One-pipe Radiator Connection

[shingles47]

Hello,

After living in my 1970s house for 6 years I decided to move one of the radiators in the living room and add a feed out to the conservatory for future connection. I was surprised to find that both radiators have both ends connected to the same pipe (see Fig 1 in the diagram). Never seen this before, and I am wondering how the radiators ever got warm. I'm planning to change this to parallel connection (Fig 2) and treat one end of the pipe into the room as a hot feed, and the other end as a cold return. The pipe diameter is 32mm. Has anyone seen this before? Are there any pitfalls in changing these connections?

 

[denso13]

Has anyone seen this before?

Yes, a one pipe system.

 

[shingles47]

OK that explains it. So to answer my own question, if I change it as proposed, I risk shutting off the feed to other radiators on this pipe (if there are any) if both living room radiators are off. A bit more investigation required, because there are radiators elsewhere in the house with 2 pipe feeds.

 

[Madrab]

Not a good idea to change part of a one pipe system into a 2 pipe system and leave the rest as a one pipe, if that's what you're proposing, it would be fraught with problems.

 

[roguetrader]

You can easily run an extra rad off a one pipe system, you just need a bit of experience on this method of heating.

 

[shingles47]

Not a good idea to change part of a one pipe system into a 2 pipe system and leave the rest as a one pipe, if that's what you're proposing, it would be fraught with problems.

Yes I agree. Leaving as it is.

 

[Madrab]

As suggested, you can add extra rads to a one pipe system, the key is the way/how it is connected, capacity and re-balancing. They are very sensitive to change but as long as they are configured properly it will carry on working ok.

Don't do what I came across recently. Previous chap obviously didn't have any experience with one pipe systems and moved/renewed and added rads, the system never worked properly again. He had added in lots of new branches and elbows and extra connections for the new rads that threw the whole system out and interrupted the convection so some rads. Rather than reconfigure the whole system again, without any guarantee of it ever working properly again without going back to the start, we just converted it over to a 2 pipe.

 

[shingles47]

The heating works well even though it seems to have a mixture of 2 pipe and 1 pipe runs. I think the fact that all but 1 rad have TRVs helps self-balancing.