Im having a problem with a honeywell tz-4 zone controller.
Using the TZ-4 with a honeywell T8511-M thermostat. Everything works fine except when in emergency heat the board makes the Y circuit on the output side of the board energizing the compressor...it energizes the electric heat and the compressor but not the reversing valve.
Ive been told that I may need to connect the "L" terminal on the thermostat to the "L" terminal on the TZ-4 board. It is supposed to tell the TZ-4 that the thermostat is calling just for electric heat.
Anyone have any experience with this board ? I have put in and worked on quite a few of the EMM and EMM 3 boards and have never encountered this "L" terminal.
On the honeywell papers with the stat the "L" circuit is supposed to be power for "Equipment monitor or Defrost Reset Control"