22, 15 and 10mm pipe everywhere!

[Patrick Hutchinson]

ok, so I bought a 1920s large 4 bed semi about a year ago, it has a condensing boiler which replaced an old oil fire unit about 2008, it feeds a hot water cylinder and rads as an open vented system. I replaced the pump with a new Grundfos Alpha2 as it was very noisy and the system worked well through the winter all be it that the rads in the kitchen is slow to heat up.
From the boiler the feed is 22mm which splits through 2 danfoss valves, hot water and rads, my confusion is how the 22mm runs through the house to all the rads. It leaves the bathroom underfloor though 2 bedrooms then goes down into the living room with no rads fed off it, below the living floor it splits, it feeds all the rads downstairs but goes straight back upstairs in the same duct to feed all the upstairs rads. Why did they not just feed all the rads off a single run rather than going to the bother of going down and up again? There could have been a back boiler in one of the downstairs fireplaces, could this explain it? I did also find a second pump lying under the floor of the living room, looked like it had been dropped out and a through pipe soldered in to do away with it.
I am replacing all the 10mm pipe with 15mm as I am replacing all the rads, the original install was pretty terrible with the rads either being too large or too small. I want to keep the 22mm and continue to use it but want to get rid of anything which serves no purpose.
So is it usual to run 22mm to feed the ground floor than back up to feed the top floor? Anything else I need to watch out for?

 

[dilalio]

Who knows mate! Repiping a whole house can only really be done efficiently when it's empty and you can have the floors (and sometimes walls) exposed in every room! When it's occupied, you have to do what you can with the least disruption possible!

 

[oilboffin]

Always a box of worms my friend just expose what you can an try to get a feel of the system
oh and best of luck

 

[Patrick Hutchinson]

Would there ever have been a reason to send the flow and return down stairs and then back up to feed the upstairs rads in an open vented s plan? Could it be to give priority to the downstairs rads? If is stick in a few reducing tees I can basically feed all the upstairs rads before the main 22mm goes down stairs this will allow me to cut out the duplication, is it optimal to feed bathroom , 4 bedrooms and upstairs landings before downstairs? Or should I leave it as?

 

[oilboffin]

Basically what to do in not so many words is run 22mm up and under the floor then tee off to upstairs rads and do drops for the downstairs rads make sure if you have a hot water tank
That the last conection to the return is the return from the hot water cylinder or you could get
Reverse circulation

 

[Patrick Hutchinson]

Current layout, should I simply put all the upstairs rads into the 22mm before they defend to below the ground floor, or leave it as is!

 

[oilboffin]

Good enough