Can I split a 22mm central heating feed into 2 branches?

[mk2phil]

I currently have 22mm feed and return running to a point under the landing where they're connecting to microbore manifolds which then feed each rad sperately.

I want to change a few rads around and would prefer to upgrade to 15mm due to the length of the pipe runs involved and the addition of radiators in certain rooms.

Is it ok to remove the manifolds and fit a 'Y' or 'T' piece and then have 2 branches in 22mm going to either end of the house where I can then tee of with 15mm spurs to radiators along each run.

I wasn't sure whether I would have to have one big 22mm loop that goes around the house with 15mm spurs coming off where necessary or whether I can split the 22mm in the way described above? I'm also worried that the pump might suffer with more water in the system and having to push it around more places (i.e. split directions in 22mm pipe)...but thinking about it, with microbore systems you have more pipes and each is filled with water so presumably it'll be roughly the same give or take..?

Also, where I need to feed a single rad I'm assuming I can just tee of a 15mm spur to that rad. But when I have a cluster of 2-3 rads in one area is it ok to run these from the one 15mm spur providing I dont exceed 3.5kw?


Cheers Guys

 

[gas4you]

Basically what you're saying is ok, but do not loop the flow and return togehter at the end, if i've understood you correctly.

You just need a flow and return to each rad and as long as the heating load is less than around 3.5Kw as you say they can al come off 15mm pipe. Up to this point you need to run in 22mm.

Draw yourself a plan on paper first therefore obtaing heat load and pipe sizes before you start.

No worries about the pump, it will probably work easier due to better flow through the larger pipes etc.

 

[ACOperson]

A good rule of thumb I use is that a 15mm pipe can very comfortably serve 3 radiators.

So, lets say for example you have 9 radiators:

-------------------------------------------------------------------------------
Take your 22mm flow pipe from the boiler, run it whatever way you are doing it. Branch one 15mm pipe off of this 22mm flow pipe and continue your 22mm run along the house, this 15mm branch then branches into 3 different 15mm pipes, one for each of the the first 3 radiators.

Then continue your original 22mm flow pipe along, until you come to the next 3 radiators, branch off in 15mm here again, again splitting into three 15mm pipes.

Then after this branch, reduce your flow pipe to 15mm. This will serve the final 3 rads in the house.

Mirror the above for the returns.
------------------------------------------------------------------------------

Obviously as gas4you says above, the whole house can be run in 15mm, but it's easier and quicker to balance the system if you have 22mm pipes available to feed the branches for radiators.

Jobs a good 'un

 

[gas4you]

I didn't make myself clear then, I was not saying the whole house would be run from 15mm Only each section of up to 3.5Kw. I totally agree that 22m is needed as the main carcass

 

[mk2phil]

Thanks for the replies guys - really helpful.

However, my 22mm feed and return pipes are first accessible under the landing floor which is pretty much in the centre of the house. So rather than snaking a 22mm backbone round all 4 corners of the house would it be ok to split the 22mm and run 1 in one direction and the other 22mm in the opposite direction. This would allow me to reduce the number of floorboards I have to lift - make the routes more direct and logical, and would adequetely serve all the rads as its a fairly small house. Both ends of the 22mm would end in a 15mm reducer feeding the last of the radiators on each run.

Does that make sense? I can do a diagram to better explain if that helps you guys see what I'm getting at..?

Thanks again guys

 

[gas4you]

Sounds ok, but you only need to use 22mm if the radiator outputs total more than 3.5Kw on each branch.

 

[mk2phil]

thanks Dave