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| Shut down HP |
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| Stg 1...Stg 2 |
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| NO |
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| YES | T’stat |
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| heat |
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| demand |
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| ? |
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| FURN |
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| Operate HP | heat |
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| lockout |
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| Stg 1...Stg 2 |
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| at |
| HP stage(s) operate first; | |
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| or above |
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| then FURN stage(s) (if | ||
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| HBP |
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| if |
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| needed; see NOTE 1) | |
T’stat |
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| outdoor |
| between | Operate HP |
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heat |
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YES | temperature | HBP and LBP | Stg 1...Stg 2 |
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demand |
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is... | (See NOTE 2) |
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? |
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| at or |
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| below |
| T’stat |
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| LBP |
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| heat |
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| demand | NO |
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| Operate FURN | ? |
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| YES |
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| Stg 1...Stg 2 |
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| Operate FURN |
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| YES |
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| Stg 1...Stg 2 |
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| T’stat |
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| heat | Heat |
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YES demand | T’stat |
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? | pump | YES | ||||||||||
heat | ||||||||||||
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| NO |
| lockout | demand |
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| ? |
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| Shut down FURN |
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| Stg1...Stg 2 |
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| NO |
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Abbreviations:
FURN = auxiliary heat provided by gas furnace
HP = compressor heat
LBP = Low Balance Point
HBP = High Balance Point
T’stat = thermostat
NOTE 1 − Each Heat Pump and Furnace Heat stage will oper- ate until it meets the demand or until its stage timer lapses (20 minutes by default). If the timer lapses before the demand is met, the system brings on the next stage in order of:
HP−stg−1, HP−stg−2, FURN−stg−1, FURN−stg−2. NOTE 2 − The chart below illustrates how the balance points control whether HP or FURN will operate to provide heat.
COMPRESSOR ONLY
OUTDOORTEMPERATURE | (defaultsshown) | 50ºF | HBP − FURNACE | ||
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LOCKOUT TEMPERATURE | |||||
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| EITHER COMPRESSOR | ||||
| OR FURN HEAT | ||||
25ºF | LBP − COMPRESSOR | ||||
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LOCKOUT TEMPERATURE | |||||
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| FURN ONLY | ||||
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NOTE 3 − If emergency heat is selected, Furnace is used.
Figure 35. Dual Fuel Operation with Balance Points
Page 33 | icomfort |
