Combined One Pipe and Two Pipe System - insane?

[DavidE]

Could anyone help with this possible insane question?

Our house has a one pipe iron central heating system. It is pumped with a hot water tank and a year old condensing boiler. There are two circuits, an upstairs and a downstairs.

I have read up on dielectric coupling to connect in copper pipe and I would like to convert the downstairs circuit to a two pipe system, but leave the upstairs circuit as a one pipe circuit. This sounds mad, but converting the upstairs circuit will mean digging up 3 tiled floors with underfloor heating. I think it could work, but I could be very very wrong.

Can anyone give me hope that this is possible?

Thanks!

 

[Onetap]

I have read up on dielectric coupling to connect in copper pipe and I would like to convert the downstairs circuit to a two pipe system, but leave the upstairs circuit as a one pipe circuit. This sounds mad, but converting the upstairs circuit will mean digging up 3 tiled floors with underfloor heating. I think it could work, but I could be very very wrong.

Can anyone give me hope that this is possible?

Thanks!

Forget dielectric couplings. They're a septic thing, you can't get them here, they don't work if you could and the insulator is bridged by earth bonding.

Proper corrosion inhibitors in a heating system will stop bi-metallic corrosion. Besides which, using plastic pipe would be a better option. There's no reason why your proposal couldn't be made to work. I'd fit some balancing valves to both circuits, the one pipe circuit will probably have a much lower hydraulic resistance and, unless regulated, you'll get very little flow to the radiators.

 

[doitall]

Lets just hope the new boiler hasn't got an aluminium heat exchanger if you have galvanized pipes

 

[Onetap]

Lets just hope the new boiler hasn't got an aluminium heat exchanger if you have galvanized pipes

He didn't mention galvanized.
Black steel is usual for heating, galvanized for HWS and CWS.

 

[Agile]

You have to carefully consider how best to ensure the system can be balanced assuming that you can ensure the iron pipes are not going to cause any problem.

If the upstairs circuit is in 1/2" then its resistance will be high and is unlikely to create a problem.

It its 3/4" then you will need to put a gate valve in the return and start by adjusting it just 1-2 turns open.

Also open the lockshields on the new rads just one turn each as a starting position. Any adjustments should be VERY small movement at a time because it will be quite critically balanced betweent he parallel and one pipe.

I think that any problem with aluminium is only from the galvanising and by now there is unlikely to be much left if its over 15 years old.

Tony

 

[doitall]

Lets just hope the new boiler hasn't got an aluminium heat exchanger if you have galvanized pipes

He didn't mention galvanized.
Black steel is usual for heating, galvanized for HWS and CWS.

Very true Onetap but why would he want an dielectric coupling if it was carbon steel tube.

perhaps I think tooooooo much

 

[doitall]

To answer the ops question, knock up a small header and treat it as two seperate circuits each with it own pump and zone valve

 

[DavidE]

Guys,

Just wanted to say thanks very much for your advice - very much appreciated.

You've given me the confidence to keep going until I find a plumber who understands this as well as you do.

Cheers!