Bosch TW25-1USC-FXXXNA, TW35-1USC-FXXXNA, TW49-1USC-FXXXNA, TW61-1USC-FXXXNA, TW71-1USC-FXXXNA Installation, Operation And Maintenance Manual

TW Series

Water to Water

Installation, Operation and Maintenance Manual

6720220047 (2016/02)

2 | Table of contents TW Series Water to Water

TABLE OF CONTENTS

Key to Symbols.................................................................. 3

Safety Warnings ................................................................ 3

Model Nomenclature.......................................................... 4

Standard TW package ........................................................ 5

General Description ..................................................... 5

Moving and Storage ........................................................... 5

Initial Inspection .......................................................... 5

Location ..................................................................... 5

Installation.........................................................................5

Piping ............................................................................... 6

Electrical .......................................................................... 6

Safety Devices and the UPM Controller ........................... 7

Options............................................................................. 9

Heat Recovery Package (HRP) ....................................... 9

DPS Water Flow Proving ............................................... 9

Pump Relay................................................................. 9

Comfort Alert Module ................................................... 9

Heat Recovery Package ................................................... 10

Water Tank Preparation .............................................. 10

HR Water Piping ........................................................ 10

Water Tank Refill........................................................ 10

Initial Start-Up........................................................... 10

Sequence Of Operation .................................................... 11

Cooling Mode ............................................................ 11

Heating Mode............................................................ 11

Sequence Of Operation Flow........................................12

Auto Changeover Mode................................................17

Unit Protection...........................................................17

Manual Lockout................................................................18

Lead-Lag...................................................................18

Pump Cycling.............................................................18

Operating Instructions......................................................18

User Interface............................................................18

UP Button..................................................................18

Down Button..............................................................18

LED Indicators............................................................19

User Adjustable Settings Chart..........................................19

Setting up the controller................... .................................19

Initial Configuration..........................................................20

Unit Check-out sheet........................................................21

Troubleshooting ..............................................................22

Unit Troubleshooting...................................................22

Confort Alert Module-Flash Codes.................................23

HRP Troubleshooting.................. .................................24

Unit Lockouts ............................................................ 24

Electrical Data Table ........................................................ 25

UPM Board LED Indicators.................................................25

Water Quality Table..........................................................26

Wiring Diagrams ..............................................................27

Dimensional Drawings......................................................33

Terminology ....................................................................36

Application Considerations .............................................. 13

Well Water Systems ................................................... 13

Cooling Tower/Boiler Systems ..................................... 13

Geothermal Systems .................................................. 14

System Checkout ............................................................ 15

Considerations...........................................................15

Unit Start-Up ................................................................... 16

Maintenance ................................................................... 16

Decommissioning.............................................................16

Water To Water Unit Controller..........................................16

Features....................................................................16

Unit Sensors.....................................................................16

Water Sensor.............................................................16

Changeover Sensor.....................................................16

Modes Of Operation..........................................................16

Off Mode...................................................................16

Heating Mode.............................................................16

Cooling Mode.............................................................17

TW Series Water to Water6720220047 (2016/02) Subject to change without prior notice

Key to Symbols | 3TW Series Water to Water

KEY TO SYMBOLS

Warnings

Warnings in this document are identified by
a warning triangle printed against a grey
background. Keywords at the start of the
warning indicate the type and seriousness
of the ensuing risk if measures to prevent
the risk are not taken.

The following keywords are defined and can be used in
this document:

• NOTICE indicates a situation that could result in

damage to property or equipment.

• CAUTION indicates a situation that could result in

minor to medium injury.

• WARNING indicates a situation that could result in

sever injury or death.

• DANGER indicates a situation that will result in

severe injury or death.

Important Information

This symbol indicates important information where
there is no risk to property or people.

SAFETY WARNINGS

WARNING: Installation and servicing of this

equipment can be hazardous due to system
pressure and electrical components. Only
trained and qualified personnel should
install, repair, or service the equipment.

DANGER: Before performing service or
maintenance operations on the system, turn
off main power to the unit. Electrical shock

could cause personal injury or death.

WARNING: When working on equipment,

always observe precautions described in
the literature, tags, and labels attached to
the unit. Follow all safety codes. Wear
safety glasses and work gloves. Use a
quenching cloth for brazing, and place a fire
extinguisher close to the work area.

NOTICE: All refrigerant discharged from this
unit must be recovered WITHOUT
EXCEPTION. Technicians must follow
industry accepted guidelines and all local,
state, and federal statutes for the recovery
and disposal of refrigerants. If a compressor
is removed from this unit, refrigerant circuit
oil will remain in the compressor. To avoid
leakage of compressor oil, refrigerant lines
of the compressor must be sealed after it is
removed.

NOTICE: To avoid equipment damage, DO
NOT use these units as a source of heating
or cooling during the construction process.
Doing so may affect the unit’s warranty. The
mechanical components and filters will
quickly become clogged with construction
dirt and debris, which may cause system
damage.

NOTICE: To avoid the release of refrigerant
into the atmosphere, the refrigerant circuit
of this unit must be serviced only by
technicians who meet local, state, and
federal proficiency requirements.

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4 | Model Nomenclature TW Series Water to Water

TW25-1CSN-FXXXCA-XKGAEXXXX 7X XX

X

XXXXX SB A

TW Code String Rev Level

Size Standard/Spec ial

035

049

061

122

Controls

Voltage X - Standard

1208-230/60/1 M - DDC - Multi-Protocol (BacNET, Modbus, N2)

L - DDC - LonWorks

Cabinet Con

guration

US - Unit Mounted Controller Transformer

Source Side Coax Options Refrigeration Circu it Options

C - Copper X - None

N - Cupro-Nickel D - Heat Recovery Package

Water Connections General Electrical Opti ons (up to 5 available per u nit)

F - Front A - EMS relay

y

X - N/A H - Flow proving switch

N - Comfort Alert

Load Side Coax Op tions X - As default for non used electrical codes

N - Cupro-Nickel Application

G - EXTENDED RANGE (Geothermal)

Revision Level

Cabinet Construction

K - Pre Paint Steel / 1/2" Standard 1.5LB Dual Density Fiberglass / EQ

Electric Heat

X - None

MODEL NOMENCLATURE

E - Pump/val ve rela

025 SS - Standard

071 X - N/A

CS - Remote Control led 7 - 75 VA

C - Copper

A - Current

TW Series Water to Water6720220047 (2016/02) Subject to change without prior notice

STANDARD TW PACKAGE

1

2

VIBRATION
PAD FULL

Figure # 1

[1] TW Series Water-to-Water
[2] Installation and Operation Manual

General Description

TW Series Water-to-Water Heat Pumps provide the best
combination of performance and efficiency available. All
units are performance certified to American Heating and
Refrigeration Institute (AHRI) ISO Standard 13256-2. All
TW Water-to-Water Heat Pumps conform to UL1995
standard and are certified to CAN/CSA C22.2 No 236 by
Intertek-ETL. The Water-to-Water Heat Pumps are
designed to operate with entering fluid temperature
source between 30°F to 90°F in the heating mode and
between 50°F to 110°F in the cooling mode on the
source side

Heat Pump operating under extreme conditions will
have limitation on fluid flow rates and/or
temperatures.

50°F Minimum Entering Water Temperature (EWT)
is recommended for well water applications with
sufficient water flow to prevent freezing. Antifreeze
solution is required for all closed loop applications.
Cooling Tower/Boiler and Geothermal applications
should have sufficient antifreeze solution to protect
against extreme conditions and equipment failure.
Frozen water coils are not covered under warranty.
Other equivalent methods of temperature control are
acceptable.

Standard TW Package | 5TW Series Water to Water

WARNING: For Storage if unit stacking is

required, stack unit as follows:
Do not stack units larger than 6 tons. For

units less than 6 tons, no more than three
high

Initial Inspection

Be certain to inspect all cartons or crates on each unit as
received at the job site before signing the freight bill.
Verify that all items have been received and that there
are no visible damages; note any shortages or damages
on all copies of the freight bill. In the event of damage or
shortage, remember that the purchaser is responsible
for filing the necessary claims with the carrier.
Concealed damages not discovered until after removing
the units from the packaging must be reported to the
carrier within 24 hours of receipt.

Location

Locate the unit in an indoor area that allows easy access
to the panels, and has enough room for service
personnel to perform maintenance or repair. Provide
sufficient room to make fluid and electrical
connection(s).

NOTICE: These units are not approved for
outdoor installation; therefore, they must
be installed within a conditioned space
inside the structure. Do not locate in areas
that are subject to freezing.

INSTALLATION

The TW series unit should be mounted level on a
vibration absorbing pad slightly larger than the base to
minimize vibration transmission to the building
structure, It is not necessary to anchor the unit to the
floor.(Figure #2).

MOVING AND STORAGE

If the equipment is not needed for immediate
installation upon its arrival at the job site, it should be
left in its shipping carton and stored in a clean, dry area.
Units must only be stored or moved in the normal
upright position as indicated by the “UP” arrows on each
carton at all times.

Figure # 2

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6 | Piping TW Series Water to Water

1

2

3

4

5

6

5

PIPING

Supply and return piping must be as large as the unit
connections on the heat pump (larger on long runs).

NOTICE: Never use flexible hoses of a
smaller inside diameter than that of the
fluid connections on the unit.

TW units are supplied with either a copper or optional
cupro-nickel Water to refrigerant Heat Exchanger.
Copper is adequate for ground water that is not high in
mineral content.

Proper testing is recommended to assure the well
water quality is suitable for use with water source
equipment. When in doubt, use cupro-nickel.(See
Water Quality Table on page #28)

In conditions anticipating moderate scale formation or in
brackish water a cupro-nickel heat exchanger is
recommended.
Both the supply and discharge water lines will sweat if
subjected to low water temperature. These lines should
be insulated to prevent damage from condensation. All
manual flow valves used in the system must be ball
valves. Globe and gate valves must not be used due to
high pressure drop and poor throttling characteristics.

NOTICE: Never exceed the recommended
water flow rates as serious damage or
erosion of the water-to-refrigerant heat
exchanger could occur.

ELECTRICAL

Refer to electrical component box layout. (Figure #3)

NOTICE: Field wiring must comply with
local and national electric codes.

WARNING: Power to the unit must be
within the operating voltage range indicated
on the unit nameplate or on the
performance data sheet.

WARNING: Operation of unit on improper
line voltage or with excessive phase
imbalance will be hazardous to the unit,
constitutes abuse and may void the
warranty.

Properly sized fuses or HACR circuit breakers must be
installed for branch circuit protection. See unit
nameplate for maximum fuse or breaker size.

The unit is provided with a concentric knock-out for
attaching common trade sizes of conduit, route power
supply wiring through this opening. Always connect the
ground lead to the grounding lug provided in the control
box and power leads to the line side of compressor
contactor as indicated on the wiring diagram (Figures on
Pg#27 To 34).

Always check carefully for water leaks and repair
appropriately. Units are equipped with female pipe
thread fittings. Consult Unit Dimensional Drawings.

Teflon tape sealer should be used when connecting
water piping connections to the units to insure
against leaks and possible heat exchanger fouling.

NOTICE: Do not overtighten the
connections.

Flexible hoses should be used between the unit and the
rigid system to avoid possible vibration. Ball valves
should be installed in the supply and return lines for unit
isolation and unit water flow balancing. (See Water
Quality Table on Page#26)

Figure # 3

[1] Comfort Alert Module (Option)

[2] Compressor contactor
[3] Capacitor
[4] Auxiliary Relay (DP/DT)
[5] Unit Protection Module (UPM)(CS Option)

TW Series Water to Water6720220047 (2016/02) Subject to change without prior notice

Electrical | 7TW Series Water to Water

1

2
3
4

5

6

7

9

10

11

1213

17

14

15

16

8

For Reference
only

Safety Devices and the UPM Controller

[1] Board Power Indicator

[2] UPM Status LED Indicator
[3]Water Source Coil Freeze Protection Temperature
Selection [R30]
[4] Load Water Coil Freeze Protection Temperature
Selection [R24]

[5] UPM Board Settings
[6] Source Coax Freeze Connection (Freeze 1)
[7] Load Coax Freeze Connection (Freeze 2)
[8] LCD Unit Display Connection
[9] 24VAC Power Input
[10] Compressor Contact Output
[11] High Pressure Switch Connection
[12] Call for Compressor Y1
[13] Low Pressure Switch Connection
[14] 24VAC Power Common
[15] Condensate overflow Sensor (not applicable on
TW)
[16] Dry Contact

[17] UPM Ground Standoff

Figure # 4

If the unit is being connected to a thermostat with a
malfunction light, this connection is made at the unit
malfunction output or relay. Refer to Figure #4.

If the thermostat is provided with a malfunction light
powered off of the common (C) side of the
transformer, a jumper between “R” and “COM”
terminal of “ALR” contacts must be made.

If the thermostat is provided with a malfunction li ght
powered off of the hot (R) side of the transformer,
then the thermostat malfunction light connection
should be connected directly to the (ALR) contact on
the unit’s UPM board.

The TW Series has an optional factory installed Unit
Protection Module (UPM) that controls the compressor
operation and monitors the safety controls that protect
the unit.

Safety controls include the following:

• High pressure switch located in the refrigerant
discharge line and wired across the HPC terminals
on the UPM.

• Low pressure switch located in the unit refrigerant
suction line and wired across terminals LPC1 and
LPC2 on the UPM.

• Water side freeze protection sensor, mounted close
to condensing water coil, monitors refrigerant
temperature between condensing water coil and
thermal expansion valve. If temperature drops
below or remains at freeze limit trip for 30 seconds,
the controller will shut down the compressor and
enter into a soft lockout condition. The default
freeze limit trip is 26°F, however this can be
changed to 15°F by cutting the R30 or Freeze1
resistor located on top of DIP switch SW1 (Refer to
Figure #4, item [3] for resistor location), Refer to
Figure #5 for sensor location

.

UPM Board Dry Contacts are Normally Open (NO)

Figure # 5

NOTICE: If unit is employing a fresh water

system (no anti-freeze protection), it is
extremely important to have the Freeze1
R30 resistor set to 26°F in order to shut
down the unit at the appropriate leaving
water temperature and protect your heat
pump from freezing if a freeze sensor is
included.

6720220047 (2016/02)Revised 02-16

8 | Electrical TW Series Water to Water

• MALFUNCTION OUTPUT: Alarm output is Normally

UPM Board Factory Default Settings

TEMP
LOCKOUT
RESET
ALARM
TEST

26°F

2

Y

PULSE

NO

Open (NO) dry contact. If pulse is selected the alarm
output will be pulsed. The fault output will depend
on the dip switch setting for "ALARM". If it is set to
"CONST", a constant signal will be produced to
indicate a fault has occurred and the unit requires
inspection to determine the type of fault. If it is set
to "PULSE", a pulse signal is produced and a fault
code is detected by a remote device indicating the
fault. See L.E.D Fault Indication below for blink code
explanation. The remote device must have a
malfunction detection capability when the UPM
board is set to "PULSE".

UPM DIP SWITCH DEFAULT POSITION

lockout 42

reset

alarm

test

The UPM Board includes the following features:

• ANTI-SHORT CYCLE TIMER: 5 minute delay on

break timer to prevent compressor short cycling.

• RANDOM START: Each controller has an unique
random start delay ranging from 270 to 300 seconds
on initial power up to reduce the chance of multiple
unit simultaneously starting at the same time after
power up or after a power interruption, thus
avoiding creating large electrical spike.

• LOW PRESSURE BYPASS TIMER: If the compressor
is running and the low pressure switch opens, the
controller will keep the compressor ON for 120
seconds. After 2 minutes if the low pressure switch
remains open, the controllers will shut down the
compressor and enter a soft lockout. The
compressor will not be energized until the low
pressure switch closes and the anti-short cycle time
delay expires. If the low pressure switch opens 2-4
times in 1 hour, the unit will enter a hard lockout. In
order to exit hard lockout power to the unit would
need to be reset.

• BROWNOUT/SURGE/POWER INTERRUPTION
PROTECTION: The brownout protection in the UPM
board will shut does the compressor if the incoming
power falls below 18 VAC. The compressor will
remain OFF until the voltage is above 18 VAC and
ANTI-SHORT CYCLE TIMER (300 seconds) times out.
The unit will not go into a hard lockout.

RY

Cont pulse

yes no

If 24 VAC output is needed, R must be wired to
ALR-COM terminal; 24 VAC will be available o the
ALR-OUT terminal when the unit is in the alarm
condition.

• DISPLAY OUTPUT: The Display output is a pulse

output connected to the Unit Diagnostic Display
(UDD) and it pulses 24VAC when the unit is in an
lockout alarm condition.

• TEST DIP SWITCH: A test dip switch is provided to

reduce all time delays settings to 10 seconds during
troubleshooting or verification of unit operation.

NOTICE: Operation of unit in test mode can
lead to accelerated wear and premature
failure of components. The "TEST" switch
must be set back to "NO" after
troubleshooting/servicing.

• FREEZE SENSOR: The default setting for the freeze

limit trip is 26°F (sensor number 1); however this
can be changed to 15°F by cutting the R24 resistor
located on top of the DIP switch SW1. Since freeze
sensor 2 is dedicated to monitor the load side coil it
is recommended to leave the factory default setting
on the board. The UPM controller will constantly
monitor the refrigerant temperature with the sensor
mounted close to the condensing water coil
between the thermal expansion valve and water coil.
If temperature drops below or remains at the freeze
limit trip for 30 seconds, the controller will shut the
compressor down and enter into a soft lockout
condition. Both the status LED and the Alarm
contact will be active. The LED will flash (three (3)
times) the code associated with this alarm
condition. If this alarm occurs 2 times (or 4 if Dip
switch is set to 4) within an hour the UPM controller
will enter into a hard lockout condition. It will
constantly monitor the refrigerant temperature with
the sensor mounted close to the evaporator
between the

thermal expansion valve and

TW Series Water to Water6720220047 (2016/02) Subject to change without prior notice

Options | 9TW Series Water to Water

evaporator coil as shown in Figure #5. If
temperature drops below or remains at the
limit trip for 30 seconds, the controller will shut the
compressor down and enter into a soft lockout
condition. Both the status LED and the Alarm
contact will be active. The LED will flash (six (6)
times) the code associated with this alarm
condition. If this alarm occurs 2 times (or 4 if Dip
switch is set to 4) within an hour the controller will
enter into a hard lockout condition.

NOTICE: Freeze sensor will not guard
against the loss of water. Flow switch is
recommended to prevent unit from running
if water flow is lost or reduced.

• INTELLIGENT RESET: If a fault condition is initiated,

the 5 minute delay on break time period is initiated
and the unit will restart after these delays expire.
During this period the fault LED will indicate the
cause of the fault. If the fault condition still exists or
occurs 2 or 4 times (depending on 2 or 4 setting for
Lockout dip switch) before 60 minutes, the unit will
go into a hard lockout and requires a manual lockout
reset.

• LOCKOUT RESET: A hard lockout can be reset by

turning the unit thermostat off and then back on
when the “RESET” dip switch is set to “Y” or by
shutting off unit power at the circuit breaker when
the “RESET” dip switch is set to “R”.

freeze

OPTIONS

Number of factory installed options are available on TW
Series of Heat Pumps. The following details the purpose,
function and components of each option.

Heat Recovery Package (HRP)

The heat recovery package is a factory installed option
on TW series heat pumps. The HRP can be used to heat
potable water during unit operation using waste heat
from the compressor discharge gas. In some cases the
HRP can provide most or all of the hot water
requirements for a typical home.
The HRP consists of three major components:

• Double wall, vented refrigerant to water heat
exchanger

• Circulating pump

• Control circuit

The heat exchanger is rated for use with potable water
and is acceptable for use as a domestic water heating
device in most building codes.
The pump circulates water between the domestic hot
water tank and HRP heat exchanger in the Heat Pump.
The control circuit ensures that the HRP only operates
when there is available heat from the compressor and
when the water is within a safe temperature range of
below 140 deg F.

When the heat pump compressor operates, the HRP will
monitor the temperature of the discharge gas from the
compressor. Once discharge gas is hot enough to
provide useful heat to the domestic water tank, the
circulating pump will be enabled, drawing water from
the tank, through the HRP heat exchanger and then
depositing the heated water back into the tank. If the
water temperature reaches 140 deg F, the circulating
pump is disabled to prevent over heating of the
domestic water. The HRP is provided with an on/off
switch in case the end user desires that the HRP be
inactivated (typically during the winter months when
space heating is most important).

NOTICE: If heat recovery unit is installed in
an area where freezing may occur, the unit
must be drained during winter months to
prevent heat exchanger damage. Heat
exchanger ruptures that occur due to
freezing will void the heat recovery package
warranty along with the heat pump
warranty.

DPS Water Flow Proving

The DPS water flow proving switch is a factory installed
option available for the WW series. The DPS prevents
compressor operation if there is inadequate water flow
through the water to refrigerant heat exchanger in the
heat pump.
The DPS operates by monitoring the water side pressure
drop across the water to refrigerant heat exchanger.
When the pressure drop between the water in and water
out lines reaches a pre-set value, compressor operation
is enabled.

Pump Relay

The factory installed pump relay can be used to energize
a supply pump or solenoid valve when there is a call for
compressor operation. This relay can be used to switch
either high or low voltage power.

Comfort Alert Module

The Comfort Alert diagnostics module (CADM) is a
breakthrough innovation for troubleshooting heat pump
system failures. (Figure #6)

Figure # 6

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10 | Heat Recovery Package TW Series Water to Water

By monitoring and analyzing data from the compressor
and the thermostat demand, the module can accurately
detect the cause of electrical and system related failures
without any sensors. A flashing LED indicator
communicates the ALERT code and guides the service
technician more quickly and accurately to the root cause
of a problem.

This module does not provide safety protection! The
Comfort Alert module is a monitoring device and
cannot shut down the compressor directly.

When an abnormal system condition occurs, the
Comfort Alert module displays the appropriate ALERT
and/or TRIP LED.

The yellow ALERT LED will flash a number of times
consecutively, pause and then repeat the process.

To identify a Flash Code number, count the number of
consecutive flashes.

Every time the module powers up, the last ALERT Flash
Code that occurred prior to shut down is displayed for
one minute.Heat Recovery Package

HEAT RECOVERY PACKAGE
Water Tank Preparation

1. Turn off electrical or fuel supply to the water heater.

2. Attach garden hose to water tank drain connection
and run other end of hose out doors or to an open
drain.

3. Close cold water inlet valve to water heater tank.

4. Drain tank by opening drain valve on the bottom of
the tank, then open pressure relief valve or hot
water faucet.

5. Once drained the tank should be flushed with cold
water until the water leaving the drain hose is clear
and free of sediment.

6. Close all valves and remove the drain hose.

7. Install HR water piping.

Concentric water fitting (p/n 8733907119) is
recommended.

(See Figure # 7)

HR Water Piping

All hot water piping MUST be a minimum of 3/8t O.D.
copper tube to a maximum distance of fifteen (15) feet.
For distances beyond fifteen feet but not exceeding sixty
(60) feet use 1/2” copper tube. Separately insulate all
exposed surface of both connecting water lines with 3/
8” wall closed cell insulation. Install isolation valves on
supply and return to the heat recovery. (Figure # 7)

3. Depress the hot water tank pressure relief valve
handle to ensure there is no air remaining in the
tank.

4. Carefully inspect all plumbing for water leaks.
Correct as required.

5. Purge all air from HR by depressing the schrader
valve on the HR Unit. Allow all air to bleed out until
water appears at the valve.

6. Before restoring the power or fuel supply to the
water heater, adjust the temperature setting on the
tank thermostat(s) to ensure maximum utilization of
the heat available from the refrigeration system and
conserve the most energy. On tanks with both upper
and lower elements and thermostats, the lower
element should be turned down to 100° F, while the
upper element should be adjusted to 120° F.
Depending upon the specific needs of the customer,
you may need to adjust the upper element
differently. On tanks with a single thermostat lower
the thermostat setting to 120° F or the “LOW”
position. After thermostat adjustments are
completed, replace access cover and restore
electrical or fuel supply to water heater.

NOTICE: All piping from HRP to domestic
water tank must be copper or any metal of
stronger alloy.

Initial Start-Up

NOTICE: Make sure all valves in heat

recovery water piping system are open.

NEVER OPERATE HR PUMP DRY.

1. Turn on the heat pump. The HR pump should not run
if the compressor is not running

2. Turn HR switch to the “ON” position. The pump will
operate if entering water temperature to HR is
below 120° F.

3. The temperature difference between the water
entering and leaving the heat recovery should be 5°
to 15° F.

4. Allow the unit to operate for 20 to 30 minutes to
ensure it is functioning properly. The pump should
shut off when the water temperature entering the
heat recovery reaches 120°F.

Water Tank Refill

1. Open the cold water supply to the tank.

2. Open a hot water faucet to vent air from the system
until water flows from the faucet, then close.

TW Series Water to Water6720220047 (2016/02) Subject to change without prior notice

Sequence of operation | 11TW Series Water to Water

NOTE: Diagram for illustration purposes only.
Ensure access to Heat Pump is not restricted.

Figure # 7

SEQUENCE OF OPERATION
Cooling Mode

Energizing the “O” terminal energizes the unit reversing
valve thus placing the unit into cooling mode. T

When the thermostat calls for first stage cooling (Y1) the
loop pump or solenoid valve if present is energized and
the first stage of compressor capacity starts.
When the thermostat calls for second stage cooling (Y2)
the second stage (or full compressor capacity) is
initiated. Once the thermostat is satisfied, the
compressor shuts down accordingly

Heating Mode

The first two stages of heating (Y1 & Y2) operate in the
same manner as cooling, but with the reversing valve de­energized. Once the thermostat is satisfied, the
compressor shuts down,

6720220047 (2016/02)Revised 02-16