Viessman 222F Not pumping hot water

IdaProEnjoyer

I have a Viessman 222F with weather compensation for Underfloor heating, I'm unsure as to how it works and am trying to gather a general understanding of this machine, it has an outdoor temperature sensor that gathers the external temperature and adjusts heating based on a heating curve. It also has sensors on the outgoing water temperature pipe (specifically the part number 7151992, viessmann contact temperature regulator), I'm unsure as to when the heating circuit pump turns on (what triggers it?). I tried to adjust the set room temperature/set reduced room temperature to 28-30C degrees just to force the pump to turn on and the heating to get going, and it displays the "common flow temp" at a temperature of 55-65C but touching the outgoing water pipe it is room temperature. Draining and adding water to the system by messing with the valves seems to turn on the pump.

I'm puzzled as to what's going on and how this stuff works.

Thanks in advance.

GGross

Depending on exactly how the installer set it up those boilers are designed to maintain a supply temperature, that is based on the outdoor temperature, at an external sensor location. This is generally the low loss header (which is a fairly large metal box with 4 pipes sticking out the sides)

If it is set up to run without a thermostat call (which is fairly common in Europe), the boiler will fire to maintain that supply temperature. By turning up or down the "set room temp" value, that will also cause the boiler to raise or lower the supply temperature.

When the boiler gets a "call for heat" whether by a thermostat, or the supply sensor, it will first kick on one of the internal pumps, the internal pump will activate a flow switch safety device when there is sufficient flow, blower kicks on, gas valve is on, spark and then flame.

In addition to all of this the 222f has a second internal pump, a flat plate heat exchanger and an approx 20 gallon storage tank to make on-demand domestic hot water, with storage . This will be prioritized over any call for heat.

Since you say that adding water and messing with valves turns on the pump, I would imagine that your system is possibly partially air locked, this will stop that flow switch safety from allowing the boiler to fire. There should also be an external pump that activates to supply your home with heating. I think you may need to get someone in to service this, possibly check the charge on the expansion tank (I think there is an internal one) and properly set system pressure, as well as purge any air from the heat exchanger. Once that is done you may need to mess with the outdoor reset curve a bit to dial it in

A picture of your install may help as well

IdaProEnjoyer

GGross said:

Depending on exactly how the installer set it up those boilers are designed to maintain a supply temperature, that is based on the outdoor temperature, at an external sensor location. This is generally the low loss header (which is a fairly large metal box with 4 pipes sticking out the sides)

If it is set up to run without a thermostat call (which is fairly common in Europe), the boiler will fire to maintain that supply temperature. By turning up or down the "set room temp" value, that will also cause the boiler to raise or lower the supply temperature.

When the boiler gets a "call for heat" whether by a thermostat, or the supply sensor, it will first kick on one of the internal pumps, the internal pump will activate a flow switch safety device when there is sufficient flow, blower kicks on, gas valve is on, spark and then flame.

In addition to all of this the 222f has a second internal pump, a flat plate heat exchanger and an approx 20 gallon storage tank to make on-demand domestic hot water, with storage . This will be prioritized over any call for heat.

Since you say that adding water and messing with valves turns on the pump, I would imagine that your system is possibly partially air locked, this will stop that flow switch safety from allowing the boiler to fire. There should also be an external pump that activates to supply your home with heating. I think you may need to get someone in to service this, possibly check the charge on the expansion tank (I think there is an internal one) and properly set system pressure, as well as purge any air from the heat exchanger. Once that is done you may need to mess with the outdoor reset curve a bit to dial it in

A picture of your install may help as well

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If it is set up to run without a thermostat call (which is fairly common in Europe), the boiler will fire to maintain that supply temperature. By turning up or down the "set room temp" value, that will also cause the boiler to raise or lower the supply temperature.
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Thank you for your advice, just a few more questions, I have the system with no thermostat, but I think it has a supply sensor, as there is a sensor on the outgoing pipe, should the pipe be the temperature on the temp curve or the desired room temperature?

GGross

If working correctly the boilers goal is get that temperature sensor to somewhere around the supply water target temp. That sensor may not be located in the best spot if it is strapped to a pipe.