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Pentair Com Port Expansion Module | 520818

Pentair SKU: 520818
Pentair Com Port Expansion Module | 520818 - Pool Automation - img - 1

Pentair Com Port Expansion Module | 520818

Pentair SKU: 520818
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Pentair Serial COM Port Expansion Board Kit (Adds RS-485 Communication Ports) | 520818

The Pentair 520818 is a Serial COM Port Expansion Board kit used to add additional RS-485 communication ports to compatible Pentair pool/spa automation systems. It’s commonly installed when you need more connection points for equipment such as variable-speed pumps, salt systems, heaters, or other RS-485 devices that communicate with the control panel.

Key Features

  • Adds more COM ports: expands available RS-485 connection points for supported automation systems.
  • Helps eliminate “no open COM port” issues: useful when adding devices to an already-populated controller.
  • Clean install: mounts inside the control enclosure using the included brackets and hardware.
  • Includes 12" (1 ft) cable: pre-made interconnect cable to link the expansion board to the automation system.
  • OEM Pentair kit: designed for correct fit, wiring layout, and long-term reliability.

Compatible Systems

  • Pentair EasyTouch automation systems
  • Pentair IntelliTouch automation systems
  • Select ComPool / TimeMaster / LX-10 power center automation applications (where specified)

Tip: Compatibility can vary by system revision and configuration. Confirm your automation model and wiring layout before ordering.

What’s Included

  • (1) Serial COM Port Expansion Board (multi-terminal RS-485 expansion PCB)
  • (1) 12" (1 ft) 4-conductor cable assembly
  • (2) Mounting brackets
  • (4) Mounting screws

Common Uses

  • Adding a second (or additional) RS-485 device when all existing COM ports are already in use
  • Expanding automation to control more equipment (pump, salt system, heater interface, accessories)
  • Replacing a damaged or corroded COM expansion board inside an automation load center

Installation Notes

  • Power off first: shut off all power to the automation panel at the breaker before opening the enclosure.
  • Mount the expansion board securely with the included brackets and screws to prevent vibration-related connection issues.
  • Route the included cable cleanly and keep low-voltage communication wiring separated from high-voltage conductors when possible.
  • Use correct polarity/terminal labeling for RS-485 connections and tighten terminals securely (loose terminals can cause intermittent comm faults).
  • Automation wiring should be performed by a qualified pool professional or electrician.

Troubleshooting Notes

  • Intermittent communication: check terminal tightness, wire strain, corrosion, and correct RS-485 polarity.
  • No device detected: confirm the device is RS-485 capable, wired to the correct terminals, and enabled/configured in the automation settings.
  • Multiple devices offline: inspect the shared communication bus, look for pinched cables, and verify there are no splices with poor connections.

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Maintenance Tips

  • Once per season, inspect low-voltage terminals for corrosion and confirm all screws remain snug.
  • Keep the automation enclosure dry and properly sealed to reduce corrosion on boards and terminals.
  • If you service wiring, label each RS-485 cable to prevent mix-ups when adding future devices.
  • Avoid running communication wires tightly alongside high-voltage conductors to reduce interference.
Questions about returns? View our return policy.

Hours Of Operation: 

Monday - Friday: 8:00 am to 4:00 pm Phoenix Time

Saturday and Sunday: Closed

  • Orders costing more than  $300 WILL be required to have signature confirmation upon delivery.
  • Handling time is typically only 1 day.   
  • Any item ordered after 1pm Phoenix time, may not ship same-day.
  • Call us if you require expedited shipping and we can give you quotes based on your needs.

Return Policy:

  • All products, except as noted below, are eligible for return up to 30 days after receipt of item.
  • For returns, an RMA form must be filled out HERE or customers can call for additional help.
  • Shipping costs will be deducted from all returned items.
  • Any item that is missing accessories, original packaging, or is not returned in the same condition that it was received in, may be subject to a re-stocking fee up to 100% based on the condition we receive it in. 
  • Items broken, damaged, or inoperable due to installer error will not be refunded.
  • Fill out the return form or give us a call to obtain an RMA and return shipping label.
  • There are no returns on the Pentair Colorsync 618031
  • No returns on pool cleaners.
  • No returns on opened seals and o-rings.
  • No returns on capacitors.
  • If a light is returned because it "doesn't work" and it tests fine, the cost to ship and a re-stocking fee will be deducted from the refund.
  • All products denied upon arrival at customers house WILL be charged the cost to ship.
  • Visa Gift Card Promotions: Gift cards are sent within 14 days of the order. When accepting the Visa Gift card, you agree that if your order is returned or refunded, this amount will be deducted from the refunded amount. All Visa Gift cards are sent via email in an E-Gift Card format and are non refundable.
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