Air source heating, how far does it run in a loop?

[saveasteading]

Do we need 2 systems to heat this building?

 

Imagine if you will, a building that is approx 22m by 22m with a courtyard in the middle. the wings are about 6m wide including  the very thick walls.

 

From what I have read, UFH loops are 50m at most. therefore to get to the opposite side of the building and back is 44m, and there is only 6m left to heat  any area.

 

Should we therefore look at a single plant room, but a long feeder to a second manifold (or more) at the opposite end?

Or might we as well use a second, smaller  ASHP with its own kit adjacent?

There is scope all round for the external appliance. Better in the daylight than the shade too, I expect.

 

The gross internal floor area, including some upper level, is about 400m2, and I am thinking this will need 15kVA, but am no expert.

Assume thermal insulation to about the Scottish target for conversions, and there will be two woodburners.

 

This is early days, but may affect room layout.

 

More info upon request.

[joth]

13 minutes ago, saveasteading said:

Do we need 2 systems to heat this building?

 

Imagine if you will, a building that is approx 22m by 22m with a courtyard in the middle. the wings are about 6m wide including  the very thick walls.

 

From what I have read, UFH loops are 50m at most. therefore to get to the opposite side of the building and back is 44m, and there is only 6m left to heat  any area.

 

Should we therefore look at a single plant room, but a long feeder to a second manifold (or more) at the opposite end?

Or might we as well use a second, smaller  ASHP with its own kit adjacent?

There is scope all round for the external appliance. Better in the daylight than the shade too, I expect.

 

The gross internal floor area, including some upper level, is about 400m2, and I am thinking this will need 15kVA, but am no expert.

Assume thermal insulation to about the Scottish target for conversions, and there will be two woodburners.

 

This is early days, but may affect room layout.

 

More info upon request.

 

One ASHP but 2x UFH manifold? While the UF loop itself has a limit in length, you can always put a longer length of (very well insulated) secondary circulation pipe to get from the main plant room to a remote manifold. You'll need to run the ASHP a wee bit hotter to allow for losses along the supply pipe, but shouldn't be crazy.

In essence, the same schematic as you'd use for UFH installed across multiple floors

 

[Olf]

16 minutes ago, saveasteading said:

UFH loops are 50m at most

I usually see 100m value, but regardless, it is more a rule of thumb than an actual physical hard limit. Pipe diameters, layout (number and radius of bends), number of loops on the same manifold and pump capability are all factors affecting the actual performance.

[saveasteading]

4 minutes ago, joth said:

(very well insulated) secondary circulation pipe

Like this?   This appears to be up to 35dia, which I guess would be needed, so something like 80mm incl wrapping. This would then need to be in the wall (warm side) rather than the screed. not so easy!       Probably worth contriving more insulation than this.   

      

[saveasteading]

8 minutes ago, Olf said:

100m

Thanks. But still probably not the best way to do it, with lots of long runs to get to the area it is wanted. There could be rooms with 4 or 5 sets of pipes running straight through.

I am guessing it gets horrible to handle in long runs.

[RHayes]

I haven't heard of a 50m maximum before, but as Olf mentiones it is down to internal pipe size, and number of bends etc. that contributes to pump duty.  The only reason the pipe work lengths are limited is to prevent having to have too big a pump, or having too high a flow rate requirement.  Typically a 16mm UFH pipe system will be quite happy with loops of 100m.  We use 17mm pipe ourselves and have a maximum of 120m as rule of thumb.

 

Have you had a UFH design done for the property.  This would be the best way of getting the pipe runs calculated and working out flow rates, pressure drops and ultimatly circulator pump sizing.

[saveasteading]

14 hours ago, RHayes said:

Have you had a UFH design done for the property. 

 

No, we haven't finished adjusting the room layout yet, as this affects forming openings in the stone wall, levels under existing lintels, strength of the structure, and immediately, whether we need an extra plantroom: we are nowhere near that far.

It will be at least a year til we are looking at UFH supply.

I had a quick think about the routes of loops, and if we were not to add another manifold at the opposite end, we would have some rooms with pipes for every other room running through, and none for themselves.

 

I think we can run the feeder through the void in the upper rooms, where boxed off to form a sensible wall. Then we will find a way down to the ground again, with a box out.  that adds 5m and 4 bends though..

 

Would you cheekily ask one of the internet suppliers to do a free design, or are you thinking of a consultant or contractor?

[RHayes]

I was thinking of a contractor but there are some who will do a pre order design for you asking them to do this for you (cheekily or otherwise) woudn't be a bad idea.  That way you'd know your pump duties and maximum loop lengths instead of it being guess work, that is if the designer you choose gives you pump duties.  Some do and some don't.

 

Look up underfloor heating designers, there is a few uk based who may be able to help out as a one off, but I doubt they'd do it FOC.

http://www.ufhcaddesigns.co.uk/

https://www.ufht.co.uk/