Old one pipe system

[Matt0029]

Been to look at a job, somebody has bought houses wanted a radiator capping off and a radiator moving. System is on a combi. Is an old one pipe system though. With the pipe runs etc I have advised repiping to a 2 pipe system. Pipes come in upstairs then drop down. 3 rads downstairs 4 up. Downstairs radiators pipe work in void underfloor boards. Cutting back on these tees on 22mm and converting to a 2 pipe system. Well I have advised repiping to a 2 pipe system everyone else suggest that's the right call.

 

[Chuck]

Check the boiler's MI's, they probably won't 'allow' a one-pipe system. Even if they do OPS were traditionally designed for 75 or 85°C operation (and no TRVs) so the boiler probably won't be able to work in condensing mode, which will add about 10 or 15% to the fuel consumption.

Now I'm not saying it's not possible to get a combi to drive a OPS and work satisfactorily, but expect it to take a lot of fiddling around (unless you have a lot of experience with the beasts, which is getting unusual these days) to get it balanced and working properly, which the customer probably won't want to you pay for.

 

[Matt0029]

Check the boiler's MI's, they probably won't 'allow' a one-pipe system. Even if they do OPS were traditionally designed for 75 or 85°C operation (and no TRVs) so the boiler probably won't be able to work in condensing mode, which will add about 10 or 15% to the fuel consumption.

Now I'm not saying it's not possible to get a combi to drive a OPS and work satisfactorily, but expect it to take a lot of fiddling around (unless you have a lot of experience with the beasts, which is getting unusual these days) to get it balanced and working properly, which the customer probably won't want to you pay for.

Thanks it's a house someone has bought. With the stage there at now I have recommended changing/repiping to a 2 pipe system. It's on a combi a moment a 2 year old gloworm

 

[Matt0029]

It also looks like the pipes still go to the old back boiler. On the one pipe circuit even thought the system is on a combi.

 

[Matt0029]

It's like the flow and return, is a loop one pipe system is still flowing through the old not in use back boiler. The 15mm that drops down is the main loop for the one pipe circuit still

 

[Last Plumber]

Probably best to start a fresh. I tend to agree with Chuck.
It will work but it is not compatible with a modern boiler.