ASHRAE Journal Supplement - AMCA InMotion - November 2022 - 16

negator springs used to close a damper likely will need
to be removed and/or replaced. Where a swivel, crank
arm, and rod are used, a new electric actuator supplied
with a built-in crank arm and mounting bracket will be
required.
With the new electric actuator (and, if required, linkPHOTO
D. Typical external actuator installation. The
electric actuator is direct-coupled to the damper
shaft, while the old mounting plate serves as an
anti-rotation strap.
externally (Photo D), the simplest solution would be a
direct-coupled, modern fi re/smoke-rated electric actuator.
Remove the existing pneumatic actuator and all of the
linkages connecting it to the control shaft. Next, place
a properly sized direct-drive fi re/smoke-rated electric
actuator over the drive shaft. If the existing mounting
bracket is not long enough to support the anti-rotation
strap of the electric actuator, a new mounting bracket will
be needed. Make sure the electric actuator is oriented
so that it will correctly power-open and, upon the loss
of power, spring-close the damper.
If an old pneumatic actuator is internally mounted
or connected via a system of linkages, a new linkage
and/or mounting plate is/are likely to be needed. Any
Inside
duct
Fusible
link
ages) in place, open the damper by hand and power open
the actuator. When both the damper and actuator are
fully open, connect the actuator to the drive shaft. Next,
disconnect power going to the damper and inspect that
the damper has fully closed. Lastly, cycle the damper
electrically-open and then closed-to ensure proper
operation.
Typically, replacing a pneumatic actuator with an
electric one is easy. In about 10 percent of cases, however,
some investigation and modifi cation is needed. Communication
with the damper manufacturer is important to
ensuring torque requirements for the damper model and
size, airfl ow conditions, and actuator location are met.
Electro-pneumatic (E/P) switches typically need to be
replaced with a relay. Air valves (Figure 1) require new
electric thermostat-type heat-responsive devices. Fusible
links and shaft springs generally can be retained, with
no changes needed.
Air to
actuator
Air supply
Outside
duct
FIGURE 1. Pneumatic air valve with fusible-link
release.
16
2022 AMCA inmot ion
What does the " 8-13 psi " on my pneumatic actuator
mean? That is the air pressure in pounds per square
inch (psi) required for the actuator's shaft to move fully
without a load. In other words, 8 psi is required for the
shaft to begin to move, and 13 psi is required for it to
fully extend without being connected to the damper. In
the same manor, an 8-13-psi spring produces the force
required to close the damper. A spring with a different
psi range can be used to produce more or less torque.
www.amca.org
Does changing out an actuator affect a damper's
UL 555S, Smoke Dampers, certifi cation? Actuator
fi eld replacement is outside the scope of UL 555S certifi
cation. UL suggests it be done in accordance with the
damper manufacturer's normal fi eld-servicing program.
Ultimately, then, it is up to the local authority having
jurisdiction (AHJ) to determine if an actuator replacement
is suffi cient. At the building owner's expense, a representative
of UL can be hired to visit a job site and inspect.
http://www.amca.org
ASHRAE Journal Supplement - AMCA InMotion - November 2022

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