is moisture present in the system. It also allows the
contractor to detect a shortage of refrigerant or flash gas in the liquid line. Bubbles are not normally
visible in the sight glass of a properly charged system, however it is normal to see bubbles appear in the
sight glass for a few minutes when the compressor starts. Bubbles in a sight glass installed on the
condensing unit must never be used as the final indicator for shortage of refrigerant in the
system.
(b)
A
LIQUID LINE FILTER DRIER (sealed or replaceable core) should be installed in the system to
remove foreign matter and moisture that may have entered the system during installation. Liquid line
driers should be installed downstream of the receiver outlet valve and upstream of the liquid line
solenoid valve (if supplied). Liquid line driers may or may not have access valves, depending on the
size and application. They should be replaced whenever there is excessive pressure drop across the
filter, or when the system becomes contaminated due to system leaks, compressor burn-outs, acid
formation, or moisture accumulation as indicated by the moisture indicating sight glass. Refer to the
specific manufacturer’s recommendation for servicing.
(c) A
DISCHARGE MUFFLER may be used to help minimize the noise created in the discharge line of the
compressor. This noise my be the result of variations in piping configuration, the pattern of the gas flow,
line sizes, operating pressures or compressor and unit mounting. A particular combination of gas flow
and piping will result in a resonant frequency, which may amplify the sound and vibration to an
undesirable level. Gas pulsations from the compressor discharge may also be amplified in a similar
manner.
(d) A
DISCHARGE OIL SEPARATOR may be used with flooded systems, low temperature systems and
systems with long runs of piping or other factors that tend to cause oil return problems. They help
maintain oil volume levels in the compressor oil sump.
(e) A
LIQUID LINE SOLENOID VALVE must be installed at the evaporator. Installing a solenoid valve will
allow all of the refrigerant to be pumped out of the low side (evaporator and suction line) when the
thermostat has been satisfied. This reduces the risk of refrigerant migrating or flooding back to the
compressor. Locating the solenoid at the evaporator (instead of the condensing unit) will minimize the
pump-down time and refrigerant capacity required by the receiver.
(f) A
SUCTION LINE FILTER (sealed or replaceable core) when used are always installed upstream of the
compressor suction service valve and any accumulators or other options that may be installed. Suction
filters are equipped with “Schrader” type access valves that allow plugged filters and elements to be
identified quickly when the pressure drops get too high. Refer to the specific manufacturer’s
recommendation for servicing.
(g)
Units equipped with spring-mounted compressors should have VIBRATION ELIMINATORS in both the
suction and discharge lines. They minimize noise transmission and provide flexibility if it is ever
necessary to remove a compressor. Vibration eliminators should be installed at ninety degrees to the
vibration for best results and whenever possible, in a horizontal position, parallel to the compressor
crankshaft. Suction vibration eliminators MUST be insulated on low temperature systems to prevent
refreezing of condensate, causing expansion damage to the bellows inside the eliminator. This
expansion can eventually fatigue the copper bellows causing rupture and loss of refrigerant.
(h) A
SUCTION LINE ACCUMULATOR is used to prevent liquid refrigerant from reaching the compressor.
Liquid flood back can occur for various reasons such as a malfunctioning expansion valve, refrigerant
overcharge, hot gas defrost cycle or extremely low load on the evaporator. An accumulator should be
used if frost or dirt collect on the evaporator coil(s). This can reduce the heat transfer. Some suction line
accumulators are equipped with a built in suction to liquid line heat exchangers. All hot gas defrost
systems must use an accumulator.
(i) A
SUCTION TO LIQUID HEAT EXCHANGER should be used if a system requires long liquid lines from
the receiver to the evaporator or if the liquid has to rise vertically upward any distance. It can help
prevent excessive frosting on the compressor body and increase superheat in the suction line reducing
the possibility of liquid refrigerant from returning to the compressor.
(j) A
PHASE / VOLTAGE MONITOR protects the system against phase loss (single phasing), phase
reversal (improper sequence), high voltage and low voltage (brownouts).