NABCEP SHSI flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- f-chart method
- A simplified sizing method that estimates annual solar fraction from two dimensionless parameters, X and Y, derived from collector area, storage volume, and monthly load.
- Collector tilt angle
- The angle of the collector aperture from horizontal. Latitude minus 15 degrees favors summer yield; latitude plus 15 degrees favors winter space heating.
- Stagnation temperature
- The maximum temperature a collector reaches when the pump is off and no heat is removed. Components near the array must be rated for this temperature.
- Solar fraction
- The portion of total heating load supplied by solar energy, expressed as a decimal or percentage. Typical residential DHW designs target 0.5 to 0.7.
- Storage-to-collector ratio
- The volume of solar storage per unit collector area. Liquid flat-plate systems commonly use 1.5 to 2.0 gallons per square foot of collector.
- Incident angle modifier
- A factor that adjusts collector efficiency for non-perpendicular solar incidence. It accounts for increased reflection and absorption losses at low sun angles.
- Drainback system
- A freeze-protected solar loop in which the heat-transfer fluid drains by gravity into a reservoir when the pump stops, leaving collectors empty.
- Closed-loop glycol system
- A sealed solar loop filled with a propylene glycol and water mixture. The glycol concentration is set to prevent freezing at the site's record low temperature.
- Row spacing
- The distance between collector rows set so the front row does not shade the next row at the design hour, usually noon on the winter solstice.
- Roof flashing
- A manufactured weatherproofing detail installed at each roof penetration. It must be compatible with the roofing material and sealed to shed water.
- Air separator
- A device installed at the pump suction that removes entrained air and microbubbles from the solar loop, preventing cavitation and reduced flow.
- Collector outlet sensor
- A temperature sensor mounted on the collector outlet header in direct contact with the pipe and insulated over, used by the controller to start the pump.
- Pressure test
- A test of the solar loop at 1.5 times operating pressure, held to verify joint integrity before charging with glycol and commissioning the system.
- Differential controller setpoint
- The temperature difference between collector and tank at which the pump starts (about 8 to 12 degrees C) and stops (about 2 to 4 degrees C).
- Loop flow rate
- The volumetric flow through the collector array, typically 0.02 to 0.05 gallons per minute per square foot of liquid flat-plate collector at design conditions.
- Refractometer
- An optical instrument used to measure glycol concentration and freeze point in a solar loop. Preferred over hydrometers because it is not affected by temperature.
- Air lock
- A trapped air pocket that stops flow in a solar loop. Symptoms include low flow, rising collector temperature, and fluctuating loop pressure.
- Sensor calibration check
- Comparing controller temperature readings against an independent thermometer. A large error can prevent the pump from starting or cause overheating.
- Commissioning log
- A record of flow, pressure, glycol concentration, sensor readings, and controller settings taken at startup and used as a baseline for future troubleshooting.
- Pump cavitation
- Noise and loss of flow caused by vapor bubbles forming at the pump inlet, usually from air in the loop or insufficient suction pressure.
- Glycol pH testing
- An annual check of loop fluid acidity. Propylene glycol degrades to glycolic acid; pH below 7 indicates the fluid should be replaced.
- Expansion tank pre-charge
- The air pressure set in an expansion tank with the system isolated at ambient temperature, typically the static pressure at the tank plus 5 psi.
- Glycol replacement interval
- Propylene glycol in a solar loop is typically replaced every 3 to 5 years, or sooner if pH testing shows degradation below the acceptable range.
- Collector cleaning
- Washing collector glazing with water and a soft brush to remove dust and bird droppings. Avoid abrasives and cold water on hot glass.
- Maintenance trend log
- A record of flow, temperature difference, pump hours, and glycol results kept across service visits to reveal gradual fouling or degradation.
- Drainback tank check
- A service check confirming the reservoir drains fully and the collector loop empties when the pump stops, preventing freeze damage in winter.
- SRCC OG-100
- A certification program for collector thermal performance. It rates collectors under standard test conditions and is used to compare collector models.
- SRCC OG-300
- A certification program for complete residential solar hot water systems, covering the collector, storage, controls, and freeze protection as an integrated package.
- ISO 9806
- The current international standard for testing solar collector thermal performance, covering efficiency, incidence angle modifier, and stagnation behavior.
- Pressure relief valve
- A safety device on the solar loop that opens at the design pressure and must be piped to a safe discharge. It must never be capped or plugged.
- Backflow prevention
- A code-required air gap or reduced-pressure-zone device at the potable water connection to a solar loop, preventing contamination of drinking water.
- ASCE 7 wind and snow loads
- The structural standard used to calculate wind uplift and snow load on roof-mounted collectors, required for permit drawings and mounting design.