2.2.8
Electronic Airflow Measurement Stations and Transmitters
a.
Station - Each station shall contain an array of velocity sensing
elements and straightening vanes inside a flanged sheet metal
casing. The velocity sensing elements shall be of the RTD or
thermistor type. The sensing elements shall be distributed across
the duct cross section in the quantity and pattern set forth for
measurements and instruments of ASHRAE Gdln3 and SMACNA HVACTAB
for the traversing of ducted air flows. The resistance to airflow
through the airflow measurement station shall not exceed 0.08 inch
water gage at an airflow of 2,000 fpm. Station construction shall
be suitable for operation at airflow of up to 5,000 fpm over a
temperature range of 40 to 120 degrees F, and accuracy shall be
plus or minus 3 percent over a range of 125 to 2,500 fpm scaled to
air volume.
b.
Each transmitter shall produce a linear, temperature compensated 4
to 20 mA or 0 to 10 VDC output corresponding to the actual air
flow. The transmitter shall be a 2-wire, loop powered device.
The output error of the transmitter shall not exceed 0.5 percent
of the calibrated measurement.
2.2.9
Energy Metering
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NOTE: The requirement for metering shall be based
on NAVFAC Maintenance Manual: Utilities Metering
(MO-221) Criteria.
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2.2.9.1
Electric Meters
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NOTE: Select the appropriate paragraph. Use the
first paragraph when additional requirements for
electric meters are covered in another specification
section and insert appropriate Section number and
title in the blanks below using format per UFC
1-300-02. Use the second paragraph when electric
meters are not covered in an additional
specification section.
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[Provide kilowatt-hour (kWh) meter as specified in [_____], for building as
indicated. [Provide contacts for kilowatt (kW) pulse accumulation].]
[Provide kilowatt-hour (kWh) meter for building as indicated. Integrate
electric meter signal into DDC system; meter signal output must be
compatible with DDC input. DDC shall measure both instantaneous and
accumulated electrical usage.
a.
Meter: ANSI C12.10. Provide watt-hour meter and socket
corresponding to the ratios of the current transformers and
transformer secondary voltage. Meters shall be selected for [ ]
-volt, three-phase, [three] [four] -wire [wye] [delta] system,
three-element type with three current transformers. Meters shall
be complete with a box mounted socket having automatic circuit
closing bypass. Provide watt-hour meter with not less than four
pointer-type kWh registers, provisions for pulse initiation, and a
universal Class 2 indicating maximum kW demand register, sweep
SECTION 15910N
Page 39
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