Burnham RTC Installation Operating Instructions

- Installation & Maintenance Manual

Input

Heat

Demand

Signal

Output

Boiler

Circulator

Input

Well Sensor

Included

Input

Universal Sensor

Optional

Input

Outdoor
Sensor

Optional

Output

Boiler

Input

120 V (ac)

Power

Supply

Do not apply power

Signal wiring must be
rated at least 300 V.

Made in Canada 912-06

L N Pmp N Ret

Boil

BoilCom Mix

R R N

Com Out

1 3 5 9 10 112

4

6

7 8 12

13 141516

Heat

Power

Demand

Boiler

Enable

Item

Test

Monitor

Demand

Power: 120 V ±10% 50/60 Hz 1300 VA
Floating Output: 24 V (ac) 0.34 A 8 VA
Relays: 240 V (ac) 10 A 1/3 hp, pilot duty 240 VA
Demand: 20 to 260 V (ac) 2 VA

H6026A

RTC/Return Temperature Control

Open

Delay

Close

24 Volt Output

Use supply wires
suitable for 120˚F
(50˚C) above ambient

158033

Output

Mixing Valve &

Actuating Motor

RTC/Return Temperature Control

The Burnham Return Temperature Control (RTC) is designed to operate a 3-way or a 4-way valve to protect the boiler against flue
gas condensation and thermal shock. The RTC can also optionally control the supply water temperature to the system based on a
setpoint temperature or an outdoor reset strategy. A boiler post purge is provided by keeping the boiler recirculating pump running
after the call for heat is removed.

Additional functions include:

• Counts boiler run time

• Counts the number of boiler cycles

• Counts boiler cold shocks

• Warns of cold boiler return temperatures

• Test sequence to ensure proper operation

• CSA C US certified

P/N 81460382 1 of 60

How To Use This Manual

Item

Item

This manual is organized into four main sections. They are: 1) Sequence of Operation, 2) Installation, 3) Control Settings, and

4) Testing and Troubleshooting. The Sequence of Operation section has four sub-sections. We recommend reading Section A:
General Operation of the Sequence of Operation section, as this contains important information on the overall operation of the
control. Then read the sub sections that apply to your installation.

The Control Settings section of this manual describes the various items that are adjusted and displayed by the control. The control
functions of each adjustable item are described in the Sequence of Operation.

Table of Contents

User Interface ..................................................Pg 2

Display .............................................................Pg 3

Sequence of Operation ..................................Pg 3

Section A: General Operation .............. Pg 3

Section B: Control Operation ...............Pg 4

Section C: Control Settings .................. Pg 5

Section D: Temperature Monitoring ....Pg 6

Installation .......................................................Pg 7

Control Settings ..............................................Pg 20

View Menu ..............................................Pg 20

Adjust Menu ...........................................Pg 21

Testing the Control .........................................Pg 22

Troubleshooting ............................................. Pg 22

Error Messages ...............................................Pg 23

Repair Parts ....................................................Pg 24

Appendix A: Mechanical And Electrical

Application Drawings ............... Pg 25

Appendix B: Boiler Circulator And Diverting

Valve Selection Charts ............. Pg 46

Appendix C: Valve And Actuator

Mounting Instructions .............. Pg 58

Technical Data................................................. Pg 60

Limited Warranty ............................................Pg 60

User Interface

The control uses a Liquid Crystal Display (LCD) as the method of supplying information. The LCD is used in order to setup and monitor
the operation of the system. The control has three push buttons (Item, , ) for selecting and adjusting settings. As the control is
programmed, record the settings in the Adjust menu table, which is found in the second half of this manual.

Item

The abbreviated name of the selected item will be displayed in the item field of the
display. To view the next available item, press and release the Item button. Once the last
available item in a menu has been reached, pressing and releasing the Item button will
return the display to the first item in the selected menu.

Adjust

To make an adjustment to a setting in the control, press all 3 buttons for 1 second (the
Item,  and  buttons). The display will then show the word ADJUST in the top right
corner. Then select the desired item using the Item button. Finally, use the  and/or 
button to make the adjustment.

To exit the ADJUST menu, leave the adjustment buttons alone for 20 seconds.

When the Item button is pressed and held in the VIEW menu, the display scrolls through all the adjust items.

Additional information can be gained by observing the status field and pointers of the LCD. The status field will indicate which of
the control’s outputs are currently active. Most symbols in the status field are only visible when the VIEW menu is selected.

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Display

Displa

y

s the

cur

r

ent

menu

Displa

y

s an abbre

viat

e

d

name of the sele

cted item

Displa

y

s the

cur

r

ent v

alue

of the sele

cted item

Displa

y

s the

cur

r

ent s

t

atus of

the

contr

ol's i

nputs, ou

tputs a

nd oper

ation

Selects Menu

s, Items

and adjusts setti

ngs

Item

Monitor Delay Open Close

Demand

Symbol Description

Sequence of Operation

Section A

General

Operation

Page 3 - 4

Section A: General Operation

POWERING UP THE CONTROL

When the control is powered up with 120 V (ac), the control displays “rtc” for 2 seconds followed by the software version for 2
seconds. The control then enters the normal operating mode

OPERATION

The control operates a floating action actuator motor connected to a 3-way or 4-way valve to control the boiler return water
temperature to prevent flue gas condensation and thermal shock. The control can also be used to provide outdoor reset or a fixed
setpoint temperature to the supply water temperature.

Pump

Displays when the boiler recirculating pump is
in operation.

Burner

Displays when the boiler relay is turned on.

Section B

Control

Operation

Page 4 - 5

Section C

Control

Settings

Page 5 - 6

°F, °C

Displays the unit of measure that all of the
temperatures are to be displayed in the
control.

Pointer

Displays the control is operating as indicated
by the text.

Section D

Temperature

Monitoring

Page 6

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Fixed PointFixed Point

By Changing
the Mix Design
and the Outdoor
Design settings
the Reset Ratio
changes.

By Changing
the Mix Design
and the Outdoor
Design settings
the Reset Ratio
changes.

70˚F

70˚F

Outdoor Reset

When the outdoor design (OUTDR DSGN) setting is set to a temperature, the control calculates a mix supply temperature based
on the outdoor air temperature and the programmed reset ratio. An outdoor sensor and a mix supply sensor must be installed.

Setpoint Control

When the outdoor design (OUTDR DSGN) setting is set to OFF, and there is a mix supply sensor installed, the control supplies a
fixed mix supply temperature equal to the MIX TARGET setting. An outdoor sensor is not required during this mode of operation.

No Diverting Valve

If a diverting valve is not installed, the outdoor design (OUTDR DSGN) is set to OFF. The boiler return sensor must be installed
to provide monitoring of the boiler conditions.

Floating Action

A 24 V (ac) floating action actuator motor is connected directly to the control on the R, R and N terminals (9, 10 and 11). The
R on terminal 9 is used to open the 3-way diverting valve to the system. The valve can open either in the clockwise or the

counterclockwise direction depending on the orientation of the valve. The R on terminal 10 is used to close the valve. The control
pulses the actuating motor to open or close to maintain the correct mixed supply water temperature at the mix sensor when
there is a heat demand. A visual indication as to whether the control is currently opening or closing the 3-way diverting valve is
displayed in the LCD.

Boiler Protection

The control is capable of providing boiler protection from cold return water temperatures. If the boiler sensor temperature is
cooler than the BOIL MIN setting while the boiler is firing, the control reduces the output to the 3-way diverting valve. This limits
the amount of cool return water to the boiler and allows the boiler temperature to recover. This feature can only be used if a 3-way
diverting valve is installed.

Exercising

The control has a built-in exercising function. If the boiler recirculating pump or valve has not been operated at least once every
3 days, the control turns on the output for a minimum of 10 seconds. This minimizes the possibility of a pump or valve seizing
during a long period of inactivity. The control ensures that the diverting valve operates over its entire range at least once each
exercising period. While the control is exercising, the Test LED flashes.

Note: The exercising function does not work if power to the control, pump, or valve is disconnected.

Section B: Control Operation

HEAT DEMAND

A heat demand is required in order for the control to provide heat by firing the boiler and opening the 3-way diverting valve. To
generate a heat demand, apply between 24 and 240 V (ac) across the Heat Demand terminals (1 and 2). Once voltage is applied,
the Demand pointer is displayed in the LCD.

When the heat demand is removed, the 3-way diverting valve is fully closed before the control is allowed to register a new heat
demand. The Demand pointer will be displayed whenever voltage is present on the Heat Demand terminals, even if the heat
demand is not registered. The 3-way diverting valve is closed to ensure the boiler is protected in the next boiler cycle.

Optionally, the control can be set up to target a setpoint mix supply temperature or outdoor reset temperature through the diverting
valve.

OUTDOOR RESET RATIO

When the control is used as a mixing reset control, the control uses
an outdoor sensor to measure the outdoor temperature. The reset
ratio increases the mix water temperature for every degree the outdoor
temperature falls. The slope of the reset ratio determines the rate at
which the temperature increases with falling outdoor temperatures.
The reset ratio is adjustable using the mix design (MIX DSGN) and the
outdoor design (OUTDR DSGN) settings.

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MIX TARGET

Parallel Shift
Using the
ROOM Setting

Parallel Shift
Using the
ROOM Setting

upup

downdown

6060

-40-40-20-20002020404060608080

8080

100100

120120

140140

160160

180180

200200

Mix

Design

Mix

Design

Mix

Maximum

Mix

Maximum

Mix

Minimum

Mix

Minimum

Outdoor
Design

Outdoor
Design

FixedFixed

Outdoor TemperatureOutdoor Temperature

Supply Water TemperatureSupply Water Temperature

WWSDWWSD

When used as a mixing reset control, the MIX TARGET temperature is calculated from the reset ratio and outdoor air temperature.
When used as a setpoint control, the installer sets the MIX TARGET temperature. The control displays the temperature that it is
currently trying to maintain as the mix supply temperature. If the control does not have a heat demand,”– – –” is displayed as the
MIX TARGET.

BOILER RECIRCULATING PUMP

The boiler recirculating pump contact (Boil Pmp, terminal 5) closes whenever there is a registered heat demand and the control is
not in warm weather shut down (WWSD). The boiler recirculating pump segment is displayed in the LCD. When the heat demand
is satisfied, the control continues to operate the boiler recirculating pump for the purge time. The diverting valve remains open
at the current setting during the purge time and will modulate to protect the boiler. Once the purge time has expired, the boiler
recirculating pump shuts off and the valve closes. If at any time the boiler return temperature falls below 135°F (57°C), the purge is
canceled. During the WWSD, the control exercises the pump for 10 seconds every 3 days of no activity.

Section C: Control Settings

OUTDOOR RESET SETTINGS

Note: For single boiler installations only. When multiple boilers are installed, use an appropriate staging control for outdoor reset

functions.

Room

The ROOM setting is the desired room temperature in the heating zone.
The ROOM setting provides a method to parallel shift the reset ratio
so that higher (or lower) mix water target temperatures are available
over the entire reset range. Adjusting the ROOM setting increases or
decreases the heat delivery to the building.

Mixing Design (MIX DSGN)

The MIX DSGN temperature is the supply water temperature required
to heat the mixing zones when the outdoor air temperature is as cold as the OUTDR DSGN Setting.

Outdoor Design (OUTDR DSGN)

The OUTDR DSGN is the outdoor air temperature that is the typical coldest temperature of the year where the building is located.
This temperature is used when doing the heat loss calculations for the building. If a cold outdoor design temperature is selected,
the mix supply temperature rises gradually as the outdoor temperature drops. If a warm outdoor design temperature is selected,
the mix supply temperature rises rapidly as the outdoor temperature drops.

Warm Weather Shut Down (WWSD)

When the outdoor air temperature rises above the WWSD setting, the control turns on the WWSD segment in the display. When
the control is in WWSD, the Demand pointer is displayed, if there is a demand. However, the control does not operate the heating
system to satisfy this demand. If the control is in setpoint mode, the WWSD feature is not functional.

Mixing Minimum (MIX MIN)

The MIX MIN is the lowest temperature that the control is allowed
to use as a mix target temperature. During mild conditions, if the
control calculates a mix target temperature that is below the MIX MIN
setting, the mix target temperature is adjusted to match the MIX MIN
setting. During this condition, the MIN segment will be displayed in
the LCD when either the MIX TARGET or MIX temperature is being
viewed.

Mixing Maximum (MIX MAX)

The MIX MAX sets the highest water temperature that the control
is allowed to calculate as the mix target temperature. If the control
does target the MIX MAX setting, and the MIX temperature is near
the MIX MAX, the MAX segment will be displayed in the LCD while
either the MIX TARGET temperature or the MIX temperature is
being viewed.

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SETPOINT OPERATION

Monitor

Monitor

Monitor

Mix Target

For setpoint control, set the OUTDR DSGN to OFF. The mix target becomes the setpoint supply temperature that the control is
to maintain. The mix target temperature is set by the installer in the ADJUST menu. An outdoor sensor is not required during this
mode of operation.

COMMON SETTINGS

The following settings are common to both the outdoor reset and setpoint operations.

Open Delay

The open delay is the amount of time that the actuating motor requires to operate the valve from fully closed to fully open.

Boiler Minimum (BOIL MIN)

Most boilers require a minimum water temperature in order to prevent flue gas condensation. The BOIL MIN adjustment is set to
the boiler’s minimum recommended operating temperature. The lowest boiler minimum temperature is 135°F (57°C).

Boiler Minimum Delay (BOIL MIN Delay)

The boiler minimum delay allows a time for the boiler temperature to rise to the boiler minimum temperature while there is a heat
demand. After the time delay, the control begins to count the boiler minimum run time (Monitor BOIL MIN run).

Pump Delay

The pump delay allows the boiler recirculating pump to purge heat from the boiler into the system after the heat demand is
removed. The amount of purge time is determined by the Pump Delay setting.

Section D: Temperature Monitoring

Boiler Temperature (BOIL)

The actual boiler return temperature as measured by the boiler return sensor.

Mix Target

The current mix target temperature if outdoor reset or setpoint operation is selected.

Mix

The actual mix temperature as measured by the mix supply sensor if a mix supply sensor is installed.

Outdoor

The current outdoor temperature as measured by the outdoor sensor, if the outdoor sensor is installed and Outdoor Design is
set to a temperature.

Monitor Items

Monitor Items are displayed using a five digit number. The display cycles between the
monitor name, the first two digits, and the last three digits.

Boiler Run Time (Monitor BOIL run)

The control records the number of hours the boiler enable contact has been closed.

Number of Boiler Cycles (Monitor BOIL CYC)

The control records the number of cycles of the boiler enable contact.

Boiler Run Time Below Return Water Minimum (Monitor BOIL MIN run)

The control records the number of hours the boiler return temperature is below the
boiler minimum temperature and the boiler enable contact is closed. The control does
not record any time while the control is within the boiler minimum delay period.

Number of Boiler Cold Shock Conditions (Monitor BOIL CS)

The control records the number of large and quick temperature swings, which could
be an indication of erratic system behavior.

Boiler Sensor Error Time (Monitor BOIL MIN Err)

The control records the number of hours the boiler return sensor is not functioning.

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Installation

Caution

Improper installation and operation of this control could result in damage to the equipment and possibly even personal injury. It is the
installer’s responsibility to ensure that this control is safely installed according to all applicable codes and standards. This electronic
control is not intended for uses as a primary limit control. Other controls that are intended and certified as safety limits must be placed
into the control circuit. Do not open the control. Refer to qualified personnel for servicing. Opening voids warranty and could result in
damage to the equipment and possibly even personal injury.

STEP ONE

Check the contents of this package. If any of the contents listed are missing or damaged, please contact your wholesaler or
Burnham representative for assistance.

Burnham RTC includes: Burnham Return Temperature Control, Return Temperature Control manual, 1 boiler return
sensor, 4 #8-32 x ½” Phillips screws.

STEP TWO

A. Return Temperature Control (RTC) – Mount the control to the boiler front jacket panel at the top right. See Figures 1 and 2
for general component placement. The RTC mounting bracket must be attached to the jacket first, using four (4) #8 x ¾” drill point
sheet metal screws. Before attaching the RTC to the mounting bracket, remove the controller from the control base/wiring chamber
by pressing the tab on the base and pulling the controller up and off. (This is to prevent accidental damage to the controller during
the mounting process.) One may find it easier to install some of the conduit connectors, along with their corresponding conduit
runs, onto the RTC control base/wiring chamber before mounting it to the bracket. Before choosing which wiring knockouts to
use, read Step Four. Mount the control base/wiring chamber to the bracket using the four (4) #8-32 x ½” Phillips pan head screws
supplied with the RTC. Then reattach the RTC controller to the control base.

B. Return Sensor – The return water temperature sensor must be mounted in a special 3”NPT x 12” long nipple with ¼” NPT side
tapping supplied by Burnham. Apply pipe dope to special nipple both threaded ends and mount the nipple into the boiler’s right
rear return port (as viewed from the rear of the boiler), so that nipple side tapping end is positioned away from the boiler. Apply pipe
dope to the sensor threads and install the sensor into the nipple ¼” NPT side tapping making sure the connection is watertight. Use
bell reducer (refer to Figure 3 or Figure 4) to adapt to recommended return piping size. See Figure 3 or 4 (depending on the boiler
being installed) for the proper location of the return nipple. See Figure 2 for return sensor wiring details. Run the sensor wiring to a
suitable junction box, using a grommet to protect the leads as they enter the box. Mount the junction box to the boiler’s rear jacket
panel, as shown in Figure 2. Connect the sensor wiring from the junction box to the RTC control at the front of the boiler, using the
appropriate conduit and connectors.

INSTALLING THE CONTROL AND RELATED COMPONENTS

GETTING READY

C. Diverting Valve and Actuator – A diverting 3-way or 4-way valve must be installed in the boiler loop piping in order for the RTC
to provide boiler protection. Only a Burnham-approved valve and actuator may be used with the RTC. The diverting valve sizing
depends upon the designed boiler delta T. See Appendix B for proper valve selection. The valve actuator is mounted to the top of
the diverting valve. Position the valve so that the actuator is not on the underside of the valve. Mount and connect the actuator as
illustrated in Appendix C. The electrical connections depend on the valve orientation.

D. Boiler Circulator – A properly selected boiler circulator will maintain a constant and minimum flow through the boiler during
each heat demand. The appropriate circulator must be selected, based upon the designed boiler delta T. See Appendix B for
appropriate boiler circulator selections for 20°F and 40°F delta T applications.

WARNING: IF THE SELECTED BOILER CIRCULATOR IS GREATER THAN 1/3 HP, AN ISOLATION RELAY MUST BE ADDED
WHEN USING THE RTC. IF A 3-PHASE BOILER CIRCULATOR OR A CIRCULATOR WITH AN AMP DRAW GREATER THAN 10
AMP IS SELECTED, AN APPROPRIATE MOTOR STARTER MUST BE USED.

STEP THREE

When using the RTC control, the boiler loop piping must contain the boiler, the boiler circulator, a 3-way or 4-way diverting valve,
and the return sensor. The boiler loop injects hot water into the primary loop, provided that the boiler return water temperature
(measured by the return sensor) is at least 135°F. If the return temperature is below 135°F, the diverting valve closes, recirculating
boiler supply water through the boiler loop until the return water has been heated to at least 135°F. The RTC controls the diverting
value actuator based upon the absolute return water temperature, as well as the rate of temperature change.

Several typical RTC applications are shown in Appendix A. Select the appropriate application before proceeding.

See Figures 5 and 6 for general component and piping arrangements when using 3-way and 4-way diverting valves. See Figure
3 for V9A piping recommendations for 3-way valve applications. See Figure 4 for V11 piping recommendations for 3-way valve
applications. As shown in these diagrams, the boiler loop’s supply and return are connected to the primary loop through two closely
spaced tees, at a maximum branch centerline distance of four times the primary loop diameter (4 x D Max).

NEAR BOILER PIPING

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Figure 1: Typical Boiler Wiring With RTC (Front)

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Figure 2: Typical Boiler Wiring With RTC Return Sensor (Rear)

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Figure 3: V9A Series Boiler Recommended Minimum Piping

- RTC With 3-Way Diverting Valve

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Figure 4: V11 Series Boiler Recommended Minimum Piping

- RTC With 3-Way Diverting Valve

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Figure 5: Typical Burnham Boiler Loop w/3-Way Diverting

Valve

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Figure 6: Typical Burnham Boiler Loop w/4-Way Diverting

Valve

13 of 60

On multiple boiler applications, each boiler is installed in the same arrangement as a single boiler application. Each boiler loop contains

5

Boil

Pm

p

Po

we

r

6

N

3

L

120 V (ac)

N

L

4

N

1

Heat

Demand

2

24 to 240 V (ac)

N

L

Po

we

r

4

120 V (ac)

L

N

3

its own boiler circulator, diverting valve and actuator, RTC control, and return sensor. A number of different boiler sequencers can be
used in conjunction with the RTC by energizing the control’s heat demand circuit. The RTC control’s outdoor reset feature cannot be
used on multiple boiler installations. The sequencer’s outdoor reset feature (if available) would have to be utilized instead.

STEP FOUR

ROUGH-IN WIRING

All electrical wiring terminates in the control base wiring chamber. The base has standard 7/8” (22 mm) knockouts, which accept
common wiring hardware and conduit fittings. Before removing the knockouts, check the wiring diagram and select those sections
of the chamber with common voltages. Do not allow the wiring to cross between sections, as the wires will interfere with safety
dividers, which should be installed at a later time.

Power must not be applied to any of the wires during the rough-in wiring stage.

- All wires are to be stripped to a length of 3/8 in (9 mm) to ensure proper connection to the control.

- If a Mix Sensor 071 or an Outdoor Sensor 070 is used, install the sensor according to the installation instructions in the Data
Brochure D 070 and run the wiring back to the control.

- Make sure the Boiler Return Sensor is installed and run the wiring back to the control.

- Run wire from other system components (pumps, boilers, etc.) to the control.

- Run wires from the 120 V (ac) power to the control. Ideally, a separate dedicated circuit should power the control.

- Use a clean power source with a 15 A circuit to ensure proper operation. Multi-strand 16 AWG wire is recommended for all
120 V (ac) wiring due to its superior flexibility and ease of installation into the terminals.

STEP FIVE

ELECTRICAL CONNECTIONS TO THE CONTROL

The installer should test to confirm that no voltage is present at any of the wires. Push the control into the base and slide it down
until it snaps firmly into place.

Powered Input Connections

120 V (ac) Power

Connect the 120 V (ac) power supply to the Power L and Power N terminals (3 and 4).
This connection provides power to the microprocessor and display of the control. As
well, this connection provides power to the Boil Pmp terminal (5). The control should
be powered from a dedicated circuit. This avoids power disruption to the control in
the event of failure on another electrical device on the same circuit. DO NOT power
the control from the boiler or burner circuit, since there may be times where the
boiler or burner circuit may be switched off in the summer. This would prevent the
exercising of the boiler recirculating pump and the diverting valve. Boiler protection
for dormant boilers, in a multiple boiler application, will not be possible if the control
is not powered.

Heat Demand

To generate a heat demand, a voltage between 24 V (ac) and 240 V (ac) must be
applied across the Heat Demand terminals (1 and 2).

Output Connections

Boiler Recirculating Pump Contact (Boil Pmp)

The Boil Pmp output terminal (5) on the control is a powered output. When the relay in
the control closes, 120 V (ac) is provided to the Boil Pmp terminal (5) from the Power L
terminal (3). To operate the boiler recirculating pump, connect one side of the boiler
recirculating pump circuit to terminal (5), and the second side of the pump circuit to
the neutral (N) terminal (6).

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Diverting Valve Actuator

Supply

from

Boiler

No Flow

to

System

Full

Flow

thru

Bypass

No

Flow

thru

Bypass

COUNTER CLOCKWISE (CCW) = OPEN TO SYSTEM

CLOCKWISE (CW) = CLOSED TO SYSTEM

Supply

from

Boiler

Full Flow

to

System

RTC Terminals

Actuator Terminals

9

R

10

R

11

N

L1

N

L1

0

0

9

R

10

R

11

N

Open

N

Close

24 Volt Output

Supply

from

Boiler

0

5

10

No Flow

to

System

RTC Terminals

Actuator Terminals

Full

Flow

thru

Bypass

CLOCKWISE (CW) = OPEN TO SYSTEM

COUNTER CLOCKWISE (CCW) = CLOSED TO SYSTEM

Supply

from

Boiler

Full Flow

to

System

No

Flow

thru

Bypass

0

5

10

9

R

10

R

11

N

L

1

N

L1

Terminals 9, 10 and 11 are powered with 24 V (ac) from the control.
There is no need to provide a separate 24 V (ac) power source for
the diverting valve actuator. R (9) is connected to the open terminal
of the actuating motor and R (10) is connected to the close terminal
of the actuating motor. N (11) is then connected to the common
terminal of the actuating motor.

The control’s Test Sequence can be used to check the motor circuit. Once the Test button is pressed, the valve should move to
the fully open position. If the motor closes instead of opening, the wiring of the actuating motor must be reversed. Next, the valve
should move to the fully closed position. If it does not, check the wiring between the terminals and the actuating motor. Refer to
any installation or troubleshooting information supplied with the motor.

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Boiler Enable Contact

7

Boiler

Enable

8

12

Com

13

Boil
Re

t

Boiler

Sensor

12

Com

13

Boil

Re

t

14

Mi

x

Mix Supply

Sensor

System

Pump

15

Com

16

Out

The Boiler Enable terminals (7 and 8) are an isolated output in the
control. There is no power available on these terminals from the
control. These terminals are to be used as a switch to either make
or break the boiler limit circuit. When the control requires the boiler
to fire, it closes the contact between terminals 7 and 8.

Sensor and Unpowered Input Connections

Do not apply power to these terminals, as this will damage the control.

Boiler Return Sensor

Connect the two wires from the Boiler Return Sensor to the Com
and Boil Ret terminals (12 and 13). The boiler return sensor is used
by the control to measure the boiler return temperature.

Mix Sensor (Outdoor Reset and Setpoint Modes)

Connect the two wires from the Mix Sensor 071 to the Com and Mix
terminals (12 and 14). The mix sensor is used by the control to mea­sure the mixed supply water temperature in the primary loop. Typi­cally the sensor is attached to the pipe downstream of the system
pump.

Outdoor Sensor (Outdoor Reset Mode)

Connect the two wires from the Outdoor Sensor 070 to the Com and
Out terminals (15 and 16). The outdoor sensor is used by the control
to measure the outdoor air temperature.

STEP SIX

Each terminal block must be unplugged from its header on the control before power is applied for testing. To remove the terminal
block, pull straight down from the control.

The following tests are to be performed using standard testing practices and procedures and should only be carried out by properly
trained and experienced persons.

A good quality electrical test meter, capable of reading from at least 0 – 300 V (ac) and at least 0 – 2,000,000 Ohms, is essential to
properly test the wiring and sensors.

TESTING THE WIRING

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13

14

15

Boi

l

Re

t

Mi

x

Co

m

12

Co

m

2

Heat

Demand

1

V

20 to 260 V (ac)

4

N

Po

w

er

3

L

V

108 to 132 V (ac)

Test the Sensors

A good quality test meter capable of measuring up to 2,000,000 Ω (1kΩ = 1000 Ω) is required to measure the sensor resistance.
In addition to this, the actual temperature should be measured with a good quality digital thermometer.

First measure the temperature using the thermometer.
Then measure the resistance of the sensor at the control.
The wires from the sensor must not be connected to the
control while the test is performed. Using the chart below,
estimate the temperature measured by the sensor. The
sensor and thermometer readings should be close. If the
test meter reads a very high resistance, there may be
a broken wire, a poor wiring connection or a defective
sensor. If the resistance is very low, the wiring may be
shorted, there may be moisture in the sensor or the
sensor may be defective. To test for a defective sensor,
measure the resistance directly at the sensor location.

Do not apply voltage to a sensor at any time as damage
to the sensor may result.

Temperature

°F

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5
0
5

10
15

°C

-46

-43

-40

-37

-34

-32

-29

-26

-23

-21

-18

-15

-12

-9

Resistance

Ω

490,813
405,710
336,606
280,279

234,196

196,358

165,180

139,402

118,018

100,221

85,362
72,918
62,465
53,658

Temperature

°F

°C

20
25
30
35
40
45
50
55
60
65
70

75
80
85

Resistance

-7

-4

-1
2
4
7

10
13
16
18
21
24
27

29

Test the Power Supply

Make sure exposed wires and bare terminals are not in
contact with other wires or grounded surfaces. Turn on
the power and measure the voltage between the Power
L and Power N terminals (3 and 4) using an AC voltmeter,
the reading should be between 108 and 132 V (ac).

Ω

46,218
39,913
34,558
29,996
26,099
22,763
19,900
17,436
15,311
13,474
11,883
10,501

9,299
8,250

Temperature

°F

90

95
100
105
110
115
120
125
130
135
140
145
150
155

°C

32
35
38
41
43
46
49
52
54
57
60
63
66
68

Resistance

Ω

7,334
6,532
5,828
5,210
4,665
4,184
3,760
3,383
3,050
2,754
2,490
2,255
2,045
1,857

Temperature

°F

160
165
170
175
180
185
190
195
200
205
210
215
220
225

°C

71
74

77
79
82
85
88
91
93
96
99

102
104
107

Resistance

Ω

1,689
1,538
1,403
1,281

1,172

1,073

983
903
829
763
703
648
598
553

Test the Powered Inputs

Heat Demand

Measure the voltage between the Heat Demand
terminals (1 and 2). When the heat demand device
calls for heat, between 20 and 260 V (ac) should be
measured at the terminals. When the heat demand
device is off, less than 5 V (ac) should be measured.

17 of 60

Test the Outputs

4

5

6

Boi

l

Pm

p

Po

we

r

N

3

L

120 V (ac)

Boiler Recirculating

Pump

N

L

N

14

13

15

12

16

Com

Com

Out

Boil

Re

t

Mix

Boiler Recirculating Pump (Boil Pmp)

The boiler recirculating pump is connected to the Boil Pmp
terminal (5). Make sure that power to the terminal block is off,
and install a jumper between the Power L and the Boil Pmp
terminals (3 and 5). Install a second jumper between Power N
and N terminals (4 and 6). When power is applied to the Power
L and Power N terminals (3 and 4), the boiler recirculating
pump should start. If the pump does not turn on, check the
wiring between the terminal block and pump, and refer to any
installation or troubleshooting information supplied with the
pump. If the pump operates properly, disconnect the power
and remove the jumpers.

Boiler Enable Contact

If the boiler limit circuit is connected to the Boiler Enable terminals (7 and 8), make sure power to the boiler circuit is off, and
install a jumper between the terminals. When the boiler limit circuit is powered up, the boiler should fire. If the boiler does not
turn on, refer to the installation or troubleshooting information supplied with the boiler. Check for proper operation of each
device in the boiler limit circuit. If the boiler operates properly, disconnect the power and remove the jumper.

Connecting the Control

Make sure all power to the devices and terminal blocks is off, and remove any remaining jumpers from the terminals.

Reconnect the terminal blocks to the control by carefully aligning
them with their respective headers on the control, and then pushing
the terminal blocks into the headers. The terminal blocks should
snap firmly into place.

Install the supplied safety dividers between the unpowered sensor
inputs and the powered or 120 V (ac) wiring chambers.

Apply power to the control. The operation of the control on power up
is described in the Sequence of Operation section of this manual.

STEP SEVEN

ADJUSTING THE CONTROL SETPOINTS

In order for the RTC to function properly, several control settings must be adjusted. Review the “User Interface” and “Sequence
of Operation” sections of this manual for descriptions of each setting and instructions on how to adjust them. Adjust the follow­ing settings as specified:

A. ROOM (Room Temperature) – Set the desired room temperature.

B. MIX TARGET – This setting can only be used on applications where the mix sensor is installed. When the outdoor reset

feature is not selected, this setting represents the fixed target supply water temperature. On this type of application, the MIX
TARGET setting should be adjusted to match the boiler operating aquastat’s setpoint temperature.

C. MIX DSGN (Mixing Design) – When the outdoor reset feature is selected, this setting represents the design system supply
water temperature. If unsure about the original design temperature, set the MIX DSGN to match the boiler operating aquastat’s
setpoint temperature.

D. OUTDR DSGN (Outdoor Design) – When the outdoor reset feature is selected, this setting represents the typical coldest
temperature of the year in the area where the installation is located. If this value is unknown, use the temperature value found
in ASHRAE Fundamentals for the area closest to the installation.

18 of 60