GUIDE SPECIFICATION
Temperature control shall use the master zone/subzone approach. Cooling/heating units as shown on the plans shall be the master zones.
Each cooling/heating unit shall be provided with 4 volt relays to control fan, compressor/cooling coils and heating source.
Each cooling/heating unit shall be subzones with Acutherm Therma-Fuser thermally powered VAV modules as shown on the plans.
An air bypass shall be provided for each cooling/heating unit which shall be controlled by an Acutherm Pressure Independence Module as
shown on the plans. (One of several available options for static pressure control/pressure independence.)
Each cooling/heating unit shall be provided with an Acutherm System Mode Control Module (SMC) which shall be capable of performing the
following:
Sequence of Operation |
Mode |
Fan |
Cooling |
Heating |
Occupied |
Runs continuously |
Energized if:
- Any sensor is above cooling setpoint,
and
- Discharge air temperature is above
discharge cooling setpoint.
|
Energized if:
- No sensor is above cooling setpoint,
and
- At least one sensor is below heating
offset setpoint, and
- Discharge air temperature is below
discharge heating setpoint
|
Unoccupied |
Runs when any sensor is below
setback setpoint. |
De-energized |
Energized if:
- Any sensor is below setback setpoint,
and
- Discharge air temperature is below
discharge heating setpoint
|
Preoccupancy |
Runs continuously |
De-energized |
Energized if:
- Any sensor is below heating offset
setpoint, and
- Discharge air temperature is below
discharge heating setpoint
|
FIELD CHANGES TO SEQUENCE OF OPERATION
The sequence of operation shall be field adjustable to:
1) |
Switch to heating priority in the occupied mode. The result is that heating is energized if any sensor is below heating offset and cooling is
energized if: 1) no sensor is below heating offset, and 2) at least one sensor is above cooling setpoint, and 3) discharge air temperature is
above discharge cooling setpoint. |
2) |
Connections for optional dry contacts by others, such as an outside air thermostat, shall be provided. Closing the dry contacts shall change
priority from cooling to heating. The dry contacts shall operate at 12v. and have capacity of 0.2VA.
a) |
Setup where cooling is energized if any sensor is above cooling setup setpoint and the discharge air temperature is above discharge
cooling setpoint. In setup, the fan runs when any sensor is above setup setpoint. |
b) |
Both setback and setup. |
c) |
Neither setback or setup. |
|
3) |
Switch from warm-up in the preoccupancy mode to both warm-up and cooling pulldown. |
4) |
Switch to allow use of discharge air thermostats by others. (A second stage discharge thermostat is available as an optional add to the
SMC.) Discharge air thermostats by others may be used to provide more than two stages of cooling or heating, to provide modulating
control or to provide pneumatic control. |
See separate specifications for other field changes when duct heating stations are used.
SETPOINTS
The SMC shall have separate cooling setpoints for each remote temperature sensor, field adjustable between 68°F and 78°F. A heating
offset (same for all sensors) shall be field adjustable from 1°F to 5°F below the cooling setpoint. The setback setpoint shall be field adjustable
between 45°F and 65°F and the setup setpoint between 80°F and 95°F. The cooling discharge air temperature setpoint shall be field
adjustable between 45°F and 65°F and the heating discharge air temperature setpoint between 80°F and 110°F. Field adjustment shall be by
measuring voltage and turning a thumbwheel on a potentiometer to get a voltage corresponding to the setpoint temperature.
DISPLAY
Input from each sensor shall be separately displayed by long life LED lights showing on the front of the SMC. A green light shall indicate that
space temperature at the sensor is above cooling setpoint and a red light shall indicate that space temperature at the sensor is below the
heating offset. The lights shall indicate the sensor number when lit.
A green light for cooling and a red light for heating showing on the front of the SMC shall indicate the mode called for as the result of the
temperature at the five sensors and the priority selected.
Output to the cooling/heating unit shall be displayed by lights showing on the front of the SMC. A yellow light shall indicate that the fan is
energized, a green light that cooling is energized and a red light that heating is energized. The green light shall light when the mode is cooling
and the discharge air is above discharge air setpoint. The red light shall light when the mode is heating and the discharge air is below the
discharge air setpoint.
When the optional add second stage is installed, a second green and red output light shall indicate that the second stage of cooling or heating
is energized. The output lights shall indicate stage number when lit.
A red light shall be provided on the front of the SMC to show when filter pressure drop is above acceptable level. Equipment to measure filter
pressure drop with dry contacts to activate the light circuit to be provided by others. The dry contacts shall operate at 12v and have a capacity
of 0.2 VA.
The clock inside the SMC shall have a liquid crystal display of:
- Day and time (hour, minute and AM or PM).
- Times programmed for occupied mode by pressing the CH1 button.
- Times programmed for preoccupancy mode by pressing the CH2 button.
ELECTRONIC CLOCK
The electronic clock shall be capable of 7 day programming for occupied times, unoccupied times and preoccupancy times. During a power
failure, a built-in nickel-cadmium battery with a 15 year life shall maintain the time, program storage and LCD display for 150 hours, and the
SMC functions shall be de-energized. The change between daylight savings time and standard time shall be made with a ±1 hour button.
