Different 'mean water temperatures' for different loops on the same manifold?

[HaloThree]

Hi all,

 

I'm looking for some advice on options where different loops (on the same floor) require different mean water temperature to meet the required heat output.

 

In this case some of the loops will be pug mix between-joist (at 45 deg) and some of it solid screed (at 35 deg). Wunda have suggested that I would need a separate manifold for the different temps. 

 

I think I came across a thread a while back suggesting this might be possible using actuators? Keen to hear thoughts on what's possible at a 10deg difference - and if a 5deg difference would make this approach more viable?

 

If it's not possible then I'll stick to two manifolds - but thought I would check-in first and see what you guys think.

 

Thanks

[JohnMo]

Basics are, the smaller the differential, between flow and return the more heat that goes into the floor/room.  You can do this by increasing a loops flow rate.

 

The opposite is also true, bigger differential lower heat output.

 

Decreasing flow rate increaces differential, to output.

 

So it's just a matter of getting the balance right.

 

Remember Wunda and other just want you to buy more products.

 

I got all my UFH from outsourced energy, good prices and products.

 

[ProDave]

You should design it so all areas give the same output at the same temperature.  Coarse "adjustment" being different pipe spacing on different floor make ups, and fine adjustment being adjusting the flow rates through each loop.

 

So if they are saying the solid screeded floors need a lower temperature, compensate by widening the spacing in those and run them at the same temperature.

 

But since you want the lowest temperature you can get it would be better instead to have closer spaced pipes in the pug mix sections and run those at the lower temperature.

[HaloThree]

Thanks for the replies.

I've got the UFH design/install guide that Wunda recommended which has the BS EN 1264-2 tables for the various subfloors and finishes.

Striking the balance between required heat output and the maximum floor surface temperatures (room temp + 9deg) across the different floor build-ups is the challenge here. 

Without having different flow temps for the different floors build-ups I'm unable to get the required heat output within an acceptable max floor surface temp. That's how I landed at 45deg (@200 centres) for the joisted space & 35deg (@100 centres) in the solid screeded area.

[ProDave]

1 hour ago, HaloThree said:

That's how I landed at 45deg (@200 centres) for the joisted space & 35deg (@100 centres) in the solid screeded area.

So try 100 centres or 150 centres in the joisted bit?

 

Room temperature + 9 degrees?  I doubt my floor is ever hotter than room temp +2