34
Heatless Desiccant Dryers
|
Instruction Manual
Section 7:
Energy Management
Using a hygrometer and process controller for purge control
The best option for purge control if the delivered dryness (pressure
Dewpoint) of the air from the dryer is critical. If the air is deemed dry
enough, then the purge can be shut off until the air’s moisture starts to
climb. If the purge is turned off, care must be taken to ensure that the
desiccant beds are not allowed to wet out too far before the purge is turned
back on. Also, after turning the purge back on, the air’s pressure Dewpoint
may increase a bit before starting to drop again. This should be taken into
consideration to ensure that the air flow remains sufficiently dry.
It is extremely important to understand that the purge may only be shut off
during periods of low or no demand. This feature, if used otherwise, can
result in permanent damage to the desiccant beds resulting in loss of drying
capacity and possibly mechanical failure. The cartridges must not be allowed
to become fully saturated at any time.
Figure 7.5 offers an overview of the device mentioned as it might be
connected for use in controlling a dryer’s purge function. Please note that
specific details differ between device manufacturers, so in all cases the
manfacturer’s specifications should be adhered to.
Making connections between a switching device & dryer Energy
Management contact
Cable / Wire Selection Criteria:
Selected wire should have:
At least 2 conductors. More conductors can be useful in the case of a
conductor break. Conductors can be swapped without having to run new
cable.
• A conductor gauge of no greater than 18 awg is recommended to fit
comfortably into the DIN connector insert.
• An outside diameter of no greater than 1/4” (6mm). Larger diameters do
not fit well into the cable gland of the EM DIN connectors.
• An insulation type compatible with the environment that it will be run in.
Figure 7.5: Process controller & hygrometer
38
Process Controller
Dewpoint
Transmitter
Relay
Signal
+VDC
COM
N.C.*
Se ct io n 7:
Energy Management
Using a hygrometer
and process controller for purge control
The best option for purge control if the delivered dryness
(pressure Dewpoint) of the air from the dryer is critical. If the
air is deemed dry enough, than the purge can be shut until
the air’s moisture starts to climb. If the purge is turned
care must be taken to ensure that the desiccant beds are not
allowed to wet out too far before the purge is turned back
on. Also, after turning the purge back on, the air’s pressure
Dewpoint may increase a bit before starting to drop again.
This should be taken into consideration to ensure that the air
It is extremely important to understand that the purge may
only be shut during periods of low or no demand. This
feature, if used otherwise, can result in permanent damage
to the desiccant beds resulting in loss of drying capacity
and possibly mechanical failure. The cartridges must not be
allowed to become fully saturated at any time.
Figures 7.8 and 7.9 er an overview of the devices
mentioned as they might be connected for use in controlling
d er between device manufacturers, so in all cases the
Making connections between a switching device &
dryer Energy Management
contact
Cable / Wire Selection Criteria:
Selected wire should have:
At least 2 conductors. More conductors can be useful in
the case of a conductor break. Conductors can be swapped
without having to run new cable.
•
•
A conductor gauge of no greater than 18 awg is
insert.
• An outside diameter of no greater than 6mm (1/4”).
EM DIN connectors.
• An insulation type compatible with the environment that
it will be run in.
Fig ure 7.8 : Process controller & hygrometer (LED Controller)
Fig ure 7.9 : Process controller & hygrometer (DMC Controller)
This setup is for example only. This configuration can be
ammended, depending on application.
DC Power
Supply
-VDC (COM) +VDC
+VDC
CO
M
Signal In Signal Ou
t
* Normally Closed, open to turn purge off
Signal Back
Signal Out
LED Controller
Pin 1
(Puts out
+5 VDC
signal)
Pin 2
1
2
3
Process Controller
Dewpoint
Transmitter
Relay
Signal
+VDC
COM
N.O.*
DC Power
Supply
-VDC (COM) +VDC
+VDC
CO
M
Signal In Signal Ou
t
Signal Back
Signal Out
Pin 1
Pin 2
Signal Out to Switch (+24VDC)
DMC
Controller
1
2
3
* Normally open, close to turn off purge
This setup is for example only. This configuration can be
amended, depending on application.
