
LP-325 Rev. 009 Rel. 004 Date 12.2.20
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E. Indirect Sensor (Optional)
1. If an indirect water heater is not used in the installation, move on.
2. The appliance will operate an indirect fired water heater with either
a thermostat type aquastat or an HTP 7250P-325 tank sensor installed
in the water heater. When a tank sensor is used, the appliance control
will automatically detect its presence and a demand for heat from the
water heater will be generated when the tank temperature falls below
the user set point by more than the user selectable offset. Demand will
continue until the indirect water heater temperature is above the set
point.
Connect the indirect sensor or mechanical aquastat to the terminals
marked 10 and 11 on the field connection board.
To control the temperature of low temperature heating circuits when
using an indirect fired water heater, a thermostatic mixing valve is
required. Failure to install a thermostatic mixing valve when using
an indirect fired water heater could result in damage the heating
circuits. Such damage IS NOT covered by warranty.
F. Optional 0-10 Volt Building Control Signal
1. If a 0-10 volt building management system is not
used in the installation, move on.
2. A signal from a building management system
may be connected to the appliance to enable
remote control. This signal should be a 0-10 volt
positive-going DC signal.
3. 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 appliance. The control interprets
the 0-10 volt signal as follows; when the signal is
between 0 and 1.5 volts, the appliance will be in
G. UL353 Low Water Cut-Off Kit (Optional)
1. If an HTP 7450P-255 UL353 Low Water Cut-Off (LWCO) Kit is not used,
move on to Section I.
2. The control box of the kit should be mounted to the left side of the
appliance near the low water cut-off probe, which is located near the
outlet nipple of the appliance.
H. Wiring of an Appliance Alarm (Optional)
An alarm bell or light can be connected to the alarm connection of
the appliance. In the event of an alarm, the alarm connection may
be used to power a 120V device. The alarm connections are rated
3 amps at 120 VAC. Connect to terminal 1 (HOT), 2 (NEUT), and 3
(GND).
I. Wiring of the Cascade System Communication Bus
1. Use standard CAT3 or CAT5 computer network patch cables to
connect the communication bus to each of the appliances. 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.
2. It is recommended to use the shortest length cable that will reach
between the appliances and create a neat installation. Do not run
unprotected cables across the floor where they may become wet
or damaged. Avoid running communication cables parallel and
close to or against high voltage (120 volt or greater) wiring. HTP
recommends the maximum length of communication bus cables
not exceed 200 feet.
3. Route the communication cables through one of the knockouts
in the cabinet.
4. Connect the appliances in a daisy chain configuration. It is best to
wire the appliances using the shortest wire runs rather than trying to
wire them in the order that they are addressed. The communication
bus jacks on the customer connection panel are interchangeable so
you can use either one or both in any order to connect the cable. If
you have connected the appliances to each other properly, two of
the appliances will have single open connection ports.
Figure 21 - Cascade Wiring
D. Outdoor Sensor (Optional)
1. If an HTP 7250P-319 outdoor sensor is not used in this installation,
move on.
2. 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.
3. 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:
Follow instructions provided with the sensor for detailed
mounting instructions.
4. When correctly mounted, connect sensor to terminals marked 12
and 13.
standby mode, not firing. When the signal rises above 1.5 volts, a
demand for heat is started. As the signal continues to rise towards its
maximum of 10 volts, the appliance will increase either its set point
temperature or firing rate depending on the setting of function 17 in
the installer menu. See Part 10 for details on the setting of functions
16 and 17 for this option.
4. 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 caution should be used to ensure
that the 16 (0-10 VOLT +) connection does not become connected
to ground.
3. Follow the complete instructions included in the kit for proper
installation.