Chilled Water Automatic control valves 2″ and smaller shall be screwed type, of red brass material and valves 2½” and larger shall be cast iron type and flanged. Valves shall be ANSI- rated to withstand the pressures and temperatures encountered.
Valves shall have stainless-steel stems and spring loaded Teflon packaging with replaceable discs. All valves shall have the manufacturers name/logo embossed on the valve.
Chilled Water Valves shall be sized for a pressure drop greater than or equal to the coil they serve. Chilled Water valves shall be two-way type as specified in the sequence of operation. Shall be PN16, bronze body. Stems shall be polished stainless-steel suitable temperature range of 2 to 110°C.
All automatically controlled devices, shall be provided with electric / electronic actuators sized to operate their appropriate loads with sufficient reserve power to provide smooth modulating action. Actuators shall be provided with suitable corrosion resistant linkages for valves or dampers.
Except as specified herein, all actuators shall be sized for the load/close off encountered in strict accordance with manufacturers recommendations. All actuators on outside air dampers, relief air dampers, and converter steam valves shall be heavy duty type with oil immersed gear train.
All actuators shall drive to their “normal” position anytime their associated AHU (etc.) is shut down. Direct coupled modulating actuators shall be 24 volt type with 2 to 10 VDC control. Direct coupled on/off actuators shall be 24 VAC. The torque and the close off ratings shall match the application used.
Firestats shall be 135 degrees manual reset type. Duct Smoke Detectors shall contain an air sampling chamber with sampling tubes extending through the width of the air duct. Alarm status indicating lights shall be visible on the front of the panel.
DDC/VAV Controller
Controller shall consist of a one piece DDC controller complete with microprocessor, power supply, self calibrating pressure transducer, and integral actuator. Provide DDC/VAV controller factory fitted and calibrated for the minimum and maximum air flows scheduled on the drawings.
Controller housing shall be UL 94-5 5V or equivalent listed material for use in ceiling plenum applications without need of special metal enclosure. Controller shall work over an ambient temperature operating range of 0-55C (32-122F), 5-95% non condensing humidity. Power supply to unit shall be 20-30 VAC, 50 Hz, maximum power consumption of 5VA.
For reheat applications, provide factory fitted power relays rated for coils as required. Mount relay in electric control enclosure and wire to DDC/VAV controller.
Controller shall be UL 916 listed, CE mark compliant, and conform to IEC 801.4 transient and surge immunity standards. UL and CE marks shall appear on product labels.
Unit shall operate properly over inlet velocity pressure range of 0.00 to 2.00 in WC (0-500 Pa). End to end accuracy shall be +/- 5% of flow measured at 250 Pa inlet velocity pressure.
Cooling only model DDC/VAV controller shall be used in cooling only applications. Cooling and reheat model DDC/VAV controller shall be used in reheat applications and contain 3 Form A relays, pilot duty rated for control of floating proportional, time proportional or staged reheat valves and coils.
Integral damper actuator shall be 53 lb-in (6 N-m) torque, over the shaft mounting type. Stroke shall be fully adjustable from 0-90 degrees rotations with visible position indicator. Actuator shall be equipped with manual position override. The actuator stroke time shall be 3.6 minutes maximum for 90 degree rotation at 50 Hz operation.
Room temperature sensor shall be complete with digital LCD display. Temperature sensor shall permit local adjustment of temperature setpoint, minimum flow, and maximum flow. Temperature sensor shall permit display of any of the four variables such as room temperature, room temperature set point, air flow and maximum flow setpoint.
The VAV room digital thermostat shall also display the following:
- Room space temperature (Degree C or in Degree F freely configurable)
- Room temperature set point (Degree C or in Degree F freely configurable)
- Maximum flow
- Minimum flow
The room temperature sensor shall be wired to the DDC/VAV controller using a two wire non polarity sensitive cable. The room thermostat shall have plug-in facility to a portable operator terminal to get the following additional operation such as:
- Damper percentage opening
- Differential pressure across flow sensor
- Flow in CFM
- VAV box maximum flow
- VAV box minimum flow
- Heater status
- Minimum flow setting for heaters
It shall be possible to modify the VAV controller parameters from the room thermostat key buttons without the use of any additional devices. The controller should have the option of working along with a duct thermostat and any dry contacts.
ELECTRONIC DATA INPUTS AND OUTPUTS
Input/output sensors and devices shall be closely matched to the requirements of the remote panel for accurate, responsive, noise-free signal input/output. Control input response shall be high sensitivity and matched to the loop gain requirements for precise and responsive control. In no case shall computer inputs be derived from pneumatic sensors or thermocouple.
Temperature sensors shall be Resistance Temperature Detector (RTD) type of 100, 1000, or 3,000 ohm platinum, or 20,000 ohm. Space temperature sensors shall be in attractive housing made from flame retardant ABS.
Duct temperature sensors shall be rigid stem or averaging type as specified in the sequence of operation. The terminal box shall be IP54 and of flame retardant plastic.
Water sensors shall be provided with a separable copper or stainless-steel well. The sensor shall have an accuracy of class B as per DIN IEC 751. Outside air, return air, discharge air, space and well sensors shall have + or – 1.0 degrees F accuracy between 32 degrees and 212 degrees.
Relative humidity sensors shall be capacitance type with 10% to 90% range. Duct mounted humidity sensors shall be provided with a sampling chamber. Wall mounted sensors shall be provided with decorative covers identical to temperature sensors.
Differential and Static Pressure Sensors and Switches
Fan proof-of-flow switches shall be of the adjustable set point and differential pressure type. Switches shall be piped to fan discharge except where fans operate at less than one inch water column (WC), they shall be piped across the fan. For fractional horsepower and non-ducted fans, relays or auxiliary contacts may be used. Maximum pressure rating shall be at least 10 inches water column.
Pump proof-of-flow switches shall be of the adjustable differential pressure or flow type as specified in the sequence of operation or data point summary. Devices shall be 150 psi rated except chilled water flow switches shall be provided with totally sealed vapor tight switch enclosure on 300 psi body. Differential pressure switches shall have valved manifold for servicing.
Air flow and duct static pressure analog sensors shall be high accuracy suitable for the low pressures to be encountered.
Water flow analog sensors shall be IP66 magnetic type, cast steel upto 25 mm and Aluminium alloy for sizes 40mm and above. Operational accuracy shall be ±5%. It shall be suitable for 240 VAC with a current output of 4-20mA. The electrodes shall be detachable for easy cleaning, it should not require the removal of the flow meter. The flow meter shall have an 3.5 segment 7 LED indicator.
Control relays and analog output transducers shall be compatible with PCP output signals. Relays shall be suitable for the loads encountered.
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