Pentair Max-E-Therm ERR PS Error
The ERR PS error on a Pentair Max-E-Therm indicates the water pressure switch is open. This safety feature prevents the heater from firing without adequate water flow through the heat exchanger.
This error will auto-clear once water flow is established through the heater.
What Causes ERR PS?
The water pressure switch detects water flow through the heater. When flow is insufficient, the switch opens and displays ERR PS.
Common Causes
- Pump not running: Circulation pump is off or not working
- Dirty filter: High filter pressure restricting flow
- Closed valves: Isolation valves partially or fully closed
- Clogged baskets: Pump or skimmer baskets full of debris
- Air in system: Pump not fully primed
- Bypass open: External bypass diverting flow around heater
- Pressure switch failed: Switch stuck open
Troubleshooting Steps
Step 1: Verify Pump Operation
- Check that circulation pump is running
- Verify pump basket is full of water (no air)
- Listen for normal pump operation sounds
- For VS pumps, ensure adequate speed for heater operation
Step 2: Check Filter System
- Check filter pressure gauge
- If pressure is 8-10 PSI above clean baseline, service filter
- Clean pump and skimmer baskets
- Backwash or clean filter as needed
Step 3: Check Valves
- Verify heater isolation valves are fully OPEN
- Ensure any bypass valve is fully CLOSED
- Check all suction and return valves
Step 4: Check for Air Leaks
- Inspect pump lid o-ring
- Check suction side fittings
- Look for air bubbles in pump basket
Step 5: Test Pressure Switch
If flow is verified adequate but error persists:
- Turn off power to heater
- Locate pressure switch
- With pump running and good flow, switch should be closed (continuity)
- If switch is open with good flow, replace it
Minimum Flow Requirements
The Max-E-Therm requires minimum water flow to operate safely. Ensure your system can provide adequate flow, especially when using variable speed pumps at lower speeds.
When to Call for Service
- Flow is verified good but error persists
- Pressure switch needs replacement
- Suspected internal blockage in heat exchanger
- Multiple components need testing