12b70 Devices

12.B7.1 Temperature Sensors: Temperature sensors shall have a range suitable to their purpose. For example, typical degree ranges should be as follows: outside air -40°F to +120°F, indoor spaces +40°F to +100°F, hot water +80°F to +260°F, chilled water +20°F to +90°F, cold duct air +35°F to +80°F, and hot duct air +60°F to +200°F. RTDs, thermocouples and sensors based on the National Semiconductor LM 34CZ chip are permitted for sensing temperature. Thermisters of nominal resistance of at least 10K ohms may be used for temperature sensing also. Thermisters shall be encapsulated in epoxy or series 300 stainless steel.

12.B7.2 Thermowells: Thermowells shall be series 300 stainless steel for use in steam or fuel oil lines, and mo-

nel for use in water lines. Thermowells shall be wrought iron for measuring flue gases.

12.B7.3 Pressure Sensors: Pressure sensors shall withstand up to 150% of rated pressure. Accuracy shall be plus or minus 3% of full scale. Pressure sensors shall be either capsule, diaphragm, bellows or bourdon.

12.B7.4 Pressure Switches: Pressure switches shall have a repetitive accuracy plus or minus 3% of range and withstand up to 150% of rated pressure. Sensors shall be diaphragm or bourdon tube. Switch operation shall be adjustable over the operating pressure range. The switch shall have an application-rated for C, snapacting wiping contact of platinum alloy, silver alloy or gold plating.

12.B7.5 Watt-hour transducers: Watt-hour transducers shall have an accuracy of plus or minus 1 percent for kW and kWh and shall be internally selectable without requiring the changing of current or potential transformers.

12.B7.6 Potential Transformers: Potential transformers shall be in accordance with ANSI C57.13.

12.B7.7 Current Transformers: Current transformers shall be in accordance with ANSI C57.13.

12.B7.8 Watt-hour Meters with Diamond Register: Meters shall be in accordance with ANSI C12 and have pulse initiators for remote monitoring of watt-hour consumption and instantaneous demand. Pulse initiators shall utilize light emitting diodes and photo-detectors. Pulse initiators shall consist of form C contacts with a current rating of 2 amps, 10 VA maximum and a life rating of one billion operations.

12.B7.9 Flow Meters: Flow meter outputs shall be compatible with the system. Accuracy shall be plus or minus 3% of full scale.

12.B7.10 Control Relays: Control relay contacts shall be rated for the application, with form C contacts, enclosed in a dustproof enclosure. Relays shall have silver cadmium contacts with a minimum life span rating of one million operations. When required, provide relays on H-0-A board with LEDs and relay status feedback.

12.B7.11 Reed Relays: Reed relays shall have been encapsulated in a glass type container housed in a plastic or epoxy case. Contacts shall be rated for the application. Operating and release times shall be five milliseconds or less. Reed relays shall have a minimum life span rating of 10 million operations.

12.B7.12 Solid State Relays (SSRs): Input/output isolation shall be greater than 10E9 ohms with a breakdown voltage of 1500V root mean square or greater at 60 Hz. The contact life shall be 10 x 10E6 operations or greater. The ambient temperature range of SSRs shall be minus 20 to plus 140 degrees F. Input impedance shall not be less than 500 ohms. Relays shall be rated for the application. Operating and release time shall be 100 milliseconds or less. Transient suppression shall be provided as an integral part of the relay.

12.B7.13 Surge Protection: Surge protection shall meet the following minimum criteria.

a. Solid state silicon avalanche junction diode device b. Response time less than or equal to 5ns (nanoseconds)

c. Voltage protection level 300 volts maximum d. Service frequency 60 Hertz e. Service voltage 110/120 volts AC

f. Life expectancy > 10 years g. Ambient operating temperatures 0 to 40 degrees Celsius h. Suppression power 12,000 watts (1 x 1000 microsecond pulse)

i. Instant automatic reset j. UL Listed

0 0

Post a comment