Orion-system VCM-X Modular E-BUS Manual de usuario descargar pdf (Pagina 62)

Zone

SEQUENCE OF OPERATIONS

VCM-X Modular E-BUS Controller Technical Guide

Building Pressure Control

The VCM-X E-BUS can maintain Building Static Pressure any time the

Supply Fan is operating by activating a Constant Volume Exhaust Fan, a

VFD Exhaust Fan, or Modulating Exhaust Damper, or by modulating the

Outdoor Air Damper. A Building Pressure Transducer must be connected

to the VCM-X’s Expansion Module. For Constant Volume Exhaust

Fan applications, only an Exhaust Fan Relay needs to be conﬁ gured

for on/off operation of the Exhaust Fan. VFD or Modulating Building

Pressure control must be conﬁ gured in order for this feature to operate.

An Exhaust Fan Relay can also be conﬁ gured along with Modulating

Building Pressure control for an Enable output. Building Pressure can

be maintained by either Direct or Reverse Acting control.

Direct Acting Modulating Control

If conﬁ gured, a VFD Exhaust Fan or Modulating Exhaust Damper will

be controlled by varying a 0-10 or 2-10 VDC control signal. If an en-

able output is required, an Exhaust Fan Relay can also be conﬁ gured.

The Exhaust Fan Relay and the Modulating Signal will activate when

the Building Static Pressure rises above the Building Static Pressure

Setpoint plus the Deadband. The Exhaust Fan Relay will remain active

until the Building Static Pressure falls below the Building Static Pressure

Setpoint minus the Deadband and the Modulating Signal falls to 0%.

Direct Acting On/Off Control

If you do not require a Modulating Control Signal, you can also conﬁ gure

one of the Relay Outputs as an Exhaust Fan Relay to activate whenever

the Building Static Pressure is above the Building Static Pressure Set-

point plus the Deadband. The Exhaust Fan Relay will deactivate when the

Building Static Pressure falls below the Building Static Pressure Setpoint

minus the Deadband. Only one Relay Output should be conﬁ gured for

this operation. There is no staging of additional Exhaust Fan Relays.

Reverse Acting Modulating Control

If conﬁ gured, on a drop in building static pressure below the building

pressure setpoint minus the deadband, a 2-10 VDC signal will modu-

late to open the outside air damper. When this option is selected, no

economizer-free cooling or IAQ operation will be available.

CAV/MUA Dual Mode ( Hood On/Off

Operation)

The VCM-X E-BUS Controller can be conﬁ gured as a CAV controller

but switch to MUA operation when an exhaust hood is energized. This

MUA force mode occurs when a 24 VOut wet contact closure is received

on the Hood On binary input on a VCM-X E-BUS Controller Expan-

sion Module. Under normal operation (CAV), the unit will operate as

a recirculating space temperature (and space humidity) controlled unit.

When the Hood On contact is made, the unit will open the Outdoor Air

Damper to its full open position. The Heating and Cooling Modes will

then be determined by the Outdoor Air Temperature Sensor using the

same Heating and Cooling Setpoints that were used in the CAV mode.

Dehumidiﬁ cation would then be initiated by an Outdoor Dewpoint Set-

point. When the Hood On Force Mode is removed, the unit will revert

to CAV operation with the Outdoor Damper returning to its minimum

position (unless economizer operation is enabled) and with mode control

initiated by the Space Temperature and Humidity Sensors.

MUA Unoccupied Operation

Normally, an MUA unit is off during the Unoccupied Mode. However, if

the unit has Return Air, it can be conﬁ gured to operate as a recirculating

Night Setback Controlled unit during Unoccupied Hours. This is ac-

complished by simply conﬁ guring Night Setback Temperature Setpoints

(anything other than the default 30ºF) on a unit that is also conﬁ gured

for Outdoor Temperature Control (MUA). With this conﬁ guration,

when the unit goes Unoccupied, it will close the Outdoor Air Damper

and begin to use a Space Temperature Sensor in conjunction with the

existing Heating and Cooling Setpoints, offset by the Night Setbacks,

to make Night Setback calls. If a Space Humidity Sensor is installed,

and the unit is conﬁ gured for Night Humidity control, the VCM-X E-

BUS Controller will use the Space Humidity Setpoint for unoccupied

Dehumidiﬁ cation calls.

IAQ ( CO

) Operation

If you have conﬁ gured the VCM-X E-BUS Controller to monitor and

control CO

levels, the Economizer operation will be modiﬁ ed as follows:

1. The Maximum Reset Position the Economizer can open to

is determined by a user-adjustable setpoint called the CO

Protection Limit Max Level.

2. The Minimum Position the Economizer can close down

to is reset higher as the level of CO

increases above the

Protection Limit Max Level programmed. As the CO

level increases above the adjustable CO

Setpoint,

the Outdoor Air Damper will start opening beyond its

Minimum Position. At the CO

Protection Limit Reset

Range above Setpoint, the Economizer will be held to its

Maximum Reset Position and not allowed to open any

further.

If doing both CO

and CFM (using an Airﬂ ow Station) control of the

Economizer, CFM control will not override the CO

Max Economizer

Position.

Pre-Heater Operation

In colder climates where freezing temperatures are sometimes experi-

enced, it is desirable to preheat the Outdoor Air being drawn into the

HVAC unit before it reaches the Water Coils to prevent freezing. The

Pre-Heater control option is available by setting a Low Ambient Protec-

tion Setpoint and by conﬁ guring one of the relay outputs as a Pre-Heater.

Only one relay can be conﬁ gured for this option, and therefore, staging

of Pre-heater relays is not available. The Pre-Heater operation will only

operate in the Occupied Mode.

The Pre-Heater sequence operates so that any time during the Occupied

mode, if the Outdoor Air Temperature is below the Low Ambient Protec-

tion Setpoint and the Supply Fan is running, the Pre-heater Relay will

activate. It will remain on until the Outdoor Air Temperature rises 1°F

above the Setpoint or until the Supply Fan shuts down. If the Proof of

Flow option is installed and conﬁ gured, its signal must also be active

for the Pre-Heater Relay to activate.

If using the Preheat-X Controller, an SCR preheater and/or stages of

preheat can be controlled. If the Entering Air Temperature (sensor con-

nected to the Preheat-X) falls below the Pre-Heat Setpoint, then preheat

will be controlled to either a Cooling, Heating or Vent Mode Preheater

Building Pressure Control and CAV/MUA

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