Chapter 4: Programming the PEC Plus Phason
52 2009-06-15
Programming curtain control relays
Curtains control the temperature by adjusting the air flow into the facility. Each curtain has six
settings.
Set point – the temperature at which the curtain holds its position.
Idle band – the buffer around the set point within which the curtains hold their position.
Open on – the duration the curtains open during the open cycle
Open off – the duration the curtains hold their position during the open cycle
Close on – the duration the curtains close during the close cycle
Close off – the duration the curtains hold their position during the close cycle
How curtains work
Curtains hold their position while the temperature is within the idle band of the set point. For
example, if the set point is 80°F and the idle band is 4°F (+2°/–2°), the curtain holds its position
when the temperature is between 78°F and 82°F.
If the temperature rises above the idle band (above 82°F in our example), the curtain opens for the
“open on” duration. After opening, it holds its position for the “open off” duration. If the
temperature is still above the idle band, the curtain again opens for the open on duration and the
process repeats.
If the temperature drops below the idle band (below 78°F in our example), the curtain closes for the
“close on” duration. After closing, it holds its position for the “close off” duration. If the
temperature is still below the idle band, the curtain again closes for the close on duration and the
process repeats.
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