CNT-SVX05A-EN
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Sequence of operation
Figure 8 — Automatic heat/cool changeover logic example
1
This is the point at which the cooling capacity equals 0%, space
temperature is less than 0.5
°
F below the cooling setpoint, and the error
integrator starts to add up. Error integration does not begin until the
capacity is 0%. See the
Error integration example
below.
2
The space temperature must fall below the active space heat setpoint
before the controller can change to heating. Conversely, the space
temperature must rise above the active space heat +0.5
°
F setpoint before
the controller can change to cooling.
3
The controller switches to heat (from cool) after the error integrator exceeds
900
°
F • seconds.
4
The controller must be able to heat before it will switch to heat. A unit that
cannot heat will not switch to heat. A unit that cannot cool will not switch
to cool.
Error integration example:
If the active space temperature is 66.5
°
F, the
current mode is cooling, and the space cooling setpoint is 70
°
F. The error
calculation is 70 - 0.5 - 66.5 = 3
°
F. If the same error exists for 60 seconds, the
error integration term is
(3
°
F x 60 seconds = 180
°
F seconds). Therefore, after five minutes
(3
°
F x 300 seconds = 900
°
F seconds), the controller will switch from cooling
to heating mode.
Cooling operation
The heating and cooling space setpoint high and low limits are always applied
to the occupied and occupied standby setpoints.
During the cooling mode, the Tracer
™
AH.540 controller attempts to maintain
the active space temperature at the active space cooling setpoint. Based on the
controller's occupancy mode, the active space cooling setpoint is one of the
following:
• Occupied cooling setpoint
• Occupied standby cooling setpoint
• Unoccupied cooling setpoint
