Instructions / Assembly

ManualsBrandsMaster Flow ManualsAttic Fans & Vents1250 CFM Black Power Roof Mount Attic Fan

1. Ensure Proper Intake Ventilation... Always

ensure there is proper intake ventilation at the

sofﬁt, undereave, and fascia areas of the roof. This

is required for a balanced ventilation system and to

help avoid premature ventilator motor failure. Use

the chart located on the outside of the package to

ensure the minimum recommended intake ventilation

is installed on the home. Always consult local building

codes for ventilation requirements.

2. Locate Position... Locate the ventilator as high as

possible on the roof, but not on the ridge line. The top

opening of the hood must be 24" (609 mm) BELOW

the ridge line (Figure 1a). Single ventilators should be

centered; multiple ventilators should be evenly spaced

over the length of the roof. Measure from the ridge line

to the top center of the ventilator hood (Figure 1b).

Using this measurement, go inside the attic and mark

the location centered between two rafters and drill a

hole. Put an object such as a pencil through the hole

so that it is visible on the outside (Figure 1c).

3. Mark and Cut Opening... Place and center the

template (included on the box) over the previous-

ly marked hole. Using a pencil or marker, use the

template as a guide to mark a circle. Note: Depending

on the ventilator model being installed, the included

cutout template on the box will be either 15" (381

mm) or 17" (432 mm) in diameter. For 24" (609 mm)

on-center rafters, make the cutout shown in Figure 2a.

For 16" (406 mm) on-center rafters, make the cutout

shown in Figure 2b. Using a power saber, jig saw, or

hand saw, cut out the opening (Figure 2c).

4. Prepare the Opening... Roll back and separate

any shingles (if existing). Remove all nails within 5 ½"

(140 mm) from the sides and top of the opening.

5. Test Ventilator Position... Test the ﬁnal position of

the ventilator by sliding the ﬂashing up under the upper

shingles. Trim any shingles as needed and remove the

ventilator (Figure 3a).

6. Seal and Fasten Ventilator... With the position

tested, apply a bead of rooﬁng cement or urethane

sealant to the underside of the ventilator’s ﬂashing.

Proceed with sliding the ventilator up under the top

shingles, with arrow on the ﬂashing pointing up. Leave

the lower portion of the ventilator ﬂashing on top of

the shingles for maximum weather resistance. Using

rooﬁng nails, fasten the ventilator at all corners of the

ﬂashing and approximately every 4" (102 mm) along

the edge of the ﬂashing (Figure 3b).

Note: For maximum wind resistance, remove

the ventilator hood and fasten the ﬂashing every

45 degrees, approximately 1" (25.4 mm) away

from the stack wall. Replace ventilator hood when

complete. Seal all exposed fasteners, ﬂashing, stack

seams, and loose shingles.

Warning: Using excess roof cement may cause

blistering in the rooﬁng shingles.

7. Wiring... Always disconnect power supply before

wiring the ventilator into an existing circuit. Remove

the thermostat cover and mount the thermostat box

to the edge of an adjacent rafter or stud using the

pre-punched holes. Make sure the thermostat element

opening on the back of the box isn’t covered. Each

ventilator must have its own thermostat. Leave the

ﬂexible conduit with some slack and begin wiring the

thermostat as shown in Figure 4a (below).

Note: The included thermostat is adjustable from

60°F (15.5°C) to 120°F (48.8°C). The factory/

recommended setting for efﬁcient operation is

105°F (40.5°C).

Note: In the unlikely event accessories or parts are

missing or this product does not operate correctly,

please contact Master Flow

Technical Services at

1-800-211-9612. Do NOT return this ventilator to

retailers or distributors.

Installation Instructions

For Roof-Mount Models: PR1, PR2, PR3,

ERV4, ERV5 & ERV6

MOTOR

POWER SOURCE

GREEN

BLACK

WHITE

Figure 4a

Note: See Figures on previous page.

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