ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 22

Prior to building commissioning, actuator replace-

use in static systems to be sized and installed within

ment may be needed to accommodate a change in actu-

the limitations of the certiﬁcation. These mullions are

ator voltage or to swap out an actuator without indication

generally fabricated in the ﬁeld. Damper manufacturers

switches for one with indication switches. Often, replace-

can provide installation details covering the fabrication,

ments can be made without a change in actuator model

installation and use of mullions.

and with little change in overall actuator conﬁguration.

Because airflow ratings of fire dampers for use in

More substantial modifications may be required if a

dynamic systems and combination ﬁre-smoke dampers are

different actuator model is needed or if an actuator has to

size dependent, the use of the mullions discussed herein

be changed from mounted on the

are only intended for application

damper sleeve to mounted within

with ﬁre dampers for use in static

the damper sleeve. Such modiﬁca-

systems. Further, the mullions are

tions may require additional hard-

limited to use in vertical partitions.

ware to complete, so it is best to
contact the manufacturer for guid-

Fa br ic at ion a nd si z i n g of

ance. Any actuator modiﬁcations

vertical steel mullions (Figure

should be done in accordance with

2) are covered in UL-approved

manufacturer instructions and

installation inst ructions. The

guidelines and, once completed,

mullions are approved for use with

followed by damper cycling.

concrete-block, masonry, brick,

Because they are not covered

or poured-concrete walls only.

under the UL certiﬁcation program,

Additionally, they are approved

actuator modiﬁcations may need

FIGU R E 2. Detail B steel mullion for

for use with dampers with a ﬁ re-

to be reviewed and approved by

dividing oversized wall openings.

resistance rating of 1½ hr, which

the local AHJ.

can be installed in barriers rated
for less than 3 hr.3

Mullions

As the above excerpt states,

All life-safety dampers are certi-

UL recognizes the use of vertical

ﬁed to a maximum overall size.

mullions only in static systems,

There are times, however, when

or systems that cut off airﬂow in

an opening exceeds that size. This

the event of a fire. For dampers

can be the case when an opening

installed in dynamic systems,

is larger than the furnace used in

opt ion s a l low i n g t he u s e of

the testing and certiﬁcation of a

mullions may be available. One

damper. In vertical wall applica-

possible opt ion for dy n a m ic

tions, steel mullions can be used

systems involves splitting duct-

to divide an opening into sections.

work to make sure mullions do not

"Dampers Marking and Applica-

experience the dynamic forces of

tion Guide" outlines the use of

FIGURE 3. Horizontal mullion for dividing

the system when dampers close.

mullions (Page 12):

oversized opening in concrete ﬂoor.

The use of vertical mullions in
dynamic systems requires approval

In certain circumstances, steel mullions can be used
to divide a large wall or vertical partition opening into
smaller individual openings, allowing ﬁre dampers for

22

2020 A M CA i n m o t i o n

from the local AHJ, who may need additional information
from the architect and engineer of record.
"Dampers Marking and Application Guide" does

w w w. a m c a .o r g
http://www.amca.org
ASHRAE Journal Supplement - AMCA InMotion - October 2020

Table of Contents for the Digital Edition of ASHRAE Journal Supplement - AMCA InMotion - October 2020
