Practical spiral layouts for UFH with closely spaced pipes.

[ringi]

The bending radius for 16mm pipes seems to be normally made 150mm, but I understand it can be 5*16=80mm.    So the required 180degree bend in the center of the spiral is at least 160mm wide.

 

How is such a bend fitted in when using 100mm (or below) pipe spacing?

 

These details seem to be "brushed over" in the fitting instructions and the example plans often don't keep to the minimal bending radius for the pipes.   Or am I missing something.....

[JohnMo]

10 minutes ago, ringi said:

How is such a bend fitted in when using 100mm (or below) pipe spacing?

Do a spiral - not a zigzag. Or you do an oversized bend and bring the pipes in.

 

Why do you need such tight pipe spacing?

 

 

[Mike]

Here's one way:

[ringi]

1 hour ago, JohnMo said:

 

Why do you need such tight pipe spacing?

 

 

Good question, unless we install EWI we will never have great insulation levels and wish to get a low flow temperature for a heat pump.   The cost of using double the amount of pipe and manifold ports is low compared to everything else about UFH.  100mm pipe space is the standard recommendation for low-temperature heating from many of the UFH companies.

[JohnMo]

22 minutes ago, ringi said:

standard recommendation for low-temperature heating from many of the UFH companies

Are you getting a grant? If so get the installer to do the UFH, it is all part of the grant allowance of £7500

[nod]

Contact Warm up

they will do you a full design FREE of charge 

[ringi]

On 12/12/2024 at 06:45, nod said:

Contact Warm up

they will do you a full design FREE of charge 

 

But they will ask (or should) for target flow temperature and heat loss from each room.  Or design for what they think is a "good enough" flow temperature, rather then the lowest that is practical.  I am paying heating biils for next 30 years not them.....

 

I am also looking at how we could phase work so remain living in half the property,  so need to play with options on the manifolds locations.  As no UFH pipes can cross the temporary dust control stud wall, but yet to decide where that will be.

 

Having closely spaced pipes should also give more tolerance for a likely oversized heatpump.   Our temperature requirements will be lower then standard calcs assume until we become old....

 

(Also need to think about bathroom layout to fit in heating, and how much floor area is needed for UFH.)

[JohnMo]

Are putting any heat loss calculation into this design?

 

What is your W/m² output target?

 

Are you investing in suitable insulation below the pipes, i.e. 150mm+ of PIR or 50% more in EPS?

 

Is screed or something else going above the pipes?

 

A quick look at 100mm centres and a realistic heat pump flow temp of no more than 40 degs, you are looking at 62W/m².

 

50mm centres closer to 70W/m²

 

150mm centres is about 57W/m².

[nod]

58 minutes ago, ringi said:

 

But they will ask (or should) for target flow temperature and heatlose from each room.  Or design for what they think is a "good enough" flow temperature, rather then the lowest that is practical.  I am paying heating biils for next 30 years not them.....

 

I am also looking at how we could phase work so remain living in half the property,  so need to play with options on the manifolds locations.  As no UFH pipes can cross the temporary dust control stud wall, but yet to decide where that will be.

 

Having closely spaced pipes should also give more tolerance for a likely oversized heatpump.   Our temperature requirements will be lower then standard calcs assume until we become old....

 

(Also need to think about bathroom layout to fit in heating, and how much floor area is needed for UFH.)

No

They don’t ask for any of that 

Just a floor drawing 

[ringi]

2 minutes ago, nod said:

No

They don’t ask for any of that 

Just a floor drawing 

 

So how do they decide the required pipe spacing?

[nod]

Gas boiler 200 HP 150 

Mate it’s free 

If it’s no good to you 

Then you haven’t lost anything 

I’ve used them on both our builds 

 

[Nickfromwales]

The last 2 UFH installs I did in near / at Passivhaus standards of insulation had 100mm centres, but that was to drop the flow temps as low as possible, and to have as much water volume in the slab as possible.
This was mostly to aid cooling via the slab in both instances, but one was an insulated (aka Passiv) raft with the UFH pipes inserted, and the other was a poorly detailed foundation where the pipes were clipped to the pre-cast constructional slab and then we screeded over.

If there is any doubt over performance then UFH should be very seriously considered / reconsidered, as it may well function but may very well be adversely uneconomical to run / operate cost wise.

Kitchens / any other rooms with reduced floor space will suffer most, further impacted if theres large glazed areas, so again you may need auxiliary heating from say a vertical ‘decorative’ radiator in there to achieve desired room temps during the worst days of winter.
Vertical rads prob not going to do much with a heat pump though so this all needs proper thought and for you to sew some headroom into the final choice / solution.

Max floor surface temps will be capped at 27°C, flow temp

will be decided by insulation / screed / floor covering type & thickness etc, so at that limit the heat output needs to be more than suffice, so you’re not ‘just there’, and are able to overshoot the stat set temp (eg the room should be able to get north of 22°C without seriously struggling).