Hold / Lockout 81 Delta T limit

What the control is telling you

Temperature difference across the heat exchanger exceeded the delta-T limit, normally from too little water flow. Also the usual cause when the boiler bangs or hisses.

Applies to: Trinity Tft60, Tft85, Tft110, Tft154, Tft201, Tft285, Tft340, Tft399

Likely causes

• Insufficient water flow
• Scale or magnetite on the heat exchanger

Test and repair steps

1. Check fuse B
2. Check the boiler pump
3. Verify the piping matches the boiler piping section and system pressure is at least 15 PSI
4. Clean scale from the heat exchanger with a descaler such as Fernox DS-40

Models that show this code

13 models in Trinity Tft

Other codes on the same units

• Hold / Lockout 67 ILK off - interlock string open
• Hold / Lockout 79 Outlet high limit
• Hold / Lockout 79 Outlet high limit
• Hold / Lockout 81 Delta T limit
• Hold / Lockout 85 Inlet/outlet inversion limit
• Hold / Lockout 85 Inlet/outlet inversion limit
• Hold / Lockout 88 Outlet temperature rise limit
• Hold / Lockout 88 Outlet temperature rise limit