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WARNING
Solder joints on domestic water lines must be
made with NO-LEAD SOLDER.
IMPORTANT
Use only approved piping and fitting materials. If
used in an open loop system with domestic hot
water, potable, lead-free piping must be used.
Thermal Expansion of Piping
In all hydronic systems, piping undergoes
temperature swings as the system operates.
This causes changes in the length of the piping
due to thermal expansion.
If the piping is rigidly mounted, this expansion
can cause annoying popping or squeaking
sounds and in extreme cases, the piping can
even buckle.
To counter expansion movement, design piping
circuits with sufficient elbows, tees or
expansion loops (only used in large systems)
or piping supports that allow the tubing to
expand and contract freely.
Another alternative is to install an expansion
compensator fitting capable of absorbing the
movement.
Hydraulic Resistance of Fittings, Valves,
and Other Devices
Before the total hydraulic resistance of a piping
circuit can be found, the individual hydraulic
resistances of all fittings, valves, or other such
components must be determined. One
approach is to consider each fitting, valve, or
other device as an equivalent length of copper
tube of the same pipe size.
By using the equivalent length of piping for all
components in the circuit, the circuit can be
treated as if it were a single piece of pipe
having a length equal to the sum of the actual
pipe length, the total equivalent lengths of all
fittings, valves, or other devices.
Hydronic Air Handler Installation and Operation Manual
Pipe Sizing Considerations
When selecting a pipe size for a given flow
rate, the resulting average flow velocity
should be between 2 ft. (0.61 m) and 4 ft.
(1.22 m) per second.
At water flow velocities of approximately 2
ft. (0.61 m) per second, flowing water will
carry air bubbles along a vertical pipe.
Average flow velocities of 2 ft. (0.61 m) per
second or higher can draw along air
bubbles in a downward flow. At the above
stated velocities air bubbles shall be routed
to an air separator where they can be
collected and discharged from the system.
Average flow velocities higher than 4 ft.
(1.22 m) per second could cause flow noise
and premature wear of piping and fittings
and should be avoided.
Expansion Tanks
All liquids used in hydronic heating systems
expand when heated. For all practical
purposes, liquids are incompressible. Any
container completely filled with a liquid and
sealed from the atmosphere will experience
a rapid increase in pressure as the liquid is
heated. To prevent this from occurring, all
hydronic systems MUST be equipped with
an expansion tank. See the following
sections for the expansion tank plumbing
location:
•
5.7.1 Rinnai Tankless Water Heater
and Air Handler Piping Diagram
•
5.7.2 Rinnai I-Series Boiler and Air
Handler Piping Diagram
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