Are freezestats (low limit switches) provided with the Magic Aire Unit Ventilators?

All Magic Aire unit ventilators with Hydronic Coils include an automatic reset,  single-pole, double-throw low limit switch that changes state at 38°F and 42°F.  This is mounted on the leaving side of the coil (heating coil for 4-pipe).  The hydronic low limit is marked as LLT on the unit’s wiring diagram.

All Magic Aire unit ventilators with DX coils include an automatic reset,  single-pole, double-throw low limit switch that changes state at 28°F and 35°F.  This is mounted on the leaving side of the coil.  The DX low limit is marked as LLR on the unit’s wiring diagram.

Both low limits are snap-acting SPDT devices, with terminal 2 as the common.  Terminal 3 closes on temperature rise and Terminal 1 closes on temperature fall.

Low Limit wiring

Are Magic Aire Unit Ventilators DDC Controls stand-alone or must they function as part of a building automation system (BAS) network?

Units with factory DDC Controls can act as stand-alone or function as part of a building automation system (BAS) network that must be field provided.

Some features to note about both the Lon and BACNet Factory DDC control packages :

• The dual-mount thermostat is provided and factory mounted in the unit for setpoint adjustment and diagnostics
• Unit Wiring Harness and 40 VA, Class 2, 24V transformer provided and factory installed
• Fan start/stop relay provided w/3-speed manual fan switch provided and factory installed
• DX relay (Dry contact) to start/stop condenser (w/DX coils) provided for field installation
• Outdoor Air and Supply Air Temperature sensor factory installed
• Return Air Temperature Sensor provided and factory installed (*not included with IAQ sequences)
• Low Limits (LLT/LLR) factory provided and installed (as needed)
• Optional Valve and Damper actuators facotry provided and installed
• Optional occupancy control are None, day/night relay, 7-day time clock, PE switch, or order *IAQ input with the controls option

* When the IAQ option is ordered an input is made available on the DDC Controller for a field supplied CO2 sensor by removing the RAT sensor and using the wall thermostat as the room air sensor.

For more information, see the UV Controls Presentation and Operation Manuals

Can I add a day/night relay or timeclock in the field to my MAU unit with factory supplied controls?

Yes.  Part numbers are MA40UV-DNR1 and MA40UV-TCO, respectively.  These assemblies include the needed wires for connecting to the controller.

Can order a Thermostat only to control my unit ventilator?

No, Magic Aire utilizes ASHRAE cycle II which requires modulating the unit ventilator’s outside air/ return air damper.   While some thermostats allow you to program the unit ventilator’s damper control  through the economizer feature, they do not allow modulation but control damper to maximum open or closed position.

Does the Magic Aire unit ventilator two pipe units have a changeover switch (aquastat)?

The changeover (aquastat) switch is factory wired to the DDC controller as shown on the unit wiring diagram.  During installation in the field, this switch must be clamped onto the pipe supplying water to the unit upstream of the valve.  See the unit ventilator IOM for more details.

For Magic Aire unit ventilators, how many stages of Electric Heat are there?

Electric Heat stages are assigned according to the number of elements of electric heat.  1 Element = 1 Stage; 2 Elements = 2 Stage; 3 or more Elements = 3 stage.

How are the Magic Aire Unit Ventilators protected from freezing?

A low limit thermostat (freezestat) is factory installed on all Magic Aire Unit Ventilators with Hydronic and DX coils.  For extra freeze protection, a face and bypass damper is recommended to protect from coil freeze-up. With a face and bypass damper there is a constant flow of hot water through the coil unlike a valve system.  The units feature a one piece Outside Air / Return Air damper that is made of heavy gauge extruded aluminum material with airtight seals to prevent unwanted air from entering the unit. The damper is insulated with closed cell foam insulation.  An optional cold weather damper section is also an option that has thicker insulation for maximum cold weather protection. With DDC Controls, if the low limit thermostat trips the outdoor air damper will be driven closed.

How do I calculate control valve pressure drop if I know Cv and flow rate?

PD = ((Q*√G)/Cv)2

PD = water pressure drop across control valve, psig
Q = water flow rate in gallons per minute
Cv = flow coefficient
G = specific gravity of fluid(1.0 for water)


I have a DDC Control Package with a Controller and MN-S4 Thermostat. Can I wall mount the MN-S4 Thermostat? And, how do I control multiple unit ventilators from one thermostat?

The MN-S4 Thermostat can be wall mounted.  See MNL or MNB Control documentation for installation details.  The MN-S4  thermostat is not set up to control more than one unit directly.  One possible solution is to contact a Controls contractor for a field installed and configured network.

If the DDC Controls are provided by an outside controls contractor, can they be mounted at the Magic Aire factory during unit assembly?

Magic Aire’s team has vast experience working together with Sales Offices and Control Contractors to customize a Control Package that will fit Customer’s specifications. Our team of Design Engineers and Product Managers will work directly with your team to ensure we are designing to your Customer’s expectations.  During the recent peak seasons, our team has coordinated and shipped dozens of custom jobs.  We have mounted and wired field supplied DDC Controllers, actuators, sensors, and thermostats plus the parts necessary to support the required control scheme , such at resistors, jumper combs, and relays.
This is almost “anything goes” option within the confines of available physical space and safety codes.

Is a CO2 sensor available for demand control ventilation?

The Magic Aire Lon controller (MNL) and BACNet controller (MNB) are setup to accept a field provided and installed CO2 sensor with our IAQ sequences.  There is an extra IO point on the controller for the field installed CO2 sensor.  Special IAQ sequences of operation are available when using a CO2 sensor.  When ordering with New Magic Software, choose the IAQ seqence within the Temperature Control selections.

My Magic Aire Unit Ventilator DDC controller is not functioning, and the red light is blinking. Does the controller need replaced?

If the red light on the MNL or MNB DDC Controller blinks at a rapid rate, the control board has a hardware failure and must be replaced.  If the red light blinks about once a second, the board is functional but the information programmed at the factory has been deleted. Please contact your Magic Aire Representative for replacement and reprogramming options.

My Magic Aire Unit Ventilator has factory installed DDC Controls, but I can not bring on the condensing units. Is there something wrong with my Controller?

For units with DX coils and Magic Aire DDC Controls, Magic Aire provides a relay that is to be field connected to the remote field supplied and installed compressor/condenser. Magic Aire’s control transformer is only to be used for factory supplied equipment. A separate transformer must be field supplied for field supplied equipment such as compressors.  See unit wiring diagram for wiring details.

My Magic Aire Unit Ventilator has field provided DDC Controls with a factory provided ECM Motor. Is there any problem shutting the unit off and on by its line voltage?

Yes.  The ECM Motor has large capacitors in the electronics section.  When the incoming power is cycled on/off, these capacitors are stressed. Starting and Stopping the motor by engaging/disengaging line voltage will significantly reduce the life of the motor.  The proper way to start/stop the motor is to break the 24V control supply to the motor.

What does the DDC READY package consist of?

The DDC Ready Package consist of terminal blocks mounted on a hinged panel (shown below), a wiring harness (shown below),a 75VA control transformer, and a fan start/stop relay with a 3 speed fan switch (not included with variable speed motor option).  The following are provided when applicable: a DX Relay and low limit; and/or a water low limit; and/or an outside air damper actuator (shown below); and/or a face and bypass damper actuator.

DDC Ready

What does the factory DDC Control Package consist of?

The factory supplied and installed DDC Control Package consists of a DDC Controller with a selection of Lon or BACNet protocol which is mounted on a hinged panel(shown below).  The package also includes a dual mount thermostat (shown below), a terminal block, temperature sensors, a wiring harness, a 75VA control transformer, and a current switch.  The following components are included when applicable: a DX Relay, and/or a low limit, and/or an outside air damper actuator, and/or a face anc bypass damper actuator.

DDC Controls

For more information, see the UV Controls Presentation and Operation Manuals