base
A
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IOM74 November 2020 R105
SH / SHX HUMIDIFIER
BASIC OPERATION
The base SH(X) humidifier controller version controls the operation of SH and SHX series gas fired humidifiers.
This includes tank water fill and drain and burner control. On a call for humidification the tank first fills with
water, then the burner gas-fired heat is enabled to produce steam. Water level is controlled by the water
level probes. Water quality dictates the minimum tank drain cycle times. Drain temperature is monitored and
cooled with the supply water if required. SHX have a secondary side tank for improved efficiency. These use
an additional fill valve for the side tank.
Control may be independent, with an internal setpoint (viewed from the interface screen) that may be
adjusted to the desired relative humidity setpoint (RH%). The base may also accept a 0-10Vdc control signal
into terminals W+/-. This input signal may be factory configured to be either setpoint only (0-100% RH), or a
direct command signal to enable the gas section of the humidifier to fire from 0 to 100% (full output). Input
signal below 0.4Vdc will disable humidification.
Direct control should only be used in conjunction with a front-end control system that has an existing humidity
sensing system.
On initial startup, with a demand for humidity, the SH will go to high fire for a timed event to raise the water
temperature to at or near the boiling point.
Never install the RH sensor in the discharge duct of an appliance. Relative humidity is relative to the
surrounding air temperature, which must be stable. Only install RH sensors in the return duct or in the room
being served.
S-XM TIMING
Dump Schedule (ppm of calcium
carbonate – pre-programmed)
0 ppm = No dump unless triggered by input (below).
Less than 60 ppm = 30 hours
60 – 119 ppm = 20 hours
120 – 179 = 15 hours
180 or greater = 10 hours
Drain initiation contact (OCC)
EnH
Drain initiated 30 seconds after terminal power loss
Drain time
SH240 and smaller = 20 minutes
SH400 and larger = 40 minutes
Improper gas valve wiring alarm
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