Hi everyone, now bare with me here as my know page of plumbing is basic at best, I currently have a horazontal calorifier which is providing my hot water from the raw water cooled engine, but I’d like to add a second heat source from the back boiler on my wood burner. Problem is am not sure whether I have a single or twin coil. Is there a way of telling by the amount of valve fittings on the tank (I have 5) or do I have to drain the system and remove the immersion and look inside? Any advice would be great. Cheers. Darren