Control Installation, Controls see Figure #28

information is relevant to all controls, factory supplied or otherwise.

A, B and C (described below) are to be wired in series (only one path for current) across terminals 8 and 10 on the low voltage control terminal strip, or replaced with a jumper wire for constant operation (see Figure #27). Caution: If any control field wiring touches ground metal unit, safeties will be bypassed.

A - Wall or Duct Mounted Control On/Off Humidistat: Wired to make on drop in humidity, break on rise to setpoint. Set to desired % RH. Can be a make/break set of contacts from a Building Automation System.

B - Duct Mounted Safety High Limit On/Off Humidistat (if used): Wired to make on drop in humidity, break on rise to safety setpoint. Set to approximately 85% RH as a safety to help prevent saturation and wetting in the duct.

C - Duct Mounted Safety Air-Proving On/Off Switch (if used): Wired to make when sensing air flow, break when no air flow. Used as a safety to prevent saturation when no air flow.

1.Liebert offers various versions of A, B and C to suit each application. In general, A is essential, whereas B and C are highly recommended in ducted applications.

2.Field wiring from humidistat to humidifier and between devices should be 18 AWG or heavier and kept as short as possible.

3.Low voltage control terminal strips are provided in the electrical compartment. Internal sides are factory wired. External sides are to be field wired.

4.Each humidifier is supplied with a wiring diagram inside.

CONTROL INSTALLATION

1.Mount any wall humidistat (control or high limit) over standard electrical box at height similar to typical thermostat. Any wall humidistat should be in location representative of overall space being humidified and not in path of blower pack or air supply grille. Do not mount on a outside wall where temperature fluctuation can affect control response.

2.Mount duct humidistat in location representative of overall air humidity, usually return duct. Do not mount it directly in front of steam distributor or in turbulent or mixing zone

or down stream from distributor. Mount it where air’s humidity and temperature are uniform and representative of spaces being humidified.

3.Mount duct high limit humidistat downstream of steam distributors far enough that, under normal humidity and air flow conditions, steam will have been fully absorbed (typically at least 10 feet). It must be located to sense high humidity only when uniform and representative air is over-humidified or approaching saturation.

4.Mount duct air-proving switch so that it is able to sense air flow or lack of it. Wire it to make when air flow is sensed and break when air flow fails. Mount prior to distributor.

5.Check operation of all on/off controls before starting humidifier.

6.Calibration of controls (on/off or modulation) in the field may be necessary due to shipping and handling. Verify humidistat accuracy before commissioning system.

OPTIONAL MODULATION (CONTINUOUS

CONTROLS) (see Figure #28)

1.Read on/off controls section first since it is necessary to all control systems.

2.Virtually any modulation (continuous control) external hardware by others (as long as it has %RH setpoint circuitry) may be interfaced with pre-specified factory-configured SGH pc board via the control terminal strip.

3.Modulation (continuous control) by others for use with SGH humidifiers involves one of several control wiring diagrams. In all cases, modulating signal interfaces through control terminal strip to main pc board inside humidifier.

Figure #26

Typical Modulation Wiring

Varies With Each

Modulation Option

See Liebert Supplied

External Wiring Diagram

External

Internal

_ y

- 10 -