Hello. We have two pumps in our central heating system, in series sat next to one another, but each pump has a separate outlet pipe. Any ideas why two pumps are needed,and in this configuration? Thanks

Tony, August 2009

If it's the first unit then this is the pump and your can replace it with any standard 15/50 pump.

John, August 2009

Thanks John. You are spot on with your answer. If I have identified the inlet side correctly, then the first pump is the faulty one. Will the system continue to function ok, or does it sound like it is heading for a full breakdown due to the strain of losing one smc unit?

Tony, August 2009

If both pumps are blue you have an SMC pump/divertor system. One unit is a pump the other a divertor, they are NOT both pumps. Your best option is to replace the the second in line unit which will have an outlet to the side with either a single zone valve or 3 port divertor valve. Either way the system will need the wiring reconfiguring. This is not a simple task and will need doing by a competent heating engineer. Another solution is to replace the lot with a combi, unless of course you can source the SMC replacement which I think unlikely.

John, August 2009

Thanks all for your answers. Even with one failed pump, the radiators heat up and so does the water. It's not a Grundfos plan pump, if the images on the web are anything to go by, but we do have 8 stat controlled rads all from 3 to 5 feet in length. Any ideas??

Tony, August 2009

You have a Grunfos Pump Plan, One Pump supplies the Hot Water Primary heating, the other provides Radiator Circuit, The inlet connection is the Branch to the side of the set, the outlets are top & bottom, each outlet has a push-in non-Return Valve fitted to prevent back flow, however they can be problematic, but can be repalced separately

www.elanar.co.uk, August 2009

assuming it's not a twin pump arrangement (only likely if it's a very large property) it sounds like you have fully pumped c/h and h/w but instead of using motorised valves to control them, whoever installed it has used separate pumps instead. it's a bit unusual but nothing wrong with it.

Ian, August 2009

to heating circut controled trought stats

brian dunne, August 2009