Optional Accessories - Domnick Hunter PNEUDRI DX102 Manuel D'installation, De Mise En Service Et D'entretien

7. OPTIONAL ACCESSORIES

A) Hygrometer
A ceramic moisture sensor based hygrometer can be integrated with the Desiccant Air Dryer to perform two main
functions. Firstly, on both Heatless and Heat Regenerative models, it can be used to constantly monitor the
outlet dewpoint of the dryer. Secondly, it can be used with additional hardware to control the dryer cycle. This
system is called 'Dewpoint Dependent Switching (DDS)'.
Hygrometer Operation
The hygrometer is located in an aperture within the instrumentation shroud.
Dewpoint in ˚C, ˚F or ppm(v) from the outlet can be continually read on the hygrometer liquid crystal display.
In addition to its ability to continuously monitor the delivered air dewpoint, the hygrometer also has the following
features:
Alarm Output
Single-pole, double-throw, voltage-free changeover contacts, suitable for switching up to 1A at 250V 50Hz non-
inductive loads. The signal can open or close a circuit at the pre-set alarm point depending upon the plug pins
selected. Adjustment of the pre-set alarm level is possible within the hygrometer.
*NB Consult the manufacturer's Service Department before attempting any adjustment.
Analogue Output
For connection to an external chart recorder or continual remote monitor a fully floating 4 to 20mA output is
provided, capable of feeding a maximum load impedance of 800 ohms. 0 to 10 V output is also provided. A
detailed manual is provided with each hygrometer.
B) Dewpoint Dependent Switching (DDS)
Because compressed air systems rarely operate at full capacity all of the time, when the dryer changes over
there is often spare drying capacity remaining in the bed about to undergo regeneration. This is the basis and
reason for operating Dewpoint Dependent Switching.
Using the hygrometer to monitor the outlet dewpoint, the drying cycle can be extended to fully utilise the drying
capacity.
In this way long periods of 'Energy Free Drying' are achievable and energy savings of up to 80% are considered
normal with greater savings possible in some systems.
For alarm outputs, refer to section 7A for additional hygrometer features.
For details of the Energy Management Dewpoint Dependent Switching (DDS) equipment for inclusion in new
product or to retrofit to your existing Desiccant Air Dryer unit, please contact your nearest domnick hunter
distributor or domnick hunter direct.
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