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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.
20
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:
•
5.9.1 Rinnai Tankless Water Heater and
Air Handler Piping Diagram
•
5.9.2 Domestic Hot Water Recirculation
Piping Diagram
•
5.9.3 Rinnai I-Series Boiler and Air
Handler Piping Diagram
•
5.9.4 I-Series Boiler with Hydraulic
Separation and Air Handler Piping
Diagram
Canadian Air Handler Installation and Operation
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