Bryant 50YEW Design Manual page 25

When soldering valves and unions, take care not to overheat the
non-metallic components. Remove synthetic gasket material from
dielectric unions before soldering. Likewise, use small strips of
damp, clean rags to keep the valve body when soldering.
Safety
Bryant is always concerned about the safety of installation
technicians. Exercise caution when soldering around combustible
materials, wood, plastic or paper. Cleaning fl uids, pressurized
containers and other hazardous materials should be removed
before beginning any solder joints.
Always wear eye protection, long sleeve shirts and gloves when
installing Bryant equipment and related systems/components. Use
shields on safety glasses. Always have the proper fi re extinguisher
and/or water near the work area.
Local codes supersede any recommendations in this manual.
System Components
Below are some general guidelines for component selection and
design/installation criteria for the piping system. Local codes
supersede any recommendations in this manual.
Shut off/fl ow regulation valves: Use full port ball valves
or gate valves for component isolation. If valves will be used
frequently, ball valves are recommended. Globe valves are designed
for fl ow regulation. Always install globe valves in the correct
direction (fl uid should enter through the lower body chamber).
Check valves: Swing check valves must be installed in the
horizontal position with the bonnet of the valve upright. Spring
check valves can be mounted in any position. A fl ow check valve is
required to prevent thermo siphoning (or gravity fl ow) when the
circulator pump is off or when there are two circulators on the
same system.
Mixing valves: Three and four port thermostatic mixing valves
are common in hydronics applications, especially when boilers are
used. Most oil and gas-fi red boilers cannot accept cool return
water without fl ue gas condensation problems. Three-way mixing
valves are limited to systems where the coolest return water from
the distribution system is always above the dew point temperature
of the exhaust gases. When this is not possible, a four-port mixing
valve should be used.
Buffer tanks: A buffer tank is required for all hydronic heating
systems using water-to-water heat pumps and chilled water
systems. Buffer tank sizing is address earlier in this section. The
buffer tank must be A.S.M.E. rated (approved for use as a heating
vessel). See note below regarding pressure relief valves.
Pressure relief valves: Most codes require the use of a
pressure relief valve if a closed loop heat source can be isolated
by valves. Even if local code does not require this device, Bryant
recommends its installation. If the pressure relief valve in the buffer
tank is rated above 30 psi [207 kPa] maximum pressure, remove
Bryant Geothermal Heat Pump Systems
Part II: Load Side Design Components
the existing valve and replace with the lower rated model. The
pressure relief valve should be tested at start up for operation.
This valve can also be used during initial fi lling of the system to
purge air. Note that the waste pipe must be at least the same
diameter as the valve outlet (never reduce), and that valves may
not be added to this pipe. The bottom of the pipe must be at
least 6" [15 cm] from the fl oor. If the piping is connected to a
drain, there must be an air gap.
Backfl ow prevention check valves: Most codes
require backfl ow prevention check/fi ll valves on the supply water
line. Note that a single check valve is not equal to a backfl ow
prevention check valve. Even if local code does not require this
device, Bryant recommends its installation. This is particularly
important if the system will use antifreeze.
Pressure-reducing valves or feed water valves: This
valve lowers the pressure from the make-up water line to the
system. Most are adjustable and directional. A "fast fi ll" valve is a
must for initially fi lling the system. Some have screens, which must
be cleaned after the initial fi lling. If there is a restriction in the
screen, the system could go to zero pressure, potentially causing
pump(s) failure or pressure relief valves to open. A valve on each
side of the pressure-reducing valve should be installed for servicing.
Both valves should have tags reading, "Do not shut this valve under
normal operation – Service valve only".
Expansion tanks: Expansion tanks are required on hydronics
systems to help absorb the pressure swings as the temperature
in the system fl uctuates. If the piping system will be used for
chilled water, the tank must be insulated. A non-metallic (plastic,
fi berglass) tank is recommended for chilled water systems to
lengthen the life expectancy of the expansion tank.
Elbows/T's: Calculate added pressure drop of elbows and T's in
the system when considering pump sizing and pipe diameter selection.
Anti-freeze: Antifreeze is required if any of the piping system
is located in areas subject to freezing. In addition, antifreeze should
be used for snow melt systems and fan coil unit installations where
design water temperatures drop below 40°F [4°C]. Consult the
antifreeze manufacturer's specifi cations catalog for concentration
amounts and recommendations.
Well-type thermistors & aqua-stats: All thermistors
and aqua-stats should be installed in a thermal well for more
accurate sensing of the water in the tank. The well should be
threaded into an opening in the tank, and the thermistor or aqua-
stat probe should be coated with conductive paste to make sure
that the sensor is in contact with the walls of the well. Figure 2-6
shows a typical well-type installation. Attaching a thermistor or
aqua-stat to piping outside of the tank only senses temperature
accurately when the pumps are running, and may create false
readings, which could short cycle the heat pump or cause
overheating of the tank.
Water-to-Water System Design Guide
23