Modine MDB Série Manuel D'installation Et De Maintenance page 13

control descriPtions
modulating temperature controls
Units are supplied with modulating temperature controls and
gas valve.
Depending on the type of gas and temperature controls ordered
with the unit, one or more of the following devices will be used.
Check the unit's model number to determine which type of
temperature controls were supplied.
modulating Gas valve (vG-07)
Controlled by the Modulating Valve control amplifier, the valve
is modulated to control the flow of gas to the burner. See page
17 for locations.
Figure 13.1 - modulating control Gas valve
modulating valve control amplifier (re-26)
The amplifier converts the temperature control signal from
the discharge air temperature sensor (and room temperature
sensor if Max 44 is used) and modulates the gas control
valve to maintain the air temperature at the sensor's set-point
temperature. Refer to Item #9 in Figure 16.2 on page 16.
discharge air sensor
1. Install the discharge air sensor in a single perimeter supply
duct, not to exceed 20 feet downstream of unit.
2. Be sure to orient the mixing tube so the air intake holes face
into the direction of airflow in the duct.
3. Be careful not to block the discharge air sensor ports with
insulation. If blocked, the air sensor will not function properly.
Figure 13.2 - maxitrol system discharge air sensor
Duct Insulation
Air Temperature Sensor
Mixing Tube
Air Intake Holes
Air Exit Holes Past Sensor
maXitrol system 14
discharge air temperature control
System 14 is an electronic modulating discharge air temperature
control system with a remote temperature dial for adjusting the
discharge air temperature set point. A field mounted and wired
discharge air sensor monitors the discharge air temperature
and controls an electronic modulating gas valve which
modulates the main burner gas flow to maintain the desired
discharge air temperature. The temperature set point range for
this system is 55-90°F.
The discharge air sensor is mounted in the junction box at
the end of the mixing tube. The air mixing tube is then field-
mounted in the discharge air duct with the air inlet holes of the
mixing tube facing the discharge air from the unit. (see Figure
13.2).
The accessory System 14 Remote Panel must be used. The
System 14 Remote Panel includes a remote Temperature Set
Point Dial, a Summer/Off/Winter Selector switch, a Main Valve
On light and a Flame Failure Alarm light (see Figure 13.4).
This system may be used with an accessory room temperature
override thermostat. Upon a call for heat from the room
override, the stat automatically overrides the discharge air
temperature setting by 15°F to provide warmer discharge air
until the room override stat is satisfied.
For return air units, model MRB, depending on design conditions,
this control may be acceptable, but requiring additional control
devices with the system. Also included are a factory installed/
set return air stat and a factory installed/set outside air stat. If
the temperature sensed falls below the setpoint for either stat,
the unit will go to 100% outside air mode until both stats are
satisfied. Please refer to the Gas Control Selection Table 14.1
for additional guidance.
Figure 13.3 discharge air sensor with mixing tube
Figure 13.4 - remote temperature dial for maxitrol 14
7-500.10
13