Product Overview

F-15070-14 Copyright 2008 TAC All Rights Reserved. 13
THEORY OF OPERATION
Refer to Figure-16. The permanently sealed, oil-filled case contains a movable hydraulic
piston assembly and an electric pump for the hydraulic system. The pump generates a fluid
pressure which is transmitted to the top of the piston, creating a hydraulic force which drives
the piston downward. Opposing the hydraulic force is the spring of the valve or damper
linkage. When the hydraulic force becomes great enough to overcome the opposing spring
force, the piston translates downward, extending the output shaft. The electric pump is
powered by the input supply voltage and runs whenever the voltage is applied. When power
is removed from the pump, it stops running, decreasing the hydraulic force above the piston.
This allows the spring force to overcome the hydraulic force, pushing the piston upward and
retracting the output shaft. The oil above the piston is allowed to flow backward through the
pump by means of a check valve.
Figure-16 MA-5xxx Series Actuators.
REPLACEMENT PARTS
The installation of replacement actuators, in place of the obsolete series of MA-5xxx
actuators (refer to Figure-17), may require additional items. These replacement items are
required for the following reasons:
1. The AM-601 damper linkage is used to convert base actuators to damper actuators when
damper models are not available.
2. The AM-602 spacer is used when current actuators are installed on old linkages (refer
to Figure-18 and Figure-19).
3. The AE-249 transformer (208 Vac to 120 Vac) is used when replacing 208 Vac
actuators (MA-5xx2) with 120 Vac actuators (MA-5xx0).
Figure-17 Current and Obsolete Actuators.
Hydraulic
Piston Assembly
Oil-Filled Case
Check Valve
Electric Pump
Switch/Thermostat
To AC
Power
Source
Orange
Brown
Red/White
Auxiliary Switch Wires
Switch Point Adjustment
for Auxiliary Switch
Position Indication and
Switch Action Cam
Auxiliary
Switch
3/4"
(19 mm)
1-5/16"
(33 mm)
1-5/16"
(33 mm)
MA-521X-XXX MA-521X-XXX-2 MA-521X-XXX-3
Obsolete Actuators
Current Actuator