Carrier |
Operating and Maintenance |
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29D |
Instructions |
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Automatic Water Strainer
Fig. 1 - Typical Automatic Water Strainer Installation
UNIT DESCRIPTION
The 29D Automatic Water Strainer cleans foreign matter from the return water of a Rotaspray® system. Figure 1 shows a typical installation.
OPERATING CYCLE
pan flushing sprays wash the foreign matter from the pan into a drain or a perforated collection basket. (The water drains from this perforated basket into a sump, and can be returned to the dirty side of the tank by a small auxiliary pump.) After the drum is cleaned of foreign matter, the water levels equalize, and the strainer stops after the timed operating cycle.
Water enters the open end of the strainer drum and passes outward thru the perforated skin. For eign matter is screened out of the water, and covers the inside surface of the drum causing the water level to rise on the dirty side of the tank. The water level on the clean side rises until it reaches the height of the high side electrode A (Fig. 2). This sets the strainer into operation. The drum begins to rotate and the drum flushing sprays are turned on. The dirty portion of the drum passes under the sprays, and foreign matter is flushed from the drum into the sludge pan. The
When the water falls below the low side elec trode B level (Fig. 2) the strainer starts to pro tect the pump suction when:
1.The "Rotaspray" units evaporate water, caus ing the water level on the clean side to drop without a corresponding rise in water level on the dirty side.
2.Changes in the system water flow requirements suddenly drop the water level in the clean side of the tank.
3.The high side electrode fails to operate.
I Carrier Corporation 1967 |
Printed in U.S.A. |
12-67 |
29D-1SO |
f
CONTROL CIRCUIT
Automatic Operation - The water strainer con trol circuit (Fig. 3) consists of a timer and level controller. The control circuit is wired thru an auxiliary contact on the recirculated or chilled water pump starter. If the fused disconnect switch is closed, the control circuit is activated when the pump starts. The strainer is then controlled automatically by the high or low side electrode. When either electrode is energized, the control circuit is completed. This starts the drive motor,
opens the spray |
water solenoid valve, |
and trips |
the timer. |
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Normally, as |
the strainer begins to |
operate, |
the water levels begin to equalize, de-energizing the electrode. However, the timer contacts remain closed for the preset timed cycle to maintain strainer operation. The length of the timed cycle can be adjusted to suit job requirements. At the end of the timed cycle, the timer contacts open. This normally stops the drive motor, and closes the spray water solenoid valve. However, if the tank water level is too low, the low side electrode will maintain the makeup valve open for several minutes, until the water level rises enough to de energize the low side electrode.
Manual Operation - A momentary contact switch is provided to bypass the automatic tank level con troller and operate the water strainer for one timed cycle. This switch permits operation of the strainer when the water pump is shut down.
II0-I-60
Cl |
S2 - Makeup Wtr Solenoid Valve |
^2 - Relay Coi Is |
TM - Timer Motor |
MSI - Strainer Motor Starter |
TR — Timer Relay Coil |
PB — Push Button |
o - Terminals on Components |
SI - Spray Wtr Solenoid Valve |
0 — Terminals on Terminal Strip |
Fig. 3 - Elementary Control Circuit
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