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Marvair Classic AVPA/HVPA/HVPSA Heat Pump I&O Manual
11/2017 Rev. 7
3.4 Ventilation System Set-Up:
Manual Fresh Air System (Configuration N)
. This is the standard ventilation system in the Classic
heat pumps. Fresh air ventilation by means of a damper can provide up to 15% of rated air flow of
outside air. The damper has four positions corresponding to 0, 5, 10 and 15% of rated air flow of outside
air.
The damper only opens when the indoor fan is operating. Position the screw on the side of the damper
hood for the desired air flow.
Manual Damper - 0 to 450 cfm of Outside Air, No Pressure Relief (Configuration Y).
The amount of fresh air is determined by the position of the collar on the rod (
Figure 3
). To
determine the desired quantity of fresh air:
a. With the indoor blower on, measure the quantity of supply air being discharged into the room with
a balometer.
b. Now measure the quantity of the return air from the room. Subtract the return air from the supply
air. The difference is the amount of fresh air.
c. Loosen the set screw that holds the collar onto the rod connected to the damper. Move the collar
and tighten the set screw.
Rod
Set Screw
Figure 8 - Damper Adjustment
d. Repeat steps a, b and c until the desired amount of fresh air is being introduced into the room.
Important Note:
Since Configuration Y does not have internal pressure relief, the fresh air must
have a passage to the outside. If a passage is not available, the desired quantity of fresh air cannot
be introduced into the room.
Motorized Damper - 0 to 450 cfm of Outside Air and Pressure Relief (Configuration B) and
the Manual Damper with Pressure Relief (Configuration Z).
The settings of the damper require a
balometer and a thermometer for measuring internal and external temperatures.
a. Measure the total supply air with a balometer. If the supply air is controlled by a manual fan speed
controller, make certain that the air flow is in accordance with Table 1, Air Flow (CFM) at Various
Static Pressures. This CFM is referred to as "C" in the illustration and equation below.
