ASHP - choices, choices. Feel like I’m back at square one

[-rick-]

2 hours ago, Great_scot_selfbuild said:

I’m not doing the loop design myself (I’m drawing the line at buying a windows laptop just to use LoopCAD), and although the suppliers don’t share their designs before we commit to using them, we’ve had some say their design has 7 circuits and others say they have designed for 11 circuits. Are you advising that we make sure we ask for more than one circuit per room for the redundancy (just to make sure they factor it into their design)?

 

Gus and I have debated this before. My position is you should design the loops to output the heat you need at very low temps. Within reason more shorter loops vs fewer longer ones makes sense. Less than 100m but close to it is about the ideal loop length IIRC. But I wouldn't deliberately add extra loops if it throws off your heat output calcs, etc. In the event of a loop failure, firstly you want to find it and fix it before the concrete gets really hard and in the event that isn't possible then because you have designed the system for very low temperatures, you should be able to compensate for the loss by running temps a bit higher and adjusting flow rates.

Edited 7 hours ago by -rick-

[Iceverge]

Don't forget physics. 

 

Meaningful energy transfer will only occur when there's enough  temperature difference. A slab at 24⁰ will impart very little heat into a room at 22⁰ but a lot into a room at 15⁰. 

 

Given identical pipe spacing, on a single zone, the room with big windows or a leaky external door will extract far more energy from the UFH all by itself than the small internal room. 

 

Its not the case that a pantry will end up at 30⁰ and the hallway at 15⁰. 

 

The pantry will probably get to 22⁰ and the hallway to 20.5⁰. 

 

In a passive class house it'll all end up at 21⁰. Regardless of pipe spacing or omitting rooms or forgetting UFH and ASHP and just plugging in a cheap oil filled rad.