1973 house, extended in 1994. New (2002) boiler is in extension.

22mm flow+return out of boiler. Changes immediately to 28mm to run to
airing cupboard (about 5m). Changes back to 22mm to go through valves
(separate for cylinder and rads, nicely done, includes bypass), and
heads back to just above boiler. Both flow+return head down side of
boiler, downstairs. So far so good.

Downstairs, both split, with 22mm pipes going back upstairs to feed
rads!

Why is it done this way? Why does it go downstairs just to go upstairs
again?! Why not split it upstairs? Is it something to do with
balancing the system? It's not some "legacy" because all this part
must have been installed in one go when the extension was built.


After this, both arms (i.e. the complete downstairs, and the complete
upstairs) are run completely in 15mm. I'm adding three new radiators
downstairs (conservatory, garage conversion, kitchen-diner re-model),
so should I convert the start of the downstairs to 22mm?

TIA.

Cheers,
David.

On 14/05/10 10:58, David Robinson wrote:
1973 house, extended in 1994. New (2002) boiler is in extension.

22mm flow+return out of boiler. Changes immediately to 28mm to run to
airing cupboard (about 5m). Changes back to 22mm to go through valves
(separate for cylinder and rads, nicely done, includes bypass), and
heads back to just above boiler. Both flow+return head down side of
boiler, downstairs. So far so good.

Downstairs, both split, with 22mm pipes going back upstairs to feed
rads!

Why is it done this way? Why does it go downstairs just to go upstairs
again?! Why not split it upstairs? Is it something to do with
balancing the system? It's not some "legacy" because all this part
must have been installed in one go when the extension was built.


Can't see a good reason.

After this, both arms (i.e. the complete downstairs, and the complete
upstairs) are run completely in 15mm. I'm adding three new radiators
downstairs (conservatory, garage conversion, kitchen-diner re-model),
so should I convert the start of the downstairs to 22mm?

No harm in doing so. Don't worry about balancing - it's never wrong to
oversubscribe the potential flow then throttle it back at each rad with
the local balancing valve. Undersubscribing the flow is where you get
problems...

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

David Robinson wrote:
1973 house, extended in 1994. New (2002) boiler is in extension.

22mm flow+return out of boiler. Changes immediately to 28mm to run to
airing cupboard (about 5m). Changes back to 22mm to go through valves
(separate for cylinder and rads, nicely done, includes bypass), and
heads back to just above boiler. Both flow+return head down side of
boiler, downstairs. So far so good.

Downstairs, both split, with 22mm pipes going back upstairs to feed
rads!

Why is it done this way? Why does it go downstairs just to go upstairs
again?! Why not split it upstairs? Is it something to do with
balancing the system? It's not some "legacy" because all this part
must have been installed in one go when the extension was built.

I suspect the 28mm pipework is a relic of a much older boiler. We have a
similarly "odd" bit of plumbing in our system after an old floor standing
boiler was removed and a new boiler fitted in a new site. Our system now
has a 22mm--28mm--22mm section like yours.

Tim

On 14 May, 12:18, "Tim Downie" wrote:

I suspect the 28mm pipework is a relic of a much older boiler. *

Yes, probably remnants of gravity flow in 28mm to the cylinder with a
pumped heating system from the boiler in 22mm; converted at a later
date. That was common in 1973.

You should keep the cylinder return separate and only connect it into
the main return after the upstairs and downstairs heating returns have
joined; you'll otherwise get a nuisance heating flow in summer. The
only illogical bit seems to be taking the heating flow from the valve
downstairs and then taking the upstairs flow back up.