LOW VOLTAGE CONTROL WIRING
Figure #9
External Wiring of On/Off Controls
A
B 
C 
EXTERNAL
8 | 10 |
INTERNAL
Controls are available from NORTEC as accessories. If controls were not ordered with humidifier, they must be purchased supplied by others. The following 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. Caution: this is the “hot” wire from the 24V control transformer; it will blow the 3A fuse if any control field wiring touches ground metal.
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
flow, break when no air flow. Used as a safety to prevent saturation when no air flow.
1.NORTEC 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. 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
4.Mount duct
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)
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
3.Modulation (continuous control) by others for use with NHMC/NHP Series humidifiers involves one of several control wiring diagrams. In all cases, modulating signal interfaces through control terminal strip to main pc board inside humidifier.
4.The modulation signal must increase from minimum toward maximum as sensed RH (actual RH) drops below desired RH (%RH setpoint). In response, humidifier’s steam output will increase from minimum toward maximum. When humidifier’s steam output (lbs/hr) matches humidification load (lbs/hr), modulation signal will stabilize.
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