1 HVACR 317 Refrigeration Core System Components Compressors
System Components Compressors
Slide 2
2 Compressor Types There are five types of compressors: Screw
Centrifugal Reciprocating Scroll Rotary There are five types of
compressors: Screw Centrifugal Reciprocating Scroll Rotary
Slide 3
3 Dunham Bush
Slide 4
4 Screw Compressors Used on large chilled water and
refrigeration systems. Available in sizes of 20 tons and up. Have
very little vibration. Use a pair of special helical rotors
(screws). Used on large chilled water and refrigeration systems.
Available in sizes of 20 tons and up. Have very little vibration.
Use a pair of special helical rotors (screws).
Slide 5
5 Trane Chiller
Slide 6
6 Trane Compressor
Slide 7
7 Inside the Screw Compressor
Slide 8
8 Compression Diagram
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9
Slide 10
10 Screw Compressors Screw compressors will operate smoothly
when capacity is reduced as low as 10%. Capacity control on screw
compressors is accomplished by re-circulating refrigerant vapor
inside the compressor. Screw compressors will operate smoothly when
capacity is reduced as low as 10%. Capacity control on screw
compressors is accomplished by re-circulating refrigerant vapor
inside the compressor.
Slide 11
11 Screw Compressors The refrigerant vapor is drawn into the
spaces between the lobes of the screws. As the void (open area)
between the screws get smaller, the gas is compressed and piped to
the condenser. The refrigerant vapor is drawn into the spaces
between the lobes of the screws. As the void (open area) between
the screws get smaller, the gas is compressed and piped to the
condenser.
Slide 12
12 Screw Compressors Screw compressors come in various types:
Hermetic Semi-Hermetic Open (external drive) Again, very little
vibration as it has a continuous pumping action. Screw compressors
come in various types: Hermetic Semi-Hermetic Open (external drive)
Again, very little vibration as it has a continuous pumping
action.
Slide 13
13 Screw Compressors
Slide 14
14 Centrifugal Chiller
Slide 15
15 Centrifugal Compressors Used in large commercial
refrigeration systems. Uses impellers or wheels Designed to operate
at high speeds Vapor is moved rapidly in a circular path using
centrifugal force. Used in large commercial refrigeration systems.
Uses impellers or wheels Designed to operate at high speeds Vapor
is moved rapidly in a circular path using centrifugal force.
Slide 16
16 Centrifugal Compressors Diagram
Slide 17
17 Centrifugal Compressors Operation: Compression is caused by
spinning the mass of vapor refrigerant at high speeds. This outward
spinning refrigerant is then caught in a channel It is then
compressed by the flow of refrigerant behind it. Operation:
Compression is caused by spinning the mass of vapor refrigerant at
high speeds. This outward spinning refrigerant is then caught in a
channel It is then compressed by the flow of refrigerant behind
it.
Slide 18
18 Centrifugal Compressors In the centrifugal compressor, there
are no valves. Refrigerant enters through the suction inlet, then
through suction passages into the first wheel. The refrigerant
enters the wheel through openings near the shaft. In the
centrifugal compressor, there are no valves. Refrigerant enters
through the suction inlet, then through suction passages into the
first wheel. The refrigerant enters the wheel through openings near
the shaft.
Slide 19
19 Multi-Stage Compressor
Slide 20
20 Centrifugal Compressors Refrigerant is then slung outwards.
It is then is forced through the discharge outlet, then onto the
compressor. Lubrication is needed only at the end bearings;
therefore, centrifugal compressors are mostly oil free. Refrigerant
is then slung outwards. It is then is forced through the discharge
outlet, then onto the compressor. Lubrication is needed only at the
end bearings; therefore, centrifugal compressors are mostly oil
free.
Slide 21
21 Centrifugal Compressors Do not need any valves or pistons.
Operate at very high speeds. Do not need any valves or pistons.
Operate at very high speeds.
Slide 22
22 Reciprocating Compressors Used in domestic and commercial
refrigeration units. They are a piston type compressor. Normal
RPMs: Older units 1725 rpm Newer unit 3450 rpm Used in domestic and
commercial refrigeration units. They are a piston type compressor.
Normal RPMs: Older units 1725 rpm Newer unit 3450 rpm
Slide 23
23 Reciprocating Compressors These compressors are hermetically
sealed. Motor and compressor are sealed in a steal dome. External
switching must be provided. These compressors are hermetically
sealed. Motor and compressor are sealed in a steal dome. External
switching must be provided.
Slide 24
24 Reciprocating Compressors Dome is on the low side of the
system. Suction line ends at the steal dome. Fills the dome with
low temperature vapor. Dome is on the low side of the system.
Suction line ends at the steal dome. Fills the dome with low
temperature vapor.
Slide 25
25 Reciprocating Compressors Optional oil cooler Not present on
all models. Is an additional loop of pipe going through the
crankshaft. Removes heat from the oil. If not used on your unit,
then cap the tubes off. Optional oil cooler Not present on all
models. Is an additional loop of pipe going through the crankshaft.
Removes heat from the oil. If not used on your unit, then cap the
tubes off.
Slide 26
26 Reciprocating Compressor Main parts: Cylinder Pistons
Connecting Rods Crankshaft Cylinder Head Valves Main parts:
Cylinder Pistons Connecting Rods Crankshaft Cylinder Head
Valves
Slide 27
27 Reciprocating Compressors The crankshaft and connecting rods
change the rotating motion of the motor into a reciprocating
motion. This reciprocating motion causes an up and down motion on
the pistons. The crankshaft and connecting rods change the rotating
motion of the motor into a reciprocating motion. This reciprocating
motion causes an up and down motion on the pistons.
Slide 28
28 Reciprocating Compressor When the piston is at the bottom:
The suction valve is open. The cylinder fills with low temperature,
low pressure vapor. When the piston is at the bottom: The suction
valve is open. The cylinder fills with low temperature, low
pressure vapor.
Slide 29
29 Reciprocating Compressors As the piston travels up: The
suction valve closes The cylinder pressure is greater than the
suction pressure. As the piston travels up: The suction valve
closes The cylinder pressure is greater than the suction
pressure.
Slide 30
30 Reciprocating Compressor When the piston is at the top The
temperature and pressure have increased. A predetermined pressure
opens the discharge valve. High temperature, high pressure vapor
flows to the condenser. When the piston is at the top The
temperature and pressure have increased. A predetermined pressure
opens the discharge valve. High temperature, high pressure vapor
flows to the condenser.
Slide 31
31 Reciprocating Compressors When piston is at the top, contd:
There is dead space between the piston and the valve space. This
dead space, or clearance volume, is one of the reasons that
reciprocating compressors are not 100% efficient. When piston is at
the top, contd: There is dead space between the piston and the
valve space. This dead space, or clearance volume, is one of the
reasons that reciprocating compressors are not 100% efficient.
Slide 32
32 Reciprocating Compressors Diagram
Slide 33
33 Reciprocating Compressors Diagram
Slide 34
34 Reciprocating Compressors Reciprocating compressors are
categorized by housing and by drive mechanisms. Housing categories:
Hermetic Semi-Hermetic Open Reciprocating compressors are
categorized by housing and by drive mechanisms. Housing categories:
Hermetic Semi-Hermetic Open
Slide 35
35 Reciprocating Compressors Hermetic (fully welded) Motor and
compressor are contained inside a single shell that is welded
closed. Sometimes called a tin can. You cannot service hermetic
compressors without cutting the shell open. These compressors are
disposable. They are cooled with suction vapor. Hermetic (fully
welded) Motor and compressor are contained inside a single shell
that is welded closed. Sometimes called a tin can. You cannot
service hermetic compressors without cutting the shell open. These
compressors are disposable. They are cooled with suction
vapor.
Slide 36
36 Reciprocating Compressors
Slide 37
37 Reciprocating Compressors
Slide 38
38 Reciprocating Compressors
Slide 39
39 Reciprocating Compressors
Slide 40
40 Reciprocating Compressors Semi-Hermetic Motor and compressor
are contained inside a single shell that is bolted together. They
can be serviced by a technician by removing the bolts and opening.
Semi-Hermetic Motor and compressor are contained inside a single
shell that is bolted together. They can be serviced by a technician
by removing the bolts and opening.
Slide 41
41 Reciprocating Compressors Semi-hermetic, contd Generally use
a splash type lubricating system in smaller compressors, or a
pressure lubricating system in larger compressors (oil pump). Often
air cooled as well as vapor cooled. Fins in the casting. Fan
mounted on top of compressor. Semi-hermetic, contd Generally use a
splash type lubricating system in smaller compressors, or a
pressure lubricating system in larger compressors (oil pump). Often
air cooled as well as vapor cooled. Fins in the casting. Fan
mounted on top of compressor.
Slide 42
42 Reciprocating Compressors Semi-Hermetic, contd Sometimes are
water cooled. By use of a water jacket around the compressor.
Semi-Hermetic, contd Sometimes are water cooled. By use of a water
jacket around the compressor.
Slide 43
43 Semi-Hermetic Compressors
Slide 44
44 Semi-Hermetic Compressors
Slide 45
45 Semi-Hermetic Compressors
Slide 46
46 Semi-Hermetic Compressors
Slide 47
47 Semi-Hermetic Compressors
Slide 48
48 Semi-Hermetic Compressors
Slide 49
49 Semi-Hermetic Compressors
Slide 50
50 Semi-Hermetic Compressors
Slide 51
51 Semi-Hermetic Compressors
Slide 52
52 Reciprocating Compressors Open Compressors The compressor
and its motor are separate, connected by belts or special
couplings. This compressor can be serviced and/or rebuilt in the
field. Will most often develop leaks at the shaft seal. Open
Compressors The compressor and its motor are separate, connected by
belts or special couplings. This compressor can be serviced and/or
rebuilt in the field. Will most often develop leaks at the shaft
seal.
Slide 53
53 Reciprocating Compressors Open Compressors (Shaft Seals)
Shaft seals are used on Open Drive Compressors They are designed to
prevent refrigerant leaks. Open Compressors (Shaft Seals) Shaft
seals are used on Open Drive Compressors They are designed to
prevent refrigerant leaks.
Slide 54
54 Reciprocating Compressors All seals use two rubbing surfaces
One surface turns with the crankshaft and is sealed to the shaft
with the O-Ring. Other surface is stationary and is mounted to the
shaft housing. All seals use two rubbing surfaces One surface turns
with the crankshaft and is sealed to the shaft with the O-Ring.
Other surface is stationary and is mounted to the shaft
housing.
Slide 55
55 Reciprocating Compressors The rubbing surface can be made
from: Hardened steel and bronze Ceramic and carbon Teflon Graphite
These surfaces must be lubricated. The rubbing surface can be made
from: Hardened steel and bronze Ceramic and carbon Teflon Graphite
These surfaces must be lubricated.
Slide 56
56 Reciprocating Compressors There are four types of shaft
seals: Packing Gland Stationary Unbalanced Diaphragm type Rotary
There are four types of shaft seals: Packing Gland Stationary
Unbalanced Diaphragm type Rotary
Slide 57
57 Reciprocating Compressors Drive Type (continued)
Semi-Hermetic The compressor and motor are combined in one housing.
This compressor can also be serviced in the field but service is
limited. Drive Type (continued) Semi-Hermetic The compressor and
motor are combined in one housing. This compressor can also be
serviced in the field but service is limited.
Slide 58
58 Reciprocating Compressors Drive types (continued) Hermetic
The compressor and motor are combined in one housing that is welded
closed. This compressor is not serviceable at all. Drive types
(continued) Hermetic The compressor and motor are combined in one
housing that is welded closed. This compressor is not serviceable
at all.
Slide 59
59 Reciprocating Compressors Piston Quantity and Arrangement
One to 16 pistons Arrangement can be: Vertical with 1-3 cylinders V
Type with 2,4, or 6 cylinders W Type in multiples of 3 cylinders
Radial with multiples of 5 cylinders X Type with multiples of 4
cylinders Piston Quantity and Arrangement One to 16 pistons
Arrangement can be: Vertical with 1-3 cylinders V Type with 2,4, or
6 cylinders W Type in multiples of 3 cylinders Radial with
multiples of 5 cylinders X Type with multiples of 4 cylinders
Slide 60
60 Compressors General Info The lifespan and efficiency of the
compressor is based on the maintenance of the system. Dirty
condenser coils, and improper charges can overheat compressors and
raise pressures too high. This will affect both efficiency and life
span. The lifespan and efficiency of the compressor is based on the
maintenance of the system. Dirty condenser coils, and improper
charges can overheat compressors and raise pressures too high. This
will affect both efficiency and life span.
Slide 61
61 Compressors, General Info Multiple compressors provide
capacity control. In other words, when you have additional load you
can use more than one compressor. If you have less load, you use
fewer compressors.
Slide 62
62 Checking Valves Instructions for Checking Valves Install
gauges on unit. Bleed air to service valves. Jump low pressure
control. Start compressor. Turn low-side valve in two turns. Read
low-side pressure Instructions for Checking Valves Install gauges
on unit. Bleed air to service valves. Jump low pressure control.
Start compressor. Turn low-side valve in two turns. Read low-side
pressure
Slide 63
63 Checking Valves Instructions for Checking Valves, Contd Turn
high-side valve in two turns. Read high-side pressure. Front seat
low-side valve. Read low-side pressure. If 20 hg vacuum is reached
in two minutes, low-side valves are good. Instructions for Checking
Valves, Contd Turn high-side valve in two turns. Read high-side
pressure. Front seat low-side valve. Read low-side pressure. If 20
hg vacuum is reached in two minutes, low-side valves are good.
Slide 64
64 Checking Valves Instructions for Checking Valves, Contd. If
20 vacuum cannot be reached in two minutes, low-side valves are
bad. Replace them. Next, stop compressor with low-side valves front
seated. Read low-side pressure. If pressure remains lower than 20
vacuum, discharge valves are good. Instructions for Checking
Valves, Contd. If 20 vacuum cannot be reached in two minutes,
low-side valves are bad. Replace them. Next, stop compressor with
low-side valves front seated. Read low-side pressure. If pressure
remains lower than 20 vacuum, discharge valves are good.
Slide 65
65 Checking Valves Instructions for Checking Valves, Contd. If
pressure remains lower than 20, vacuum discharge valves are good.
If pressure rises higher than 20 vacuum, then discharge valves are
bad. Replace them. Never front seat discharge service valve while
running. To finish up, back seat both valves and remove gauges.
Instructions for Checking Valves, Contd. If pressure remains lower
than 20, vacuum discharge valves are good. If pressure rises higher
than 20 vacuum, then discharge valves are bad. Replace them. Never
front seat discharge service valve while running. To finish up,
back seat both valves and remove gauges.
Slide 66
66 Lubrication Systems There are three types of lube systems:
Splash Type Forced Lubrication 3HP and Larger Systems There are
three types of lube systems: Splash Type Forced Lubrication 3HP and
Larger Systems
Slide 67
67 Lubrication Systems Splash Type: Use fingers on a shaft
which splashes oil up onto the pistons and shaft. Used in older
compressors. Splash Type: Use fingers on a shaft which splashes oil
up onto the pistons and shaft. Used in older compressors.
Slide 68
68 Lubrication Systems Forced Lubrication: Small systems 3 HP
and below use the crankshaft and piston movement to force oil to
the bearings. Sometimes a combination of fingers on the shaft and
the forced lubrication is used. Forced Lubrication: Small systems 3
HP and below use the crankshaft and piston movement to force oil to
the bearings. Sometimes a combination of fingers on the shaft and
the forced lubrication is used.
Slide 69
69 Lubrication Systems Larger Systems - 3HP and above A pump is
mounted on the rear bearing housing. Oil is forced through a
machined series of holes to the compressor bearings and connecting
rods. Oil pump intake is connected to the compressor crankcase.
Larger Systems - 3HP and above A pump is mounted on the rear
bearing housing. Oil is forced through a machined series of holes
to the compressor bearings and connecting rods. Oil pump intake is
connected to the compressor crankcase.
Slide 70
70 Lubrication Systems Oil pump intake pressure is always equal
to the crankcase pressure (low side pressure). Oil pump outlet
pressure is the sum of the crankcase pressure plus the pump
pressure. Oil pump intake pressure is always equal to the crankcase
pressure (low side pressure). Oil pump outlet pressure is the sum
of the crankcase pressure plus the pump pressure.
Slide 71
71 Lubrication Systems So, net oil pressure is equal to the
suction pressure subtracted from the oil pump discharge pressure.
Note: Oil pressure switch works off the net oil pressure. Net oil
pressure will vary, normally between 30- 40 psig. So, net oil
pressure is equal to the suction pressure subtracted from the oil
pump discharge pressure. Note: Oil pressure switch works off the
net oil pressure. Net oil pressure will vary, normally between 30-
40 psig.
Slide 72
72 Lubrication Systems A bypass valve can be added in cases of
high oil pressure to keep the pressure under 60 psig. The bypass
valve is not adjustable. A bypass valve can be added in cases of
high oil pressure to keep the pressure under 60 psig. The bypass
valve is not adjustable.
Slide 73
73 Refrigerant Migration Refrigerant Migration refers to the
movement of liquid refrigerant to the compressor crankcase. The
presence of this liquid refrigerant can affect the operation of the
oil pump. Violent foaming on startup results in the loss of oil
from the crankcase. Refrigerant Migration refers to the movement of
liquid refrigerant to the compressor crankcase. The presence of
this liquid refrigerant can affect the operation of the oil pump.
Violent foaming on startup results in the loss of oil from the
crankcase.
Slide 74
74 Refrigerant Migration The use of crankcase heaters and pump
down controls can reduce and stop the refrigerant migration during
the compressor off cycle.
