Bard MC4000 installation instructions Humidity Control Option

HUMIDITY CONTROL OPTION

Note: This function is not available if controller is configured for heat pump.

The standard air conditioning system can be adapted to perform dehumidification control by addition of a simple humidity controller that closes-on-rise, and is connected to terminals H1 and H2 on the main controller board. Recommended Bard Part #8403-038 (H600A 1014). Both HVAC units must be equipped with electric heat for this sequence to work properly. See appropriate connection diagram - Figures 1 - 12 for this connection:

1.Temperature control always has priority over dehumidification. If there is any stage of cooling demand active, the dehumidification sequence is locked out.

2.If all stages of cooling are satisfied, and relative humidity is above the set point of humidity controller:

a.The green “Dehumid. Operation” light will come on, and the lag unit compressor and blower will operate until the set point of humidity controller is satisfied (or cancelled by a call for cooling).

b.If the space temperature drops to 67F, the electric heater of the lead unit will cycle to help maintain building temperature. It will cycle off at 69F.

c.If space temperature drops to 64F, the Stage 2 Heating light will come on and the lag unit compressor operating for dehumidification mode will cycle off until the building temperature rises above 65F from 1st stage heat and building load. The green “Dehumid. Operation” light stays on during this sequence, and when Stage 2 Heating light is Off, the compressor is On. The electric heater in lag unit is locked out in dehumidification mode.

Lag unit outputs G, Y1 and Y2 are all switched on during dehumidification sequence. This is true for both alternating and non-alternating controller configurations.

CAUTION

Humidity controller set point should be in 50-60% relative humidity area: Setting controller to lower settings will result in excessive operating time and operating costs for the electric reheat, and in extreme cases could cause evaporator (indoor) coil freeze-up if there are periods of light internal equipment (heat) loading.

COOLING OPERATING SEQUENCES FOR ALTERNATING LEAD/LAG/LEAD/LAG CONFIGURATION

1.1-Stage Compressor Units No Economizer

1st stage cooling set point is the setting (SP) input into the controller. Factory default is 77F (25C). On a call for cooling the blower of the lead unit will come on immediately (if not already on – See Blower Operation), and the Stage 1 LED will blink for 10-seconds before going solid, at which time the compressor will start.

2nd cooling set point is 4F (default setting, user selectable 2-6F) warmer than Stage 1. On a call for 2nd Stage cooling the blower of the lag unit is turned on (if not already on – See Blower Operation), and the Stage 2 LED will blink for 10-seconds before going solid, at which time the compressor will start.

3rd and 4th stages are functional outputs but there is nothing to be controlled.

2.2-Stage Compressor Units No Economizer

1st stage cooling set point is the setting (SP) input into the controller. Factory default is 77F (25C). On a call for cooling the blower of the lead unit will come on immediately (if not already on – See Blower Operation), and the Stage 1 LED will blink for 10-seconds before going solid, at which time the lead unit compressor will start in compressor Stage 1 partial capacity operation.

2nd cooling set point is 4F (default setting, user selectable 2-6F) warmer than Stage 1. On a call for 2nd Stage cooling the blower of the lag unit is turned on (if not already on – See Blower Operation), and the Stage 2 LED will blink for 10-seconds before going solid, at which time the lag unit compressor will start in compressor Stage 1 partial capacity operation.

3rd cooling set point is 2F (default setting, user selectable 2-3F) warmer than Stage 2. On a call for 3rd Stage cooling the Stage 3 LED comes on solid (no delay), and the lead unit compressor will switch to compressor Stage 2 full capacity operation.

Manual	2100-563C
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