McQuay PE046 Installation Manual

GENERAL

UNIT NAMEPLATE

The Model PE less condenser centrifugal water chiller
has been factory assembled, checked and shipped with
a holding charge of R-12 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 responsible personnel in the operation and
maintenance of this water chilling 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 PE water chiller 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.

Whenever requesting information or assistance on the
Model PE chiller, the unit model number, shop order
number, and serial number should be copied from the
unit nameplate. A reproduction of this nameplate is

shown in Figure 3.

HOLDING

CHARGE

ONLY

STYLE
SERIAL
S.O. NO. PE-5210

\

-~

lPE5210-GO1

5NAl234~0

FACTORY CHARGED

~

LBS. REFRIGERANT

LEAK TEST PRESSURE 100

MOTOR - COMPRESSOR CONTROLLER

AND OVERLOAD PROTECTION FIELD

SUPPLIED. SEE SPEC.

R12

PSIG

PE-D4

mccbuw k.

198PlMHOl A

MADE IN U S A

Note Typical Serial Number

l Prior to January 1, 1983 =

1,

l

After

January

1983

LZ1320

=5NA1234500

INSTALLATION

Information pertaining to the installation of Model PE

water chilling units is available in Installation Bulletin

number PE-L-Gl. A copy of this manual was included

in the envelope shipped with the unit.

MODEL CODE

PE

063J

AN 30 R G A 2 L

UNlT FA::::E-I 1

SPEED CODE

MOTOR CODE

COMPRESSOR MOTOR VOLTAGE

~k;;~~;~;::~R

TYPE OF CHILLER
TUBING

CHILLER CODE

FIGURE 3. UNIT NAMEPLATE

OPERATING INFORMATION

OPERATOR’S RESPONSIBILITY

1.

Before operating the Model PE unit, become famil­iar with the machine and accessory equipment.

2.

If possible, arrange to attend a McQuay centrifugal
operators school.

After the unit has been checked out and approved

3.
for operation by a McQuay centrifugal service
technician, work with him to learn how to prepare
the system for startup. Start and stop the machine
a number of times while observing the operation of
the interlock function(s). The interlock circuit must

be satisfied before the compressor will run. After

operating the unit, place it in the shutdown mode.

Monitor operation and periodically inspect the

4.
equipment, making routine adjustments where
essa ry

nec-

Maintain a log of operating conditions on a daily

5.

basis. (Log sheets are available in pad form from

McQuay.

PRE-START SYSTEM CHECKLIST

p&q

All of the following will have been checked
out by the
during the initial startup procedure. *Items
should always be verified by the unit opera­tor on a routine basis during the operating
season.

A. UNIT

"1.

All service valves are in the operating position.
The control circuit is energized.

“2.

The oil heaters have been operating for a

“3.

minimum of 24 hours. Oil should be hot
(approximately 130 to 140

“4.

The oil charge is visible in the sight glass.
(Mark level on sight glass while machine is
shut down, check level weekly).

Check control circuit, verify that all safety

“5.

switches interrupt compressor starter holding
coil.

“6.

The water flow through the condenser is
correct. (This can be checked from condenser
water pressure drop curves available from

McQuay).

reduced by a plugged strainer which can

cause operating problems and nuisance
outs. New systems are generally susceptible

to blocked water strainers from foreign mate-

rial washing out of the piping.

B. ELECTRICAL

McQuay

On any system, water flow can be

startup technician

F).

trip-

All load equipment is operative (main system

“3.

fans, pumps, etc.).
Condenser fan(s) and controls are operative.

“4.

Condenser water bleed and water treatment

“5.

are adequate (if required).

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.
The external failure light will glow and the external

2.
“R9”)

alarm circuit (energized through Relay

activated.
Push the RESET Button on the control panel. The

3.

external failure light will go out and the external
alarm circuit will be reset (de-energized).

Set the compressor “ON-OFF” switch to “ON”, the

4.
light in this switch will glow. The unit control circuit

has been re-established.

The unit safety circuits have now been reactivated

5.
and the operating portion of the control circuit is

ready to function. (Before the operating portion of

the control circuit can function, the chilled water

pump will have to be running).
The “LRT” (unit cycling thermostat) will, on a call

6.

for chiller operation;

Start the oil pump. (Providing 20 minutes have
elapsed since the unit last stopped and the anti
recycle time delay has timed out and closed its
contacts).

will be

1.

The wire size is correct.

2.

The phase sequence is correct.

“3.

Voltage within plus or minus 10 percent of
rated compressor nameplate voltage.

“4.

Phase voltage unbalance 3 percent or less.

5.

All wiring connections correct per the unit
wiring diagram.

6.

All electrical connections are tight and made

with copper conductors and lugs.

“7.

All starter parts move freely and contacts meet
evenly.

8.

Motor overloads correct size (filled with dash-

C.

SYSTEM

“1. The condenser pump is rotating in the right

direction.

“2. The condenser pump and motor are lubricat-

ed.

When the oil pump develops oil pressure ade­quate to close the oil differential pressure switch

“OD”

(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
gized the condenser pump relay “CWR” the
pump starter interlock contacts will close and
energize relay “MCR” located in the unit starter.
The compressor starter will now be energized
and the compressor will start.

“VC”

has closed and ener-

OPERATING

1. With the compressor running, capacity is controlled
by positioning variable inlet vane(s) located in the
suction gas inlet to the compressor. Opening the
vane(s) allows the compressor to pump more gas
and, as a result, increases capacity. Closing the
vane(s) reduces gas flow and reduces capacity. The

5

capacity control system is capable of modulating
the vane position to any capacity from 10 percent
to 100 percent.

The inlet vane(s) are controlled by means of 3
different devices. The capacity will always be
controlled by temperature unless the temperature
control is overridden by Items “b” or “c” below.

a. A temperature sensor located in the leaving

chilled water translates temperature changes
into an electrical signal and through the control
module loads or unloads the compressor (opens
or closes the vane(s).

b. The solid state control module in conjunction

with a current transformer and resistor 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 the tempera­ture control and will, whenever motor current
exceeds its setting, open or close the compres­sor vane(s) 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. The current limit control can be set to
limit current from 30 to 100 percent of name­plate full load current. The control is easily
adjusted by a knob on the face of the control

module.

c. 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 de-energizes relay

gizes

“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.

During normal operation, the compressor will con­tinue to operate and unload to a minimum of 10
percent until the cycling thermostat is satisfied.
When this occurs, the condenser relay
the motor control relay “MCR” are de-energized
and the compressor motor is stopped.

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

“R4”,

this in turn ener-

“CWR”

and

adequate lubrication for the compressor during the
spin down period.

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) through relay

energize the unload portion of the unit capacity

control circuit. If the vanes were not fully closed

when the compressor was stopped, oil pressure

will continue to be applied to the unloading piston

through the “SA” portion of the four-way solenoid

valve. This pressure continues to drive the vanes to

the closed position while the oil pump is still
running. This will permit the compressor with a
minimum delay to start on the next call for cooling.
(The compressor will not start until the vanes are in
the closed position).

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 re­start after power failure with reduced timed off

cycle” accessory option is used.

In the event of a power interruption during unit

operation,

damage by an emergency oil reservoir and spring

loaded 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.

CONTROL CENTER
The control center contains all of the unit protective

controls and most of the operating devices. Table 1
“Control Summary” (on page
control information including electrical diagram sym-

bol, 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 air conditioning serviceman or
by a

McQuay
damage. Details of the control center are shown in
Figure 5.

the compressor is protected against

15)

contains general

service technician to avoid costly

“R8”