ACV Heat Master HM 60 N heating separate from DHW?

[Sam007]

I just moved into a house with an ACV Heat Master HM 60 N boiler in the garage, providing hot water for two heating systems (plus of course domestic hot water). One is an underfloor system for the ground floor controlled by a Honeywell CM67. The other is a radiator system for upstairs controlled by a Drayton LP722. The boiler is about 20 years old and has what is described as an “optimiser” in the form of an old style 24 hour mechanical timer with pegs/pointers the you slide in or out to turn the boiler on or off. It has a bath symbol on it, and to quote the manual “Pointer recessed: domestic hot water off. Pointer not recessed: domestic hot water on”. So I assume this should be independent of the state of the heating systems, and is to allow you to make sure you’ve got DHW at certain times of the day.

I’d assumed that if either of the heating systems had demand for heat, that the boiler would fire up as needed to provide hot water. However, that doesn't happen. Instead, I have make sure that domesitic hot water is on using the optimiser at the same time as I want heating. If I don’t do that, the heating pumps end up just circulating water at ambient temperature. It means if I want a heat boost at any point, I have to go out to the garage, activate the boiler DHW and then go and activate the heating.

So, finally my question. Does anyone know if this boiler can be wired to do what I had assumed it would do, i.e. provide hot water for heating as and when demanded, and separately let me program guarantedd DHW at times I choose using the “optimiser”?

Many thanks.