Greenheck Fan 470654 Operation VAV Units optional, Variable Volume Operation, Speed, Modulating

85

55

90

GREENHECK

Potentiometer

Control

Operation - VAV Units (optional)

NOTE

Blower Start-Up, as shown on page 14, should be performed before the blower is run.

NOTE

For maintenance issues associated with variable frequency drives, consult the drive’s manual supplied with the unit. The drives are programmed at the factory and should not need any adjustment during installation and start-up. For kitchen applications, the drive may be located in the kitchen or in the unit.

Variable Volume Operation

The variable volume option is recommended when a building’s exhaust volume may vary. This option enables the make-up air volume to track with the exhaust volume, providing only the amount of make- up air required. Control strategies include 2-speed and modulating blowers. Before the unit is left in service, the variable volume control system should be tested.

2-Speed

A variable frequency drive (VFD) is used to control air volumes. The VFD can be switched to low or high speed from a remote control panel. Turn the fan speed switch on the remote control panel to each position and confirm that the fan speed adjusts accordingly.

Modulating

Potentiometer Control — a variable frequency drive is controlled by input from a remote

speed selector (potentiometer). This	EXHAUST
	(OPTIONAL)
unit allows easy manual adjustment	SUPPLY
	MAIN VALVES
	HEAT
of make-up air volumes. To test

BLOWER

Building Pressure Control —	SUPPLY		BLOWER
a variable frequency drive is
	EXHAUST
controlled according to input from		(OPTIONAL)
			MAIN VALVES
	HEAT
a pressure sensing device.
Turn both knobs to the upper	75 70		DIRTY FILTERS
most pressure setting. You may	80	65	(OPTIONAL)
	85	60
	90	55
have to remove the outdoor
pressure tap tubing. VAV systems			PHOTOHELIC
should go to maximum speed. Set
both knobs at the lowest setting			GREENHECK
and the VAV systems should go to	With Maxitrol 44 Room Thermostat
minimum speed.	Building
	Pressure Control
Reset the correct pressure limits
before starting the unit.
Pressure Indicating			Pressure Setting
This picture depicts a typical	Needle		Needles
photohelic setting. Typical
settings are 0.0 in. wg for
the lower pressure setting
and 0.10 in. wg for the upper
pressure setting. The needle
indicates a negative building
pressure. During correct
operation, the indicating
needle will remain between or	Pressure Setting Knobs
near the setting needles.	Photohelic Gauge

External Signal — a variable frequency drive is controlled according to input from an external 2-10 VDC or 4-20 mA signal (by others).

A 2 VDC or 4 mA signal will send the blower to low speed. The blower will go to maximum speed with a 10 VDC or 20 mA signal.

Variable Kitchen Control — A variable frequency drive is controlled by input from a remote speed control. This unit allows automatic adjustment of make-up air volumes based on varying cooking loads.

Burner Bypass Damper (optional)

The self-adjusting burner bypass damper is a device

potentiometer operation, turn the			DIRTY FILTERS
potentiometer to the two extremes.
	75	70
		65	(OPTIONAL)
	80	60

With variable volume, make sure the fan goes to maximum and minimum speed.

When the potentiometer is at 0, the fan speed will be at its minimum. When the potentiometer is at 100, the fan will be at its maximum speed.

used in variable volume units. Its function is to maintain proper combustion by providing a constant airflow over the burner when outside air volumes are changed. It is located underneath the burner as shown in the picture.

Burner

Bypass Damper

Burner Bypass Damper

warning

The burner bypass damper is set-up at the factory. The weights should not be adjusted in the field. The damper may not fully close during minimum outside air mode.

Model VSU Make-Up Air 19

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