Quick UFH question: 2 or 3 manifolds

[BartW]

Hi,

We are currently in the process of self building, and have got UFH designed on all three floors.

 

GF is living kitchen dine (all open ) + utility + guest

FF is 3 bedrooms and 2 bathrooms

SF is gym only

 

My question relates to UFH on FF and SF. Do I go for separate manifolds with piping and pumps on those two floors, or can they share one manifold? Gym only adds 22m2 so around so less than 200m with flow and return (i.e. 2 ports / valves / zones / whichever way you read it).

FF is 72m2 but excludes bathrooms from, as they will be electric UFH, so really just 64m2, i.e. around 500m of pipes.

 

The options I considered (not necessarily favoured all of them):

 

- separate manifolds for both floors - doubles up the pump and manifold / ancillaries cost, so adds about £300 - £400. + supply pipes more complex / more to run

 

- one manifold to share on FF level - optimal for pipe runs on the first floor with height drop from the manifold to floor within 400mm - 500mm. Most cost effective, but runs a risk of air locks in the SF loops that would run from here. Also, I assume I would need to make sure whatever pump is capable of pushing water up by 3metres. Would an in-line "proprietary" bleed valve solution be a thing to consider, or are we into risk of leaks at couplings and junctions?

 

- one manifold to share on SF level - addresses risk of air locks in the gym. But less optimal, as all my flow and returns need extending by at least 3 - 5metres each to account for the drop from the upper floor. My FF hallway will remain unheated as no pipes would coincide in this area (hallway alcove is where the manifold would otherwise sit.

 

 

 

Your opinions are, as always, very welcome and valued

 

Thanks

Bart

[Adsibob]

As far as I know, but someone like @Nickfromwales will confirm, you need three manifolds, one per floor. You can have a small height change between two levels and get away with one manifold for those two, but we are talking about a level different of up to 50cm or so, not a whole floor. 
The floor area will dictate how many loops you need, so for a very big floor area you will need a manifold with more ports so you can run more loops. But it’s still one manifold.

Also, there are suppliers that will do a design for free, or for a nominal sum if you don’t buy from them. I wish I had done that. My design, which was cobbled together the day my installer installed the pipes, has one mistake in it: two rooms on the same loop, but the two rooms have different heat losses, so one gets a bit hotter than the other. A properly designed loop layout would have avoided this.

Edited January 3, 2023 by Adsibob

[Nickfromwales]

The gym ( SF ) shouldn't really need much heat, if any? To save money I'd just install the FF manifold at the SF level, take off an output to, but lay 50% less pipe for the SF, and run the pipes down to the FF as normal. Running 50% less pipe on the SF will reduce the heat output there and allow you to set the flow temp high enough to deal with what's required on the FF. Again, I doubt that will be much either tbh!!

 

@Adsibob, I've gone down 2 floors on my current project, with zero issues whatsoever ( basic Welsh law's of physics applied; "what goes down must come up" ) and I've done this many times to rid a space of manifold(s), works perfectly well.

Just keep the runs well below 100m and it'll work like a dream, saving the extra manifold, pump and mixer ( and having to find somewhere to locate it ).

Edited January 4, 2023 by Nickfromwales

[Adsibob]

3 minutes ago, Nickfromwales said:

 

 

@Adsibob, I've gone down 2 floors on my current project, with zero issues whatsoever ( basic Welsh law's of physics applied; "what goes down must come up" ) and I've done this many times to rid a space of manifold(s), works perfectly well.

Just keep the runs well below 100m and it'll work like a dream, saving the extra manifold, pump and mixer ( and having to find somewhere to locate it ).

So my plumber mis advised me again! I didn’t think to challenge his recommendation as I thought it was standard.

[Nickfromwales]

1 hour ago, Adsibob said:

So my plumber mis advised me again! I didn’t think to challenge his recommendation as I thought it was standard.

He may have simply erred on the side of caution, in fairness  

It's only pioneering people like me, eg those who do trial and error, at my (their ) own expense and then run with what is known that will / did work, that can make these proclamations lol.

[BartW]

Thanks guys,

 

So as I suspected the shared manifold at the top floor is being favoured and deals with the air locking issue rather well.

 

 

Many thanks!

 

Bart

[Thorfun]

13 hours ago, Nickfromwales said:

The gym ( SF ) shouldn't really need much heat, if any? To save money I'd just install the FF manifold at the SF level, take off an output to, but lay 50% less pipe for the SF, and run the pipes down to the FF as normal. Running 50% less pipe on the SF will reduce the heat output there and allow you to set the flow temp high enough to deal with what's required on the FF. Again, I doubt that will be much either tbh!!

 

@Adsibob, I've gone down 2 floors on my current project, with zero issues whatsoever ( basic Welsh law's of physics applied; "what goes down must come up" ) and I've done this many times to rid a space of manifold(s), works perfectly well.

Just keep the runs well below 100m and it'll work like a dream, saving the extra manifold, pump and mixer ( and having to find somewhere to locate it ).

while i agree with this (caveated with the fact that i'm nowhere near close to being a professional plumber as my diy plumbing thread will attest to!) i would question the 50% less pipe for the second floor, simply because the room may not always be used as a gym. i do agree that you probably won't need heating on the 2F but for the very small cost of a bit more pipe i would simply lay it as normal and put a separate thermostat in the room so as to keep the heat down to the level required. that way if in the future it becomes a study, bedroom, play room or whatever that needs more heat than a gym you have that facility.

 

just my 2 cents.

[Nickfromwales]

If the SF actually ever needs heat, it’ll be next to zero. My bag-of-shit 500mm thick stone walled house / pitiful levels of insulation needs air conditioning on 24/7 to manage overheating up there for prob 10 months of the year, for context. It would be early to mid 20’s up there today without it. 

 

Putting the same flow temp into the OP’s SF ( from one shared manifold, ergo set to a higher flow temp than the SF would ever need ) with a full spread of pipes will likely overheat / overshoot the stat settings and be a little unmanageable, unless this is a mansion with 4/5 spaces up there.