ADDENDUM

DOOR COMPATIBILITY FOR MODEL 3950 IMPORTANT INSTALLATION INSTRUCTIONS
It is important to identify the door type before attempting an installation of the Model 3950 door operator. MOUNTING OPTIONS: 1 Standard wall mount using the brackets included with the operator. 2 Outside bracket mount using the optional mounting bracket Model 3950MB. Inside bracket mount using the optional mounting bracket Model 3950MB. 3 If standard wall mount brackets are not acceptable for installation, optional Model 3950MB mounting brackets may be required. To order visit www.liftmaster.com or contact door supplier. NOTE: The inside mounting option takes away from clear door opening.
LIVE OR DEAD SHAFT DOOR IDENTIFICATION
LIVE SHAFT DOOR - The axle rotates with the drum and door assembly when the door is opened or closed. DEAD SHAFT DOOR - The axle is locked in place while the door opens and closes.

Rotating Axle

Fixed Axle
Live Shaft Door Figure 1 - Door Type Identication

Dead Shaft Door

LIVE SHAFT REQUIREMENTS
Live Shaft doors are automated by the Model 3950 driving a chain which spans the drive sprocket and the door sprocket. The door sprocket is attached to the door axle which spins the drums and rolls the door curtain. The assembly is held up by door brackets and the door guides. (Figure 2)

Axle Wall

Drum Bracket

Door Guide

Figure 2 - Live Shaft Components

Minimum Side Room

The minimum amount of side room depends on the mounting option for the Model 3950. For a standard wall mount or outside bracket mount using the optional mounting bracket Model 3950MB, a minimum of 11" is required to the outside of the door opening. If inside mounted, minimum of 3.75" clearance for Wall dimension is required. (Figure 3)

2.5"

11" Wall
Figure 3 - Live Shaft Clearances
Minimum Shaft Length Past Door Bracket
A minimum of 1.5" of shaft is required (2.5" recommended) for mounting the door sprocket to the Live Door Shaft. (Figure 3)

DEAD SHAFT REQUIREMENTS

Dead Shaft Door Construction

Drum 2nd Drum Spring

Door Bracket
Figure 4 - Dead Shaft Door Construction

Spring Clearance

The Model 3950 requires that the internal door springs do not interfere with the 4.5" mounting pattern on the end drum (Figure 4 ). Some door manufacturers require the door to be ordered with a modication (ex. Prep for Operator), so that an extra drum (Figure 4 2nd Drum) is added on the end of the door barrel to provide an unobstructed platform for door sprocket mounting. Inspect for interference by sliding the sprocket on the door shaft to drum and aligning with the 2.25" from center, 3 equally spaced hole pattern. Sprocket mounting holes should not be obstructed by the door spring for a minimum depth of 3". (Figure 6 Bolt Clearance). See Figure 8 for Mounting Template.
Mounting Hole (PEM nut may be present)

5"

Figure 5 Drum Holes To Inspect For Obstruction

Door Construction

The Dead Shaft Door must not have more than a 2" inset from the curtain edge to the drum. The Model 3950 comes with a selection of spacers that can be used in conjunction to provide a maximum 3" of spacing.

2" Max Inset

2.5" Min. Clearance

3" Bolt Clearance

Figure 6 - Dead Shaft Door Offset

Drum Condition

The door drum on the side on which the Model 3950 is to be mounted must not be bent or damaged in order for installation to be successful. If bent, the drive chain may not align to the sprocket well and could derail the chain.
The minimum amount of side room depends on the mounting option for the Model 3950. For a standard wall mount to the outside of the door opening, a minimum of 11" is required for the operator, however, the door brackets must also be considered if they interfere with operator installation. Dead Shaft Door brackets should be moved away from the door assembly to provide enough room for the desired operator mounting position.

OPERATOR DRIVE OPTIONS WHEN USING MODEL 3950MB MOUNTING BRACKET
The operator drive sprocket can be attached in one of three positions when inside mounted or one of two positions if outside mounted that provide offset from the outer edge of the door guides: Refer to table below (Figure 7) for details. Figure 7 Operator Drive Options

Outside Mount Alignments

Inside Mount Alignments

OUTSIDE MOUNT ALIGNMENTS

Sprocket inner position 1" Sprocket middle position 5/8"

INSIDE MOUNT ALIGNMENTS

Sprocket inner position 1" Sprocket middle position 1-3/8" Sprocket outer position 1-5/8"

6.5"

3.25"

1.625"

.39" holes 120 apart
Figure 8 - Mounting Hole Template

01-35863B

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