Worked examples

The installation representations in this section show piping, appliances, and components that serve as guidelines for planning and designing an optimal multi-load heating system.

Systems should be designed with appropriate controls, pumps, heat loss calculations, flow rate as well as heat source sizing.

  Note

It is very important to use the correct outdoor climate information (outdoor design conditions) for the location of the system you are installing to calculate the building heating load. This can be used to determine the required cubic feet per minute (CFM) for each room, and design the appropriate duct work for the application.

Each of the four concept drawings below include instructions for piping, wiring, and programming:

  1. Space heating with an indirect tank
  2. Space heating with an indirect tank and zone control relay
  3. Two-sided space heating with an indirect tank
  4. Multiple boiler network with indirect water tanks and space heating.

These drawings are simple concept representations, and may not include all necessary components required for certain installation applications.

Space heating with an indirect tank

The diagram below shows:

  • A two-load system with DHW and radiant on a primary loop.
  • Radiant wired using a zone valve module.
  • Domestic hot water (receives priority operation).

Piping with DHW and radiant on a primary loop

Boiler pump connections are located behind the control board. Do not wire the boiler pump to P/V1 or P/V4.
Load is defined as DHW - DHW pump wired to Load 2 (P/V2).
DHW sensor is a Type 2 10k ohm sensor located at the DHW tank.
Load is defined as Reset Heating - Radiant pump wired to Load 1 (P/V1). Outdoor reset and lower design temperatures are recommended for higher combustion efficiency.
Outdoor air sensor mounted on north-facing exterior wall above the snowline and protected from any heat source other than ambient temperature.

Wiring for DHW and radiant on a primary loop

Sample wiring for two-load system with DHW and radiant on primary loop

No external voltages to be applied to TB2 control terminal strip connections 1-20.
DHW sensor is a type 2 10k ohm sensor; if an aquastat is used connection will be to Therm 24Vac and Therm 2, DHW sensor terminals will be vacant.
Outdoor sensor installed on North exterior wall, exposed to actual outdoor air temperature.
Pump circuits are fused for a total draw of 5A - maximum amperage draw of 4A is recommended.
No external voltages to be applied to TB2 control terminal strip connections 1-20.

Programming for DHW and radiant on a primary loop

The steps here apply to a first-time setup of a boiler controller.

To program the controller:

  1. On the Express - Loads screen, select Load 1- Off.
  2. Select DHW.
  3. For boiler pump operation, leave Boiler Pump set to On.
  4. Make changes as desired, and select the Save button.
  5. Select Load 2 - Off.
  6. Do one of the following:

    • If using an outdoor sensor, select Set Point and make other changes as needed.
    • If not using an outdoor sensor, select Reset Heating and make other changes as needed.
  7. Select the Save button.

Space heating with an indirect tank and zone control relay

The diagram below shows:

  • A two-load system with DHW and baseboard on a primary loop.
  • Baseboard is wired using a zone valve module.
  • Domestic hot water receives priority operation.

Piping for baseboard heating with an indirect water tank

Boiler pump connections are located behind the control board. Do not wire boiler pump to P/V1 or P/V4.
Load is defined as DHW - DHW pump wired to Load 1 (P/V1).
DHW sensor is a Type 2 10k ohm sensor located at the DHW tank.
Load is defined as Reset Heating - Baseboard pump wired to Load 2 (P/V2). Outdoor reset and lower design temperatures are recommended for higher combustion efficiency.
Outdoor air sensor mounted on north-facing exterior wall above the snowline and protected from any heat source other than ambient temperature.

Wiring for baseboard heating with an indirect water tank

Baseboard with an indirect water tank  

Do not apply external voltages to TB2 control terminal strip connections 1-20.
If using an aquastat, connection will be to Therm 24Vac and Therm 1. DHW sensor terminals will be vacant.
Outdoor sensor installed on North exterior wall, exposed to actual outdoor air temperature.
When using a zone control relay, the heating pump must be controlled by the boiler to maintain DHW priority. During priority DHW operation, the boiler must be able to turn off the heating pump.
Pump circuits are fused for a total draw of 5A. Maximum amperage draw of 4A is recommended.
Therm 24Vac is a common connection for enabling Therm 1-4.

Programming for baseboard heating with an indirect water tank

The steps here apply to a first-time setup of a boiler controller.

To program the controller:

  1. On the Express - Loads screen, select Load 1- Off.
  2. Select DHW.
  3. Accept the default settings, or make changes as desired.
  4. Select the Save button.
  5. Select Load 2 - Off.
  6. Do one of the following:
    • If using an outdoor sensor, select Reset Heating.
    • If not using an outdoor sensor, select Set Point.
  1. Accept the default settings, or make changes, as desired, and select the Save button.

Two-sided space heating with an indirect tank

The diagram below shows:

  • A two-sided installation with two loads.
  • Domestic hot water (receives priority operation).
  • A space heating load operated by outdoor reset or on setpoint.

Piping for radiant floor heating with an indirect water tank

Load is defined as Reset Heating - Space heating pump wired to Load 1 (P/V1). Outdoor reset and lower design temperatures are recommended for higher combustion efficiency. Space heating will be paused during DHW call.
Boiler pump connections are located behind the control board. Do not wire boiler pump to P/V1 or P/V4.
Load 2 is defined as DHW. When using a DHW sensor you can use Load 1-4. When using two-sided piping option, DHW Load is configured for Boiler Pump to turn Off during priority domestic hot water operation.
DHW sensor is a type 2 10k ohm sensor located at the DHW tank.
Outdoor air sensor mounted on north-facing exterior wall above the snowline and protected from any heat source other than ambient temperature.

Wiring for radiant floor heating with an indirect water tank

  Note

Many other Therm. and P/V connections are possible, as long as the number (1-4) of the Therm. connection agrees with the number of the P/V (pump) connection and with the load (1-4) that the installer chooses for that number.

No external voltages to be applied to TB2 control terminal strip connections 1-20.
DHW sensor is a type 2 10k ohm sensor; if an aquastat is used connection will be to Therm 24Vac and Therm 2, DHW sensor terminals will be vacant.
Outdoor sensor installed on North exterior wall, exposed to actual outdoor air temperature.
Pump circuits are fused for a total draw of 5A - maximum amperage draw of 4A is recommended.

Programming the controller for radiant floor heating with an indirect water tank

The steps here apply to a first-time setup of a boiler controller.

To program the controller:

  1. On the Express - Loads screen, select Load 1- Off.
  2. Select Set Point or Reset Heating.

    If using Reset Heating, check that the outdoor sensor is correctly installed, and enter the Design Outdoor Temperature appropriate for the outdoor conditions. The Design Supply temperature is the water temperature delivered when the outdoor temperature has dropped to the design temperature.

  3. Accept the default settings, or make changes as desired, and select the Save button.
  4. Select Load 2 - Off.
  5. Select DHW.
  6. Set the Boiler Pump to Off.
  7. If using a DHW sensor, you can adjust the Tank Setpoint temperature (typically 125°F / 52°C).
  8. Select the Save button.

Multi-boiler network with indirect water tanks and space heating

The diagram below shows a two-boiler network serving two indirect tanks and space heating through a reverse-return primary loop.

Piping for multi-boiler network with indirect water tanks and space heating

Master boiler - all field wiring to be connected to Master except for subordinate boiler pump and Boiler Net connections.
Master boiler pump wired to primary pump connections on Master.
Subordinate boiler pump wired to primary pump connections on subordinate boiler.
Secondary loop sensor is required for multi-boiler applications. Type 2 10k ohm sensor installed where both boiler supplies meet. Wired to Master.
Load is defined as DHW - DHW pump wired to Load 1 on the Master (P/V1).
Load is defined as Set Point - Space heating pump wired to Load 2 on the Master (P/V1).

Wiring for multi-boiler network with indirect water tanks and space heating

Sample diagram of wiring for two-boiler network serving two indirect tanks and space heating

No external voltages to be applied to TB2 control terminal strip connections 1-20.
DHW sensor is a type 2 10k ohm sensor; if an aquastat is used connection will be to Therm 24Vac and Therm 1, DHW sensor terminals will be vacant.
Secondary sensor is a Type 2 10k ohm sensor secondary loop.
Outdoor sensor is installed on the northern exterior wall, exposed to actual outdoor air temperature.
Pump circuits are fused for a total draw of 5A - maximum amperage draw of 4A is recommended.

Programming for multi-boiler network with indirect water tanks and space heating

You must set up the master and subordinate boilers before settings loads. The steps here apply to a first-time setup of a boiler controller.

To program the Master controller:

  1. On the Master boiler touchscreen controller:
    1. Navigate back to the Main Menu.
    2. Tap Installer Settings>Multi-Boiler.
    3. Tap inside the Master box, and select Yes>OK.
    4. Tap inside the Boiler ID box, and from the keypad select 1>OK.
  1. Go to a subordinate boiler's touchscreen controller:
    1. Navigate back to the Main Menu.
    2. Tap Installer Settings.
    3. Tap Multi-Boiler.
    4. Tap inside the Boiler ID box, and from the keypad select 2, and then select OK.
    5. Leave the Master box set to No.
  2. Go back to the Master boiler:
    1. Navigate to the Main Menu.
    2. Tap Express Setup.
    3. Select Load 1- Off.
    4. Select DHW.
    5. Do one of the following:

      • If using an outdoor sensor, select Reset Heating.
      • If not using an outdoor sensor, select Set Point.

    1. Accept the default settings, or make changes, as desired, and then select the Save button.

      You may need to adjust the operating limits for Load 2. The maximum supply temperature acts as a high limit. Ensure that the operating limits for the Design Supply Temperature (for Reset Heating) and Supply Set Point (for Set Point) remain below the maximum supply temperature.

  3. In Installer Settings, select Load 2 and using the Edit button, check the Design Supply temperature or Supply Set Point temperature, and make changes if necessary in the Maximum Supply box.
  4. If changes have been applied, select the Save button.