How can I roughly calculate UFH output at given flow temps.

[SimonD]

1 hour ago, jimseng said:

This may be a stupid question but is it then impossible to balance the system so all rooms heat up to similar temperatures without the mixer valve control? Would one not be able to achieve something by having a manual mixing valve to balance between the GF and FF zones.

Like I say, I haven't had/used low flow temp heating before.

I thought the whole point nowadays was to treat the house as a single thermal envelope and not zone. Particularly for me as it is a new build rectangle with high insulation and high performance windows. There may be carpet on the first floor (eventually) but the target temp would be lower than ground floor.

 

Normally what you would do is design the heating system to do this naturally. Each room would have its ufh output designed for the specific heat load - this means you might have different pipe spacing etc.

 

The problem with a manual mixing valve is that it only works reliably with fixed flow temperatures, and many of them only really work well with high flow temperatures. They don't work well when you have modulation from the heat source that you will get with weather compensation.

Using an electronic mixer is not the same as zoning, because you are not cutting flow to the zone, think of it as a heat area instead. What you're doing is controlling the constant flow of heat to that area, appropriate to its heating requirements. So, for example, on a cold day you might need a flow of 45C but on a mild day, it might be as little as 27C, depending on the house heating co-efficient (W/K). Therefore the house is still being treated as a single thermal envelope.

 

The issue with target temperature is down to the floor buildup. If you have a buildup that has a higher TOG value, you need a higher flow temperature - and this may still be the case, even if your target room temperature is lower. None of us can answer this question because we know so little about the house design conditions.

 

The reason we're suggesting a mixed circuit as a possibility is because you already have the existing one in place and we don't know anything about its design other than it's at 150mm spacings. We also don't know about the proposed design for the FF - is it going to be using speader plates, or is it screed too? 

 

There are so many variables you need to consider and then put together your FF design that complements the existing GF, then you'll be able to decide whether you actually need to have a mixed circuit or not. 

 

I think the whole mixer circuit thing was suggested as the alternative to hydraulic separation, not as a dictate about your design. So at the moment, if you're going to attempt the design yourself, spend your time learning about the design and then complete that process, including reverse engineering your existing UFH installation and go from there. Don't spend your time right now worrying about mixers. That will come later.

Edited 4 hours ago by SimonD

[Nickfromwales]

2 hours ago, SimonD said:

The problem with a manual mixing valve is that it only works reliably with fixed flow temperatures, and many of them only really work well with high flow temperatures.

Not so with the Ivar sets. Totally different beasts, have you used these before?

 

2 hours ago, SimonD said:

So, for example, on a cold day you might need a flow of 45C but on a mild day, it might be as little as 27C, depending on the house heating co-efficient (W/K). Therefore the house is still being treated as a single thermal envelope.

How do you achieve disenable segregation of the GF and FF if there not two stats (and therefore 2 zones)? Not a stab btw, I'm still at school every day I'm concious.

 

3 hours ago, SimonD said:

None of us can answer this question because we know so little about the house design conditions.

This...

3 hours ago, SimonD said:

There are so many variables you need to consider and then put together your FF design that complements the existing GF, then you'll be able to decide whether you actually need to have a mixed circuit or not. 

....with this on top.

 

3 hours ago, SimonD said:

Don't spend your time right now worrying about mixers. That will come later.

When we know 'TOG' and anticipated floor coverings, plus the GF situation. Don't worry about it, but don't discount it quite yet, is my 2 cents.

 

It would be a bugger if you design for x floor coverings, and then cannot have anything else, ever, in its place for eg.