Vaillant Ecotec plus 837 - hot water fine, radiators upstairs fine, wet UFH downstairs not working - S30

[FrankZappo]

The UFH is controlled with Heatmiser slimline panels in each room. I have reset all the units but the S30 code still shows when the thermostats are calling for heat.

Hot water is fine and the upstairs radiators (controlled with a wireless Honeywell thermostat) are coming on as normal.

I'm wondering what I can try myself before getting an engineer out.

Any advice please?

 

[Stuckinarut]

Do you have an integral time clock?

 

[FrankZappo]

Do you have an integral time clock?

No I don't think so. Why?

For a short while in the run up to the S30 code being permanent (in relation to any call for heat from the UFH) sometime I would notice that the heating hadn't come on and the boiler was showing S30. I could get it to fire up and start heating by turning the target temp on the Heatmiser unit room thermostat down and then up again so the call for heat turned off and on again. Most of the time the boiler would then fire up but it was temperamental. It's stopped reacting to the coaxing now and just displays S30 all the time when the UFH is asking it for heat.

 

[Stuckinarut]

No I don't think so. Why?

It’s an additional switch that can affect the heating coming on. That said, should change to s31.

For a short while in the run up to the S30 code being permanent (in relation to any call for heat from the UFH) sometime I would notice that the heating hadn't come on and the boiler was showing S30. I could get it to fire up and start heating by turning the target temp on the Heatmiser unit room thermostat down and then up again so the call for heat turned off and on again. Most of the time the boiler would then fire up but it was temperamental. It's stopped reacting to the coaxing now and just displays S30 all the time when the UFH is asking it for heat.

Could be the motorised valve not engaging the microswitch.

 

[FrankZappo]

It’s an additional switch that can affect the heating coming on. That said, should change to s31.

Could be the motorised valve not engaging the microswitch.

This makes sense and sounds likely - thanks!