Airtek 4087 Walden Avenue, Lancaster, NY 14086 TEL: (716) 685-4040 FAX: (716) 685-1010 E-MAIL: airtek@airtek.com WEB SITE: www.airtek.com
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E) Disconnected or Faulty Jumper Wire (Very rare) -
There is a violet jumper wire that runs from the
outgoing current on the low-pressure switch to
terminal 18 on the main dew point controller. This
terminal must see power at all times in order for
the unit to function. If the low-pressure switch
opens it severs power to terminal 18 and the unit
shuts down on “E6”, However if the jumper wire is
faulty or disconnected terminal 18 does not see
power and will shut down on a false “E6”. To check
remove power from the unit and check for continu-
ity through the jumper wire if there is none inspect
and/or replace wire. Reapply power. If the unit still
shows “E6” and the low-pressure switch has
checked good, the problem is in the board.
Diagnostic code “E7”
Shutdown on High Head PSI
*
Pressures referenced in this section refer to units
using R-22. For other refrigerants, please refer to
service tag for specifications.
If the discharge or “head” pressure of the dryer refrigeration
unit exceeds 350 psi it breaks contact through the high-
pressure switch. This in turn breaks power to the refriger-
ant compressor shutting it down for protection.
To correct this, 1. Bypass the compressed air around
the dryer. 2. Based on the size of the unit you will have
either manually resetting pressure switches, or a reset
through the control panel by pressing the mode selection
button off then on again after 10 seconds. If the condition is
not corrected you may have to repeat this step. If it contin-
ues after that, check the following probable causes:
A) Dryer Overload
This causes the freon to evaporate gas faster than the
compressor can remove it, thus raising the suction
and head pressures and the compressor discharge
temperature. Probable causes are:
1. High Ambient - Take a temperature reading at the
condenser, anything over 100ºF is no good.
2. High Compressed Air Flow - Compare HP or CFM
and run time to the rating of the dryer.
3. High Inlet Compressed Air Temperature - To test
take a temperature reading with an infrared
temperature gun on the inlet pipe. Remember
when taking a temperature reading off a steel pipe
you must add a minimum of 10º due to heat
dissipation off the steel itself.
B) Poor Condenser Performance
1. Fan or Fan Switch Failure - If the fan is not running
you could use a jumper wire to bypass the switch,
if your fan runs chances are the switch is faulty. If
the fan still does not run take an amp reading off
the wire that runs from the fan to the contactor, or
with power off physically try turning the fan blade, if
it does not turn the fan motor is bad.
2. Condenser Dirty - This restricts airflow, allowing
poor cooling. To correct this inspect condenser
coils for dirt build up, blowout dirt with com-
pressed air generally in an inward to outward flow.
3. Condenser Fans Recirculating Warm Air -Not
enough cool air makes the condenser unable to
provide enough cooling for freon. The liquid line
should be less than 20ºF over the ambient
temperature or inlet water temperature. Check to
make sure the unit isn’t pulling warm air from
another source, air compressor, air discharge
from after cooler or poor ventilation in room.
4. Restricted Air Flow to Condenser - If the intake to
the condenser is restricted it can not pull in
enough air to provide proper cooling. There should
be a minimum of 3' from any wall or structure in
order for the dryer to perform properly.
5. Non Condensables in the Refrig. System - If due
to a leak or improper recharging air or water was
introduced into the refrigeration system this would
cause high head pressure. To check this, examine
sight glass for air bubbles and a wet moisture
indication.
C) Freon Over Charge
To check this, use an infrared temp gun to measure
the level of freon in the liquid line receiver. You want to
see a level of 1/3 to 1/2 full. Anything more than this
could mean over charge. Another check would be to
compare the temperature at the liquid line in correla-
tion with freon pressure. (E.g. At a 100º R-22 freon has
a pressure of 195 psi.) See chart.
D) Water Cooled Condensers
1. Low Water Flow, Low Water Pressure-Higher than
this usually shows up as high delta temp. be-
tween the water in and water out. There is usually
a 15ºF approach across the condenser if it is
more; chances are you have low flow and/or
pressure. 25 psi of water pressure is the mini-
mum level to operate correctly.
2) Faulty Water Valve - This could restrict water flow,
thus not providing enough water to cool. The valve
could be restricted due to the use of dirty water.
Another possibility is a valve setting too high, thus
water flow is to fast and not enough heat exchange
across the condenser. This would show up as a
low differential for inlet and outlet temperatures.
3) Water Inlet Temperature - Maximum inlet water
temperature is 85ºF, anything higher than this
does not provide enough cooling.
E) Defective High Pressure Switch - The high-pressure
switch is set to trip or open electrically at 350 PSI of
refrigerant pressure. If the switch is out of adjustment it
could be tripping prematurely. The only way to deter-
mine this is to contact a refrigeration technician.
Pressures can be verified through manifold gauges. An
adjustment or replacement may be necessary.
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