controllers specifically for solar energy systems.
The guidance contained in TM 5-804-2 discusses
desired diagnostic capabilities of controllers that
are presently not available. As these controllers
again become more widespread, it is anticipated that
manufacturers will include such diagnostic
capabilities. Until that time, paragraph
Differential Temperature Control Equipment may be
considered sufficient. The designer should check
updates to this guide specification for additions or
refinements to this and other equipment covered
under this guidance.
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Differential temperature control equipment shall be supplied as a system by
a single manufacturer. Controller shall be solid-state electronic type
complete with an integral transformer to supply low voltage, shall allow a
minimum adjustable temperature differential (on) of 4 to 11 degrees C 8 to
20 degrees F, a minimum adjustable temperature differential (off) of 2 to 3
degrees C 3 to 5 degrees F, and shall include a switching relay or solid
state output device for pump control. Thermostat shall operate in the
on-off mode. Controller accuracy shall be plus or minus 0.5 degree C 1
degree F. Controller shall be compatible with 10-kOhm thermistor
temperature sensors. Differential control shall provide direct digital
temperature readings of all temperatures sensed. Control shall indicate
visually when pumps are energized. Control ambient operating range shall
be a minimum of 0 to 49 degrees C 32 to 120 degrees F.
2.8.2
Thermistor Temperature Sensors
Temperature sensors shall be 10-kOhm thermistors supplied by the
differential temperature controller manufacturer, with an accuracy of plus
or minus 1 percent at 25 degrees C 77 degrees F. Model supplied must have
passed an accelerated life test conducted by subjecting thermistor
assemblies to a constant temperature of 204 degrees C 400 degrees F or
greater for a period of 1000 hours minimum. Accuracy shall have remained
within plus or minus 1 percent as stated above. Thermistors shall be
hermetically sealed glass type. Operating range shall be minus 22 to plus
204 degrees C minus 40 to plus 400 degrees F. Immersion wells or
watertight threaded fittings shall be provided for temperature sensors.
2.8.3
Sensor and Control Wiring
18 AWG minimum twisted and shielded 2, 3, or 4 conductor to match analog
function hardware. Control wiring shall have 600 volt insulation.
Multiconductor wire shall have an outer jacket of PVC.
2.8.4
Flowmeters
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NOTE: Venturi pressure differential is dependent on
the flow rates to be measured. System flow rates
are dependent on recommended collector flow rates.
TM 5-804-2 and paragraphs Piping and Heat Exchanger
should be used to determine both the collector side
and storage side flow rates.
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Flowmeters shall consist of a venturi, 150 mm 6 inch dial differential
SECTION 13600A
Page 22
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