Run pipes behind boiler

[phloaw]

Hi, I have an old traditional gas boiler (two pipe, fully pumped system, if that matters) sitting on the floor and touching the wall, as from the first pic. The second pic zooms in on a hole the boiler has in the rear, leaving a gap with the wall.
I am planning to run two 15mm copper pipes through that gap to bring water to radiators I am adding to the house.

Would that be ok? Is there any safety/practical consideration I should keep in mind? Thanks

 

[Madrab]

You need to be careful where you add radiator returns into existing boiler pipework. I presume you have a hot water cylinder?

Any radiator return needs to be piped in before the return from the cylinder, to avoid the chance of reverse circulation.

 

[Hugh Jaleak]

As above, and note taking any feed from before the motorised valve would cause that radiator to be on every time time the boiler is firing, regardless of Roomstat position or Central Heating selection. (Radiator on in Summer?)

 

[phloaw]

You need to be careful where you add radiator returns into existing boiler pipework. I presume you have a hot water cylinder?

Any radiator return needs to be piped in before the return from the cylinder, to avoid the chance of reverse circulation.

Yes, thanks, I made sure of that: on the return leg, there is first the tee for the new radiators, then the tee taking in the cylinder return, then everything goes to the boiler's return inlet.

As above, and note taking any feed from before the motorised valve would cause that radiator to be on every time time the boiler is firing, regardless of Roomstat position or Central Heating selection. (Radiator on in Summer?)

Yes, I already placed the new feed tee + valve (visible at the bottom of the first pic) for the new radiators after the two-position valve governing the radiators. The other valve for the cylinder is on another leg.

Thank you both for your help.