We currently have a 16 year old 78 kW oil fired commercial boiler heating an old Edwardian house (8500 sq ft). It is ridiculously inefficient and we are struggling to ehat the house sufficiently (radiators won't warm on the second floor unless you turn off the radiators on the ground floor). In addition the hot water and heating can't be separated and there is no thermostatic control (heating on completely or not at all). I've resigned myself to the fact that actually we need to replace the boiler and pump and install some sort of zoning but I'm not sure what size pump to go for? Any ideas or advice? I'm hoping to have a plan in my head before I approach companies for quotes. Unfortunately DH passed away unexpectedly last year and I'd feel more in control if I actually knew just exactly what was needed and required...
you need advice from a trustworthy local installer. Midwinter is not a good time to find someone free.
Try the person who maintains your old boiler.
Apart from personal recommendations, go to the websites of Vaillant, Viessmann and Worcester Bosch, who should have a list of approved installers in your area. You need someone quite experienced who has worked on more than just ordinary houses.
Look at upgrading your insulation and draughtproofing first. You may get a subsidised fit from BG even if you are not their customer, or one of the large electricity companies.
Edit I know nothing about oil boilers. I have heard Grant Vortex mentioned favourably