Buderus not heating in auto

MichaelH68

I have a Buderus G125. The burner does not kick on in auto, the boiler temp is only 77, but it still heats for the indirect water tank. The light on the taco zone switch is on and the circ pump is running but the boiler will not kick on. I put it on hand and it works that way but it makes the water tank too hot since it’s just running off the aquastat and not the thermistors. Any ideas why? No error codes either. I will add that the OA sensor isn’t reading correctly but I forced the boiler into winter mode so it would ignore the sensor.

HVACNUT

This is an R2017 Logamatic?
When in Manual 🖐 Mode, turn the dial on the left to 140°. There should be a thermostatic mixing valve on the indirect anyway.
I'm asking because I'd have to look it up, (and that manual has a lot of words) but does Winter mode bypass ODR?

You state "circulator", as in singular. Why does the space heat zone go to a Taco relay rather than to the Logamatic?

MichaelH68

> @HVACNUT said:
> This is an R2017 Logamatic?
> When in Manual 🖐 Mode, turn the dial on the left to 140°. There should be a thermostatic mixing valve on the indirect anyway.
> I'm asking because I'd have to look it up, (and that manual has a lot of words) but does Winter mode bypass ODR?
>
> You state "circulator", as in singular. Why does the space heat zone go to a Taco relay rather than to the Logamatic?

So there is a mixing valve to protect from scalding. And the manual says winter mode bypasses the OA sensor and acts independently of it. And I’m not sure why it goes to the taco, I could t understand thy either but what I can surmise from the Wiring is that the boiler supply’s the 120 that goes to the taco and the thermostat completes the circuit in the taco to energize the relay and send the 120 to the circ. And once it circulates enough water it drops the boiler temp below the internal boiler set point and it kicks on to maintain its own temp. In short the boiler is only looking at its own internal temp and the circ and Tstat work independently from the boiler to pull heat from the boiler and heat the space... make sense to you?

HVACNUT

What, if anything is connected to terminals 10 and 11 in the 2107? Is anything connected to terminal 63?

When the system is 1 space heat zone, the thermostat and circulator wiring should come into and get controlled by the 2107.
With multiple space heat zones, terminal 63 is energized by the zone control board to tell the 2107 there's a demand.
I'm thinking your setup has terminals 10 and 11 on the 2107 connected to 5 and 6 N/O on the Taco relay.
The circulator is running but it seems as if the 2107 isn't getting the signal from the Taco relay (SR501?).

Unless there was a plan of future zones, I cant understand why a separate switching relay was used.

MichaelH68

The taco is only connected to the controller by the 120v output to the taco, no communication back to the controller from the taco. It’s always been this way and nothing has been changed...

HVACNUT

Something needs to tell the 2107 what's going on. The 2107 is not an aquastat. It's an operating control and only does what the sensors or dry contacts from other sources tell it to do.
Check out the wiring I mentioned. Pics help too.
Good thing you have the 🖐 switch for now.
BTW, no error codes on the 2107 right? Because it doesn't know something's wrong with the space heat circuit.