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67 Cards in this Set
- Front
- Back
- 3rd side (hint)
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This N.C switch prevents short cycling |
Lock out relay |
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Lockout relays are ______ impedance |
High |
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Short cycling causes?(2) |
Poor oil return Wear on compressors |
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Before what circuit can operate (1) -what must happen to a lock out relay? (2) |
Low voltage Power cycle Or Tstat reset |
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Heat pumps are classified by? |
Type of heat sink |
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If a lockout relay is in parallel with "all controls" how can operation be resumed after lockout? |
Power cycle the system. |
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Heat pump operations are also known as ? |
Reverse cycle heating |
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A lower outdoor temp on heatpump operations will provide a lower? |
C.O.P |
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C.O.P raises and lowers with |
Outdoor temperature |
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3 Deciding factors of heat pump purchases are? (3) |
Cost of Hydro Natural Gas Installation |
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Geothermal heat pumps use _____ or ______ to transfer heat |
Groud loops Drilled heat sinks |
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In Vancouver Dig line is typically |
2.5ft |
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The standard dig rate for Geo units is |
1 hole per ton |
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Most common refrigerant change over is done by |
Reversing valve |
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Reversing valve can also be called a? (2) |
3 way or 4 way valve |
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These two types of compressors in heatpumps are PSC driven |
Scrolls Rotary |
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A loss of charge switch is generally located where? |
On the discharge line |
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A reversing valve is generally _____ operated, and controlled by ______ pressures? (2) |
Pilot operated Refrigerant differential |
Planes (1) |
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Reversing valves can fail one of two ways - what are they? What are their terminal designations |
Fail to heat - O Fail to cool - B |
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When a reversing valve is energized to cooling, which 24v terminal is being used / programed |
O |
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A common diagnostic for reversing valves is to check? |
Temperature differential between suction in and out |
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How many degrees in rise across the suction line of a reversing valve proves faulty |
12F rise |
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Heat pumps utilized which type of txv? Why? |
MOP To prevent diaphragm damage |
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what is reduced during the heating cycle? What does this cause a rise in? |
Mass flow rates Condensing temperatures |
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These metering devices can be bi-flow or have internal check valves |
TXVs |
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Cap tubes are longer in heat pumps to achieve what? |
Higher head pressures |
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A charge compensator is basically a? |
Low pressure reciever |
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This device was used in recips for low ambient operation and switching modes? |
Accumulator |
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Cooling loads are ___% latent and ___% sensible |
30% 70% |
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This device will reduce mass flow rates |
Cap tube |
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Cfm rule of thumb for heat pumps is generally? |
400-450 cfm |
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Vapour pipe can be as high as ____ degrees? |
190F |
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Air discharge off coil can be approx ______ degrees |
100F |
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Vapour line acts as as what in heating? Cooling? |
Discharge in heating Suction in cooling |
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Liquid line acts as what in heating? Cooling? |
Liquid line |
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Mass flow rates are reduced in which mode |
Heating |
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Why are mass flow rates reduced? |
To increase head pressure |
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The outdoor coil TD is generally how much lower than ambient? |
20-30F |
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Spht of air is? |
0.24 BTU |
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These loads are 100% sensible |
Heating loads |
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Microbes and bacteria building during off seasons on indoor coil causing smells |
Dirty sock syndrome |
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Cannot run at the same time? Why? |
Fossil fuels and heat pumps Over heating the indoor coil will cause head pressure to rise, and over heating the coil will to degrade |
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When suction pressure rises, volume of suction gas does what? |
Decreases |
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Volume of suction gas rises - volumetric efficiency does what? |
Decreases |
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Volumetric efficiency lowers, compression ratios does what? |
Lowers |
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Compression ratio lowers, discharge temp does what? |
Rises |
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COP = |
Output/ electrical input |
Division of two things |
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Formula for COP is |
Ton X kw X heat rejection ratio |
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Seer = |
Cooling season output / electric Watt hours |
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Defrost can be initiated by (4) |
Time Pressure OD Coil TD Air pressure |
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Axial fans dont like? |
Blocked coils - will burn out fans |
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If coil sensing switch closes what happens? |
Defrost will initiate |
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Demand defrost constantly looks at? |
Coil and ambient temp |
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Demand defrost wont work above? |
50F ambient |
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What is the best determination for a need of defrost? |
Od coil temp |
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How should water source loops be piped? |
In parallel with each other |
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Speed of water flow during heating |
Faster |
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Water flows slower during |
Cooling |
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Most efficient form of heat pump |
Geothermal |
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Remove or reject heat from the ground through a water glycol loop |
Geothermal |
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Why are geothermal unit efficient |
Ground temp is stable as long as loops are large enough |
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Temperature at which building loads provide heat is called? |
Zero degree day |
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When Capacity lost = capacity provided |
Balance point |
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When balance point drops below capacity provided what must be added |
Supplementary heat |
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Cannot exceed cooling design loads by how much |
25% |
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Where should electric heat be installes |
Downstream of the coil |
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True or false: supplementary heat does not equal same heat requirement as primary source |
False |
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