Changing one pipe system to two pipe

[desiguy]

Hello

I wonder if anyone can help. I have an annexe in my garden and the builder installed the pipe for the heating as a one pipe system. I would like to change it to a two pipe system.

My question is does the flow and return to the boiler from upstairs have to come downstairs at the same point? He has one pipe going up to one rad from one corner of the building and the other pipe going downstairs from the other end of the building. The boiler is on the ground floor.

I intend to use one pipe for the flow and the other pipe for the return,would this be ok?

The boiler will run two rads upstairs and two downstairs plus one towel rail.

Thank you

 

[stem]

To answer your question, generally. It is not necessary for the flow and return to be at the same point, and I have seen one pipe systems converted in the way that you describe. The downstairs radiators on the same loop would also need to be converted, you couldn't convert just the upstairs section, and leave the downstairs as it is.

You don't give enough specific detail for a definitive answer, for example, a one pipe loop, being unobstructed can be used as a boiler by-pass circuit which if needed by your system would be lost if you made it a two pipe system.

So a bit more information about the rest of the system would be required. What boiler do you have? Does it require a by-pass? Is there a hot water system connected to it? what controls are there? Are all of the radiators connected to it in one single pipe loop. Does it have a pump, or does it rely solely on gravity circulation? What size are the existing pipes? Finally what are you looking to achieve by converting it?

 

[desiguy]

Thank you for your reply.

At the moment the rads(upstairs and down) are connected in and out in one continuous loop like a ring circuit.

I intend to use a combi boiler for the heating and hot water there is no hot water cylinder or any by-pass or pump.

The pipe work is 15mm.

It is a new build annexe that was going to be used as my den/home cinema however my daughter now want it as a dance room!!!

Thank you

 

[stem]

This all sounds very odd to me. It's a "new build annex" yet "the builder installed the pipe for the heating as a one pipe system" something that generally hasn't been installed for over 40 years! and you "intend to use a combi boiler" so it's that new it hasn't even been finished!

If you are having a new boiler, do it properly and install a new two pipe system from scratch and have a pro size everything properly. The flow and return from the boiler will be at least 22mm.

 

[Terrywookfit]

As said. Why the fook would anyone install a one pipe system............Unless it was for a solid fuel boiler and no pump.

 

[Nige F]

Thank you for your reply.

At the moment the rads(upstairs and down) are connected in and out in one continuous loop like a ring circuit.

A one pipe system has a continuous loop under the rads. Each end of the rad connects to this.