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Hi,

I'm looking for an explanation related to the Relative modulation level.

Quite often I see that the the flame status is on, while the relative modulation level is equal to 0.00:
Not only does OTGW report that the flame status is "on", the Gasmeter is running at the same time, so I guess that 0.00 is not always 0.00.

On the other hand, I see as well that that the Celcia-20 reports "Delivered output 1" while otgw reports "Relative modulation level: 0.00"
From the Celcia-20 manual: Is this something related to my boiler (Quinta-35C), or do other people see the same with other boilers?


Once again, not sure if something is wrong, just want to satisfy my curiosity.

Same situation with my Ferroli BlueHelix Pro 32c. It seems to me that the flame status is controlled by rising/lowering the "control setpoint", that looks like the maximum water temperature the thermostat allows (the "Max. central heating water setpoint" is set by boiler's contrl panel)

I think (but I have no proof, thus it's just a guess) relative modulation 0.0 instructs boiler to deliver the minimum possible power, that would be different depending on the boiler make/model.

Modulation is one parameter only, but boilers can modulate at least two things: flame and circulation pump. Maybe boilers have onboard logic to decide wether to modulate one or the other, appearently OT controls one overall relative modulation.

Anyway, before adopting OpenTherm control, I was driving my boiler with the zone valves end switches, in an on/off style. By observing the boiler's display, I could notice flame was being modulated anyway, and the pump noise used to vary, so I guess there's some logic on the boiler itself that would modulate even in an on/off control situation.