Open fire back bolier integration

[Duncan]

I have an open brick built wood/coal burning fire with integral back boiler. The back boiler was disconnected and the pipes left open when we had CH installed about 18 years ago when we first moved in.

Fireplace in living room is adjacent to cuboard where the HW cylinder, pump and controls are. The back boiler pipes c. 1 1/2" bsp terminate in this cubboard so easy to connect to.

My question is and subject to the back boiler being safe and sound, can the back boiler be connected into the system to provide HW & CH when the fire is lit. I am thinking this is just an extension to the heating cirucit but have concernes that when the room stat switchs the pump/boiler off the back boiler keeps on heating the water.

The exsiitng system has vent to both tanks CW and CH in the loft. System is not combination boiler type.

Will have any resulting work undertaken by professional.

Your thoughts please.