HTP EL-110 Installation & Start-Up Manual Download Page 48

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LP- 293 REV. 9.2.14

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 26) in the electrical junction box.

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.

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.

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 10 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 26). 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 26) from A to B.

4. See Part 9, Section D, Function 17 to program the 0-10 volt signal.

NOTE:

When a 0-10 volt building management system is installed, the return sensor temperature cannot be monitored through the

appliance display.

K. OPTIONAL UL353 LOW WATER CUT-OFF INTERFACE KIT

If an optional UL 353 Low Water Cut-Off (LWCO) Interface Kit is used, the control box of the kit should be mounted to the left side of
the boiler cabinet near the low water cut-off probe, which is located on the outlet nipple of the boiler.

Follow the complete instructions included in the kit for proper installation.

L. WIRING OF CASCADE SYSTEM COMMUNICATION BUS

1. A Cascade Bus Termination Plug has been installed on the customer connection board of this boiler. The purpose of this plug is to
stabilize communication between multiple boilers and reduce electrical “noise”. See Figures 28 and 29 for Cascade Bus Termination
Plug installation detail.

2. Use standard CAT3 or CAT5 computer network patch cables to connect the communication bus between each of the boilers. These
cables are readily available at any office supply, computer, electronic, department or discount home supply store in varying lengths. If
you possess the skills you can also construct custom length cables.