How to Link Multiple Aerators
Once a farm grows past one pond, aerators multiply. The common shortcut is to wire them all to one circuit and switch everything on together — which wastes power and hides the fact that oxygen is uneven across the pond. The correct approach is zone by aerator group, bring them in stages by measured oxygen.
Why "all in parallel, all on together" fails
- Wasted power — oxygen differs across the pond: the windward side may already be at 6 mg/L while a sheltered dead corner sits at 3.5 mg/L. Running everything serves zones that do not need it.
- Hidden problems — with everything running you cannot see which zone was actually short of oxygen, so bottom treatment and feeding adjustments lose their evidence base.
- Inrush current — several motors starting at once concentrate surge current on the distribution and contactors; staged starting is gentler.
- Failures stay invisible — a welded or burnt contactor is undetectable when everything runs anyway. Only zoned control turns "this group did not start" into an alarmable event.
Step one: zone by aerator group, one DO point per zone
Rule: each aerator group needs a representative dissolved oxygen point. On large ponds a single probe cannot stand for the whole surface — shape, wind and feeding points all create uneven oxygen.
- Long, narrow pond: split by upstream/downstream or bank into 2~3 groups, one probe each.
- Large square pond: zone by each aerator's water-circulation coverage; make sure dead corners are not probeless.
- Shrimp ponds: besides planar zoning, add one probe at a second depth — shrimp are bottom dwellers.
Step two: bring groups in stages
| Trigger (measured DO in a zone) | Action |
|---|---|
| Falls below the warning line (e.g. 3 mg/L) | Start that zone's aerator group first |
| Keeps falling and a neighbouring zone nears its warning line | Bring in adjacent groups one by one, minutes apart |
| Whole pond below the danger line (e.g. 2 mg/L) | Start all groups — emergency aeration |
| Recovers into the safe band and holds | Exit in reverse order of start-up |
Step three: how grouping combines with VFD speed control
Grouping answers "which units"; a VFD answers "how fast". Together they make a complete system:
- Grouping + fixed speed — only decides on/off; once started the unit runs full speed, so waste remains.
- Grouping + VFD — bring groups in by zone, then modulate speed by that zone's measured DO (below 3 mg/L full 50 Hz, 3~5 mg/L about 35 Hz, 5~6 mg/L about 20 Hz, above 6 mg/L standby).
- Size each VFD with 15%~20% power headroom (e.g. 2.2 kW VFD for a 1.5 kW aerator) and use IP65 protection outdoors.
How one output drives several aerators
Take the Kantangren TK-R12-SC4S-BG twelve-channel control board as an example: three-phase U/V/W × 4 groups = 12 high-current relay outputs, usable on both 380 V three-phase and 220 V single-phase ponds. Each output drives one aerator or one group through a contactor; "zoning" simply means wiring the aerators of one zone to the same output.
How many units one output can carry depends on that channel's rated current and the aerator power — parallel connection must be sized by current, not by counting units. That is why a site survey first records each aerator's power and the distribution capacity before a zoning plan is drawn.
Three practical recommendations
- Place probes before you zone — without per-zone DO data, zoning is guesswork.
- Run one full cycle before finalising — 24 hours × a production cycle shows which zones consistently go hypoxic first.
- Alarm on "commanded but not started" — if the board commands a start and the current does not rise, a contactor or aerator has failed. That is more dangerous than simply not running, because it fails silently.
FAQ
- Should multiple aerators run together or be controlled separately?
- Zone them and bring them in stages by measured oxygen. Running everything at once wastes power and hides uneven oxygen across the pond; staged starting also reduces the inrush current of several motors starting simultaneously.
- How should aerators be zoned?
- By aerator group with one measurable DO point per zone. Long narrow ponds split into 2~3 groups by axis or bank; large square ponds zone by each aerator's circulation coverage, making sure dead corners are covered; shrimp ponds should add a second probe at a different depth.
- How many aerators can one controller output drive?
- The Kantangren TK-R12-SC4S-BG twelve-channel board provides three-phase U/V/W × 4 groups = 12 high-current relay outputs for both 380 V and 220 V ponds. Each output drives one aerator or a group through a contactor; capacity depends on the channel's rated current and aerator power, so parallel connection must be sized by current rather than by counting units.
- How does grouping relate to VFD speed control?
- Grouping decides which units to run; a VFD decides how fast. Grouping with fixed speed only decides on or off, while grouping with a VFD brings zones in stages and then modulates speed by that zone's measured DO, improving both safety and energy use.
- What failure do multiple aerators hide most often?
- Silent failure: the controller commands a start but the current does not rise, meaning a contactor or aerator has failed. Everything running at once hides this; zoned control with a 'commanded but not started' alarm catches it.
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