Rooftop Units .

Gus-fired rooftop units are normally vented through:

• Double-wall vent pipe connected to the side of the unit.

• Double-wall vent pipe connected to the top of the unit.

• A separate power venter

• Draft hoods connected directly to the unit.

The condensate drain on a rooftop unit:

• Is normally run through the curb to an inside drain connection.

• Does not require any type of drain line.

• Must include a trap unless the unit has an integral trap.

• Does not require a trap because of the short distance.

What type of blower configuration requires a water-filled P-trap to ensure proper condensate draining?

• Push-through evaporator with blower upstream

• No P-trap is needed on rooftop installations.

• Draw-through evaporator with blower downstream

• Blower configuration does not affect drainage.

When installing a rooftop package unit, proper airflow through the condenser fan is critical. The minimum free clearance air space above the condenser fan should be:

• 72 in

• 12 in

• 48 in

• 60 in

To avoid cutting extra holes in the roof, power is normally provided to curb-mounted rooftop units:

• Through the same conduit as the low-voltage control wiring

• Directly from the power company's utility pole.

• Wirelessly using Wireless Power Connectors (WPC).

• From underneath through the curb.

Rooftop units should be leveled when they are installed so that:

• The oil will return to the compressor.

• The condensate can drain properly.

• The airflow will travel in the right direction through the evaporator.

• The refrigerant will travel through the system correctly.

Water and air leakage between the rooftop unit and the rooftop curb are prevented by:

• UL-rated duct tape applied over the outside of the curb.

• UL-rated duct tape applied to both the inside and outside of the curb.

• Gasket material between the curb and the unit.

• UL-rated duct tape applied from the inside of the curb.

When installing units requiring three-phase power, the voltages between any two power leads must be

• Within 10 percent of each other.

• Exactly the same

• Within 15 percent of each other.

• Within 3 percent of each other.

To ensure that the rafters or joists do not interfere with installation of the plenums on a curt-mounted rooftop unit:

• The roof curb must be installed diagonal to the roof joists or rafters.

• The roof curb must be square with the roof joists or alters.

• The plenums are fabricated in place with the roof joists or rafters passing through them

• The roof joists or rafters are cut out where the curb is installed.

Gas pressure should be checked at the rooftop valve prior to installation. The gas line pressure for natural gas in inches of water column should not exceed:

• 105 in WC.

• 35 in WC.

• 5.0 in WC.

• 2 psi