Trane RT-PRC010-EN manual VAV/CV Units

Controls (VAV/CV Units)

Control Sequences of Operation Common to Both VAV and CV Units

1

Space Pressure Control — Statitrac™

A pressure transducer is used to measure and report direct space (building) static pressure.The user- defined control parameters used in this control scheme are space static pressure setpoint and deadband. As

the economizer opens, the building pressure rises and enables the exhaust fan and dampers or exhaust VFD.The exhaust dampers or VFD then modulate to maintain space pressure within the deadband.

2

MorningWarm-up

This feature is available on all types of factory-installed heat units and on units with no heat, this function may still be selected to support systems with heat sources not provided by the rooftop unit. At the conclusion of Unoccupied mode, while the economizer (if supplied) is kept closed, the selected zone is heated to the user-defined Morning Warm-up setpoint. The unit is then released to Occupied mode.There are two types of Morning Warm-up: full capacity or cycling capacity.

A

Full Capacity MorningWarm-up (MWU)

Full capacity Morning Warm-up uses full heating capacity, and heats the zone up as quickly as possible. Full heating capacity is provided until the Morning Warm-up setpoint is met. At this point, the unit is released to Daytime mode.

B

Cycling Capacity MorningWarm-up

(MWU)

Cycling capacity Morning Warm-up provides a more gradual heating of the zone. Normal zone temperature control with varying capacity is used to raise the zone temperature to the MWU zone temperature setpoint.This method of

warm-up is used to overcome the “building sink” effect. Cycling capacity MWU will operate until MWU setpoint is reached or for 60 minutes, then the unit switches to Occupied mode.

Note: When using the Morning Warmup option in a VAV heating/cooling rooftop, airflow must be maintained through the rooftop unit.This can be accomplished by electrically tying the VAV boxes to the unoccupied output relay contacts on the Rooftop Module (RTM) or by using changeover thermostats. Either of these methods will assure adequate airflow through the unit and satisfactory heating of the building.

3

Ventilation Override (VOM)

The user can customize up to five (5) different override sequences for purposes of ventilation override control. If more than one VOM sequence is being requested, the sequence with the highest priority is initiated first. Priority schedule is that sequence “A” (unit off) is first, with sequence “E” (purge with duct pressure control) last.

UNIT OFF sequence “A”

When complete system shut down is required the following sequence could be used.

-Supply fan - Off.

-Supply fan VFD - Off (0 Hz) (if equipped)

-Inlet guide vanes - Closed

(if equipped).

- Exhaust fan - Off, exhaust dampers - Closed (if equipped).

-Exhaust fan VFD - Off (0 Hz) (if equipped)

-Outside air dampers - Closed.

-Heat - all stages - Off, Modulating heat output at 0 vdc.

-Occupied/Unoccupied output - Deenergized

-VO relay - Energized

PRESSURIZE sequence “B”

Perhaps a positively pressurized space is desired instead of a negatively pressurized space. In this case, the supply fan should be turned on with inlet

RT-PRC010-EN 79