tekmar 275 User Manual

Installation & Operation Manual

Boiler Control 275

Multi-Staging

275_D

11/12

Replaces: 01/12

The Boiler Control 275 is designed to stage up to four condensing or non-condensing, modulating or on-off boilers using

P.I.D. staging to accurately maintain temperature. The control supports hybrid boiler plants that contain both condensing and non-condensing boiler groups. Water temperature is controlled by outdoor reset for space heating applications or a fixed setpoint for Domestic Hot Water (DHW) tank heating or industrial process heating applications. The control will also accept an analog signal from an Energy Management System (EMS) to control the water temperature. Boiler equal run-time rotation, pump exercising and stand-by system pump operation increase boiler plant reliability. The control is tekmarNet® communication compatible allowing for internet connectivity using an optional Gateway 483.

Additional functions include:

tN4 Compatible

• BTC I Compatible

• 24 Hour, 5-11, 5-2, 7 Day Schedule

• Flow or Combustion Air Proof

• Four Modulating or On/Off Boilers

•

Equal Run Time Rotation

• Primary Pump Sequencing

• DHW Operation

• Optional DHW Sensor

• Setpoint Operation

•

tN4

Boiler

Bus

Menu Item

Boiler Control 275

One tN4, Four Modulating Boiler & DHW / Setpoint

Do not apply power

tN4

–

BRet/

Mod1

Com

Out10Com

Boil

DHW

Sup

Mod2

–

Mod3

Mod4

–

Boiler Demand

DHW / Setpoint Demand

Proof Demand

Zone Load Shedding

Priority Override

EMS Input Signal

Relay1Relay2Relay3Relay4C.A. /

Setback Oﬀ

Exercise

Rotate

BTC I

Oﬀ

EMS

Demands

Test

Designed and assembled in Canada by tekmar Control Systems Ltd tektra 1020-01

Power 115 V ±10% 60 Hz 7 VA, 1150 VA max. Relays 230 V (ac) 5 A 1/3 hp Demands 20 to 260 V (ac) 2 VA

Signal wiring must be rated at least 300 V.

Alert

23 251615 1817 2 019 2221

DHW

/ P2

Prim

Power

P1 L N

Boiler

Demand

28271413

Pump Sequencer Fixed Last

Fixed Lead First On / Last Oﬀ

First On / First Oﬀ

oﬀ red red

For maximum heat, press and hold Tes t button for 3 seconds.

Meets Class B: Canadian ICES FCC Part 15

Com

DHW /Setp

Dem

not testing testing testing paused

Pr.

Date Code

H2048B

Input

Flow OR C.A. Proof

Input

DHW OR Setpoint

Outdoor Sensor

Input

Demand Signal

Included

0-10 or 2-10 V (dc)

from EMS

Input

Boiler

Demand Signal

Input

Universal

Sensor

Included

Input

Universal

Sensor

Included

Output

Up to 4

Modulating

Boilers

Output

Up to 4

Boiler Pumps

OR Boiler Enable

Output

Combustion

Air Damper

OR Alert

Output

DHW Pump

Primary Pump

Output

Primary

Pump

Input

115 V (ac)

Power Supply

How to Use the Data Brochure

This brochure is organized into three main sections.

They are: 1) Sequence of Operation,

2) Installation,

3) Control Settings and

4) Testing and Troubleshooting.

Table of Contents

The Control Settings section of this brochure 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.

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

Display and Symbol Description ................................... 3

Access Level.................................................................4

Sequence of Operation .................................................4

Section A: Boiler Demand ........................................4

Section B: Outdoor Reset.........................................4

Section C: Boiler Operation ......................................6

Section D: Modulating Boilers ..................................8

Section E: On / Off Boilers ..................................... 10

Section F: OEM Boilers Equipped With A BTC I .... 10

Section G: Fixed Lead and Fixed Last ................... 10

Section H: Condensing and Non-Condensing Boiler

Groups ................................................................... 10

Section I: Domestic Hot Water Operation .............. 11

Section J: Setpoint Operation ................................ 14

Section K: Energy Management System (EMS) .... 16

Section L: Pump Operation .................................... 17

Section M: Combustion Air and Alert Settings ....... 18

Section N: Setting the Schedule ............................ 19

User Interface

The control uses a Liquid Crystal Display (LCD) as the method of supplying information. You use the LCD in order to setup and monitor the operation of your system. The control has four push buttons (Menu, Item, ▲, ▼) for selecting and adjusting settings. As you program your control, record your settings in the ADJUST menu table, which is found in the second half of this brochure.

Section O: Time Clock ...........................................20

Section P: Boost .....................................................20

Section Q: Exercising ............................................. 20

Section R: tekmarNet

4 Communication ................20

Section S: Scene Operation ................................... 21

Installation .................................................................. 22

Control Settings ......................................................... 28

Cleaning the Control ..............................................28

DIP Switch Settings ................................................28

VIEW Menu ............................................................30

ADJUST Menu ....................................................... 32

TIME Menu .............................................................39

SCHEDULE Menu ..................................................40

MISC Menu ............................................................ 43

Testing the Control ......................................................44

Error Messages .......................................................... 45

Technical Data ............................................................ 48

Limited Warranty ....................................................... 48

releasing the Item button will return the display to the first item in the selected menu.

The items can be quickly scrolled through by holding the Item button and then pressing the ▼ button. To rapidly

scroll through the items in the reverse order, hold the Item button and press the ▲ button.

All of the items displayed by the control are organized into five menus (View, Adjust, Time, Schedule, and Misc). These menus are listed on the top left hand side of the display (Menu Field). To select a menu, use the Menu button. By pressing and releasing the Menu button, the display sequences between the five menus. Once a menu is selected, there will be a group of items that can be viewed within the menu.

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 you have reached the last available item in a menu, pressing and

Adjust

To make an adjustment to a setting in the control, begin by selecting the ADJUST, TIME, SCHEDULE or MISC menu using the Menu button. Then select the desired item using the Item button. Finally, use the ▲, and / or ▼ button to make the adjustment.

Additional information can be gained by observing the Status field 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.

Display

Menu Field

Displays the

current menu

Status Field

Displays the current

status of the

inputs, outputs and

control’s

operation

Buttons

Selects Menus, Items

and adjusts settings

Number Field

Displays the current value

of the selected item

Menu Item

Item Field

Displays the current

item selected

Symbol Description

PRIMARY PUMP

Displays when primary pump 1 or primary pump 2 is in operation

BOILER

Displays which modulating output is operating

LOCK

Displays when adjusting Access level if Switch is set to lock.

WARNING

Displays when an error exists.

COMMUNICATION BUS

Displays when tN4 thermostats are connected.

DHW PUMP

Displays when the DHW Pump is operating

Schd Wake

UnOcc Sleep

Away

BOILER PUMP

Displays when the boiler pump 1, 2, 3, or 4 are operating

COMBUSTION AIR DAMPER

Displays when the combustion air damper relay is closed

SCHEDULE MASTER

Displays when the 275 is a schedule master

WARM WEATHER SHUT DOWN

Displays when the control is in warm weather shut down

MINIMUM & MAXIMUM

Displays when the boil target or the boil supply is at a minimum or maximum

Schd, Wake, UnOcc, Sleep, Away

Displays the current event of a schedule or scene

°F, °C, MINUTES, AM, %, PM, HOURS

Units of measurement.

POINTER

Displays the control operation as indicated by the text

Access Level

The access level restricts the number of Menus, Items, and Adjustments that can be accessed by the user. The Access Level setting is found in the Miscellaneous (MISC) Menu. Select the appropriate access level for the people who work with the control on a regular basis. There are three Access Level Settings:

•

User (USER): Select this access level for building supervisors and other non-technical staff to prevent unauthorized access to installer and advanced level

Installer (INST): Select this access level to limit some of

•

the settings available to the installer. This is the factory default access level.

Advanced (ADV): Select this access level to have complete

•

access to all of the control settings. In the display menu tables, the appropriate access level needed to view each item is shown in the Access column.

Note: the Lock / Unlock switch on the front of the control

must be set to unlock to change the access level.

settings.

Sequence of Operation

In order for the control to have a target water temperature there must be a demand. There are three different demands the control can have: boiler demand, DHW demand, and setpoint demand.

Boiler Demand Section A

Once the control receives a boiler demand it calculates a target water temperature based on the characterized heating curve to provide outdoor reset for space heating. The control can receive a boiler demand three different ways:

1. By applying 20-260 V (ac) to the boiler demand terminals (27 & 28) when the DIP switch is set to Demands.

2. From an Energy Management System (EMS) by applying a 0-10 or 2-10 V (dc) signal to terminals 2 & 3 when the DIP switch is set to EMS.

3. From a tN4 device. This requires a tN4 thermostat to be wired to terminals 1 & 2 so that the call for heat can go over the communication bus.

20-260 V (ac)

2827

Boiler

Demand

OutCom

–

OR OR

0-10 or

2-10 V (dc)

from EMS

tN4 Com

–

tN4

Demand

Outdoor Reset Section B

In a heating system, the rate of heat supplied to the building must equal the rate at which heat is lost. If the two rates are not equal, the building will either cool off or over heat.

The rate of building heat loss depends mostly on the outdoor temperature. Outdoor Reset allows a hot water heating system to increase the water temperature, adding heat to the building, as the outdoor temperature drops. The rate at which the water temperature is changed as a function of outdoor temperature is defined by the characterized heating curve.

Characterized Heating Curve

A characterized heating curve determines the amount the target water temperature is raised for every 1° drop in outdoor air temperature.

The characterized heating curve takes into account the type of terminal unit that the system is using. Since different types of heating terminal units transfer heat to a space using

different proportions of radiation, convection and conduction, the supply water temperature must be controlled differently. The control uses the terminal unit setting to vary the supply water temperature to suit the terminal unit being used. This improves the control of the air temperature in the building.

Boiler Characterized Heating Curve

Boiler

Design

Terminal

Unit

Outdoor

Design

Boiler

Indoor

Decreasing Outdoor Temperatures

Increasing Water Temperatures

Terminal Unit Setting in Adjust Menu

Select the appropriate terminal unit in the adjust menu. This will change the shape of the characterized heating curve to better match the heat transfer properties of that specific terminal unit.

Hydronic Radiant Floor (HRF1)

A heavy or high mass, hydronic radiant floor system. This type of a hydronic radiant floor is embedded in either a thick concrete or gypsum pour. This heating system has a large thermal mass and is slow acting.

Hydronic Radiant Floor (HRF2)

A light or low mass, hydronic radiant floor system. Most commonly, this type of radiant heating system is attached to the bottom of a wood sub floor, suspended in the joist space, or sandwiched between the subfloor and the surface. This type of radiant system has a relatively low thermal mass and responds faster than a high mass system.

Radiator (RAD)

A radiator terminal unit has a large heated surface that is exposed to the room. A radiator provides heat to the room through radiant heat transfer and natural convection.

Baseboard (BASE)

A baseboard terminal unit is similar to a radiator, but has a low profile and is installed at the base of the wall. The proportion of heat transferred by radiation from a baseboard is greater than that from a fin-tube convector.

Boiler Terminal Unit Defaults

When a terminal unit is selected for boiler zones, the control loads default values for the boiler design, boiler maximum supply, and boiler minimum supply temperatures. The factory defaults can be changed to better match the installed system. Locate the Terminal Unit setting in the Adjust menu.

Fancoil (COIL)

A fancoil terminal unit or air handling unit (AHU) consisting of a hydronic heating coil and either a fan or blower. Air is forced across the coil at a constant velocity by the fan or blower and is then delivered into the building space.

Fin–tube Convector (CONV)

A convector terminal unit is made up of a heating element with fins on it. This type of terminal unit relies on the natural convection of air across the heating element to deliver heated air into the space. The amount of natural convection is dependant on the supply water temperature to the heating element and the room air temperature.

Terminal Unit

High Mass Radiant

Low Mass Radiant

Fancoil

Fin-Tube Convector

Radiator

Baseboard

BOIL DSGN BOIL MAX BOIL MIN

120°F (49°C) 140°F (60°C) OFF

140°F (60°C) 160°F (71°C) OFF

190°F (88°C) 210°F (99°C) 140°F (60°C)

180°F (82°C) 200°F (93°C) 140°F (60°C)

160°F (71°C) 180°F (82°C) 140°F (60°C)

150°F (76°C) 170°F (77°C) 140°F (60°C)

Room Setting in Adjust Menu

The Room setting is the desired room air temperature, according to the outdoor reset heating curve. The Room setting parallel shifts the heating curve up or down to change the target water temperature. Adjust the Room setting to increase or decrease the amount of heat available to the building. Once the heating curve has been set up properly, the Room setting is the only setting that needs to be adjusted. The default Room setting is 70°F (21°C), and it can be adjusted for both the occupied and unoccupied periods.

Outdoor Design Setting in Adjust Menu

The outdoor design temperature is typically the coldest outdoor air temperature of the year. This temperature is used when doing the heat loss calculations for the building and is used to size the heating system equipment. If a cold outdoor design temperature is selected, the supply water temperature rises gradually as the outdoor temperature drops. If a warm outdoor design temperature is selected, the supply water temperature rises rapidly as the outdoor temperature drops.

Boiler Indoor Setting in Adjust Menu

The boiler indoor design temperature is the indoor temperature the heating designer chose while calculating the heat loss for the boiler water heated zones. This temperature is typically 70°F (21.0°C). This setting establishes the beginning of the boiler characterized heating curve.

Boiler Design Setting in Adjust Menu

The boiler design supply temperature is the boiler water temperature required to heat the zones at the outdoor design temperature, or on the typical coldest day of the year.

(Default automatically changes based on terminal unit setting)

Warm Weather Shut Down (WWSD) Setting in Adjust Menu

Warm Weather Shut Down disables the heating system when the outdoor air temperature rises above this programmable setting. When the control enters into WWSD, the LCD will indicate this in the status field. WWSD is only available when the DIP switch = Demands. The boilers will operate when a Domestic Hot Water (DHW) demand or a Setpoint Demand is present.

Boiler Operation Section C

The 275 is able to operate up to four modulating or on-off boilers as a heat source. For proper operation of the boilers, the 275 must be the only control that determines when a boiler is to fire.

*Important note: The boiler operator, or aquastat, remains in the burner circuit and acts as a secondary upper limit on the boiler temperature. The boiler aquastat temperature setting must be adjusted above the 275’s boiler maximum setting in order to prevent short cycling of the burner.

Boiler Target Temperature

The boiler target temperature is determined by connected tN4 devices or by a Boiler, DHW or Setpoint demand received by the control. An Energy Management System (EMS) can also give a boiler target. The tN4 devices determine the highest water temperature required and then request this temperature on the tN4 boiler bus. The temperature request creates a Boiler Demand and this is indicated on the display. A DHW demand and a Setpoint demand have temperature settings to which the boilers are operated to meet and are able to override the tN4 bus temperature if required. The control displays the temperature that it is currently trying to maintain as the boiler supply temperature in the View menu. If the control does not presently have a requirement for heat, it does not show a boiler target temperature. Instead, “– – –” is displayed in the LCD.

Boiler Minimum Setting in Adjust Menu

The boiler minimum is the lowest temperature that the control is allowed to use as a boiler target temperature. During mild conditions, if the control calculates a boiler target temperature that is below the boiler minimum setting, the boiler target temperature is adjusted to at least the boiler minimum setting. The MIN segment is displayed in the LCD while viewing the boiler supply or target and when the boiler target is boiler minimum and the boiler supply is less than boiler minimum plus 5°F (2.5°C). Set the Boiler Minimum setting to the boiler manufacturer’s recommended temperature.

Boil MIN + 5°F (2.5°C) Boiler Diﬀerential

MIN segment on

Boil MIN

Boiler Maximum Setting in Adjust Menu

The boiler maximum is the highest temperature that the control is allowed to use as a boiler target temperature. The MAX segment is displayed in the LCD while viewing the boiler supply or target and when the boiler target is boiler maximum and the boiler supply is greater than boiler maximum minus 5°F (2.5°C). Set the boiler maximum setting below the boiler operator or aquastat temperature. At no time does the control operate the boiler above 248°F (120°C).

MAX

segment

MAX

segment

Boil MAX

Boil MAX – 5°F (2.5°C) Boiler Diﬀerential

Stage Delay Setting in Adjust Menu

The Stage Delay is the minimum time delay between the firing of each stage. After this delay has expired the control can fire the next stage if it is required. This setting can be adjusted manually or set to an automatic setting. When the automatic setting is used, the control determines the best stage delay based on the operation of the system.

Boiler Relay Setting in Adjust Menu (per boiler)

The 275 provides a dry contact for either burner ignition or boiler pump. Selection is made through the Boiler RELAY setting in the adjust menu. Select ‘burner’ for boilers that require a boiler enable signal as well as a modulating signal

The boiler differential can be fixed or automatically determined by the control. The Auto Differential setting balances the amount of temperature swing in the boiler supply temperature with boiler on times, off times, and cycle times. This reduces potential short cycling during light load conditions.

Manual Differential

Diﬀerential = 10°F (6°C)

165°F (74°C)

160°F (71°C)

155°F (68°C)

Boiler

Target + 1/2 Diﬀerential

Target

Target – 1/2 Diﬀerential

in order to operate. Select pump to operate a boiler pump with post purge capabilities.

Automatic Differential

Boiler Mass Setting in Adjust Menu (per boiler)

Match the boiler mass setting with the thermal mass characteristics of each boiler. The modulation of the boiler

Off

can become unstable if the incorrect Boiler Mass setting is chosen. A key sign of unstable boiler modulation is that the flame will continue to increase and then decrease in short periods of time. By choosing a lower boiler mass setting,

Differential

the boiler response will become more stable.

The LO setting is selected if the boiler that is used has a low thermal mass. This means that the boiler has very small water content and has very little metal in the heat exchanger. A boiler that has a low thermal mass comes up to temperature quite rapidly when fired. This is typical of many copper fin-tube boilers.

The Lo mass setting provides a fast response to the heating system.

MED

The MED setting is selected if the boiler that is used has a medium thermal mass. This means that the boiler either has a large water content and a low metal content or a low water content and a high metal content. This is typical

Time

Rotation

The Rotate feature changes the firing order of the boilers whenever one boiler accumulates 48 hours more run time than any other boiler. Rotation will be forced if any boiler accumulates 60 hours more run time. After each rotation, the boiler with the least running hours is the first to fire and the boiler with the most running hours is the last to fire. This function ensures that all of the boilers receive equal amounts of use. When the Rotate / Off DIP switch is set to the Off position, the firing sequence always begins with lowest boiler to the highest boiler.

Heating Load

of many modern residential cast iron boilers or steel tube boilers.

The Med mass setting provides a moderate response to

1 2

2 1

the heating system.

The HI setting is selected if the boiler that is used has a high thermal mass. This means that the boiler has both large water content and a large metal content. A boiler that has a high thermal mass is relatively slow in coming up to temperature. This is typical of many commercial cast iron and steel tube boilers.

720 hours

To reset the rotation sequence (without regard to historical running hours), toggle the Rotation DIP Switch Off for 3 seconds and on again. Note that the running hours (see Run Time) in the View menu also need to be reset if you want the rotation sequence and running hours display to be synchronized.

672 hours

720 hours

The Hi mass setting provides a slow response to the heating system.

Boiler Differential Setting in Adjust Menu

A modulating boiler must be operated with a differential while operating at Minimum Modulation. When the boiler

Boiler Run Time in View Menu

The running time of each boiler is logged in the view menu. To reset the running time, select the appropriate Boiler Run Time in the View menu and press and hold the Up and Down buttons together until CLR is displayed.

is modulating above Minimum Modulation, the differential does not apply. Instead, the modulation output signal is determined using Proportional, Integral, and Derivative (PID) logic in order to satisfy the boiler target temperature.

Modulating Boilers Section D

The 275 can operate up to four modulating boilers. The control also provides dry contacts for either burner ignition or boiler pump. Selection is made through Boiler Relay setting in the Adjust menu.

Once a boiler is required to operate, the control outputs an analog signal corresponding to the Start Modulation setting and then turns on the boiler relay. Once the Fire Delay time has elapsed, the modulating output is adjusted to the Minimum Modulation setting. The control then holds the modulating output at Minimum Modulation until the Minimum Modulation Delay time has elapsed. Proportional, Integral and Derivative (PID) logic is used in order to satisfy the boiler target temperature.

Modulation Mode Setting in Adjust Menu

The control includes a Modulation Mode setting that selects either Sequential or Parallel Modulation. Sequential modulation should be used on boilers that are more efficient when operating at high fire. Parallel modulation should be used on boilers that are more efficient when operating at low fire.

The 275 is restricted to sequential staging if:

1. 1 or more boilers are configured to be On/Off.

2. Condensing mode is selected.

3. The plant is configured for direct DHW.

Boiler Start Modulation Setting in Adjust Menu

(per boiler)

The Start Modulation setting is the lowest modulation output required to obtain proper ignition. Whenever boiler operation is required, the control outputs an analog signal corresponding to the Start Modulation setting and closes the boiler contact to turn on the burner. After the Fire Delay has elapsed and the burner is ignited, the control modulates the firing rate between the Minimum Modulation setting and the Maximum Modulation setting.

40% 40% 40% 40%

Sequential Modulation

In sequential modulation, the first boiler is turned on and is modulated to satisfy light loads. Once the first boiler does not have enough capacity to satisfy the load, the first boiler reduces its modulation to provide a smooth transition when the second boiler fires at low fire. The first boiler then modulates up to maximum modulation as the load increases. Only then is the second boiler able to increase its output as the load continues to increase. When the third boiler is required, the second boiler reduces its modulation to allow the third boiler to operate at low fire. As the load continues to increase, the second boiler is modulated to its maximum and then the third boiler is modulated. The operation is reversed when shutting off the boilers.

100% 60% Off Off

Parallel Modulation

In parallel modulation, the first boiler turns on at low fire and begins to increase its modulation. Once the first boiler’s output is greater than the combined output of the first and second boiler’s low fire, the first boiler is modulated down to low fire and the second boiler is fired at low fire. The two boilers now modulate together. Once the two boiler’s combined output is greater than the combined output of all three boilers operating at low fire, the first and second boilers are modulated down to low fire, and all three boilers are operated at low fire. The boilers are then modulated as the load increases. The operation is reversed when shutting off the boilers.

Boiler Fire Delay Setting in Adjust Menu

(per boiler)

The Boiler Fire Delay sets the time it takes for the boiler to generate flame from the time the boiler turns on.

Boiler Contact Closed

Fire Delay

Burner On

Time

Boiler Motor Speed Setting in Adjust Menu

(per boiler)

The Motor Speed is the amount of time the boiler requires to go from 0% modulation to 100% modulation.

Gas valve actuating motors have a design time from fully closed to fully opened which can be found in the manufacturer’s manual. The Motor Speed should be set to this time.

The Motor Speed setting for a Variable Frequency Drive (VFD) is the amount of time required to go from a stopped position to 100% fan speed. Since a VFD has a very quick response rate, it may be necessary to increase the Motor Speed setting in order to increase the stability of the boiler modulation.

Boiler % Modulation in View Menu

View the current % modulation of each boiler in the View menu.

Boiler Minimum Modulation Setting in Adjust Menu

(per boiler)

The Minimum Modulation setting is the lowest modulation output to obtain low fire. The Minimum Modulation setting is typically based on the turndown ratio of the boiler. The control adjusts the modulating output signal from Minimum Modulation to 0% after the burner turns off and boiler operation is not required.

To calculate the Minimum Modulation, use the following formula:

For 0 to 10 V (dc):

Minimum

Modulation

0 V (dc) –

Boiler’s Minimum

Input Signal

0 – 10 V (dc)

x 100%

Example:

A boiler requires a 1.8 V (dc) signal to fire the boiler at low fire. The boiler can be modulated to 10 V (dc) where it reaches high fire. This means the boiler’s input signal range is 1.8 to 10 V (dc). The 275 control has an output signal range of 0 to 10 V (dc).

To make the two signal ranges the same, the Minimum Modulation required is:

Minimum Modulation = (0 – 1.8) ÷ (0 – 10) x 100% = 18%

10 V (dc)

Control’s

Output

Signal Range

Minimum Modulation

0 V (dc)

100%

88%

18%

10 V (dc)

Boiler’s Input Signal Range

1.8 V (dc)

Boiler’s Minimum Input Signal

Minimum Modulation Delay Setting in Adjust Menu

(per boiler)

The Minimum Modulation Delay is the time that the boiler burner must hold the modulation of the boiler at a minimum before allowing it to modulate any further.

Boiler Maximum Modulation Setting in Adjust Menu

(per boiler)

The Maximum Modulation defines the maximum output signal from the control to the boiler burner. It is based on a percentage of the control’s output signal range. The maximum modulation setting for boilers with power burners is typically set to 100%.

For boilers with electronic operators, the boiler’s input signal range may not match the output signal range of the 275 control. The Maximum Modulation setting limits the control output range in order to match the boiler’s input range.

To calculate the Maximum Modulation, use the following formula:

For 0 to 10 V (dc):

Maximum

Modulation

0 V (dc) –

Boiler’s Maximum

Input Signal

0 – 10 V (dc)

x 100%

Example:

A boiler’s input signal range is 0 to 9 V (dc). The 275 control has an output signal range of 0 to 10 V (dc). To make the two signal ranges the same, the Maximum Modulation required is:

Maximum Modulation = (0 – 9) ÷ (0 – 10) x 100% = 90%

10 V (dc)

Maximum Modulation

Control’s

Output

Signal

Range

100%

88%

9 V (dc)

Boiler’s Input Signal Range

0 V (dc)0 V (dc)

Boiler’s Maximum Input Signal

Minimum and Maximum Boiler Outputs (MBH) Setting in Adjust Menu

(per boiler)

In order to accommodate different boiler capacities in the same system, a minimum and maximum boiler output for each boiler can be set. This allows the control to properly operate the boilers using either sequential or parallel modulation. Each boiler typically has a rating plate that specifies the minimum and maximum output. This information is also available in the boiler manual.

The minimum and maximum boiler output is expressed in MBH. 1 MBH = 1,000 BTU / hour. The range is from 1 MBH to 1,999 MBH.

For example, if a boiler has a maximum output of 100,000 BTU / hr and a minimum output of 20,000 BTU / hr (turn down ratio of 5):

Maximum Boiler Output =

100,000

= 100 MBH

1,000

Minimum Boiler Output = 20,000 = 20 MBH

1,000

On / Off Boilers Section E

The 275 can operate up to four modulating or on/off boilers in any combination. Each boiler stage has a Boiler Mode setting in the the Adjust menu that allows the selection of either modulating (Mod) or on/off (OnOF). By selecting a

boiler stage to on/off, the 275 then uses sequential boiler staging, the stage relay is set to operate a burner, and settings related to modulation are removed from the boiler settings.

OEM Boilers Equipped With A BTC I Control Section F

The 275 can sequence up to four boilers equipped with an integral BTC I control. Boilers that include the BTC I control may have multi-stage or modulating burners. Each boiler is connected to the 275 using two wires connected to the Mod + and - wiring terminals for each boiler stage. The 275

also allows combinations of multi-stage boilers together with modulating boilers. In total, the 275 is able to control up to 16 stages. For information on BTC I equipped boilers and how to installed with the 275, please see tekmar Service Bulletin SB 055.

Fixed Lead and Fixed Last Section G

Fixed Last

In some applications, it may be desirable to have the last boiler fire last at all times while the firing sequence of the remaining boilers is changed using Equal Run Time Rotation. This configuration is typical of installations where the boiler plant includes higher efficient boilers and a single lesser efficient boiler. The lesser efficient boiler is only desired to be operated when all other boilers in the plant are on and the load cannot be satisfied. This rotation option is selected by setting the Fixed Last / Off DIP switch to Fixed Last. With a fixed last rotation, the last boiler is the last to stage on and the first to stage off. The Fixed Last is always applied to the boiler 4 output.

Fixed Lead & First On / First Off

In some applications, it may be desirable to have the first boiler fire first at all times while the firing sequence of the remaining boilers is changed using Equal Run Time Rotation. This rotation option is selected by setting the Fixed

Lead / Off DIP switch to the Fixed Lead position. The Fixed Lead is always applied to the boiler 1 output.

When using the Fixed Lead rotation option, a selection must be made between First On / Last Off and First On / First Off using the DIP switch.

When First On / First Off is selected, the lead boiler is always staged on first and staged off first. This configuration is typical of installations where the boiler plant includes similar boilers but the first boiler is required to be the first to fire in order to establish sufficient draft for venting.

Fixed Lead & First On / Last Off

When First On / Last Off is selected, the lead boiler is always staged on first and staged off last. This configuration is typical of installations where the boiler plant includes a single higher efficient boiler with lesser efficient boilers. The lead boiler is the high efficiency boiler, therefore it the last boiler to be sequenced off.

Condensing and Non-Condensing Boiler Groups Section H

Operating a boiler plant that contains both condensing (high initial cost) and non-condensing (lower intial cost) boilers allows the boiler plant to achieve nearly the same operating efficiencies as operating all condensing boilers but at a much lower installed cost to the building owner. High system efficiency can be acheived as long as the condensing boilers are the first to operate in the firing sequence. During mild weather, the lead condensing boilers operate at lower boiler temperatures and achieve their peak boiler effiencies while the non-condensing boilers are rarely operated. During very cold weather, the boiler target is often above the boiler’s condensation point and the condensing and non-condensing boilers operate together at roughly the same efficiency level.

The 275 supports the operation of condensing and noncondensing boilers as separate groups through either the Fixed Lead or Fixed Last options. When a condensing boiler is operating, it is desirable to operate the boilers without a boiler minimum temperature being applied to the boiler target. This allows the condensing boiler to operate at its maximum efficiency. When a non-condensing boiler is operating, a boiler minimum temperature should be

applied to the boiler target to prevent damage to the noncondensing boiler heat exchanger from sustained flue gas condensation.

To operate one to three condensing boilers as the lead boiler group, and operate a single non-condensing boiler as the lag boiler, set the Fixed Last / Off DIP switch to the Fixed Last position and select the Condensing Lead (COND LEAD) setting to on. The boilers within the condensing lead group can be operated using Equal Run Time Rotation to balance running hours.

To operate a single condensing boiler as the lead boiler, and operate one to three non-condensing boilers as the lag group, set the Fixed Lead / Off DIP switch to the Fixed Lead position and select the Condensing Lead (COND LEAD) setting to on. The boilers within the non-condensing lag group can be operated using Equal Run Time Rotation to balance running hours.

In the event that Fixed Lead or Fixed Last is selected and all boiler are non-condensing, select the Condensing Lead (COND LEAD) setting to off.

Domestic Hot Water Operation Section I

DHW operation is only available when the Pump Sequencer DIP Switch is set to Off.

DHW Demand

DHW Demands come from one of three sources: an external aquastat, a DHW tank sensor, or a tN4 Setpoint Control.

Once the control detects a DHW Demand, the DHW Demand segment is displayed in the LCD. If an External Powered DHW Demand is applied while the DHW sensor is enabled in the 275, an error message is generated and both demands are ignored.

A DHW demand from a tN4 Setpoint Control can coexist with another DHW demand without generating an error message. The 275 will then use the higher of the two targets.

Powered DHW Demand

The control registers a DHW Demand when a voltage between 20 and 260 V (ac) is applied across the DHW Demand terminals 29 and 30. An aquastat or setpoint control is used to switch the DHW Demand circuit. Program a DHW Exchange temperature for the Occupied and UnOccupied events in the Adjust Menu.

• DHW Sensor must be set to Off.

DHW Sensor

The control can register a DHW Demand when A DHW Sensor is wired to terminals 5 and 6. Once the DHW Sensor drops 1/2 of the DHW Differential setting below the DHW Setpoint, the control registers a DHW Demand. Program a DHW Tank temperature for the Occupied and UnOccupied events in the Adjust Menu.

The DHW Sensor must be set to On. There cannot be

• an externally powered DHW demand when using a DHW sensor.

tN4 Setpoint Control in DHW Mode

The control can register a DHW Demand when a tN4 Setpoint Control in DHW Mode is wired to terminals 1 and 2. The DHW Demand is sent over the tN4 communication bus when the Setpoint Control calls for heat. Program a DHW tank temperature for the Occupied and UnOccupied events and the desired supply water temperature required on the tN4 bus in the Adjust Menu of the tN4 Setpoint Control.

DHW Differential Setting in Adjust Menu

Due to large differences between the heating load and the DHW load, a separate DHW differential should be used whenever a DHW Demand is present. This will improve staging and boiler cycling. When using a DHW Sensor, a DHW Demand is registered when the DHW sensor drops 1/2 of the DHW Differential setting below the DHW setting. The DHW Demand is satisfied once the DHW Sensor rises 1/2 of the DHW Differential setting above the DHW setting.

OFF

Boiler Target Temperature during a DHW Demand

If a Powered DHW Demand is present, the boilers are operated to maintain the DHW Exchange temperature. If a DHW sensor demand is present, the boilers are operated to maintain a temperature of 40°F (22°C) above the DHW tank temperature. If a tN4 demand is present, the primary pump is turned on according to the device’s reported requirements and the boilers are operated to maintain the devices requested target on the bus. The DHW Demand overrides the boiler reset target temperature, except when the boiler reset target is higher than the DHW target. Regardless of DHW settings and requested targets, the boilers will maintain a target temperature no higher than the Boil MAX setting.

DHW During UnOccupied

When using a Powered DHW Demand, the control has a DHW Exchange UnOccupied setting that allows the installer to select On or Off. When set to On, and the control receives a DHW Demand during an UnOccupied or Sleep period, the control continues operation of the DHW system as it would during the Occupied and Wake periods. When set to Off, the control will ignore a DHW Demand for the duration of the UnOccupied and Sleep periods.

When using a DHW Sensor, a second DHW temperature setting is available for the UnOccupied or Sleep period.

DIP Switch must be set to Setback to view UnOccupied items.

During the Away Scene, DHW demands are ignored.

DHW Mode Setting in the Adjust Menu

The control has six different DHW Modes that affect pump operation. The required DHW Mode setting will depend on the piping arrangement of the DHW tank and whether or not priority for DHW is necessary. DHW Priority stops or limits the delivery of heat to the building heating system while the DHW tank calls for heat. This allows for quick recovery of the DHW tank.

Mode OFF / No DHW Generation

All DHW demands are ignored. If this mode is selected while DHW generation is underway, all DHW operation ceases.

DHW Differential

DHW Target

Mode 1 - DHW in Parallel with No Priority

When a valid DHW Demand is present, the DHW relay (terminal 23) turns on. The primary pump can operate when a Boiler Demand is present. It is assumed that the DHW pump will provide adequate flow through the heat exchanger and the boiler. Heating zones are unaffected by DHW operation.

Mode 4 - DHW in Primary/Secondary with Priority

When a valid DHW Demand is present, the DHW relay (terminal 23) and Primary Pump relay (terminal 24) turn on. If the boilers are unable to maintain the boiler target temperature, space heating zones are shut off sequentially using tN4 communication in order to provide priority to the DHW tank. For non-tN4 systems, priority requires the use of an external relay to force the heating zones off.

Mode = 1

DHW Pump

Primary

Pump

Mode 2 - DHW in Parallel with Priority

When a valid DHW Demand is present, the DHW relay (terminal 23) turns on. The primary pump can operate when a Boiler Demand is present. If the boilers are unable to maintain the boiler target temperature, space heating zones are shut off sequentially using tN4 communication in order to provide priority to the DHW tank. For non-tN4 systems, the primary pump shuts off to provide priority. It is assumed that the DHW pump will provide adequate flow through the heat exchanger and the boiler.

Mode = 2

OFF

DHW Pump

Primary

Pump

Mode = 4

DHW

Pump

Primary

Pump

OFF

Mode 5 - DHW in Parallel / Last Boiler with Priority

When a valid DHW Demand is present, the DHW relay (terminal 23) turns on and boiler pump 4 turns off. The control uses the DHW Exchange Supply Sensor in order to measure the boiler supply temperature supplied to the indirect tank. There are two boiler target temperatures, one for the heating system (BOIL TARGET) and one for the indirect DHW system (BOIL DHW TARGET). In this mode, the DHW Demand can only be provided from an External Powered Demand or tN4 Setpoint Control in DHW mode.

All boilers are used for space heating requirements

• Boiler 4 is used for DHW when there is a DHW demand

•

The dedicated DHW boiler is always boiler 4 (relay 4),

• even if there are less than 4 boilers.

If boiler 4 is disabled and mode 5 is selected then the

• dedicated DHW boiler (boiler 4) will not operate.

DHW Exchange

Supply Sensor

Mode = 5

Mode 3 - DHW in Primary/Secondary with No Priority

When a valid DHW Demand is present, the DHW relay (terminal 23) and Primary Pump relay (terminal 24) turn on. Heating zones are unaffected by DHW operation. This mode can be used if the DHW tank is piped in parallel and a DHW valve is installed (need to use an external relay to power the valve with 24 V (ac) since the DHW pump output is a 120 V (ac) powered output).

Mode = 3

DHW

Pump

Primary

Pump

OFF

DHW Pump

Boiler

Supply

Sensor

Primary

Pump

Mode 6 – Dedicated DHW

When a valid DHW Demand is present from the DHW Sensor, the primary pump relay turns on. The DHW Relay in this mode is used as the DHW recirculation pump and operates continuously in the Occupied period and cycles with the primary pump in the UnOccupied period. The boiler plant is sequenced based only on the DHW Sensor.

All boilers are used for DHW requirements

• Requires DHW demand from DHW sensor

• DHW Pump Relay is used for DHW recirculation pump

• Boiler Supply Sensor Not Required

•

DHW Post Purge

After the DHW Demand is removed, the control performs a purge. The control shuts off the boilers and continues to operate the DHW Pump and the primary pump if applicable. This purges the residual heat from the boilers into the DHW tank. The control continues this purge until one of the following occurs:

1. A Boiler Demand is detected

2. The boiler supply drops 20°F (11°C) below the DHW target temperature

3. The DHW tank temperature rises above the DHW setpoint plus 1/2 DHW Differential

On/

Off

Mode = 6

On/

Off

4. Two minutes elapse

DHW Mixing Purge

After DHW operation, the boiler is extremely hot. At the same time, the heating zones may have cooled off considerably

DHW Sensor

after being off for a period of time. When restarting the heating system after a DHW demand with priority, the

Recirculation

Pump

control shuts off the boiler and continues to operate the DHW pump while the primary pump is turned on. This allows some of the DHW return water to mix with the cool return

DHW Priority Override Setting in Adjust Menu

DHW Priority Override applies to DHW MODE 2 and 4, as well as Mode 5 if there is a tN4 device with DHW. It prevents the building from cooling off too much or the possibility of a potential freeze up during DHW priority.

When set to auto, the priority time is calculated based on outdoor temperature. At or below the design outdoor temperature, 15 minutes are allowed for DHW priority. At or above 70°F (21°C), 2 hours are allowed for DHW priority. The time allowed for DHW priority varies linearly between the above two points. There is a manual setting also available in the adjust menu.

The priority timer does not start timing until priority is selected and both a DHW Demand and a Boiler Demand exist together. Once the allowed time for priority has elapsed, the control overrides the DHW priority and resumes space heating.

Automatic Priority Override

2 hours

water from the zones and temper the boiler return water.

DHW with Low Temperature Boilers

If DHW heating is to be incorporated into a low temperature system such as a radiant floor heating system, a mixing device is often installed to isolate the high DHW supply temperature from the lower system temperature. If a mixing device is not installed, high temperature water could be supplied to the low temperature system while trying to satisfy the DHW demand. This may result in damage to the low temperature heating system.

The control is capable of providing DHW heating in such a system while minimizing the chance that the temperature in the heating system exceeds the design supply water temperature. In order to do this, the following must be true:

tN4 Present

•

DHW MODE 2 or 4

•

Boil MIN OFF

•

On a call for DHW, the control provides DHW priority by sending a message on the boiler temperature bus to the tN4 thermostats to shut off the heating zones for a period of time. The length of time is based on the outdoor air temperature as described in the DHW Priority Override section. However, if the DHW Demand is not satisfied within the allotted time, the boiler shuts off and the heat of the boiler is purged into the

15 mins

DHW tank. A DHW mixing purge occurs in order to reduce the boiler water temperature and once the boiler supply

70°F (21°C)

Design Temperature

Conditional DHW Priority

If the boiler supply temperature is maintained at or above the required temperature during DHW generation, this

temperature is sufficiently reduced, the DHW Pump contact shuts off. The heating system zones are allowed to turn on for a period of time to prevent the building from cooling off. After a period of heating, and if the DHW Demand is still present, the control shuts off the heating system and provides heat to the DHW tank once again.

indicates that the boilers have enough capacity for DHW and possibly heating as well. As long as the boiler supply temperature is maintained near the target, DHW and heating

DHW Boilers Setting in Adjust Menu

Select the number of boilers to use for DHW generation.

occurs simultaneously.

Setpoint Operation Section J

Setpoint operation is only available when DHW Mode is set to Off.

The control can operate to satisfy the requirements of a setpoint load in addition to a space heating load. A setpoint load overrides the current outdoor reset temperature in order to provide heat to the setpoint load.

Setpoint Demand

Setpoint Demands come from one of two sources: a Powered Setpoint Demand, or a tN4 Setpoint Control.

Powered Setpoint Demand

The control registers a Setpoint Demand when a voltage between 20 and 260 V (ac) is applied across the Setpoint Demand terminals 29 and 30. An aquastat or setpoint control is used to switch the Setpoint Demand circuit. Program a Setpoint target for the Occupied and UnOccupied events in the Adjust Menu.

• DHW Mode must be set to Off.

tN4 Setpoint Control

The control can register a Setpoint Demand when a tN4 Setpoint Control is wired to terminals 1 and 2. The Setpoint Demand is sent over the tN4 communication bus when the Setpoint Control calls for heat. Program a Setpoint temperature for the Occupied and UnOccupied events and the desired supply water temperature required on the tN4 bus in the Adjust Menu of the tN4 Setpoint Control.

• DHW Mode must be set to Off.

A demand from a tN4 Setpoint Control can coexist with another setpoint demand without generating an error message. The 275 will then use the higher of the two targets.

DIP Switch must be set to Setback to view UnOccupied items.

During the Away Scene, Setpoint demands are ignored.

Setpoint Mode Setting in the Adjust Menu

The control has four different Setpoint Modes that affect pump operation. The required Setpoint Mode setting will depend on the piping arrangement and whether or not priority is necessary. Setpoint Priority stops or limits the delivery of heat to the building heating system while the Setpoint load calls for heat. This allows for quick recovery of the Setpoint load.

Mode OFF - No Setpoint Operation

All Setpoint demands are ignored. If this mode is selected while Setpoint operation is underway, all Setpoint operation ceases.

Mode 1 - Setpoint in Parallel with No Priority

Whenever a Setpoint Demand is present, the boilers are operated to maintain the setpoint target. The primary pump does not turn on, but may operate based on a Boiler Demand. It is assumed that the Setpoint pump will provide adequate flow through the heat exchanger and the boiler.

Mode = 1

Setpoint

Primary

Pump

Boiler Target Temperature during a Setpoint Demand

If a Powered Setpoint Demand is present, the boilers are operated to maintain the Setpoint target. If a tN4 demand is present, the primary pump is turned on according to the device’s reported requirements and the boilers are operated to maintain the devices requested target on the bus. The Setpoint Demand overrides the boiler reset target temperature, except when the boiler reset target is higher than the Setpoint target. Regardless of Setpoint settings and requested targets, the boilers will maintain a target temperature no higher than the Boil MAX setting.

Setpoint During UnOccupied

When using a Powered Setpoint Demand, the control has a Setpoint UnOccupied setting that allows the installer to select On or Off. When set to On, and the control receives a Setpoint Demand during an UnOccupied or Sleep period, the control continues operation of the Setpoint system as it would during the Occupied and Wake periods. When set to Off, the control will ignore a Setpoint Demand for the duration of the UnOccupied and Sleep periods.

Mode 2 - Setpoint in Parallel with Priority

When a Setpoint Demand is present, the boilers are operated to maintain the setpoint target. The primary pump can operate when a Boiler Demand is present. If the boilers are unable to maintain the boiler target temperature, space heating zones are shut off sequentially using tN4 communication in order to provide priority to the Setpoint Load. For non-tN4 systems, the primary pump shuts off to provide priority. It is assumed that the Setpoint pump will provide adequate flow through the heat exchanger and the boiler.

Mode = 2

Setpoint

OFF

Primary

Pump

Mode 3 - Setpoint in Primary/Secondary with No Priority

Whenever a Setpoint Demand is present, the primary pump is turned on and the boilers are operated to maintain the setpoint target.

Mode = 3

Setpoint

Automatic Priority Override

2 hours

15 mins

Primary

Pump

Mode 4 - Setpoint in Primary/Secondary with Priority

Whenever a Setpoint Demand is present, the primary pump is turned on and the boilers are operated to maintain the setpoint target. Space heating zones will be shut off if the boilers are unable to maintain the boiler target temperature using tN4 communication. For non-tN4 systems, an external relay is required to force off the heating zones.

Mode = 4

Setpoint

OFF

Primary

Pump

Setpoint Priority Override Setting in Adjust Menu

Setpoint Priority Override applies to SETPOINT MODE 2 and MODE 4. To prevent the building from cooling off too much or the possibility of a potential freeze up during setpoint priority, the control limits the amount of time for setpoint priority.

When set to auto, the priority time is calculated based on outdoor temperature. At or below the design outdoor temperature, 15 minutes are allowed for Setpoint priority. At or above 70°F (21°C), 2 hours are allowed for Setpoint priority. The time allowed for Setpoint priority varies linearly between the above two points. There is a manual setting also available in the adjust menu.

The priority timer does not start timing until priority is selected and both a Setpoint Demand and a Boiler Demand exist together. Once the allowed time for priority has elapsed, the control overrides the Setpoint priority and resumes space heating.

Design Temperature70°F (21°C)

Conditional DHW Priority

If the boiler supply temperature is maintained at or above the required temperature during setpoint generation, this indicates that the boiler has enough capacity for setpoint and possibly heating as well. As long as the boiler target temperature is maintained, setpoint and heating occur at the same time.

Setpoint Post Purge

After a tN4 Setpoint Demand is removed, the control performs a purge. The control shuts off the boilers and continues to operate the Setpoint Pump and the primary pump if applicable. This purges the residual heat from the boilers into the Setpoint load. The control continues this purge until one of the following occurs:

1. A Boiler Demand is detected

2. The boiler supply drops 20°F (11°C) below the Setpoint target temperature

3. Two minutes elapse

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