Cambridge Engineering, Inc.
66
M-Series Technical Manual
Maxitrol Series 44 / Tamperproof
The Maxitrol Series 44 / Tamperproof controls
function identically to the Maxitrol Series 44 con-
trols (see gas control system) except the space
temperature selector (T244A) is replaced with
two devices. The adjustable portion, the space
temperature selector (TD244A), is mounted inside
the Remote Control Station, and the non-adjust-
able
(tamperproof) space sensor (TS244A) is mounted in the
space being heated.
Maxitrol Series 44 / Hazardous Area
The Maxitrol Series 44 / Hazardous Area is the same as the
Maxitrol Series 44 / Tamperproof, except the space sensor
(TS244A) is replaced by a space sensor with epoxy coated
circuitry (ES225A). The standard Remote Control Station
is not suitable for hazardous areas and would need to be
mounted outside of the hazardous area.
Operating Electronic Thermostat
The operating electronic thermostat is
wired between terminals Z1 and Z2 to
control heater ON/OFF operation in the
heating mode (see pages 65).
Non-Adjustable Thermostat
The non-adjustable thermostat is a fixed temperature,
solid state, epoxy sealed thermostat with a specified
temperature setpoint, either: 41
°
F, 50
°
F, 55
°
F, 60
°
F, or
65
°
F. It is wired between terminals Z1 and Z2.
Temperature Setback System
The temperature setback system is a com-
bination seven-day programmable timer
with
independent programs for summer ventila-
tion/heating modes and integral electronic
thermostat with separate selectable day/
night setback temperatures (see page 67).
The thermostat contact is wired between
Z1 and Z2.
Clogged Filter Light
The clogged filter light is an alarm light mounted in the
Remote Control Station to indicate a clogged filter con-
dition. Includes an adjustable pressure switch mounted in
the make-up air heater control enclosure to monitor the
pressure drop across the filters.
Manual Make-Up Air Switch
A manual make-up air toggle switch is used to manu-
ally turn the heater on and off. It is either mounted on
the exterior of the door of the Remote Control Station or
mounted inside the Remote Control Station for tamper-
proof applications.
Exhaust Fan Interlock
An exhaust fan interlock is used to interlock the make-
up air heater as a slave to an exhaust fan. Terminals are
provided in the Remote Control Station for wiring of dry
contacts (by others).
INDIVIDUAL HEATER COMPONENT
DESCRIPTIONS
AIR FLOW SWITCH (High and Low)
The air flow switches sense the pres-
sure drop across the burner profile
plate. They are factory set and not
adjustable. They are designed to pre-
vent burner operation if the pressure
drop across the burner drops below
0.40
inch
WC or increases above
0.85
inch
WC for natural gas applications or below
0.60
inch
WC or above 1.12
inches
WC for LP gas
applications.
AMPLIFIER
The amplifier creates a voltage output
to drive an electronic proportioning gas
valve to maintain the selected discharge
temperature (Maxitrol Series 14) or
space temperature (Maxitrol Series 44).
On Maxitrol Series 14 control systems,
the discharge temperature is set either
on the amplifier (AD1014) or the
Remote Heat Adjust (TD114). On Maxitrol Series 44
control systems, the range of the discharge temperature
is set on the amplifier (A1044), but the space tempera-
ture selector controls when more or less heat is required.
CONVENIENCE OUTLET
A convenient 115 volt GFI duplex receptacle is provided
inside the heater’s electrical enclosure. The electrical
supply source for this device can be either the heater’s
control power transformer (5 amps max.) or a separate
outside source (15 amps max.).
