Product Overview, Subassemblies | Greenheck Fan 470654 guide

Product Overview

The model is a vertically-configured make-up air unit designed for outdoor installations. It contains a highly efficient direct-fired gas burner to provide a heat source for the building or to simply temper the air. The unit is designed to provide sufficient air to replace air that is exhausted from the building and will also produce heat as needed. The make-up air volume produced by the unit can be regulated in a number of different ways, depending on the characteristics of the building.

The unit draws in fresh, outdoor air through a filter bank in the bottom of the unit and it then moves upward through a combustion chamber or through an optional burner bypass damper. A blower mounted in the top of the unit then forces the air into the building ductwork.

Airflow Arrangement

The unit can be ordered in a number of different configurations to provide 100% outdoor air or 80% recirculated air and 20% outdoor air. These units can also be ordered with a variable air volume (VAV) capability for flexibility in response to building air handling needs.

100% Outdoor Air

If the unit is configured only for 100% outdoor air, it draws outdoor air as needed through the filter bank at the bottom. The air moves upward through the combustion chamber and then it is blown into the building through user-supplied ductwork. The supply air volume is typically constant and can only be altered by changing the blower or motor pulleys.

80/20 Recirculated Air

When the unit is used as a primary heat source for the building, the unit will draw 80% of the needed air from the building and mix it with a minimum of 20% fresh outdoor air. Outdoor air is drawn through the combustion chamber and then mixed with the indoor air after the direct-fired gas heater has heated the air. The supply air volume is typically constant but the percentage of recirculated air can be modulated.

Variable Air Volume (VAV)

The VAV function can be selected when the outdoor air volume required by the building varies. This requires the installation of one bypass damper and selection of an appropriate motor/blower control system. This may involve installation of a Variable Frequency Drive (VFD) controller. Both bypass damper and VFD are factory installed.

4Model VSU Make-Up Air

Subassemblies

Filter Section / Vertical Mounting Stand

The filter section of the unit is factory installed in the mounting stand and shipped ready for installation on the concrete mounting pad. Each filter unit has a large access panel on the control end of the unit except for the housing size 50, which has an access door on both ends. Filters are either 2 in. thick pleated paper or 2 in. thick permanent metal type. Filters are changed by removing the access door(s) and sliding the filters in or out on their tracks.

The unit’s vertical mounting stand is fabricated of heavy-gauge, painted angle iron and flat stock steel. The nominal 24 in. high stand will support the entire unit so that the bottom of the filter unit is held 24 in. above ground level. For housing size 50, a nominal 48 in. high stand is minimum. In locations where heavy snowfall is common, greater minimum clearance should be specified in order to minimize the possibility of clogging filters with snow or debris. The stand with filter bank is shipped to the jobsite as a separate assembly. The unit filter bank is permanently installed in the mounting stand prior to shipment.

Optional Service Platform

A service platform is available

for permanent

attachment to the mounting stand. The platform

is shipped unassembled and requires field assembly. It is attached to the vertical mounting stand

by installing bolts with spacers between the two assemblies. The service platform should be attached to the unit only after the burner and blower assemblies are permanently set in place.