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7
Hydronic piping
System water piping methods
The Knight XL is designed to function in a closed loop
pressurized system not less than 12 psi (83 kPa) (Non-
metallic system piping must have an oxygen barrier to be
considered a closed loop). A temperature and pressure
gauge is included to monitor system pressure and outlet
temperature and should be located on the boiler outlet.
It is important to note that the boiler has a minimal amount
of pressure drop which must be figured in when sizing
the circulators. Each boiler installation must have an air
elimination device, which will remove air from the system.
Install the boiler so the gas ignition system components
are protected from water (dripping, spraying, etc.) during
appliance operation or basic service of circulator replacement,
valves, and others.
Observe a minimum of 1/4 inch (6 mm) clearance around all
un-insulated hot water pipes when openings around the pipes
are not protected by non-combustible materials.
Low water cutoff device
On a boiler installed above radiation level, some states and
local codes require a low water cutoff device at the time of
installation.
Chilled water system
If the boiler supplies hot water to heating coils in air handler
units, flow control valves or other devices must be installed to
prevent gravity circulation of heater water in the coils during
the cooling cycle. A chilled water medium must be piped in
parallel with the heater.
Freeze protection fluids
Freeze protection for new or existing systems must use
glycol that is specially formulated for this purpose. This
includes inhibitors, which prevent the glycol from attacking
the metallic system components. Make certain to check that
the system fluid is correct for the glycol concentration and
inhibitor level. The system should be tested at least once
a year and as recommended by the producer of the glycol
solution. Allowance should be made for the expansion of the
glycol solution in the system piping.
General piping information
Basic steps are listed below along with illustrations on the
following pages (FIG.’s 6-7 through 6-11), which will guide you
through the installation of the Knight XL (reference FIG.’s 7-2A
and 7-2B).
1. Connect the system return marked “Inlet”.
2. Connect the system supply marked “Outlet”.
3. Install purge and balance valve or shutoff valve and drain
on system return to purge air out of each zone.
4. Install a backflow preventer on the cold feed make-up
water line.
5. Install a pressure reducing valve on the cold feed make-up
water line, (15 psi (103 kPa) nominal). Check temperature
and pressure gauge (shipped separately), which should read
a minimum pressure of 12 psi (83 kPa).
6. Install a circulator as shown on the piping diagrams in this
section. Make sure the circulator is properly sized for the
system and friction loss.
7. Install an expansion tank on the system supply. Consult the
tank manufacturer’s instruction for specific information
relating to tank installation. Size the expansion tank for the
required system volume and capacity.
8. Install an air elimination device on the system supply.
9. Install a drain valve at the lowest point of the system.
Note:
The boiler cannot be drained completely of water
without purging the unit with an air pressure of 15 psi
(103 kPa).
10. This appliance is supplied with a relief valve sized in
accordance with ASME Boiler and Pressure Vessel Code,
Section IV (“Heating Boilers”). Pipe the discharge of the
safety relief valve to prevent injury in the event of pressure
relief. Pipe the discharge to a drain. Provide piping that is
the same size as the safety relief valve outlet. Never block
the outlet of the safety relief valve.
11. Install a field supplied strainer/filter to prevent damage
to the heat exchanger caused by debris entering from the
system piping. When installing in a pre-existing system, a
strainer/filter capable of removing debris left in the system
is recommended.
12. Install a field supplied magnetic separator in the heating
system return line as close as practical to the boiler per the
manufacturer’s instructions.
Use only inhibited propylene glycol
solutions, which are specifically formulated
for hydronic systems. Ethylene glycol is
toxic and can attack gaskets and seals used
in hydronic systems.
⚠
WARNING
The relief valve, tee and any other necessary
fittings are shipped in the install kit with the
boiler and are to be field installed (FIG. 7-1).
Installation & Operation Manual
NOTICE
IMPORTANT
All boiler piping must contain an oxygen
barrier. This will help prevent any excess
oxygen from entering the system.
