Htp EFT-399 User Manual download pdf (Page 55)

LP-387 REV. 6.10.14

H. OUTDOOR SENSOR

NOTE: If the system requires a fixed operating temperature, the outdoor sensor is not required and should not be installed.

There is no connection required if an outdoor sensor is not used in the installation.

1. Use a minimum 22 AWG wire for runs of 100 feet or less and minimum 18 AWG wire for runs of up to 150 feet.

2. Mount the outdoor sensor on an exterior surface of the building, preferably on the north side in an area that will not be affected by

direct sunlight and will be exposed to varying weather conditions.

NOTE: For correct mounting procedures, follow instructions provided with the sensor.

NOTE: If sensor wires are located in an area with sources of potential electromagnetic interference (EMI), the sensor wires should be

shielded, or the wires routed in a grounded metal conduit. If using shielded cable, the shielding should be connected to the common

ground of the boiler.

I. INDIRECT SENSOR

There is no connection required if an indirect water heater is not used in the installation.

1. The boiler will operate an indirect fired water heater with either a thermostat type aquastat installed in the indirect tank or an HTP

7250P-325 tank sensor. When a tank sensor is used, the boiler control will automatically detect its presence and a demand for heat

from the indirect water heater will be generated when the tank temperature falls below the user set point by more than the user

selectable offset. The demand will continue until the sensor measures that the indirect water heater temperature is above the set point.

2. Connect the indirect sensor (7250P-325) to the terminals marked DHW SENSOR (shown in Figure 31) in the electrical junction box.

Caution should be used to ensure neither of these terminals becomes connected to ground.

NOTE: If sensor wires are located in an area with sources of potential electromagnetic interference (EMI), the sensor wires should be

shielded, or the wires routed in a grounded metal conduit. If using shielded cable, the shielding should be connected to the common

ground of the boiler.

Failure to use the correct sensor may result in tank temperature being either above or below set point, and could result in decreased

performance, substantial property damage, or heightened risk of injuries due to scalds.

J. OPTIONAL 0-10 VOLT BUILDING CONTROL SIGNAL

1. A signal from a building management system may be connected to the boiler to enable remote control. This signal should be a 0-10

volt positive-going DC signal. When this input is enabled using the installer menu, a building control system can be used to control the

set point temperature of the boiler. The control interprets the 0-10 volt signal as follows; when the signal is between 0 and 1.5 volts, the

boiler will be in standby mode, not firing. When the signal rises above 1.5 volts, the boiler will ignite. As the signal continues to rise

towards its maximum of 10 volts, the boiler will increase in set point temperature. See Part 11 for details on the setting of function 16.

2. Connect a building management system or other auxiliary control signal to the terminals marked 16, 0-10 VOLT + and 17, 0-10

VOLT – in the electrical junction box (shown in Figure 31). Caution should be used to ensure that the 0-10 VOLT + connection does not

become connected to ground.

3. Move jumper on connection board (shown in Figure 31) from A to B.

4. See Part 10, Section D, Function 17 to program the 0-10 volt signal.

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Htp EFT-399 User Manual Page 55