RCS TR-40 external 24 volt transformer

[paulbernot]

I have a TR-40 serial thermostat and have been very happy with the performance. One issue that is a problem is that the furnace uses an internal transformer, and when the heating burner reaches its upper limit it kills power to the transformer. This in turn kills power to the TR-40 control unit. It keeps powering up an down with no issues, but I would like to use an external transformer to fix this issue. Here comes the problem, I purchased a 24 volt 20va transformer as RCS recommended but it will not trigger the furnace on. The TR-40 is getting power from the external transformer but not triggering the gas valve or fan with the external transformer. I did note that the internal furnace transformer is rated 24 volt 40 va. not 20 va as RCS recommends. Would this make a difference triggering the valve?

[Uncle Michael]

This is probably a question to put to RCS directly. I'm wondering if there is a way to power the thermostat with its power supply, but maintain the furnace power supply for its own relays. A quick look at the wiring diagram was not encouraging, but I'm certainly no expert.