Can I connect radiator return to ANY point on return circuit

[jonnyplatt]

I want to add 2 new radiators to the central heating system. It's 22mm piped from boiler to pump then motorised valve splits the feed to either the hot water or rads. Lots of 10mm pipes then come off the 22mm main flow and return pipes feeding each existing radiator. 22mm return pipe goes back to the boiler about 12ft away.

In order to add 2 more rads I'm proposing to tee into these 22mm flow and return pipes with a 15mm pipe feeding the 2 new rads (10mm pipework will be used where the 15mm splits nearer the rads). I'll tee in on the pumped side (after the pump and motorised valve) just before the 'octopus' end (LHS of photo). I was going to tee into the return side near the return 'octopus' (RHS of photo) but as this just goes back to the boiler could I tee in nearer the boiler (which is closer to the new rads positions)?

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• jonnyplatt
• 19 Jul 2012
• 1

 

[mysteryman]

You can, but make sure the cylinder return is the last one nearest to the boiler. Otherwise you will get stray currents in the central heating circuits during hot water only operation.

 

[jonnyplatt]

Thanks for that. However, as far as I can tell, the cylinder return connects before ANY of the radiators. The design is such that the motorized valve diverts to either heating only or water only - don't know if that makes any difference. Haven't noticed any problems with it in 10 yrs.

 

[doitall]

All the returns most join together before they join the common return.

 

[jonnyplatt]

Thanks for your comments.

If I understand you correctly, I shouldn't join nearer to the boiler then. What about joining at the position marked with paper on the right hand side of the photo

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• jonnyplatt
• 19 Jul 2012
• 1

. This is the common return pipe which goes to the boiler about 12feet away and no other rads join after this point. The returns from the rads at the front of the house all join 6 feet or so before this point.

As a matter of interest, why should all the rad returns join at the same place?

 

[doitall]

In that area will be fine.

The returns should all join before the common return, nothing between the cylinder return and the boiler, in other words.

 

[jonnyplatt]

Thanks guys. I've done a search under the floorboards and have found a 15mm pipe that is the return from the cylinder. This pipe joins the common return a few feet nearer the boiler beyond the area shown on the photo. It all makes sense now - brilliant!