Can hot & cold pipes to boiler touch?

[BenjyK]

Hi all,

I'm looking to reorganise some copper pipework to where a combi boiler will be installed.

Planning to chase out a section of a conrete floor for the pipework and using fixing band instead of clips too so the chase doesn't have to be too wide or deep. My question is can all these pipes be touching over a run of about 3 metres or so.

The run will include
- 2 x 22mm (CH flow & return)
- 4 x 15mm (upstairs rad circuit flow & return, boiler hot & cold)

Thinking the pipes would be covered by mild steel plate (not screeded over) and carpeted over.

The hot & cold feed to the boiler are new additions, the existing CH pipes are currently clipped to the wall covered by some ugly boxing in.

 

[FiremanT]

Cold pipes should never touch hot pipes.

Your diagram implies that the entire upper floor is fed from 15mm?

Also, consider expansion noise.

 

[BenjyK]

Thanks for replying. Yes after the CH pump, the 22mm flow branches off to the upstairs and downstairs circuits in 15mm. 3 rads and a towel rail upstairs, 3 rads downstairs.

So even if the cold main is kept apart, having the hot pipes bunched together and touching could still be an issue due to not having enough room for expansion? Could wrapping in felt solve the problem of expansion noise?

 

[oldbuffer]

1. The pipes need to be insulated and allowed room for expansion.
2. As stated above, the cold must never touch hot.
3. Don't use steel band (particularly galvanised) in contact with copper. You'll get electrolytic action.
4. You could use saddle clips.
5. Make sure the pipes don't come into direct contact with concrete or plaster. Use plastic covered pipe, or plastic pipe, or Denso tape.
6. Make sure you don't damage the damp proof membrane.

 

[BenjyK]

Thanks @oldbuffer. I didn't realise that about galvanised and copper - glad I asked!

There's stainless steel fixing band... but I think saddle clips might be the way to go as you say. As sounds like even if I separated out the cold so it's not touching the hots, having any pipes strapped up together is a bad idea due to expansion.

The current pipework isn't lagged or insulated in any way. Wondering whether filling the new chase with expanding foam could help in this regard as there wouldn't be enough room for lagging?