Series 20/30 & 21/31 Condensed Catalog
Electronic Modulation Gas-Fired Temperature Controls
Indirect Fired Applications
Selectra® systems from Maxitrol maintain precise, stable gas-fired temperatures. Selectra's unique electronic
Modulator-Regulator valves control gas flow with instantaneous response and continual adjustment. They are the
superior alternative to mod motors and butterfly valves.
OEM or retrofit applications include environmental climate control, as well as industrial or commercial heating
processes. Suitable for application in natural, manufactured, mixed gases, liquified petroleum gases and LP gas-air
mixture piping systems.
Available standard companion electronics include temperature selectors, amplifiers, and temperature sensors, in a
variety of configurations. The amplifier supplies output voltage to the MR valve.
Space Heating Applications -
Series 20/30 System
Selectra® Series 20/30 systems are designed primarily
for commercial and light industrial space heating, as
components of indirect fired units with atmospheric
burners.
The Series 20 is designed for single furnace operation,
and the Series 30 is capable of handling up to four
furnaces.
A wall mounted Selectrastat® senses space temperature
and has an integral selector. Standard temperature
adjustment range 60° to 85° F.
Amplifiers are available with high-fire ignition.
Also optional:
• A remote temperature sensor paired with a separate
temperature selector can be substituted for the
Selectrastat.
Make Up Air Applications -
Series 21/31 System
Selectra® Series 21/31 systems are designed primarily
for make-up air heating, as components of indirect fired
units with atmospheric burners.
The Series 21 is designed for single furnace operation,
and the Series 31 is capable of handling up to four
furnaces.
A discharge air temperature sensor is mounted within a
mixing tube housing. Standard temperature adjustment
range 55° to 90° F.
Amplifiers are available with options such as high-fire
ignition and integral or remote temperature selection.
Also optional:
• A room override thermostat provides space
temperature control by raising the discharge air
temperature to a pre-selected point - when used in
conjunction with the remote temperature selector.
• An inlet air sensor (and mixing tube) provides inverse
change in discharge air for each degree change in inlet
air - when installed in a convenient duct location
upstream of the burner.
© 2008, Maxitrol Company, All Rights Reserved
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Space Heating Applications - Series 20/30 System
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Selectrastat
Series 20 Amplifiers:
A1010A - single furnace
A1010B - w/ high fire ignition
Series 30 Amplifiers:
A1011A - multiple furnace
A1011B - w/ high fire ignition
Modulator-Regulator Valves:
MR410 (3/8" & 1/2" pipe size)
MR510 (1/2" & 3/4" pipe size)
MR610 (3/4" & 1" pipe size)
H-1 models for higher outlet pressure
(such as for LP applications)
CSA certified to Z21.18 and CAN 1-6.3-M82
TD120
Space Temp. Selector
TS120
Space Temp. Sensor
Selectrastat: selector and integral sensing
T120 - (60° to 85° F) - supersedes T107A-1
or optional pair to replace Selectrastat:
Space Temperature Selector: selection only
TD120 (60° to 85° F) - supersedes TD107A
Optional: ETD-1 enclosure,
EFP-1 cover plate only - no enclosure
Space Temperature Sensor: remote sensing
TS120 - supersedes TS2003A
© 2008, Maxitrol Company, All Rights Reserved
2