UFH

[nod]

I’m just reading through the Greenstar boiler instructions prior to installing 

ive come across a section that says that I need to install an external blender to limit the water tempriture that is fed to the UFH 

The fitter that will comision the boiler says it’s overkill 

Any thoughts

 

[PeterW]

UFH manifold will do that for you. 

[nod]

8 minutes ago, PeterW said:

UFH manifold will do that for you. 

That’s exactly what my mate said

He also pointed out that the UF pipe wouldn’t be effected by heat 

 

[PeterW]

Boiler will need to modulate right down - buffer would be ideal then it won’t short cycle etc 

[recoveringbuilder]

Hubby says you need a mixing valve to take it down to 45-50degrees otherwise you’ll crack the slab (if it’s a slab )or floor tiles , wood flooring etc

[PeterW]

1 minute ago, Christine Walker said:

Hubby says you need a mixing valve to take it down to 45-50degrees otherwise you’ll crack the slab (if it’s a slab )or floor tiles , wood flooring etc

 

You need to be much less than that. 35-40c tops, some run even lower (27-32c in low energy houses) so you get issues with boiler flows as they can rarely go below 45c in heating mode. 

[Jeremy Harris]

13 hours ago, Christine Walker said:

Hubby says you need a mixing valve to take it down to 45-50degrees otherwise you’ll crack the slab (if it’s a slab )or floor tiles , wood flooring etc

 

 

As @PeterW says, it needs to go a LOT lower than that.  I never. ever, have our flow to the UFH above about 24 to 25deg C, any more and the house just over shoots the set temperature when the heating turns off.

[Nickfromwales]

If going combi > UFH manifold without buffer then you really need a bypass between flow and return just before the manifold. Use a 22mm lock shield gate valve so it cant be inadvertently adjusted. Try it first set at 75% open and see if the UFH manifold still gets to the set flow temp. The UFH manifold will still pull all the hot water it needs so dont worry about the bypass being open, just VERY important not to have the boiler pump going 70MPH and the manifold pump going 30MPH and them fighting it out. It should really go to a low loss header or buffer to hydraulically isolate the two pumps from each other. Boiler can blast into the buffer, and the UFH can just trickle through the other side of the buffer and do its own thing. Boiler will then only fire to reheat the buffer instead of constantly running its internal pump and adding a lot more mileage ( and shortening its life cycle ), same with the boiler fan.

Should be ;

Boiler fires up at 55oC ( no higher eg to promote condensing ) and heats the buffer. 

Buffer gets to temp and the buffer stat tells boiler to go dead / standby.

UFH pulls from the other side of the buffer.

Buffer then cools and the buffer stat tells the boiler to fire again. 

Repeat.

Everything gets to temp and the boiler cycles get further apart.

When heatings not needed the buffer stays cold. 

 

Best solution is to put the buffer in the airing cupboard ( or the hot-press if your a big fan of potatoes   ) so the seasonal heat given off goes towards airing the laundry.