18 Installing the System Piping
Backflow Preventer
Install a backflow preventer valve in the make-up
water supply to the unit as required by local codes.
Expansion Tank
An expansion tank must be installed in the space
heating piping to prevent excessive pressure
from building in the system. See the examples of
system application at the end of this section for the
installation location. Refer to the expansion tank
manufacturer’s instructions for additional details.
Follow the guidelines below when installing an
expansion tank.
●
Connect an air separator to the expansion tank
only if the air separator is located on the suction
side of the system pump.
●
Install the make-up water connection at the same
location as the expansion tank’s connection to
the system.
●
When replacing an expansion tank, consult the
expansion tank manufacturer’s literature for
proper sizing.
●
For diaphragm expansion tanks, always install
an automatic air vent on the top side of the air
separator to remove residual air from the system.
Isolation Valves and Unions
●
Full port ball valves are required for the boiler
system. Failure to use full port ball valves could
result in a restricted flow rate through the boiler.
●
Check valves are recommended for installation.
Failure to install check valves could result in a
reverse flow condition during pump(s) off cycle.
●
Unions are recommended for unit serviceability.
Pressure Relief Valve
To complete the space heating system installation,
you must install a
3
/
4
in, 30 to 80 psi (max.) pressure
relief valve on the space heating hot water outlet.
An ASME approved Watts 174A pressure relief valve
(
3
/
4
in, HV, Max 30 psi) is provided with the boiler.
External LWCO
If local codes require a separate LWCO device,
install one separately. Combining the LWCO with
the air vent simplifies the installation. The following
illustration shows an example of a separately
installed external LWCO.
6" (152 mm) min.
External
LWCO
The external LWCO must be installed at least 6 in
(152 mm) above the top of the heat exchanger.
Refer to “3.6.2 Wiring Diagram - External LWCO” on
page 34 for typical wiring connections of the
LWCO to the boiler PCB.
WARNING
Electric Shock Hazard
ALWAYS check that the power to the boiler is
turned off before making the boiler may fail
and result in serious injury, or death if power
is supplied during wire connection. Product
failures caused by incorrect installation are not
covered by warranty.
