DIY Doctor UK DIY Forums

The Grundfos central heating pumps that most people have (in the airing cupboards) - are they standard ? Or do you have different wattage, etc for larger properties? What is the standard one to buy for a normal 3-bedroom house? And what pipe exactly does it need to be installed on? Primary Flow??? I know it should also have isloating valves either side, for easy removal/repair, without having to drain down the whole system.

normally a 15-50 (5 metre head) an yes you do need isolating valves on either side of the pump.

It will be fitted to the boiler flow or return, not the primaries - as these are for hot water heating on gravity systems.

Why do you ask ?

if there's a heating system there - surely there'll already be a pump. ?

Fit a grundfos selectric 15/50 pump, cost around £60. Note which direction the pump is fitted and speed setting its at and fit the new one the same way. Depending on the pumps/valves age, the connections can sometimes be stiff/siezed, and so a hammer and wd40 may be reqd, OR a hacksaw and new union nuts. If they are ball-type (quarter turn) isolation valves, dont bother touching them (90% chance they will leak), just replace them (which means draining or 'bunging system)

The flow from the Hot water cylinder to the boiler is called the Prmiary flow and return (on an indirect cylinder). Maybe it's also known as the boiler flow and return in some places!!! Anyhow, I was just wondering as I'm trying to learn a bit about central heating basics!