Honeywell DT90e Problems

Honeywell DT90e is a popular room thermostat known for its efficiency in regulating indoor temperatures. However, like any other gadget, it can occasionally run into problems. This article delves into the challenges faced by a Honeywell DT90e user and possible remedies.

Problem Statement: A Honeywell DT90e thermostat user reported a challenge where the central heating was not activating, even though the light on the programmer indicated that the central heating was on. This was puzzling because when the hot water was turned on, the radiators warmed up. The heating system in question consists of an Ideal Classic SE15 FF boiler, a Horstman CentaurPlus C27 programmer, a Honeywell tank stat, and the Honeywell DT90e room thermostat.

Possible Solutions:

1. Issue with the Synchronous Motor:
   • One potential problem could be a faulty synchronous motor, which is responsible for turning the pump on. A previous user shared an experience where a similar issue was resolved by replacing this motor.
   • Solution: A replacement of the synchronous motor, which is relatively affordable and can be self-installed.
2. Seized 3-Port Mid-Position Valve:
   • If the 3-port valve seizes up in the mid-position, it can lead to heating in the radiator circuit as well as the hot water.
   • Solution: The user might need to replace the valve body and actuator to prevent future occurrences. There should be a position indicator on the actuator which can show if it’s moving when calling for heating or hot water.
3. Damaging Plastic Part on the Switch Lever:
   • Users should be cautious when dealing with the switch lever, particularly if it has a plastic part. There’s a risk of it breaking if forced.
   • Solution: Handle with care. If broken, you may need to replace the part.
4. Seized Valve:
   • It’s possible that even after replacing the motor, the valve might still be seizing. If this happens, it can burn out the motor if the valve refuses to move.
   • Solution: Remove the actuator and check how freely the valve moves using a wrench. If the valve is indeed seized, replacement may be necessary.
5. Electrical Issues:
   • If proficient, users can test the wires with a meter to determine if there’s an electrical issue.
   • Solution: Consult with a professional if unsure about the electrical components.
6. Programmer Fault:
   • The programmer could be malfunctioning, leading to no movement in the motor even when heating is called for. The programmer is responsible for instructing the motor on the valve’s position.
   • Solution: Check the functionality of the programmer. If found faulty, consider replacement.

Conclusion:

While the Honeywell DT90e thermostat is highly effective, issues can arise over time. The above solutions provide guidance on potential problems and how to resolve them. If ever in doubt, consulting with a professional or plumber is always the best course of action.