Display of the current burner modulation rate (bar graph display)
The boiler modulation rate shows the level that the burner is firing at from minimum to maximum rate. The level that it is at can give some indication as to how the boiler is performing and in some cases can show some sort of fault. In the default setup, the burner rate will ramp to maxiumum and then start decreasing to a lower level once the return water temperature starts rising ie the heating system require less heat.
If you have installed modulating controls, the modulation rate will be at the level immediately of what is required at the time the room sensor feeds back the current temperature and therefore the required power level, so it could be low or high depending on the timings of the system. If hot water is being heated in combi boilers, usually it will be at maximum power level unless set differently. In stored hot water systems the same principle applies, the power level will usually be maximum unless set otherwise.
Powerlevel is staying low and not reaching the maximum
If your powerlevel is staying low no matter what the demand, then there may be an issue that requires an engineer visit. We have experience in this area and may be able to come out to you or provide remote consulting to fix the issue. Please get in touch if you have this issue.