Relative modulation level 0.00??

[yjb]

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:

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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:

Code: Select all

delivered output (0 means: the boiler is off, 5 means: the boiler is
delivering the maximum output)

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.

[emmeesse68]

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.