18063 Rev E 06/17
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Environmental Technology, Inc.
Model EDH–4 Rev E Installation and Operation Manual
OPERATION
Control
The EDH–4 makes use of a single switch called the Mode selector [MODE]. This is located just below the
PRESSURE LED display window (Figure 6). [MODE] allows the user to
• switch between English/imperial and metric units (press and hold [MODE]; metric displays “.”)
• display the percentage of desiccant remaining (quick press on and off)
• desiccant timer re-set (power off, press and hold during power up).
Information Display
The front panel’s “PRESSURE” display, a pair of seven-segment LED characters, reports pressure and
status information.
The default display reports the air pressure level passing through the unit. Pressure may be displayed in
either the default English customary units (hundredths of psig) or SI metric (mbar) units.
The display units may be switched by pressing and holding [MODE] for five (5) seconds. When units are
set to English, the unit displays “
99
” for 0.99 psig, the maximum displayable pressure in English custom-
ary units. The maximum displayable pressure in SI units is 99 mbar, displayed as “
99
.
”–
the decimal point
displayed to the lower right of the numerals indicates mbar mode
.
To assess the Percentage Desiccant Absorption Capacity remaining, quickly press and release [MODE].
The LED displays some number “
nn
” where
nn
is 2-digit percentage of absorption capacity. “
99
” = 99%/
new desiccant/full capacity ; “
51
” is 51% capacity (and so
forth); “
00
” = 0% left /desiccant regeneration required.
The LED display is used with [MODE] to reset the desic-
cant timer. Hold [MODE] during power-up; after LED initializa-
tion, the display reports “
99
”; release [MODE] to continue
normal operation. [Note: What is actually measured is sim-
ply the number of hours the compressor is running. This is
somewhat correlated with how much useful time is left to the
desiccant. The software is written with the assumption that
moist air moves through the EDH–4; if the relative humidity
is low, the desiccant may last longer.]
In the event of an alarm condition, an alarm code will be
displayed. See Table 1. If no alarm conditions exist, only the
system pressure will be displayed.
Figure 6.
PRESSURE
display window,
MODE switch
Table 1.
Alarm Codes
DISPLAY
ALARM
LP
Low Pressure
LE
Leaky System
CD
Change Desiccant
HF
Verify electronic enclosure
temperature > 5°C
un
EEROM unknown
(uninitialized or corrupted)
CA
uncalibrated