McQuay PFS150A Installation Manual

Introduction

I

Refer to Installation and Maintenance Bulletin 549 for additional information on the MicroTech controller.

General Description

McQuay
plete, self-contained automatic refrigerating unitsthat include
the latest in engineering components arranged to provide a
compact and efficient unit. Each unit is completely assembled,
factory wired, evacuated, charged, tested and comes com­plete and ready for installation. Each unit consists of twin
water cooled condensers with integral subcooler sections,
multiple accessible semi-hermetic single screw compres­sors, replaceabletubedual circuit shell-and-tubeevaporator,
and complete refrigerant piping. Liquid line components

included are manual liquid line shutoff valves, charging valves,

StarGateTM

water cooled water chillers are com-

Nomenclature

filter-driers, liquid line solenoid valves, sightglass/moisture
indicators, and electronic expansion valves. Other features
include compressor heaters, automatic one time pumpdown
of refrigerant circuit upon circuit shutdown, and an advanced
fully integrated microprocessor control system.

The electrical control center includes all safety and operat­ing controls necessary for dependable automatic operation,
(the high and low pressure controls are external from the
electrical control center). Compressors are protected by
state overload protection and over temperature protection.
Field installed fused disconnect offers additional protection.

solid-

PFS-XXXA

TTT IT

Watercooled
Dual
Screw

compressor

When the equipment is received, all items should be carefully
checked against the bill of lading to insure a complete
shipment. All units should be carefully inspected for damage

upon arrival. All shipping damage must be reported to the

carrier and a claim must be filed with the carrier. The unit

serial plate should be checked before unloading the unit to

2

1

1
( (

Inspection

150=150
165=165

180=180
190=190
200=200

be sure that it agrees with the power supply available.
Physical damage to unit after acceptance is not the
sibility of McQuay International.

Note: Units shipping and operating weights are available

in the physical data table on page 15.

tons
tons

tons
tons
tons

respon-

IM 609 / Page 3

Installation & Start-up

Note:

Start-up by McQuay Service is included on all units sold for

installation within North America excludinq Mexico. Two
weeks prior notification of start-up is required. The contrac­tor should obtain a copy of the Start-up Scheduled Request

Form from the sales representative or from the nearest office
of McQuayService.

Installation and maintenance are to be performed only by qualified personnel who are familiar with local codes

and regulations, and experienced with this type of equipment.

Handling

Care should be taken to avoid rough handling or shock due
to impact or dropping the unit. Do not push or pull the unit
from anything other than the base.

Never allow any part of the unit to fall during unloading or

moving as this may result in serious damage.

Every PFS is shipped with a full refrigerant charge. For
shipping reasons, thechargewill be stored in the condensers
and is isolated by the manual condenser liquid valve and the

Moving the Unit

The PFS water chiller is shipped mounted on heavy wooden

skids to protect the unit from accidental damage and permit
easy handling, and moving.

It is recommended that all moving and handling be

performed with the skids under the unit when possible and

that the skids not be removed until the unit is in the final

location.

When moving the unit, dollies or simple rollers can be

used under the skids.

Never put the weight of the unit against the control box.
In moving, always apply pressure to the base on skids

only and not to the piping or shells. A long bar

the unit easily. Avoid dropping the unit at the end of the roll.

If the unit must be hoisted, it is necessary to lift the unit
by attaching cables or chains at the lifting holes in the
evaporator tube sheets. Speader bars must be used to
protect the control cabinet and other areas of the chiller (see
Figure 1).

Do not attach slings to piping or equipment. Move unit in

the upright horizontal position at all times. Set unit down
gently when lowering from the trucks or rollers.

will

help move

Sharp edges are a potential injury hazard. Avoid contact
with them.

discharge valve.

Should the unit be damaged, allowing the refrigerant to
escape, there may be danger of suffocation in the equipment
area since the refrigerant will displace the air. Be sure to
review Environmental ProtectionAgency(EPA) requirements
should unit damage occur. Avoid exposing an open flame to
refrigerant.

Figure 1. Suggested lifting arrangement

Location

Unit is designed for indoor application and must be located in the control box is supplied as standard fortemporary protec­an area

(4°C) or above. A good rule of thumb is to place the unit where

ambients are at least 5°F (3°C) above the leaving evaporator
water temperature.

because of the electrical control devises. A plastic cover over

where the

The unit should not be exposed to the elements (weather)

surrounding ambient temperatures

are40”F tion during shipment.

The PFS should be mounted on a solid and level founda-

tion. The foundation must be level [within

length and width] and able to support the unit’s operating

weight. If necessary, additional structural members should be
provided to transferthe weight of the

‘/a”

(6mm) over its

unit to

the nearest beam.

Compressor Condensation

Screw compressors, sealed by means of liquid injection,
separate at very cold surface temperatures. Where those

temperatures are below the ambient dew point temperatures,

I

Page 4

IM 609

condensation occurs. If condensation is excessive, provi­sions

must be made to drain off the accumulation. A drain

connection may be required.

Clearances

Service access to the evaporator, compressors, condensers,
electrical control panel and piping components must be
provided as per the following limitations: The chilled water
piping for all units enters and leaves the cooler from the rear,
with the control box being on the front side of the unit. A
clearance of 3 to 4 feet (914 to 1219mm) should be provided
for this piping and for replacing the filter-driers, for servicing
the solenoid valves or changing the compressors, in the
unlikely case where this would be required.

The condenser water piping enters and leaves the shell

from the ends. Work space must be provided in the casewater
regulating valves are being used and for general servicing.

Clearance should be provided for cleaning condenser
tubes or removing cooler tubes on one end of the unit as
specified in Table 1. It is also necessary to leave a

worK

area
on the end opposite which is used for replacement of a cooler
tube.

Table 7. Clearance

Notes:

1.

Dimension B
and replacement of evaporator and condenser tubes (either end).

2.

Electrical disconnect is required. It should not be located where it
with component service.

and D reflect the minimum clearance required for the removal

will

Interfere

Figure 2. Clearance requirements

Front

Control B

OX

1

Disconnect all power to the unit while servicing compressor motors. Failure to do so may cause bodily injury or death.

Vibration Isolators

It is recommended that isolators are used on all upper level
installations where vibration transmission is a consideration.

When spring isolators are required, install springs running

under the main unit supports. Adjust spring type mounting so

‘/4”

the upper housing clears lower housing by at least

and not more than

5%”

(13mm). A rubber anti-skid should be

(6mm)

used under isolators if hold-down bolts are not used. Vibra-

tion eliminators in all water piping are recommended to avoid

straining the piping and transmitting vibration and noise.

Table 2 lists spring and rubber-in-shear Isolators for all PFS

unit sizes. Figure 2 shows isolator locations in relation to the
unit control center.

I

20

I

Table 2. Vibration isolators (PFS

Table 3. Isolators

Note: The spring is fully compressed at approximately 3900 Ibs. (1769 kg).

(PFS150A - 200A)

75OA - 200A)

Figure 3. Rubber-in-shear isolator

L 5”

(127mm) ,I

6%” (165mm)

?/IS”

(1

Omm)

dla

IM 609 / Page 5

Figures 3 and 4 gives dimensions that are required to
secure each McQuay isolator section to the mounting sur­face. Table 4 shows the isolator loads at each location as
shown in Figure 5. The maximum loads for each McQuay
selection are shown in Table 3.

Tab/e 4. Weights

.s__._-

UN’TS

f$iZE

,!

105A

‘fc--

BOA

z

Ibs

jDA11

ko

il

Ibs

kg 1015 1050 1010 975 4050

Ibs

WA

ka 1 1015 1 1050 1 1015 1 975 1 4055 I 3916

1-1

Ibs

kq

Ibs1 2238 1 2325 / 2238 1 2161 1 8960 1 8650

xIA kg]L1015 1 1050 / 1015 1

__ . . . . _..

1

1

2

1

2227

1

2315 1

I

I

1

ioifl

I

.-

2236 2315 2227 2150 8930

2238

,

1

1

2230

1

1

1015

1

--_._...

1 3 1

2227

1

/

1050

---

2315 2238 2150 8940

2315
1050

I

I

1010

I

I

1

/

2238

1

1

1015

1

_. _. . .

4

WEIGHT

2150

1I8920

975

I

4046

I

2161

1

8950

980

1

4059

960 1

4064 I 3924

__.-.

WEIGHT

8610

I

I

3YO5
?620
3910
a630

I

1

8640

1

3919

Figure 4. Spring flex isolator

6

9)/r’

6”

(1

1

Figure 5. Corner weight locations

7%“(196:6mm)

(234

9mm)

C-C FOTN Bolt

10%” (266.70mm)

-

t

Mounting so that Upper

6 3mm)

and Not More Than

Acoustical Non-skld

Water Piping

Due to the variety of piping practices, it is advisable to follow
the recommendations of local authorities. They can supply
the installer with the proper building and safety codes re-

quired for a safe and proper installation.

Basically, the piping should be designed with a minimum

number of bends and changes in elevation to keep system
cost down and performance up. It should contain:

1.

All piping should be installed and supported to prevent
the unit connections from bearing any strain
the system piping.

2.

Vibration eliminators to reducevibration and noise trans-

mission to the building.
Shutoff valves to isolate the unit from the piping system

3.
during unit servicing.

Manual or automatic air vent valves at the high points of

4.
the system. Drains should be placed at the lowest points
in the system.

5.

Some means of maintaining adequate system water
pressure (e.g., expansion tank or regulating valve).

Temperature

6.

and

pressure Indicators located within 3
feet (0.9 meters) of the inlet and outlet of the vessels to
aid in unit servicing.

or weight

of

Control Box

A strainer or some means of removing foreign matter

7.
from the water before it enters the pump is recom-

mended. It should be placed far enough upstream to
prevent cavitation at the pump inlet (consult pump
manufacturerforrecommendations).Theuseofastrainer

will prolong pump life and thus keep system perfor-

mance up.

A cleanable strainer should aiso be placed in the water

8.

lines

just

prior to the inlets of the evaporator and con­denser. This will aid in preventing foreign material from
entering and decreasing the performance of the evapo­rator and condenser.

water

9

Any

prevent

piping to the unit must be protected to

freezing.

Consult the

ASHRAE

handbook for

standard industry practice.

10.

If the unit

IS used as a replacement chiller on a previously

existing piping system, the system should bethoroughly

flushed prior to unit installation and then regular water

analysis and chemical water treatment on the evapora-

tor and condenser is recommended immediately at

equipment start-up.

The total quantity of water in the system should be

11

suffic

ient to prevent frequent “on-off” cycling. The total

Page 6

/

IM 609

quantity of water, in the system, turnover rate should not
be less than 15 minutes.

12. In the event glycol is added to the water system, as an
afterthought for freeze protection, recognize that the
refrigerant suction pressure will be lower, cooling per­formance less, and water side pressure drop is greater.
If the percentage of glycol is large, or if propylene is
employed instead of ethylene glycol, the added pres­sure drop and loss of performance could be substantial.
Reset the freezestat and low leaving water alarm tem-

Figure

6. Typical field evaporator water piping

peratures. The freezestat is factory set to default at 36°F
(2.2%). Reset the freezestat setting to approximately

4”-5°F (2.3”-2.8%) below the leaving chilled water

setpoint temperature. See the section titled “Glycol
Solutions” for additional information concerning glycol.

13. A preliminary leak check of the water piping should be
made before filling the system.

A water flow switch or pressure differential switch

must be mounted in the water lines to the evaporator
assuring water flow before starting the unit.

Note:

1. Chilled water piping should be insulated.

Chilled water piping

The system water piping must be flushed thoroughly
making connections to the unit evaporator. It is recom­mended that a strainer of 40 mesh be installed in the return
water line before the inlet to the chiller. Lay out the water
piping so the chilled water circulating pump discharges into
the evaporator inlet.

The return water line must be piped to the evaporator inlet
connection and the supply water line must be piped to the
evaporator outlet connection. If the evaporator water is
piped in the reverse direction, which is not recommended, a
substantial decrease in capacity and efficiency of the unit will

be experienced.

A flow switch must be installed in the horizontal piping of
the supply (evaporator outlet) water line to assure water flow

before starting the unit.

Drain connections should be provided at all low points in

the system to permit complete drainage of the system. Air

vents should be located at the high points in the system to
purge air out of the system.
of the evaporator vessel, permits the purging of air out of the
evaporator. Air purged from the water system prior to unit
start-up insures adequate flow through the vessel and pre­vents safety cutouts on the freeze protection. System pres-

Avent

connection, located on top

prior to

sures can be maintained by using an expansion tank as a

combination pressure relief and reducing valve.

Pressure gauges should be installed in the inlet and outlet

water lines to the evaporator. Pressure drop through the
evaporator should be measured to calculate proper gpm
(Ips) as specified in Table 8. Vibration eliminators are recom-

mended in both the supply and return water lines.

Chilled water piping should be insulated to reduce heat
loss and prevent condensation. Complete unit and system
leak tests should be performed prior to insulating the water
piping. Insulation with a vapor barrier would be the recom­mended type of insulation. If the vessel is insulated, the vent
and drain connections must extend beyond the proposed
insulation thickness for accessibility. Chillers not run in the
wintershould havetheirwatersystemsthoroughlydrainedto

protect against freezing. If the chiller operates year-round, or
if the system is not drained for the winter, the chilled water
piping exposed to outdoor ambient should be protected
against freezing by wrapping the lines with a heater cable.
Also, an adequate percentage of glycol should be added to
the system to further protect the system during low ambient

periods.

IM 609

/

Page 7

Condenser Water Piping

Arrange the condenser water so the water enters the bottom

connection of the condenser. The condenser water will dis­charge the condenser from the top connection. Failing to
arrange the condenser water as stated above
affect the capacity and efficiency.

Pressure gauges should be installed in the inlet and outlet
water lines to the condenser. Pressure drop through the con­denser should be measured to calculate proper gpm (Ips) as
specified in Figure 12. Vibration eliminators are recom­mended in both the supply and return water lines.

Water cooled condensers may be piped for use with
cooling towers or well water applications. Cooling tower
applications should be made with consideration to freeze
protection and scaling problems. Contact the cooling tower
manufacturer for equipment characteristics and limitations
for the specific application.

will

negatively

Head pressure control, tower system

Some means of operating head pressure control must be

provided. Fan cycling and/or modulating discharge dampers

on the cooling towers is often used; sometimes a three-way

bypass valve around the tower is used. The minimum ac­ceptable condensing temperature is 80°F (27°C). The mini­mum entering tower condenser water temperature is 60°F
(156°C).
a three-way pressure actuator water regulating valve used
for cooling applications. In Figure 8 the capacity of the cool­ing tower is controlled through damper and/or fan modula­tion. These typical systems, depending on the specific appli­cation, must maintain a constant condensing pressure, re­gardless of temperature conditions and must assure enough
head pressure for proper thermal expansion valve operation.

Note that both systems assure full water flow to the tower.

Figures 7 and 8, are typical systems. Figure 7 shows

Figure 7. 3-Way water valve

J-WAY WATER

REGULATlhlG

Figure 8. Fan modulation

VALVES

Head pressure control, well water system

When using city or well water for condensing refrigerant, a
direct acting water regulating valveshould be installed in the
outlet piping of each condenser (see Figure 9). The con­denser purge valve provides a convenient pressure tap for
the regulating valve. The valve can modulate in response to
head pressure. On shutdown it closes, preventing water from

siphoning out of the condenser. Siphoning causes con-

denser waterside drying and accelerates fouling. Figure 9

illustrates the recommendation of a loop at the outlet end
when no valve is used.

Figure 9. Well water cooling system

LOOP RECURED

REGULATING

WHEN NO

VALVE IS

USED

Page 8 / IM 609

Relief Valve Piping

The

ANSI/ASHRAE
sure relief valves on vessels containing Group 1 refrigerant
(R-22) “shall discharge to the atmosphere at a location not
less than 15 feet (4.6 meters) above the adjoining ground
level and not less than 20 feet (6.1 meters) from any window,
ventilation opening or exit in any building.” The piping must
be provided with a rain cap at the outside terminating point
and a drain at the low point on the vent piping to prevent
water buildup on the atmospheric side of the relief valve. In
addition, a flexible pipe section should be installed in the line
to eliminate any piping stress on the relief valve(s).

The size of the discharge pipe from the pressure relief
valve shall not be less than the size of the pressure relief
outlet. When two or more vessels are piped together, the
common header and piping to the atmosphere shall not be
less than the sum of the area of the relief valve outlets
connected to the header. Fittings should be provided to
permit vent piping to be easily disconnected for inspection or
replacement of the relief valve.

Note: Provide adequate fittings in piping to permit repair

or replacement of the relief valve(s).

Standard 15-l 978 specifies that pres-

Figure 10. Relief valve piping

RELIEF

VALVE

(SET AT 450

PSI)

(3104

kPa)

Note: The above drawing reflects one circuit only. Each condenser is
equipped

with

a relief valve requiring field piping.

Temperature and Water Flow Limitations

PFS units are designed to operate in conditions from 40°F

(4.4%) to 50°F (10°C) leaving water temperature on the

evaporator side and 60°F (15.6%) to 105°F (40.6%) entering

water temperature on the condenser side.

On the evaporator side, the maximum water pressure is

225 psig (1552

kPa).

Glycol in the evaporator is required on

all applications below 40°F (4.4%) leaving evaporator water
temperature. The maximum allowable water temperature to
the cooler in a non-operating cycle is 105°F (40.6%). The
maximum entering evaporator water temperature in the
operating cycle is 90°F (32.2%) for start-up purposes.

The maximum condenser water pressure is 250 psig

(1724

kPa).

The non-operating leaving condenser water

Evaporator Insulation Considerations

The presence of humidity and condensation may become an

issue on the evaporator of a water cooled chiller. Insulation

Evaporator Freeze Protection

Evaporator freeze protection can be a concern in some water

cooled chiller applications. The following practices may

want to be incorporated in the system design:

Drain and flush the evaporator and chilled water piping
withglycoliftheunitwillnotbeoperatedduringthewinter.
Drain and vent connections are provided on the evapora­tor to facilitate draining.
In some applications such as matching the chiller with a
cooling tower, adding glycol solution to the chilled water
system will provide freeze protection. Freeze point should
be approximately 10°F (5°C) below minimum design am­bient temperature.

Bypass water from the heating system through the evapo­rator when the unit is shutdown during the winter months.

temperature maximum is 115°F (46.1%). The minimum

en-

tering condenser water temperature is 60°F (15.6%).

The minimum and maximum evaporator flow rates are
given in Table 8. Flow rates below the minimum values may
result in laminar flow causing freeze-up problems, scaling
and poor control. Flow rates above the maximum values will
result in unacceptable pressure drops, excessive nozzle and

tube erosion and potentially lead to tube failure. The mini-

mum and maximum condenser flow is shown in Table 9.

Note: When operating with a higher evaporator and con­densertemperature a less than nominal water gpm (Ips) is not
recommended.

is applied to the evaporator of the PFS as a standard factory
feature. This insulation will alleviate evaporator sweating.

This can be accomplish by using a small circulating
pump arranged to operate independent of the heating
system. Pipe the pump to maintain a small flow of water
continuously through the evaporator.

4. Field water piping, especially on the chilled water side,
can be insulated to reduce condensation on the piping.

It is the responsibility of the installing contractor and/or
on-site maintenance personnel to insure this additional
protection is provided. Routine checks should be made to
insure adequate freeze protection is maintained.

Failure to do so may result in damage to unit compo-

nents. Freeze damage is not considered a warranty failure or

the responsibility of McQuay International.

IM

609 I Page 9

Condenser Protection and Design Considerations

Applications exist where low temperature pond and river
water are utilized as a condensing medium. If the water
valves leak, the condenser and liquid line refrigerant tem­perature could drop below the equipment room temperature
on the “off” cycle opening the expansion valve. This problem
occurs when cold water continues to circulate through the
condenser and the unit remains off due to satisfied cooling

Chilled Water Thermostat

The PFS water cooled chiller is built with the MicroTech
leaving water controller. Refer to IM Bulletin 549 for proper
setup and calibration of the MicroTech controller. Care
should be taken working around the unit to avoid damaging
leadwires and sensor cables. Check leadwires, before

run-

Refrigerant Charge

All units are designed for use with HCFC-22 and are compat-

ible with HCFC alternatives and are shipped with a full

Flow Switch

A water flow switch must be mounted in either the entering
or leaving water line to insure that there will be adequate
waterflowtotheevaporatorbeforetheunit
safeguard against slugging the compressors on start-up.
Also, it serves to shut down the unit in the event that water
flow is interrupted to guard against evaporator freeze-up.

A flow switch is available

from McQuay under part number

0017503300. It is a “paddle” type switch and adaptable to
any pipe size from 1” to 6” (25mm to 152mm) nominal.
Certain minimum flow rates are required to close the switch

can start. This will

load. If this occurs:

1.

Cycle the condenser pump off with the unit.

2. Verify that the liquid line solenoid valves are operating
properly. If the valves are closing liquid tight as designed,
no recycling of pumpdown should occur.

ning

the

unit,

to avoid rubbing the leadwires on the frame or

other components. Verify the leadwires are firmly anchored.

If the sensor is removed from the well for servicing, do not

wipe off the heat conducting compound supplied in the well.

operating charge. The operating charge for each unit is
shown in the Physical Data Table on page 15.

and are listed in Table 5. Installation should be as shown in
Figure 11.

Electrical connections in the unit control center should be

made at terminals 62 and 63. The normally open contacts of

the flow switch should be wired between these two termi-

nals. Flow switch contact quality must be suitable for 24

VAC, low current (16ma). Flow switch wire must be in

separate conduit from any high voltage conductors (115

VAC and higher).

_

Figure

11.

Flow switch

Flow

Direction

Marked on

5” Pipe Dia. - Minimum

After Switch

L 5”

Pipe Dia.

After Switch

Minimum

Switch

L

Glycol Solutions

The system glycol capacity, glycol solution flow rate for the
evaporator in gpm (Ips), and pressure drop through thecooler
may be calculated using the following formulas and table.

Note: The procedure below does not specify the type of

glycol. Use the derate factors found in Table 6 for corrections
when using ethylene glycol and those in Table 7 for propylene
glycol.

Table 5.

Note:

1.

1.

Flow switch minimum flow rates

NOMINAL

Water pre ssure differential switches are not recommended for outdoor
applications.

Capacity

PIPE SIZE

(inches)

5

6

-

Cooling capacity is reduced from that with

MIN> REQUIRED

ACTIVATE

58.7 (3.7)

79.2 (5)

FLOW TO

SWITCH - gpm (lps)

plain water. To find the reduced value multiply the chiller’s
water system tonnage by the capacity correction factor
(Cap) to find the chiller’s capacity in the glycol system.

2,

GPM -To determine evaporator gpm (or

hT)

knowing

(or gpm) and tons:
Glycol gpm = 24 x tons

(Glvcol) x Flow (from table)

AT

AT

Page 10 / IM 609

For metric applications:
LPS -To determine evaporator Ips (or
Ips) and

Glycol Ips =

kW:

kW

4.18

x Flow (from table)

x/IT

LIT)

knowing

LIT

(or

Pressure Drop -To determine pressure drop through the
cooler, when using glycol, enter the water pressure drop
curve (Figure 12) at the actual glycol gpm (Ips). Multiply
the water pressure drop found there by (PD) to obtain
corrected glycol pressure drop.

To determine glycol system power
system power

kW

by the (Power) factor.

kW,

multiply the water

Test coolant with a clean, accurate glycol solution
hydrometer (similar to that found in service stations) to
determine the freezing point. Obtain percent glycol from
the freezing point table below. On glycol applications it is
normally recommended by the glycol supplier that a
minimum of 25% solution by weight be used for protec­tion against corrosion.

Note: The effect of glycol in the condenser is negli­gible. As glycol increases in temperature, its characteris­tics have a tendency to mirror those of water. Therefore
for selection purposes, there is no derate in capacity for
glycol in the condenser.

Table 6. Adjstment factors for ethylene glycol

Table 7. Adjustment factors for

propylene

glycol

Do not use an automotive grade antifreeze. Industrial grade glycols must be used. Automotive antifreeze contains
inhibitors that will cause plating on the copper tubes within the chiller evaporator. The type and handling of glycol used
must be consistent with local codes.

Evaporator and Condenser Water Flow and Pressure Drop

Balance the water flow through the evaporator and con­denser. The flow rates must fall between the minimum and
maximum values shown on the appropriate evaporator and
condenser curves. Flow rates below the minimum values
shown will result in laminar flow that will reduce efficiency,
cause erratic operation of the electronic expansion valve and
could cause low temperature cutouts. On the other hand,
flow rates exceeding the maximum values shown can cause
erosion on the evaporator water connections and tubes.

McQuay encourages a minimum glycol concentration of
25% be provided on all glycol applications. Glycol concen­trations below 25% have too much dilution in the inhibitor
content that is necessary for long-term corrosion protection
of ferrous metals.

Measure the chilled water pressure drop through the
evaporator at field installed pressure taps. It is important not
to include valves or strainers in these readings.

It is not recommended varying the water flow through the

evaporatorwhilethecompressor(s) areoperating.

MicroTech
control setpoints are based upon a constant flow and vari­able temperature.

Figure 12. Pressure drop - (PFS 150 -

Flow (LPS)

40

30

25

20

10

9
8

6

5

2OOA)

90

75

60

45

30
27

24

21

18

15

P

zi

8

G

?!
;

I

p‘

3

2

200 300

Flow (GPM)

400 500600

800 1000

IM

609/Page

11