DIY Doctor UK DIY Forums

We're in the process of renovating a new house and we've just discovered what seems a rather unique central heating design - The house looks to be made up of 3 seperate 'one pipe' systems.

Looking at the boiler (which needs to be replaced) all 3 initially are feed from a single pipe and the same pump, but after that they're split off into 3 different directions, each with their own isolation valve (on both the flow and the return legs).

To test it out I closed off all the 'flow' isolation values first and then opened them up one by one, the first value heated up the upstairs back bedrooms and bathroom. The second did the kitchen, lounge and another or the bedrooms. And the last one basically heated the remainding ones..

(Rather quirkily it seems a sort of early zonal CH configuration)

We had intially thought about upgrading the system to a 2 pipe, flow and return, however that was when we thought it was just the one continuious pipe :-(

Now there seems to be 3.. So my question is - what should I do ?

Do we change it all to just a singel flow and return system, or do we convert the existing 3 x one pipe circuits/zones into 3 two pipe circuits..

I hope that makes sense :-)

Any advice would be much..

Basically it's up to individual preference.
Can you see yourself ever wanting to have one of the zones turned off ? or programmed to come on and off at different times to the other zones ?

If not then it's pointless zoning the new heating system.

It will also consist of more pipework, more motorised valves and thermostats, more wiring - which in my opinion = more things to go wrong.

Hope this helps

Thanks - htg engineer

(just to re-emphasize) The central heating is fed as normal from just one pipe from the boiler, but this is quickly slit off in to 3 directions, each with their own isolation taps.. One on each end..

My main question is...

Do I convert each of the 3 one pipe sections into a flow and returns (2 pipe) or do I remove the spliters and simply create one single (though out the whole house) flow and return configuration?

I hope I'm making the set up clear..

Ideally you want a two pipe system, Flow and return, the flow to going to one end of each radiator and the return to the other. The flow and return should be 22mm then the radiators tee'd into this with 15mm this will distribute the heat evenly.

The two pipes coming off the boiler, are the Flow and Return, you can have 5 or 6 tee's into them - but you still only have one flow and one return.

Shouldn't be any problems - as long as each rad is tee'd into the flow once and the return once.

You don't need the zone/isolation valves.