Basic Documentation

Table Of Contents
Project Name 230900 - 4 BAS AND CONTROL FOR HVAC
Date
4) Provide in reverse return, variable speed pumping systems where the
differential pressure between the systems will vary more than the pressure
drop of the circuit or loop.
5) Provide in systems that have direct return headers and reverse return branch
lines where with the system at full flow the pressure differential between the
supply connection and the return connection is more than double the
pressure drop of the branch at design flow (including piping, fittings,
devices, control valve and coil).
3. Piping for circuits with PICVs
a. Systems installed with PICVs shall not require balancing valves.
b. Calibrated balancing valves shall not be required in branches or loops where PICV
are installed.
c. Automatic flow control valves are strictly prohibited in branches or loops where
PICVs are installed.
d. Circuit setters may be required for coils with multiple sections. Follow the piping
details.
e. Install pressure ports on either side of the coil for the balancer to test the flow
across the coil at different system flows.
4. Sizing Criteria (Pressure Independent):
a. Two-way modulating service:
1) Determine the design GPM of the actual coil that is selected be used (may
be different than the coil and GPM on the design coil schedule).
2) Select the PICV valve with a GPM rating higher than the GPM required.
3) If more than one valve fits the GPM rating, then pick the valve that matches
or is closest to the line size of the circuit piping.
4) If the maximum GPM of the valve exceeds the design GPM required, then
adjust the Flow Limiter setting on the valve to the GPM required plus 10%.
5) Traditional flow coefficient and pressure drop sizing is not applicable to
PICV valves.
5. Flanged Valves, line size 2 ½” and larger
a. Controlled Media Specific Items
1) The control valve shall be suitable for chilled water to a minimum of 34°F
(1°C) and hot water to a maximum temperature of 248°F (120°C).
2) The control valve shall be suitable for up to 50% ethylene or propylene
glycol solutions, chilled glycol/water solutions to a minimum of 34°F (1°C)
and hot glycol/water solutions to a maximum temperature of 248°F (120°C).
b. General Construction Materials/Applicable
1) Control valve bodies shall be constructed of cast iron and shall meet
requirements of ANSI 125 or ANSI 250 pressure classes.
2) Inlets and outlets shall be clearly marked on the valve bodies.
3) Valves shall be constructed with a single chamber and multiple seats to
provide flow limiting, pressure compensation and flow control.
4) Valves shall contain a mechanical, spring-loaded pressure independent
regulator to maintain a consistent differential pressure across the control
port of the valve.
5) Valves shall contain an actuated flow control portion that responds to the
modulating signal from the controller. This control valve portion shall have
a linear flow characteristic.
6) Valves shall contain a field adjustable flow limiter. The flow limiter shall
be easily adjustable in the field without the use of special tools. The
adjustment dial shall be set for and indicate maximum flow. It shall be