Table 2-1. Direct Support Troubleshooting Guide (Continued)
TEST OR INSPECTION
Backwash cycle problems. (Also, see automatic valve troubleshooting if problem is valve cycling).
Electrical high voltage can cause serious injury or death. Some tests performed in
troubleshooting require power to be connected, Always take proper measures to ensure
Ensure that all circuit breakers are set. Refer to electrical drawings in Appendix D.
There are four distinct electrical phases to the media filter backwash cycle and the
troubleshooting will be broken down into these phases to eliminate unnecessary steps.
Since these phases are cascaded each part of the cycle must be accomplished before
the next one starts, Determine which part of the cycle is not operating correctly and then
start troubleshooting at that part of the cycle. If nothing happens when backwash is
initiated, start at phase 1.
Phase 1: The media filter flush valve opens and the pressure in the media filter pushes
the water out until the water level reaches the bottom switch on the media filter
level assembly. The media filter pressure switch (PSL8) (REF: Interconnection
diagram FO-2, Sheet 14), located on the back of the control panel, monitors
the pressure in the filter and closes when the pressure is above 3 psig. The
closing of the level and pressure switches allow phase 2 to start.
Phase 2: The raw water pump starts running and the backwash air solenoid opens
which puts air into the bottom of the media filter. The backwash chlorine
pump also starts pumping chlorine into the media filter. Time TDK2 (REF:
Interconnection diagram FO-2, Sheet 8) controls the length of time (1.5-2
minutes) air is allowed to enter the filter. When it has timed out, the backwash
air solenoid valve closes and phase 3 begins. Typical air consumption during
this phase is 300-500 pounds as indicated on the air system high pressure
Phase 3: The boost pump starts running and time TDK3 (REF: Interconnection
diagram FO-2, Sheet 8) starts timing. When it has timed out (about 10
minutes), the raw water pump and the backwash chlorine pump shut down
and phase 4 begins.
Phase 4: The clean/flush tank outlet valve opens and clean water is flushed through the
filter by the boost pump. Timer TDK4 (REF: Interconnection diagram FO-2,
Sheet 8) starts timing the length of the clean water flush. When it has timed out
(1 .5-2 minutes), the boost pump shuts down and the backwash complete
alarm sounds. The clean/flush tank level switch (LSL1) (REF: Interconnection
diagram FO-2, Sheet 14) monitors the level of water in the tank during this
phase of the cycle and shuts the boost pump down if the clean/flush tank
water level drops too low. The optimal time setting on TDK4 shuts the boost
pump down just prior to the level switch (LSL1) shutting down the boost
6. Timer problems.
Check that the times are set properly before doing backwash cycle troubleshooting. Shut down the ROWPU and open
the control panel. The outer pointer on TDK2 should read 1 minute 36 seconds, TDK3 should read 10 minutes, TDK4
should read 1.5 minutes. The inner pointer on each timer should read the same as the outer pointer.