01 08 Low water pressure lockout (water pressure switch)

What the control is telling you

The water pressure switch trips at 8 psi to protect the boiler. When pressure drops too low, the boiler shows Error 108. Once pressure is restored the error clears and the boiler goes back into the 7-minute purge cycle.

Applies to: TRX150 and related TRX models

Likely causes

• Boiler water pressure has dropped below the 8 psi switch setting, often while air is being purged from the system

Test and repair steps

1. Bring system pressure back up to at least 12 psi on the pressure gauge.
2. Let the boiler complete the 7-minute purge cycle again.
3. Check the system for leaks if the pressure keeps falling.

Models that show this code

5 models in TRX

Other codes on the same units

• 01 04 Insufficient circulation or low water pressure
• 01 05 Insufficient circulation or low water pressure
• 01 06 Insufficient circulation or low water pressure
• 01 07 Insufficient circulation or water
• 1 10 CH flow temperature probe open or short circuit
• 1 12 CH return temperature probe open or short circuit
• 1 14 External (outdoor) sensor open or short circuit
• 1 16 Floor thermostat contact open