36
Section 7:
Energy Management (LED Controller)
Using a Standard Pressure Switch for Purge Control
Many compressors come equipped with pressure switches
with extra contacts that can be utilised to switch off the
dryer’s purge when the compressor is in an unloaded state.
Unfortunately, many of these switches have significantly large
dead bands (difference between the load (on) and unload (off)
settings that in most cases cannot be altered). The amount of
air that can pass downstream, through the dryer, while the
compressor is unloaded must be taken into consideration as it
can be significant, especially if there is a large dead band and/
or large wet receiver.
Often, a stand-alone pressure switch is a better option
as it allows the user to adjust it independently from the
compressor’s pressure switch. When selecting a stand-alone
pressure switch, the smaller the dead band the better.
When using a stand-alone pressure switch, the dryer is wired
into the normally closed (LED Controller) or normally open
(DMC Controller) contacts on the pressure switch. When the
switch is actuated (at 100 psig in the example), the purge
shuts off until the pressure switch deactuates (at 95 psig in
example). The point at which the switch deactuates, may be
adjusted to suit the system.
If it is determined that the dewpoint drops to an unacceptable
level, the deactuation point must be increased. Please note
that with most standard pressure switches, the dead band is
fixed such that the activation and deactuation points move
together.
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.
Figures 7.3 and 7.4 offer an overview of the devices
mentioned as they might be connected for use in controlling
a dryer’s purge function. Please note the specific details
differ between device manufacturers, so in all cases the
manufacturer’s specifications should be adhered to.
Fig 7. 3 Standard pressure switch purge control (LED Controller)
36
PRODRY PD0046 - PD0360 Instruction Manual
|
Walker Filtration
|
Se ct io n 7:
Energy Management
Fig 7. 3 Standard pressure switch p
urge c ontro l (LED Controller)
Pressure Switch
(Field Installed)
* Normally Closed, open to turn purge off
LED Controller
Pin 1
(Puts out
+5 VDC
signal)
Pin 2
Signal Out to Switch
Signal Back
Fig 7.4 Standard pressure switch p
urge c ontro l (DMC Controller)
(Field Installed)
* Normally open, close to turn off purge
Pin 1
Signal Out to Switch (+24 VDC)
Pin 2
Signal Out to Switch
Signal Back
DMC
Controller
1
2
3
1
2
3
Using a standard pressure switch for purge control
Many compressors come equipped with pressure switches
with extra contacts that can be utilised to switch the
dryer’s purge when the compressor is in an unloaded state.
dead bands (d erence between the load (on) and unload ( )
settings) that in most cases cannot be altered. The amount of
air that can pass downstream, through the dryer, while the
compressor is unloaded must be taken into consideration as it
/
or large wet receiver.
Often, a stand-alone pressure switch is a better option
as it allows the user to adjust it independently from the
compressor’s pressure switch. When selecting a stand-alone
pressure switch, the smaller the dead band the better.
When using a stand-alone pressure switch, the dryer is wired
into the normally closed (LED Controller) or Normally open
(DMC Controller) contacts on the pressure switch.When the
switch is actuated (at 100 psig in the example), the purge
shuts until the pressure switch deactuates (at 95 psig in
the exampl
he point at which the switch
deactuates, may be adjusted to suit the system.
If it is determined that the dewpoint drops to an unacceptable
level, the deactuation point must be increased. Please note
that with most standard pressure switches, the dead band is
together.
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 7.3 and 7.4 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
N.C.*
N.O.
N.C.
N.O.*
Pressure Switch
Fig 7.4 Standard pressure switch purge control (DMC Controller)
36
PRODRY PD0046 - PD0360 Instruction Manual
|
Walker Filtration
|
Se ct io n 7:
Energy Management
Fig 7. 3 Standard pressure switch p
urge c ontro l (LED Controller)
Pressure Switch
(Field Installed)
* Normally Closed, open to turn purge off
LED Controller
Pin 1
(Puts out
+5 VDC
signal)
Pin 2
Signal Out to Switch
Signal Back
Fig 7.4 Standard pressure switch p
urge c ontro l (DMC Controller)
(Field Installed)
* Normally open, close to turn off purge
Pin 1
Signal Out to Switch (+24 VDC)
Pin 2
Signal Out to Switch
Signal Back
DMC
Controller
1
2
3
1
2
3
Using a standard pressure switch for purge control
Many compressors come equipped with pressure switches
with extra contacts that can be utilised to switch the
dryer’s purge when the compressor is in an unloaded state.
dead bands (d erence between the load (on) and unload ( )
settings) that in most cases cannot be altered. The amount of
air that can pass downstream, through the dryer, while the
compressor is unloaded must be taken into consideration as it
/
or large wet receiver.
Often, a stand-alone pressure switch is a better option
as it allows the user to adjust it independently from the
compressor’s pressure switch. When selecting a stand-alone
pressure switch, the smaller the dead band the better.
When using a stand-alone pressure switch, the dryer is wired
into the normally closed (LED Controller) or Normally open
(DMC Controller) contacts on the pressure switch.When the
switch is actuated (at 100 psig in the example), the purge
shuts until the pressure switch deactuates (at 95 psig in
the exampl
he point at which the switch
deactuates, may be adjusted to suit the system.
If it is determined that the dewpoint drops to an unacceptable
level, the deactuation point must be increased. Please note
that with most standard pressure switches, the dead band is
together.
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 7.3 and 7.4 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
N.C.*
N.O.
N.C.
N.O.*
Pressure Switch
