Pentair Com Port Expansion Module | 520818
Pentair
SKU: 520818
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.
Related Products
- Search Aqua Pool Supply for 520818
- Pentair EasyTouch parts
- Pentair IntelliTouch parts
- Pentair IntelliFlo RS-485 pump parts
- Pentair IntelliChlor parts
- RS-485 communication cable & accessories
- Pool automation accessories
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: 7:00 am to 5:00 pm Phoenix Time
Saturday: 8:00 am to 2:00 pm
Sunday: Closed
- We do not ship on Saturday or Sunday.
- Orders totaling more than $300 will require signature confirmation upon delivery.
- We process and prepare orders for shipment within 1 business day. Please note that many other pool supply retailers require 3–5 days of handling time before shipping.
- Orders placed after 1:00 pm Phoenix Time may not be eligible for same-day shipment.
- Expedited shipping options are available at checkout.
Return Policy:
- Products that are received damaged will receive a refund in store credit.
- Most products are eligible for return within 30 days of receipt, except where noted below.
- To initiate a return, please complete an RMA form prior to sending your item back.
- Original shipping costs are non-refundable and will be deducted from the return credit.
- Items returned missing accessories or original packaging, or that are not in the same condition as received, may be subject to a restocking fee of up to 100% depending on the condition of the item upon return.
- Some returns will be charged an automatic 15% restocking fee.
- We are unable to issue refunds for items that have been damaged or rendered inoperable due to installer error.
- Please complete the return form to receive your RMA number and return shipping label.
- Chemical products are not eligible for return under any circumstances.
- The Pentair Colorsync 618031 is not eligible for return.
- Pool cleaners are not eligible for return.
- Opened seals and o-rings are not eligible for return.
- Capacitors are not eligible for return.
- Plastic popup tools are not eligible for return.
- Automation components and circuit boards are not eligible for return.
- If a light is returned due to a reported malfunction and is found to be fully operational upon testing, return shipping costs and a restocking fee will be deducted from the refund.
- Orders refused at the time of delivery will be subject to the original shipping costs being deducted from the refund.
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