In an earlier contribution to this discussion,
mike. buckley wrote:

We've just moved into a house and they've not left the full
instructions for the boiler controls. I've figured out how to set the
programs but there are 4 settings on the control for both CH and HW.
These are Off, On, Once and Twice. I've worked out the first two :-)
but the "Once" and "Twice" have me stumped. When selected both seem
to kick the HW on, but after that?


As you say, OFF is obvious - and ON pretty certainly means on all the time -
regardless of any timer settings.

TWICE almost certainly means that you can have two on/off periods per day -
e.g. one in the morning and one in the afternoon/evening, by setting the
clock appropriately.

I've not come across ONCE as such, but I guess that it equates to the ALL
DAY setting which some controllers have - coming on at the start of the
first period, and remaining on until the end of the second period.
--
Cheers,
Roger
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