McQuay SEH 046 Installation Manual

INSTALLATION AND

MAINTENANCE DATA

WATER COOLED

CENTRIFUGAL CONDENSING

Models SEH

046,048,050,063,079,087

UNITS

& 100

Installation and maintenance are to be performed by qualified personnel who are familiar with local codes
and regulations, and experienced with the type of equipment.
are a potential injury hazard. Avoid contact with them.

CAUTION: Sharp edges and

coil

surfaces

GENERAL

The model SEH centrifugal condensing unit has been fac­tory assembled, checked and shipped with holding charge
of refrigerant.

The purchase price of this equipment includes checkout
of the unit and initial startup by a McQuay service technician.
An integral part of the startup procedure includes instruction
of the responsible personnel in the operation and mainte­nance of this condensing unit.

It is most important that this equipment be properly
operated and maintained if it is to perform the operating ser­vice it was designed and built to provide.

McQuay offers equipment maintenance and/or inspection
programs that can be tailored to fit individual job require­ments. Information on the various service programs is
available through the McQuay Service Department or your
local McQuay sales representative.

WARRANTY
The McQuay model SEH condensing unit is covered by a
standard published warranty which covers parts only. A com­plete published description of that warranty and its limitations
is provided in a warranty certificate included with each unit.

First year warranty labor can be purchased separately.
Check your local McQuay sales representative to establish
what additional coverage (if any) was purchased for your unit.

INSTALLATION
Information pertaining to the installation of model SEH con­densing units is available in the installation bulletin
A copy of this manual was included in the envelope shipped
with the unit.

IM

308.

UNIT NAMEPLATE
Whenever requesting information or assistance on the model
SEH condensing unit, the unit model number, shop order
number and serial number should be copied from the unit

Figure 1.
Figure

1.

1 MODEL

STYLE
SERIAL
S.O. NO. SE1010

LBS. REFRIGERANT

I

I-

NOTE 1

model, style, serial, and shop order (SO.) numbers with your inquiry.
NOTE 2

occurred; sample serial numbers follow:

-

Whenever inquiring about this unit please forward unit

-

On January 1, 1983, a change in serial number coding

l Through
l After l/1183

SEH063JAUZlRKA2X

ISE1009GOl

5NA 1234500

FACTORY CHARGED

LEAK TEST PRESSURE

MOTOR COMPRESSOR CONTROLLER

AND OVERLOAD PROTECTION

SUPPLIED SEE SPEC PE-D4

111183 - LZ1320

-

5NA1234500

100 PSIG.

x

FIELD

is shown innameplate. A reproduction of this nameplate

UNIT MODEL DESIGNATION

-

COMPRESSOR

1

2 Compressor Size

3 Gear Ratio Code

4 Motor Electrical Power
5 Open-Drive Motor Description
6 Sound Control
7 Compressor Model Revision

r

-I-

r

7/

I

SEH063KAR26RYYYBE26123B2RAAlO45OCCYA

01 02030405 0607060910

”

1

2

-

SEH WATER COOLED CENTRIFUGAL CONDENSING UNIT, HERMETIC

3 4 5

11

12

13 1415 16 1716 192021 222324

\

\I

6 7

l

C22123CYY2RAYYYB1140OCCYYYYA

3738334041 4243 4445464746 495051 52 535455 56575659 6061 62 6364

MODEL CODING

EVAPORATOR

8

Evaporator Description

9

Tube Description

10

Head Description

11

Design Pressures
12 Leaving Water Temperature
13 Tube Sheet
14 Tube Cleaning System
15 Evaporator Model Revision

I

8

16 17 18 19

&

Head Material

9 10

11

252627 262930 313233 343536

CONDENSER

16 Condenser Description
17 Tube Description
18 Head Description
19 Design Pressures
20 Maximum Leaving Water Temp.
21 Tube Sheet
22 Tube Cleaning System
23 Condenser Model Revision

12 13 1415

&

Head Material

1

\

20

I

21

\

22 23

Page 4 I IM 309

OPERATING INFORMATION

OPERATOR’S REPONSIBILITY

1.

Before operating the model SEH unit, become familiar with

the machine and accessory equipment.

2.

If possible, arrange to attend a McQuay centrifugal

operator’s school.

3.

After the unit has been checked out and approved for
operation by a McQuay centrifugal service technician,
work with him to learn how to prepare the system for start-

up. Start and stop the machine a number of times while
observing the operation of the interlock function. The in­terlock circuit must be satisfied before the compressor will

run. After operating the unit, place it in the shutdown

mode.

4.

Monitor operation and periodically inspect the equipment,

making routine adjustments where necessary.

5.

Maintain a log of operating conditions on a daily basis.
(Log sheets are available in pad form from McQuay.)

PRESTART SYSTEM CHECKLIST

NOTE: All of the following will have been checked out

by the McQuay startup technician during the initial

up procedure. Items preceded by an asterisk (*) should
always be verified by the unit operator on a routine

basis during the operating season.

Unit:

*1.

All service valves in operating position.

*2.

Control circuit energized.
Oil heaters have been operating for a minimum of 24

*3.

hours. Oil should be hot (approximately 130°F to

*4.

Oil charge visible in sightglass. (Mark level on sightglass
while machine is shut down; check level weekly.)

Check control circuit. Verify that all safety switches in-

l

5.

terrupt compressor starter holding coil.

l

6.

Water flow through the condenser is correct. (This can
be checked from condenser water pressure drop curves
available from McQuay.) On any system, water flow can
be reduced by a plugged strainer which can cause
operating problems and nuisance tripouts. New systems
are generally susceptible to blocked water strainers
caused by foreign material washing out of the piping.

Electrical:

1.

Wire size correct.

2.

Phase sequence correct.

*3.

Voltage within plus or minus 10% of rated compressor

nameplate voltage.

*4.

Phase voltage unbalance 3% or less.

5.

All wiring connections correct per unit wiring diagram.

6.

All electrical connections tight and made with copper
conductors and lugs.

l

7.

All starter parts move freely and contacts meet evenly.

8.

Motor overloads correct size. (Filled with dashpot oil,

sizes 079 and larger.) Do not attempt to field calibrate

adjustable overloads.

System:

‘1. Condenser pump rotating in right direction.

l

2. Condenser pump and motor lubricated.

start-

140°F).

*3.

All load equipment operative (main system fans, variable

volume boxes, etc.).

*4.

Tower fan(s) and controls operative.

*5. Tower water bleed and water treatment adequate.

STARTING
When the 115 volt AC control power supply is applied to the
control panel for the first time or after a power failure has oc­curred, the following will take place.

1.

The oil sump heater(s) will be energized.

2.

With “on-off” switch in either “on” or “off” position, its

indicating light will be out.

3.

The external failure light will be lit. In addition, the exter-

nal alarm circuit will be de-energized indicating a unit

problem.

4.

Push the reset button. The external failure light will go out
and the external alarm circuit will be reset (de-energized).
The pilot light in the “on-off” switch will now glow when
the switch is pushed to “on.”

The unit safety circuits have now been reactivated and

5.
the operating portion of the control circuit is ready to
function.

6.

A thermostat or other controller external to the unit panel

will, on a call for condensing unit operation, energize and
close relay SR. (Relay SR is field supplied and is located
external to the unit control panel.) Energizing this relay
will close its contacts and:

Start the oil pump.
When the oil pump develops oil pressure adequate to

close the oil differential pressure switch (50 psig above
suction pressure), the switch will close.

A time delay relay PLT injects a 10 to 60 second time
delay into the compressor starting control circuit and
prevents this portion of the circuit from being ener­gized while oil pressure is being developed. At the end
of this delay, if the vane closed switch VC has closed,
relay MCR (located in the unit starter) is energized as
well as relay R3. The compressor starter will now close.

OPERATING

1. With the compressor running, capacity is controlled by
positioning variable inlet vanes located in the suction gas
inlet to the compressor. Opening the vanes allows the

compressor to pump more gas and, as a result, increases
capacity. Closing the vanes-reduces gas flow and reduces
capacity. The capacity control system is capable of

modulating the vane position to any capacity from 10%

to 100%.

2.

The inlet vanes are controlled by means of four different
devices. The capacity will be controlled by either tempera­ture or pressure and the system design will determine
whether “a” or
always used on every unit.

a. A temperature sensor located in leaving airstream from

cooling coils or in leaving chilled water when a water
chiller is used.

b. A suction pressure transducer, sensing system suction

pressure variations, translates changes in pressure into
an electrical signal and through the control module
loads or unloads the compressor (opens or closes the
vanes).

“b”

below is used. Items “c” and

“d”

are

IM 309 I Page 5

c. The solid-state control module in conjunction with a cur-

rent transformer located in the compressor motor
starter senses and will limit current drawn by the com­pressor motor, depending on the setting of the current
limit control. This controller will override either control
described in items “a” or
motor current exceeds its setting, open or close the
compressor vanes in response to changes in current.
Whenever the motor current is less than the setting on
the current limit controller, unit capacity control is
returned to the temperature sensor or transducer. The
current limit control can be set to limit current from 30%
to 100% of nameplate full load current. The control is
easily adjusted by a knob on the face of the control
module.

d. The low pressure override switch LPO, built into the

unit control panel, senses suction pressure and is set
to open at 2 to 5 psig above the low pressure safety
switch. Whenever the setting is reached, the override
switch opens and in turn opens control circuit
of the temperature controller. This in turn energizes SA
and de-energizes SB solenoids in the four-way valve.
Full oil pressure is applied to the unloader piston driv­ing the vanes closed. This action will in most cases
catch a momentary “sudden” drop in suction pressure
such as may be caused by a slow acting expansion
valve, a drop that without this unloading feature would
open the low pressure switch and stop the compressor.
The LPO pressure switch is automatically reset; it will
close when the pressure rises to a safe limit and return
control of capacity to the temperature sensor or
transducer.

3. During normal operation, the compressor will continue to
operate and unload to a minimum of 10% until the cycl-

ing thermostat is satisfied. When this occurs, relay SR is
de-energized. Opening relay SR will then cause the liquid
line solenoid valve ahead of the expansion valves to close.

4. The unit control circuit incorporates a one-time
arrangement. The compressor will continue to run after
the system control thermostat is satisfied and has closed
the liquid line solenoid valve. The compressor starter
through the MCR relay is held in by a parallel circuit in­cluding a low pressure switch LPC and a set of normally
open compressor motor starter auxiliary contacts (2Mb).
As the compressor continues to run with the liquid line
solenoid closed, the system suction pressure is reduced

“b”

above and will, whenever

ABl-#6.2

pumpdown

to the setting of cutout LPC, opening the switch and
energizing relay MCR and stopping the compressor. The
pressure switch LPC is automatically reset, but it cannot
restart the compressor when its contacts reclose because
the compressor starter auxiliary contacts 2Mb are now
open. These contacts cannot reclose until the system sen­sor calls for cooling and energizes relay SR. Relay SR has
a set of contacts in parallel with low pressure switch LPC
and contacts 2Mb. These SR contacts when closed will
permit the operating portion of the control circuit to call
for the compressor to run.

5. The unit oil pump will continue to run for a minimum of
one minute after the compressor starter has been
energized. This will assure adequate lubrication for the
compressor during the

In addition, on the next call for cooling, the compressor
capacity control vanes must be in a closed position before
the compressor is allowed to restart. Contacts VD (aux­iliary contacts located in the compressor starter) signal the
unload portion of the unit capacity control circuit and, if
the vanes were not fully closed when the compressor was
stopped, continues to energize solenoid SA and drive the
vanes to the closed position while the pump is still run­ning. This will then permit the compressor to start on the
next call for cooling with a minimum delay. (The com­pressor will not start unless the vanes are in the closed
position.)

6. Rapid cycling of centrifugal compressor motors is not
desirable. A time delay through relay TDR is built into the
unit control circuit to prevent rapid cycling. Relay TDR will
prevent the compressor from restarting for a period of 20
minutes after the compressor is stopped unless the “auto­matic restarter after power failure with reduced timed off
cycle” accessory option is used.

7. In the event of a power interruption during unit operation,
the compressor is protected against damage by an
emergency oil reservoir and spring load piston. During nor­mal operation enough oil is stored in the emergency
cylinder to lubricate the bearings during spindown. The
oil is forced into the various passages by a spring loaded
piston contained and compressed in the emergency oil
cylinder. The spring is compressed by normal machine

oil pressure while the compressor is running and on a loss
of power is available along with the piston to act as an
emergency oil pumping device.

spindown

period.

de-

de-

Page 6 I IM 309

VANE OPERATION

Capacity variation for the unit is accomplished by opening
and closing vanes located in the suction inlet to the com­pressor. Vane movement is controlled by positioning a floating
piston to which the inlet vanes are linked. The piston (and
as a result the vanes) are positioned by building up oil
pressure on one side of the piston and draining or not drain­ing the other side, depending on how far the piston must move
to satisfy the capacity requirements of the system.

Figures 2, 3, and 4 schematically illustrate the control of

the floating piston.
CONTROL SATISFIED

When the system capacity control is satisfied, an electrical
signal is sent to the control module calling for no change in
capacity. Such a condition is illustrated in Figure 2. The con­trol module has de-energized both sections SA and SB of the
four-way solenoid valve. With both sections de-energized,

ports Cl and C2 are open and outlet port

#3

is closed. This
directs full pressure to both sides of the piston, holding it in
a stationary or satisfied position.

INCREASE CAPACITY

When the unit capacity is not high enough to satisfy the load

(such a condition is illustrated in Figure

3),

a signal from the
control module will energize section SB and de-energize sec­tion SA. This will drain oil from the right-hand side of the piston
and allow it to move to the right and open the vanes. Oil in
the right-hand side of piston will continue to drain through

#3

the open port C2 and outlet

and the piston will continue
to move to the right until the control module de-energizes sec­tion SB, thus holding the piston at that position.

DECREASE CAPACITY

When the unit has been running at a higher level of capacity

and the load falls off, the system is required to reduce com-

pressor capacity. Such a condition is illustrated in Figure 4.
The control module energizes section SA and de-energizes
section SB. This permits oil to drain from the left side of the

piston through open port Cl to the outlet

#3.

With section
SB energized, full oil pressure is applied to the right end of
the compressor piston, moving it to the left. The piston can

be stopped at any point in its leftward movement when the

capacity is satisfied and the control module signals to

de-

energize SA.

Figure 2.

COMPRESSOR
UNLOADER
CYLINDER

I

Figure 3.

1

OPENING

Figure 4.

rzzq

- OIL UNDER PRESSURE

-

FLOATING PISTON
LINKED TO INLET VANES

-

OPENS VANES

-

CLOSES VANES

FOUR WAY
SOLENOID VALVE

J

LOCATED IN

NOTE ADJUSTABLE

NEEDLE VALVES
INTEGRAL
WITH FOUR WAY
SOLENOID VALVE
ARE NOT SHOWN

1

DRAIN FROM PISTON

--)

-)

Xl INLET

-

r

X3 OUTLET

oc2

-LEGEND-

OIL SUMP PRESSURE

PISTON DRAIN TO OIL

-

SECTION
ENERGIZED

SECTION

DE

-- PUMP

SECTION

“SE”

DE-ENERGIZED
SECTION “SA”

DE-ENERGIZED

FROM OIL
PUMP
DISCHARGE
VALVE

I--)

“SE+”

“SA”

ENERGIZED

FROM OIL

-PUMP

DISCHARGE

VALVE

TO OIL

PUMP

SUMP

SUMP

The above descriptions are simplified versions of what ac­tually happens, neglecting the complicated control function

provided by the control module as it pulses to control the ac­tion of solenoids SA and SB.

METERING VALVES
The hydraulic control system utilizes needle type adjusting

valves built into the four-way solenoid valve. These valves

are used to adjust the response time for the floating piston
to move through its full length of travel. The valves are fac­tory set and under normal operating conditions should not

need to be reset. Attempts to reset the valves by unqualified

personnel will result in very poor operation of the capacity

control system.

DISCHARGE
VALVE

IM 309 I Page 7

CONTROL CENTER

The control center contains all of the unit protective controls
and most of the operating devices. Table 1, “Control Sum­mary” (on page 15 and
mation including electrical diagram symbol, control descrip­tion, setting, reset information, location, signal light, and in­formation on the control function.

Eleven indicating lights are utilized on the unit control
panel. Nine of these lights are normally out and only glow
when a safety circuit has tripped.

Repeated tripping of a given control should be investigated
by a competent service technician to avoid costly damage.
Details of the control center are shown in Figure 5.

Two important safety circuits incorporated in the model

SEH control system are:

1.

GUARDISTOR
motor protection against damage from motor overheating.
Thermistors buried in the motor winding are super­sensitive to changes in motor winding temperature. These
thermistors have been calibrated to de-energize the GDR
(Guardistor relay) whenever the motor winding tempera­ture exceeds the maximum allowable.

The motor protection system, because it is sensing in­ternal motor winding temperature, provides positive pro­tection against motor damage from such heat causing pro­blems as loss of motor cooling, low voltage, etc., and is
in our opinion the finest motor protection system available.

The Guardistor control circuit is a manual reset system
which when actuated will require manual resetting by
pushing the reset button on the unit control panel.

In the event of a power failure to the unit or control panel,
the Guardistor relay will trip and require manual resetting
when power is restored.

2.

SURGEGARDTM -

mal operating condition for a centrifugal compressor.
Under some abnormal operating conditions, a surge con­dition can occur and if allowed to continue can cause com­pressor damage. A surge is caused by many things such
as dirty condenser tubes, increase in condenser water
temperature above design, or any other factor which can
act to increase the pressure difference between suction
and discharge pressure.

The McQuay centrifugal compressor is protected
against damage from a surge condition by a unique pro­tection system which senses a surge condition should it
occur and shuts the machine down before damage can
result.

Once shut down, the unit should not be operated until
the cause of the surge has been determined and cor­rected.

Whenever the machine has been stopped as a result
of a surge condition, the
control panel will glow.

SOLID-STATE CAPACITY CONTROL
The solid-state control module combines temperature and
current limit control in a single solid-state package. In addi­tion, indicating lights on the module indicate whether the con­trol is calling for the compressor to load or unload or whether
the current override feature is in control. By setting a switch,

it is possible to place the unit under manual or automatic con-

trol of unloading.

The control module, through the capacity control system,

is capable of extremely close control
point temperature. Dials provide for manual adjustment of
the unit control setpoint and/or for limiting the current drawn
by the compressor motor at any level between 30% and 100%
of rated full load current.

The standard control module described above has the abili-

ty to:

16),

contains general control infor-

Motor Protection - Provides positive

A surge or rotating stall is not a nor-

SurgeGard

indicating light on the

( *

0.5”F) of design

set-

1. Accept a remote signal to automatically reset the capaci­ty control point(s) (for example) in response to changes
in return air or outside air temperature, etc.

2. Remote setting of unit cycling control setpoint(

3. Limit unit capacity in response to a remote electrical de-

mand controller.

4. Ability to accept a signal to balance the load on multiple
units operating on a common signal.

All of the above are accessory options which require addi-

tional components not a part of the standard control circuit.

The pulsing action built into the electronic control module,
coupled with needle valve adjustment of the hydraulic por­tion of vane control, provides a very stable temperature con­trol arrangement. During normal operation, it will take approx­imately 3 to 5 minutes to move from minimum to maximum
capacity and
capacity.

The condensing unit can be applied to many different cool­ing applications and is adaptable to many different types of
control systems. The loading and unloading can be in
response to variations in temperature at a remote location
or from a change in system suction pressure. The particular
control arrangement used will be incorporated as a part of

the total job control system. Details on the total system con­trol should be available in the job file. The vane control system

is explained on page 7.
CONTROL MODULE CALIBRATION

The control module supplied as a standard part of the unit
control center is a solid-state electronic device which operates
from a 24V A.C. power source. Except for its external sen­sor(s) and a 5 volt (full load) signal from a current transformer,

and resistor located in the compressor motor starter, it is com­pletely self-contained. The module can provide many features
and functions, some of which are:

1.

Proportional temperature control (within f
setpoint).

2.

Current limit control (manually adjustable).

3.

A pulse rate adjustment which permits the module

response speed for loading or unloading to be varied to
meet application requirements encountered on different
systems and/or applications.

4.

A “ramp-up” adjustment which can be utilized at com­pressor startup to control the time to load and the point
at which the controlled loading begins. For example, this
adjustment can be used to reduce the power that would
be consumed by the unit if it were allowed to load the
machine without a time restriction.

5.

Indicating lights which glow when the controller is calling
for loading (green), unloading (red), or current override
(amber).

6.

A selector switch to permit manual or automatic control
of unit capacity.

7.

A selector switch to permit manual control of loading or
unloading.

8.

Can be adapted to accept a signal to reset the control point
in response to a change occurring at another location such
as outside air, return chiller water or energy management
device.

9.

Can be adapted to unload in response to a signal from
an energy management device used to shed electrical
power loads. The compressor capacity can be reduced
as a function of building entrance power.

1

minute to move from maximum to minimum

0.5”F

of

Page 8 I IM 309

The control module is factory calibrated and should not nor-

mally require field calibration. In the event calibration must
be checked, a procedure covering the steps required for both

current and temperature calibration is outlined in the follow-

ing paragraphs.

CURRENT CALIBRATION

1.

Equipment needed -An accurate

Start the unit and place the control module selector

2.

amprobe

or ammeter.

switch in the manual position.
Open the starter door and place the amprobe on the

3.
power lead drawing the highest current on the load side
of the starter.

4.

Remove the control module cover.
Set current demand limit selector switch clockwise

5.

(m)

against the stop (100%).
Set the blue current limit calibration screw (located just

6.
to the left of the temperature control stem) to the full
counterclockwise

7.

Check the compressor motor nameplate rated load
amperes

(RLA)

(0)

position.

against the amperage reading on the

am-

probe. Manually adjust the load until the amperes drawn

by the motor match the motor rated load amperes.

When the nameplate and amprobe ampere values are

8.
equal, turn the current limit calibration screw clockwise
until the amber light just comes on and stop. This places
the unit in current hold. The internal circuitry of the

module will now insure that, should the current increase
to 105% of rated load amperes, the controller will unload
the compressor.

To verify that the calibration is correct, manually unload
and then reload the compressor to the rated load ampere
value and verify that the current override light glows. The
current limit control portion of the module is now in
calibration.

Check the knob setting. If it needs correcting, snap the

9.

top off the control knob, loosen the screw and rotate the
knob to indicate 100% of current. Tighten screw and
replace top.

Replace module cover, remove amprobe and close

10.
starter door.

TEMPERATURE CONTROL CALIBRATION

Equipment needed - Temperature calibration resistor

1.
rated 951 ohms at 1%.

Start the unit.

2.
Remove sensor leads from terminals ISA and +6.2

3.
located on the control module upper terminal strip.

Connect the calibration resistor across terminals ISA and

4.

+ 6.2.

Check the voltage across terminals

5.

101

and COM on the

upper terminal strip. Manually load the compressor un­til a reading of 7.5 volts is obtained across these
terminals.

Switch the control to auto and turn the temperature con-

6.
trol knob to a point where both the load and unload lights

remain out.
Remove the control stem and position the pointer until

7.
it shows 47 on the temperature scale.

Snap the top off the control knob, loosen the screw and

8.
rotate the knob until it indicates 47 on cover temperature

scale. Tighten the screw and replace the cap.

Remove the calibration resistor and reconnect the sen-

9.
sor leads back onto terminals ISA and + 6.2.

Replace the control module cover and tighten cover

10.
screw.

The method for temperature calibration covered above will

result in a reasonable calibration. If closer calibration is re­quired, McQuay Service has specialized equipment which
will permit a finer adjustment to be made.

Page 10

/

IM 309

LUBRICATION SYSTEM

A separate motor driven oil pump assembly supplies oil at
controlled temperature and pressure to all bearing surfaces
and in addition is the source of hydraulic pressure for the
capacity control and emergency oil supply.

The unit control system on a call for cooling will not permit
the compressor to star-l until oil pressure has been established
for at least 1 minute. When the system controller is satisfied
and stops the compressor, the oil pump runs for another
minute to assure adequate lubrication during spindown. In

addition, during this period the compressor is unloaded
through the action of the vane closed switch VC. The com-

pressor will then be ready to start unloaded on the next call

for cooling.

The oil pump is completely self-contained and located in

the oil sump. On model SEH046, 048 and 050 units, it is

located inside the compressor housing. For model SEH063
units the oil pump is located in the oil pump assembly which
is mounted at the rear of the unit adjacent to the condenser.
In either case, it includes the pump, pump motor, oil heater

and oil separator. The model SEH063 includes shutoff valves
for discharge, oil return and suction.

Figure 6. Oil Circuit

sump. On model SEH063 units oil from the gear housing and
capacity control is dumped into the scavenger line and re­turned to the oil sump. Oil as it circulates in the oil system
will always have some refrigerant mixed in it (because of the
ability of oil and refrigerant to mix in all proportions). Most
of this refrigerant flashes from the oil as it enters the oil sump
or is driven from the oil by the oil heater. This refrigerant gas
as it is removed from the oil sump passes through a cen­trifugal oil separator located on top of the oil pump rotor.

The oil sump is vented to the suction side of the system

just ahead of the compressor wheel eye. Gas flowing from

the oil sump has to pass through the spinning oil separator
where entrapped oil is removed by centrifugal force and is
thrown back to the oil sump. The refrigerant gas flows on
through to the compressor suction.

The main oil sump on all units is provided with an electric
heater and, in addition, the model SEH063 units also include
a heater in the gear housing.

CAUTION

THESE OIL HEATERS MUST REMAIN ON AT ALL
TIMES THE COMPRESSOR IS NOT RUNNING.

SHOULD AN EXTENDED POWER LOSS OCCUR
ENERGIZING THE HEATERS) AND ALLOWING THE

OIL TO COOL, IT WILL BE NECESSARY WHEN

POWER IS RESTORED TO KEEP THESE HEATERS
ENERGIZED FOR A MINIMUM OF 24 HOURS BE­FORE ATTEMPTING TO RESTART THE COMPRES­SOR.

(DE-

Oil is pumped through an externally adjustable oil relief
valve which is factory adjusted to limit the discharge oil
pressure from 100 to 110 psig above the operating suction
pressure. After leaving the relief valve oil flows through a
refrigerant cooled oil cooler where the temperature is re­duced to approximately 90°F to 100°F. From the cooler it
passes through a replaceable 5 micron oil filter located in the
compressor casting. On model SEH046,048 and 050 units

the oil first passes through the oil filter and thrust pump before

entering the oil cooler. Filtered oil is then distributed through
internal passages in the compressor casting to the control
system and before entering the bearings. On model SEH063
units it passes into the thrust pump where the oil pressure

to the bearings is boosted.

Oil leaving the compressor and motor bearings is releas-

ed under pressure into the low pressure gear housing where

some of this oil vaporizes. This oil vapor is used to lubricate

the gearing. The remaining oil leaving the bearings drops to
the bottom of the gear housing where it is drained to the oil

If conditions require the compressor to be restarted im­mediately, it will be necessary to drain the system oil and
recharge the unit with new oil which is free of refrigerant.

The low oil temperature thermostat LOT (set for 120°F) sup­plied as part of the unit safety controls will, if adjusted pro­perly, prevent the compressor from starting with cold oil. This

thermostat is a manual reset type and when tripped will cause
the oil temperature light to glow.

OIL CHARGE REQUIRED
Quantities of oil required for model SEH units as well as the

recommended oil specifications are:

.1.75

Models SEH046, 048, 050
Models SEH065, 079, 087 .8 gallons
Model SEH 100

RECOMMENDED OIL
Models 046, 048, 050, 063, 079, 087:

Suniso

Model 100: Suniso 5GS or Texaco 100 WF
EMERGENCY OIL SYSTEM

An oil cylinder with a spring loaded piston is incorporated in
the compressor casting on all sizes of compressors to sup­ply emergency lubrication for bearings in the event of a power
loss. During normal operation, pressure from the oil pump
fills the emergency oil cylinder and compresses the
piston/spring assembly contained in the cylinder. On a loss
of power (and as a result, a loss of oil pressure), oil is forced
into the bearing lubrication passages as the spring behind
the piston expands and forces oil from the emergency
cylinder. The emergency oil system contains an adequate oil
supply under pressure to assure adequate bearing lubrica­tion during the spindown period.

4G/4GS

or Texaco Capella 68WF

.11

gallons

gallons

IM 309 / Page 11

MAINTENANCE

It is important that this unit and the air conditioning system
it is part of receive adequate maintenance if full equipment
life and all system benefits are to be realized.

On a new system, maintenance should begin with a

follow­up inspection of the system after 3 to 4 weeks of normal
operation. This inspection can be performed by McQuay Ser­vice on an invoiced basis.

FACTORY MAINTENANCE SERVICE
McQuay offers a variety of maintenance services through its
nationwide service organization. These contract services in­clude regular inspections and emergency service by factory
trained technicians. Services are available around the clock
to keep your equipment running in top condition.

With a McQuay Assured Maintenance contract, all parts,

labor and materials are furnished

-

with no additional cost

to the customer.

It is widely recognized that a good maintenance program
is the essential first step in controlling energy costs. And
through McQuay’s Assured Maintenance and Energy
Management programs, the owner is assisted in establishing
a comprehensive energy management plan to meet his
needs. For further information concerning the many services
available contact your local McQuay Service representative.

LUBRICATION
Once the unit has been checked out and is placed in ser­vice, no additional oil should be required. The oil level in the
oil sightglass should be marked when the system is shut down
and the level checked periodically. The oil sightglass level
should be approximately full when unit is shut down and about

l/3

full while the unit is running.

OIL FILTER
The oil filter must be changed annually. We do not recom­mend that untrained personnel attempt to replace the filter.
The filter is contained in a system under refrigerant pressure,
as well as oil pressure. If proper care is not taken when chang­ing the filter, personal injury could occur. In addition, air
and/or moisture could enter the system and cause equipment
problems.

1. Model SEH046, 048 and 050 units have an internal oil

pump and require that the system refrigerant charge be
pumped into the condenser before attempting to change
the filter. After the unit is pumped down, break the seal
on the oil filter access cover and permit the pressure to
bleed off before removing the cover. After replacing the
filter, crack open the condenser liquid valve and permit
the pressure to build up and purge the oil filter housing.
Replace the cover and check for leaks.

2. Model SEH063,079,087 and 100 units have an external

oil pump assembly. Close the oil pump discharge valve.
Loosen the flair fitting feeding oil to the filter and bleed
off the pressure by purging slowly. When the pressure has
been relieved, remove the cover and replace the filter.
When reassembling, vent as much air as possible from
the oil lines before placing the compressor back into
operation.

REFRIGERATION CYCLE
Since the model SEH unit has a semi-hermetic compressor
and utilizes R-12 or R-500 refrigerant, normal system
pressures, whether the system is operating or shut down, will
always be above atmospheric. Unit maintenance generally
will consist of proper inspection and maintenance of an
operating log. Visual inspection of oil level as shown in the
sightglass and noting operating suction, discharge and oil
pressures will generally indicate if the unit operating charac­teristics are changing.

ELECTRICAL SYSTEM
Generally, maintenance of the electrical system only involves
keeping operating controls clean and electrical connections
tight. In addition, the following items should be inspected:

The compressor amperage (current) drawn should be corn-

pared to the nameplate rating. Normally the current read

will be less than nameplate since the nameplate value

represents design full load current.

Check that oil heaters are operative. Heaters are cartridge
type and can be checked by an amperage reading. They
should be energized whenever the compressor is not

operating. When the compressor runs, the heater should

be automatically de-energized.

Once a year all safety controls except compressor

overloads should be made to operate and the operating

point checked. Any control as it ages can shift its operating

point and this should be detected.

Pump interlocks and flow switches should interrupt the
control circuit cleanly. A chattering flow switch can be a
source of trouble as well as irritation.

Motor starter contacts should be inspected and cleaned
annually. All terminal connections should be tightened.

Compressor motor resistance should be checked annually.
This will track any insulation deterioration that might be

occurring.

AUXILIARY EQUIPMENT

It is important that auxiliary equipment used in conjunction
with the model SEH unit be adequately maintained. Malfunc­tions in this equipment often affect the operation of the con­densing unit. For example, improperly maintained air filters

in the system can restrict airflow to the cooling coils and as

a result cause suction pressure to fall to a point where a

nuisance

tripout

on the low suction pressure cutout could oc­cur. Items such as the following should be checked and
maintained.

1.

All filters must be cleaned or replaced. The frequency
of this service will vary with different installations.

2.

Keep condenser pump water strainer clean. Inspect and
service on a regular basis.

3.

Maintain cooling tower water treatment to limit buildup
of scale in condenser tubes.

4.

Inspect and maintain operating portion of variable volume
boxes when used.

5.

Inspect condenser tubing at least annually (or more often)
depending on condenser scaling conditions.

6.

All fans and belts checked and adjusted.

7.

All condensate drains clean.

8.

All motors lubricated.

9.

All electrical connections tight.

10.

Starter contacts clean and mechanism moves freely.

SEASONAL SERVICING

At the end of the cooling season and before the unit is started
in the spring, the following service procedures should be
completed.

Annual Shutdown

When the unit may be exposed to freezing temperatures,

water piping should be disconnected from the supply and

drained of all water. The condenser is not self-draining.
Dry air blown through individual condenser tubes will help
in forcing the water out of the condenser.

Pa

.ge

12 / IM 309

When it is possible to have the unit and/or piping ex­posed to freezing temperatures, the only sure method of
protection is forced circulation of an antifreeze solution
through the water circuit.

When a cooling tower is used and the water pump will be

2.
exposed to freezing temperatures, be sure to remove the
pump drain plug and leave it out so that any accumula­tion of water will drain away.

Take measures to prevent the water supply line shutoff

3.
valve from accidentally being turned on.

Open the compressor disconnect switch and remove the

4.

Fusetrons. If a control circuit transformer is used for con­trol power, the disconnect must remain on to supply power
to the oil sump and gear housing oil heaters. Set the com-

pressor on-off switch to “off.” To guard against the

possibility of an accidental compressor start, remove relay

R7 from the control panel (see Figure 5).

Annual

1.

2.

StartuD

Before proceeding with the seasonal startup procedures,

we recommend that the compressor and oil pump motor

resistance be checked. Annual checking and recording

of this resistance will provide a record of deterioration in

the motor winding insulation should it occur. All new units

have a compressor stator resistance well over 100

megohms between any motor terminal and ground.

Whenever a marked change in resistance shows or
uniform readings of less than 5 megohms are obtained,
THE UNIT SHOULD NOT BE STARTED SINCE MOTOR

FAILURE WOULD BE PRACTICALLY CERTAIN. In all
probability, the motor will have to be repaired or re­placed. Your McQuay Service representative should be
called for recommendations and/or repair.

The unit control circuit should have been energized at all
times. If the control circuit has been shut off and the oil

is cool, the machine should not be started until the heaters

in the oil sump (and gear casing SEH063 only) have been

energized for a minimum of 24 hours. If it is necessary
to start the machine without waiting 24 hours, then the
oil in the unit should be drained and replaced with fresh oil.

3.

Check and tighten all electrical connections.

4.

Install Fusetrons in the main disconnect switch (if they

have been removed).

5.

Replace relay R7 (if it was removed).

6.

Replace drain plug in water pump if it had been removed.

7.

Reconnect water lines, turn on supply water and check
for leaks.

8.

Clean and flush water tower.

Make sure tower bleed is adequate.
Be sure water treatment is adequate to prevent a
buildup of solids in the condenser. Air circulated
through the tower contains many contaminants which
are flushed out by the tower water. The use of untreated
water in most installations can result in a reduction of
heat transfer in the condenser tubes or damage to the
tubes as a result of corrosion, erosion, sliming, scal­ing, or algae formation.

Recommendation: The service of a competent water
treatment organization be obtained to determine what, if
any, water treatment is required and their recommenda­tions implemented.

McQuay assumes no responsibility for operating pro-

blems or damage occurring as a result of untreated con­denser water.

9.

Clean all surfaces and remove all litter. A clean, well main­tained unit is the sign of a good operator.

REPAIR OF THE SYSTEM

Information on pumping unit down, pressure testing, leak
testing, evacuation and charging is contained in installation
manual IM 308.

IM 309

/

Page 13

OPERATOR’S CHECKLIST

UNIT CHECKS

1.

Suction, discharge and oil pressure normal.

2.

Oil level correct.
Voltage within tolerance (plus or minus 10% of compressor

3.
nameplate rating). Phase unbalance should not exceed
3%.

4.

Motor amperage proper for load conditions.
Vanes open and close under manual and automatic

5.
control.

Motor current limiting control operational.

6.
Safety interlocks interrupt compressor operation.

7.
Unit cycling thermostat set 3 to 5 degrees below unit con-

8.
trol setpoint.

SYSTEM CHECKS

1. All motors checked for voltage and running amperes.

2. All pumps and motors lubricated.

3. Water strainer(s) clean.

4. All fans checked, belts tight, bearings lubricated.

5. Air filters clean.

6.

All electrical connections tight, starter contacts clean,
starter movement proper.

7.

The system expansion valves should have been properly
sized and selected for the anticipated design and operating
loads for which they are expected to function. The valves
used must be capable of controlling refrigerant flow to the
evaporator over the full capacity modulating range of the
centrifugal compressor (10% to 100%).

Particular attention should be paid to the operation of
the unit and system during the initial cooling period. Dur­ing this period, if the expansion valves have not been pro­perly sized and selected or the total system load is
substantially less than anticipated, problems will develop.
They should be caught and corrected as quickly as
possible.

The operator should double check that the expansion
valve control bulbs have been securely clamped to the suc­tion line and that the bulbs are well insulated. An improper­ly sized or faulty operating expansion valve will lose con­trol of the refrigerant feed to the cooling coils and can be
the cause of low suction pressure, as well as overfeeding,
either of which could cause nuisance tripping or com­pressor damage.

Page 14 I IM 309

TABLE 1. CONTROL COMPONENT SUMMARY - STANDARD APPLICATIONS

CONTROL

Alarm Relay

Chiller Pump,
Waterflow interlocks

Cold Oil Temperature
Switch Section

Condenser Pump,
Waterflow Interlocks

Flow Switch
Time

Delav

Guardistor Relay

Hot Gas Override
Solenoid

Hot Gas Solenoid

Hot Gas Thermostat

High Oil Temperature

Switch
High Pressure

High Suction Temp.
Switch

High Discharge

Temo.

Switch

Interval On Timer

Low Casting Temp.
Thermostat

Injection

Liquid
Solenoid

Load Meter
Low Oil Temp.

Thermostat

Low Pressure
Switch

Pumpdown
Switch

Low Pressure
Override Switch

Load Recycle
Thermostat

Liquid Line Solenoid
Valve

Oil Pump Contactor

Motor Control
Relay

Motor Cooling
Solenoid Valve

Oil Cooler
Solenoid

Oil Pressure

Diff.

Oil Pump
Overload

Oil Pump Safety
Timer

Control

Switch

SYMBOL SETTING

R9

CHWI None

COT

CWI

FSTD

GR

HGO None

HGS

HGT

HOT

Swatch HP

HST

HT

IOT

LCT

LIS None None Refrig.

LM None None Panel None Drsplays

LOT

LP

LPC 2-5 psig

LPO

LRT

LS

MCR

MCS

ocs

OD

OL

OPT

105°F

Field Set

140°F
Temp.

Function Section

150°F Auto/Man

225°F Manual

Field Set

110°F

130°F

Function

above LP

2

above LP

Field Set

IM None None

50 psig Auto/Man

opens

Adjust. Box Press. circurt.

60 sec.

None

None

None

None

None None

See

See Manual Switch

Ps’g

None None

None None

None None Refrig. None

None None Chiller None

Non-

RESET

(Note 1)

Auto/Man

Auto/Man

Auto/Man

Auto/Man

Auto

Auto/Man

None

None

Manual Switch

(Rt2)

Manual Switch

None

Auto

Auto Temp.

Auto Side of

Auto

None Temp. Load

Auto/Man

Auto/Man

LOCATION

Relay None

Section

Field Ext.

Suoolied

Switch

Field Ext.

Supplied

Relay

Section

Relay

Section

Hot Gas

Piping

Hot Gas

Piping

Condenser

Frame

Section Temp.

Temp.

Section

Switch High

Sectron Temo.

Lead/Lag

BOX

Temp.

Sectron

Piping

Section Temp.

Sectron

Panel one-trme pumpdown

Switch None

Section

Section Recycle

Freld

Supplied

Relay

Sectron

Starter

Piping

Piping

Lube

Box

Lube

Relay

Section Press

SIGNAL

LIGHT

Actuates circuit for remote alarm.

Prevents chiller operation until chilled water pump is energized and

Fall

flow is established.

011

Temp.

Motor

Temp.

None

None

None

Disch.
Press.

Surgegard Stops compressor when suction temperature exceeds setting; prevents

None

Temp.

None

Press.

None

None

None

Comp.

Press.

Stops compressor if oil temperature entering compressor drops below
setting.

R114

Templifiers only.

Prevents chiller operation until condenser water pump is energized

Fall

and flow IS established.

Ext.

Delays water flow loss for three seconds to prevent false shutdown.

Fail

Stops compressor motor when winding temperature exceeds limit.

Opens hot gas bypass at starting of 2nd compressor oil pump to
reduce starting head. Dual compressor units only.

Opens hot gas bypass from discharge to evaporator, providing false
evaporator load. Helps prevent surge conditions.

Energizes hot gas solenoid on drop in water temperature entering

evaporator (senses entering condenser water in Templifier).

Oil

Stops compressor if oil temperature entering compressor exceeds
ing (reset auto/man with

Stops compressor when discharge pressure exceeds setting. Set

lo-12

psig above design saturated condensing pressure (not to ex-

ceed 90% condenser nameplate maximum working pressure).

compressor surge (CEO50 compressor only).

Stops compressor when discharge gas temperature exceeds setting

Actuates

trme

Oil

Opens liquid injection valve after compressor starts-standard on
CE126. (Optional for CE063, 079,

Oil

LOW

Overrides control module, unloads compressor when suction pressure

compressor 3°F below control point. (See PF manual for
setting.)

or controller is satisfied.

Run

energized.
Opens to feed liquid refrigerant for motor cooling during compressor.

operation.

Oil

drops to

Oil

Oil

close within 60 seconds after oil pump starts.

crrcurt

delav.

Assures
(CE126 compressor

Prevents compressor start with cold oil. Set as high as conditions
allow. Protects compressor bearings from refrigerant diluted oil.

Stops compressor when suction pressure drops below setting. Set
5 psig below shop order suction pressure.

Stops compressor when suction pressure setting is reached-part of

.-.

approaches setting of LP cutout-prevents nuisance trip.
Starts/stops compressor in response to load changes-stops

Opens on call for cooling or

Starts oil pump when energized.

Energizes compressor motor starter when unit control circuit is

Opens valve to permit coolant flow during oil pump operation.

Stops compressor when difference between oil and suction pressure

Stops oil pump and compressor if oil pump motor overloads electric

Stops pump by interrupting safety circuit if vane closed switch fails to

for specific time and returns to normal position after

mrnrmum

compressor casting temperature at startup.

onlv).

percent of full load amps when compressor runs.

control feature-SEH units only.

settmg.

Closes at 60 psig to permit compressor start.

FUNCTION

R114

Templifiers).

heatrng.

067,

100) (Not used on

Closes when system thermostat

RI14

LRTP

units).

set-

IM

309 / Page 15

TABLE 1 Continued. CONTROL COMPONENT SUMMARY - STANDARD APPLICATIONS

CONTROL

Oil Pump Time
Delay Switch

Pushbutton Switch

Prelube

Timer

Protective Signal

Interlock

Phase Voltage Relay

Range Shift

Resistor

Capacity Control
Solenoid

Capacity Control
Solenoid

Starts Counter
Surgegard Relay

System Monitor
Timer

Sump Oil
Thermostat

Sequence Relay

Source Water

Thermostat

Anti-Recycle Time
Delav

Relav

Transition Resistor
Protector

Pilot Expansion
Valve Solenoid

Vane Closed
Switch

Vane Delay
Contacts

Voltage Relay

SYMBOL SETTING

RESET

(Note 1) LIGHT

OTD

PLT 60 sec.

PVR

RSR

SGR

SOT

SWT

TDR

TRP

TXS

60 sec.

PB None

PS

SA None None Lube

S0

SC None None Panel None

SM

SR

vc 40 psig

VD None

VR

None None

None

None

None None Lube

Non-

Adiust. Section

60 sec.

140°F

None

Field Set

20

Min.

None

None None

Differential

Non-

Adjust.

None

None

None

Auto/Man

None

Auto/Man

Auto/Man

Auto Control None

None

Auto

None Relay

Auto/Man Starter

None Lube

None

None

LOCATION

Relay

Section

Switch

Section

Relay

Section

Starter

Starter

Control
Module

Box

BOX

Relay

Relay Ext.

Section

BOX

Field

Supplied

Temp.

Section

Section

Piplng

Box

Starter

Lube

Box

SIGNAL

None

None

None

Ext
Fail

Ext.
Fail

None

Module Part of

Red

Module Part of

Green

Surgegard

Fail

None

Load

Recycle

None

Ext.
Fail

None

Oil

Press.

None

None

FUNCTION

Keeps pump running for 60 seconds after compressor is stopped.

Pushbutton switches reset the safety circuit when the RESET button

on the control panel is pushed.

Provides a pre-lubrication period for bearings prior to compressor

start.

De-energizes system
delta contactor

Protects compressor against damage from single phase, phase
sal or undervoltage.

Provtdes

temperature range shift for control module on Templifier

units.

4-way

on control piston and closes vanes-UNLOAD.

4-way

on control piston and opens vanes-LOAD.
Counts number of compressor starts
Works with thermistor to sense impeller cavity temperature. Protects

oressor

from a

If compressor fails to start in 60 seconds after system monitor IS
energized, system monitor terminates start effort.

On

units with

maintain set temperature.
Relay controlled by system thermostat (or other control) to start unit

on call for
Stops compressor when water temperature entering evaporator is too

low for
Prevents compressor from restarting for 20 minutes afler previous

shutdown.
Abort compressor starting sequence if starter fails to make transition

from star to delta within 1 second.
Opens when 2nd compressor starts, closes when 2nd compressor

stops (PF063 only).

Prevents compressor starting unless capacity control vanes are closed

(fully
Auxiliary contacts in compressor starter prevent compressor loading

and liquid solenoid valves from opening (SEH units only) until com-

pressor motor connected across the line.
Disconnects

coolmg.

pracbcal

unloaded).

monitor

timer when compressor starter closes

rever-

solenoid valve. When energized, applies full oil pressure

solenoid valve. When energized, applies full oil pressure

surqe

ICE063 thru 126

refrigerant cooled oil cooler, controls oil sump heater to

heat recovery.

011

pump motor capacitor after start (CEO50 only).

comoressors).

com-

NOTE

#l

Auto-This control automatically resets itself
Manual-This control requires manual reset which is done mechanically with RESET button
Auto/Man-This control automatically resets itself but electrical lockout circuit

NOTE #2

This table contains all standard and most optional control components used in
Controls for specific units can be identified by referring to control diagram and/or the unit control center.

Page 16 / IM 309

requires

that RESET button be pushed to reset the circuit.

McQuay centrifugals.

All listed controls are not necessarily used on all

units.