The boiler modulates down its power.
But most boilers only reduce the power to about 33 % and in a seriously oversized situation like yours the boiler will then have to cycle on/off.
That is not very efficient but thats the result of an over powered boiler which is why its so important NOT to oversize.
Furthermore the anti cycle delay will result in the boiler only actually firing for about 25% or less of the time. That will cause a much longer reheat time. Again another result of an oversized boiler.
Some boilers enable the anti cycle to be adjusted to the minimum and many allow the max power to be reduced to a minimum. Doing these two will extend the firing time and significantly reduce the reheat time.
Tony
But most boilers only reduce the power to about 33 % and in a seriously oversized situation like yours the boiler will then have to cycle on/off.
That is not very efficient but thats the result of an over powered boiler which is why its so important NOT to oversize.
Furthermore the anti cycle delay will result in the boiler only actually firing for about 25% or less of the time. That will cause a much longer reheat time. Again another result of an oversized boiler.
Some boilers enable the anti cycle to be adjusted to the minimum and many allow the max power to be reduced to a minimum. Doing these two will extend the firing time and significantly reduce the reheat time.
Tony