HEAT − Using the Heat Mode
Normal Heat Mode
In normal heat mode, both the heat pump and the backup heat source are used to provide heat. If the thermostat de- tects that the heat pump is not able to provide enough heat (as may be the case in very cold weather), then the backup heat source is activated.
Emergency Heat Mode
In emergency heat mode, only the backup heat source provides heat
heat source is activated only when there is a heat demand.
Enabling Normal Heat Mode
Use the HEAT button to select normal heat mode, emer- gency heat mode, or to disable heat modes as desired. If the thermostat is in off or cool mode, pressing the HEAT button enables heat mode. This is indicated by HEAT in the lower right corner (see figure 4).
| Normal Heat Mode Enabled |
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| Heat | Cool |
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| 5:30 | Prog | Auto |
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| 82 | Copy Day/Time |
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70 | 70 | Fan | Hold | (DOOR |
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| OPEN) |
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| Settings Enter |
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| (Outside) |
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Figure 4
Enabling Emergency Heat Mode
If the thermostat is in heat mode, pressing the HEAT button enables emergency heat mode (see figure 5). If the ther- mostat is in normal heat mode when the HEAT button is pressed, then emergency heat mode is enabled.
Emergency Heat Mode Enabled
ROOM |
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62° | HEAT SETPOINT EMG. |
75° HEAT |
Figure 5
Disabling Heat Mode
If the thermostat is in emergency heat mode when the HEAT button is pressed, then heat modes are disabled. This is indicated by OFF near the right side of the display as shown in figure 6.
Heat Mode Disabled | |||
ROOM |
| OFF |
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75° | 75° |
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| HEAT SETPOINT | ||
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Figure 6 |
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Heating Demand
The thermostat must be in either normal or emergency heat mode in order to properly control the heating equip- ment. In either heat mode, when the actual temperature is lower than the temperature setpoint (as shown in figure 7), the thermostat detects a heating demand and activates the heating equipment to satisfy the demand. Heating opera- tion is indicated by a flame icon in bottom right−hand corner of the display.
Heating Demand
ROOM |
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72° | HEAT SETPOINT |
75° HEAT |
Figure 7
When the actual temperature rises above the temperature setpoint, the flame icon will disappear. This indicates that the heating demand has been satisfied and that the heat- ing equipment has been turned off.
Heat pump operation is locked out for 5 minutes after a de- mand has been satisfied. If another heat pump demand occurs during this 5−minute interval, the flame icon will flash; however, the heat pump will not run until the 5−min- ute delay has elapsed.
NOTE − The heat pump is activated for at least 4 minutes if no buttons are pressed during the demand interval. The backup heat source is activated for at least 3 minutes if no buttons are pressed during the demand interval.
If your system supports 3−stage heating (as does the 51M42 thermostat), you may notice various heating levels being delivered during a demand.
If a small heat pump heating demand is present, "Lo" is dis- played in the SYSTEM box; if a large heat pump heating demand is present, "Hi" is displayed (see figure 8).
Large Heat Heating Demand
ROOM |
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65 | ° | 75° | Hi |
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| HEAT SETPOINT |
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| HEAT |
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| Lo |
Figure 8
Page 3
51M42 SERIES 5/2
