HTP 850 LPHL - Manual (Page 41)

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LP- 205 REV. 3.28.14
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 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 selected set point by more than the user selected
offset. The demand will continue until the sensor measures that the indirect water heater temperature is above the set point.
2. Connect the indirect tank sensor (7250P-325) to the terminals marked DHW SENSOR (shown in Figure 23) 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.
I. 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
either the set point temperature or the heat output of the boiler. The control interprets the 0-10 volt signal as follows: When the signal is
between 0 and 1 volt, the boiler will ignite. As the signal continues to rise towards its maximum of 10 volts, the boiler will increase either
in set point temperature or firing rate depending on the setting of parameter 17 in the installer menu. See Part 10 for details on the
setting of parameters 16 and 17 for this option.
2. Connect a building management system or other auxiliary control signal to the terminals marked 0-10 VOLT + and 0-10 VOLT
– in
the electrical junction box (shown in Figure 23). Caution should be used to ensure that the 0-10 VOLT + connection does not become
connected to ground.
J. OPTIONAL HIGH GAS PRESSURE SWITCH
1. If an optional high gas pressure switch is used, it should be installed on the outlet side of the gas valve. This is normally closed and
will open if the pressure goes above 1.5” w.c. on the outlet side.
2. Locate the two pigtails hanging from the electrical box inside of the boiler cabinet. Remove and discard the jumper plug from one of
the unused pigtails.
3. Connect the high gas pressure switch to the pigtail that you removed the jumper plug from.
K. OPTIONAL LOW GAS PRESSURE SWITCH
1. If an optional low gas pressure switch is used, it should be installed on the inlet side of the gas valve. This is normally closed and will
open if the pressure goes below 1” w.c. on the inlet side.
2. Locate the two pigtails hanging from the electrical box inside of the boiler cabinet. Remove and discard the jumper plug from one of
the unused pigtails.
3. Connect the low gas pressure switch to the pigtail that you removed the jumper plug from.
L. OPTIONAL FLOW SWITCH
NOTE: Follow the more detailed instructions included with the flow switch kit for proper installation steps.
1. Attach the correct flow paddle to the flow switch.
2. Thread brass tee onto outlet nipple using pipe dope. Make certain the branch points up on horizontal runs.
3. Thread flow switch into tee using pipe dope. Make certain the FLOW arrow points in the correct direction.
4. Disconnect red wire on the low water cut off probe and connect it to the red wire from the wire harness (included in kit).
5. Feed green ground wire into boiler through the wire access.
6. From the front of the boiler, feed the ground wire up into the control box.