I have been called out to quote a back boiler exchange to a wall hung combi boiler.
I would like some advice on the install as the back boiler has gravity hot water feeds to it and the new combi is being fitted where the hot water tank is. My question is would it be good practice to connect the flow and return from the new boiler to the hot water flow and return and then connect the (what was) the hot water flow and return to the flow and return from the old boiler in the builders opening. I ask this as the flow and return pipes are quite away from the new boiler position and it would save on costs and time.
No because the flow and retrun will probably be 28mm, will be full of limescale and crap and probably have old compression fittings, if you are just connecting on, then you need to connect on to the heating flow and return - renewing or at least checking the manifolds (if any)
If 8mm or 10mm, unless tee'd into flow and return individually - they will be connected to a manifold. A brass or copper manifold with 4 or 5 8/10mm connections - if it's a compression manifold I would change it.