UFH - Supply and Return pipes...

[JohnMo]

2 hours ago, Mulberry View said:

I've raised concern about heat striping

Depends on the depth of pipes, ours are in 100mm screed and there is zero.  So thats should not be a concern.  Even when I used the boiler at 34 degs there were none. 

 

300mm is generally fine, one thing it does bring is a fall off of heat transfer at very low flow temps, so to counter that on 7 to 10 deg days I just flow at 29 and in Cosy periods and the runs are good.  Have a WC curve that runs 29 to 32 (10 degs to -5 degs).  Running 29 degs gives a very stable run time of over 3 hours and also excellent CoP, just finished a run I did as I was getting free electricity, ran in manual for 3 hours and got a CoP average of 6.6 at one point it was doing over 7.

 

2 hours ago, Mulberry View said:

but I am minded to want closer pipe spacing as I'd prefer some headroom

At 300mm spacing you can very easily hit very high room temps, just flow too high for too long and you go into melt down.  Just use the chart I posted on 30 Aug to work out how little flow temp increase you need to add to increase output hugely.

 

If you are concerned just drop the spacing to 200-250mm, but tighter in bathrooms due to the limited floor area

 

[Mike]

5 hours ago, Mulberry View said:

The designer has gone for 300mm pipe centres

FWIW, French regulations specify a maximum of 250mm between pipes - more here:

 

 

Edited 1 hour ago by Mike