base
A
15
IOM74 November 2020 R105
ambient compensation package. This option requires a modulating damper actuator and opposed blade
dampers.
ECONOMIZER
Economizer damper control will mix the return and outside air streams to achieve the required discharge air
temperature.
It is possible for the economizer to operate while in heating or cooling mode. While the display will show
either heating or cooling, the analog output to the economizer will be active until there is a heating (or
cooling) demand.
MINIMUM DAMPER POSITION
The minimum position setting is preset in factory and may be adjusted using a computer interface.
HIGH AMBIENT LOCKOUT
This feature is required in order to disable the economizer if there is no cooling available from the ambient air.
LOW LIMIT
Low limit, or freeze protection, may be enabled or disabled depending on application. Based on discharge air
temperature sensing, the low limit will disable unit operation if the temperature falls below 40°F (4°C). The
setpoint is not adjustable. The low limit bypass has 2 timers, the main bypass timer that occurs at initial
startup of the supply fan, and an anti-nuisance timer. The anti-nuisance timer has a duration of 30 seconds
and resets once the discharge temperature rises above the low limit setpoint. The main bypass time is 4
minutes for all types of equipment.
On variable air volume systems the main low limit bypass time is reset if the economizer minimum position is
suddenly increased by over 15%, or if the VFD speed increases by over 20%, both within 10 seconds.
The bypass time is reduced to 2 minutes if the heating has been disabled. The low limit is not active in cooling
mode.
HEATING
The base may control simple fluid based heating devices from the auxiliary heating 0-10Vdc output (MHW).
Expansion modules are necessary for gas fired heating to monitor and control the increased complexity and
safety requirements of gas fired equipment.
The MHW (Modulating Hot Water) output is a 0-10Vdc signal, with 0V=no heat and 10V=max heat, typically
associated with a hot water coil. Reversing function must be done at the actuator. A spring return actuator
would be required for applications desiring full open, full closed or full bypass when the equipment is off.
GAS FIRED HEATING
The base can directly control direct fired (HE) and indirect fired burners (DJ and DG). DJ burners will require
the CD-XM burner motor speed controller expansion module connected via an internal Modbus network.
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