8mm supply to radiators

[ZACCCC]

I am putting two new rads in my house. The other rads are fed by 8mm microbore so I want to feed the new ones with the same so as to have an even supply throughout the system. My plan for each rad is to put a 22 to 15 reducing tee on both the CH flow and the CH return and then on each 15mm line from the tees put a 15 x 8 reducing coupler to the 8mm microbore. I'm only a DIYer so I just wanted to check with the pro's that this sounds ok.

So this will involve two tees off the flow and two off the return. Is there a more efficient way to do it. I have seen 2-port 8mm manifolds but I think they involve soldering, which I've never done, so that option's out I think.

I want to put 8mm TRVs on the rads but the only one I've seen has been the Danfoss RAS-C2 in the Screwfix catalogue, where it gives the diameter as 8-10. Does this mean that it will fit both sizes?

Thanks.

 

[jackthom]

Can the two new radiators maybe share the one teed-off 22 to 15mm feed/return or are they in different parts of the house?

Should say that I doubt many folks here will be keen on adding any 8mm pipework to a system these days, knowing the potential problems with sludge. If balancing the system is your only concern it is still possible with larger bore pipes.

Whether you go with 8mm or 10mm that TRV should connect Ok to either.

 

[ZACCCC]

Thanks for your reply jack. The two rads are near enough to each other but I thought it was advisable to to take the supply for a new rad from the main 22mm pipe.

Would your suggestion work like this:- a 22 to 15 reducing tee on both the CH flow and the CH return and then on each 15mm line from the tees put a 15 x 8 reducing coupler to the 8mm microbore and then put a tee into this with the tee-off going to the second rad?

Regarding using 10mm bore, I thought that if I used this for the two new rads then the system would favour these over the original rads and they might not get an adequate supply. Is this not the case?

 

[St0rmer66]

You can adjust the radiators down using the lockshield valve to reduce flow or "balance" them. Most TRV's only have around an 8mm hole in them anyway but you'd still need to balance them a bit.

 

[ZACCCC]

Thanks Stormer

 

[jackthom]

Probably best to run the single pair of 15mm pipes until reasonably close between the two radiators where possible, then use two 15mm tees to double up the feed and returns, and then reduce each of the (now four) 15mm pipes to 8mm for the radiators.

Basically you wouldn't want to have the feed for 2 radiators going through a single section of 8mm pipe

 

[ZACCCC]

Thanks Jack. I take your point about not having 2 rads both feeding through one 8mm pipe.

 

[mfarrow]

You can go straight from 22mm down to 8 using a 22mm coupler and manifold. They're a cheap fitting as well.

 

[ZACCCC]

Thanks mfarrow. I've also seen 2-port ones, which is what I would need. The problem is that they need soldering in, I think, and I've never done any soldering.