Installation & Maintenance Manual
10
5. Connect Control Wiring
5.1. Controls Placement
A typical humidifier control system includes a wall or return duct sensor or controller, a high limit duct humidistat, and
an air proving switch. Placement of these devices is critical to proper operation of the overall system.
The return air RH sensor must always be located BEFORE any outside air intake, in order to insure accurate
sensing of the air from the space. Alternatively, a room RH sensor or humidistat can be used. Room sensors should
be located on an inside wall or post and should not be hit by any discharge air streams from ducts. In a 100% outside
air system, the RH sensor may be placed in the supply duct, at least 10 feet down stream of the distributor pipe to act
as both hi-limit and control.
The airflow switch must be positioned to accurately open on a loss of air flow, to prevent the humidifier from running
when there is no air to absorb the moisture.
The hi-limit humidistat must be positioned far enough down stream of the steam distributor pipe(s) to prevent it from
getting wet, but still allow it to accurately prevent overhumidification of the duct that could result in condensation.
5.2. Controls Wiring
The SD humidifier controllers are preprogrammed from the factory to operate either as On/Off (CDC), Proportional
from a control signal (CDP), or Proportional from a sensor input (CDH, CDD).
Wiring the CDC On/Off Controller:
The CDC controller is for On/Off control in response
to an external closed contact as from a humidistat or
DDC relay.
DO NOT apply voltage to any input on a CDC
controller.
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