Ufh with weather compensation

[Robin80]

Hi All,

I am renovating a 1970's 95m2 3 bed 1 bathroom bungalow. I have spent a lot of time on here reading about boilers/ufh/weather compensation and mixing rads with ufh. I have decided i would like to install ufh throughout on one zone using a vaillant or veissmann boiler with weather compensation.

I was wondering whether you can run the ufh manifold directly from the boiler without a pump on the manifold? Having found out today that the sub mounting kit for the viessmann is now over £1200 i hope so. Cant quite believe its dobled in price in the last 2 years.

Thanks

 

[Richardthe3rd]

Well, given that you'll need primary water of about 60C for HW & at about 30-50C for UFH. I'd say you need to give it considerably more thought!!

 

[Dan Robinson]

I'd say a better choice of boiller and control regime along with suitably sized rads would simplify things no end.


I have mixed UFH and rads on compensated heating with no mixer valves (just the manifold blender to act as a limiting valve to the UFH).

I do run hot water priority though so the boiler is set to two temps.

This is achievable with the Vaillant and Viessmann but at a cost.

The boiler pump will not cope with the UFH on its own. You will need a manifold pump, or LLH.

Not a difficult system to do, but easily screwed up at the same time.

 

[Agile]

Why do you think the boiler pump will not manage the UFH Dan?

Its only in the UK where we are accustomed to second pumps and blending valves. Most of Europe directly drive the UFH from the boiler.

Tony

 

[Dan Robinson]

And rads? And a cylinder? Off a giannoni HEX? Or an IG hex for that matter?

Try that with a 6 series bunny and see how far you get

 

[Agile]

They don't mix rads and UFH and nor should anyone here who wants an easy life!

Obviously water heating needs a priority circuit. But that's already built into some Viessmanns just for that purpose.

Tony

 

[Dan Robinson]

Nothing complicated about the operation of my heating T. Haven't touched the programming since last winter. Turned itself off months ago, brought itself on a week or so ago.

The key is to plan and setup properly.


Although I do have a top secret box of tricks at work which is forcing me to paraphrase a little .

But in the context of the OP..... if you are starting from a blank slate then it is perfectly feasible. With proper planning.

 

[Robin80]

Thanks for the replies.

Maybe i should have gone into more detail in the opening post.

We are having an extension built at the rear and side of the property. The whole interior has been removed, including electrics and plumbing, and it will be brought up to at least modern building regs.

There are only a few hours a day that no-one is home. Most of the house will be in use and tbh with the size of the property/ rooms and our inability to keep bedroom doors closed, it seemed inefficient and expensive to have separate zones.

I have done several heat loss calculations and taken an average. The only rooms that im unsure ufh will be enough in, are the 2 spare bedrooms and the bathroom. The 2 spare bedrooms are just over 8m2 and require 85w/m2 at a room temp of 20c and outside temp -3c. Do you think there is enough floor spare to give adequate heating with only ufh?

I have spoken to a few local ufh companies but they all seem to want to sell me way too many things with thermostats for every room, which i cant see the sense in. The next ufh company i speak to is also a veissmann trained installer. Thats why im asking here so that i can get a better idea of what i want/need before speaking to him.

 

[Agile]

Depending on the floor coverings its usually easy to get 100W/m2 from UFH if you are not using carpet.

The problem with UFH is usually with small rooms where the floor area is small when its often not possible to get enough heat out. But leaving doors open helps to equalise the heat.

My friend has 26 separately controlled UFH zones. Including the seven toilets!

All supplied directly from the boiler in case Dan asks.

Tony

 

[Robin80]

I also cant imagine needing 20c in the spare room. In our house now we rarely have it higher than 19c in our main bedroom. Is there much truth in being able to have a room a couple degrees lower, due to the radiant heat delivery of ufh?

We were intending to use engineered wood in the bedrooms but we have seen concreate interlocking tiles which are 10mm concrete with 4mm of wood on top so that could solve the problem.

I would like to have a towel rail in the bathroom to help heat the room. am i right in thinking i could oversize it run it at the same temp as the ufh?

 

[Dan Robinson]

Tony, what boiler? What pump? What pipe size? What pipe centre? 100w/m on anything other than tiles is also a fools errand.

Radiant heat does allow a slightly lower target temperature AS LONG AS THE DRAFTS ARE ELIMINATED.

Ufh in bedrooms IMHO is pointless. There is not enough free floor area to radiate heat in my experience. Rads are fine possibly with programmable valves if you feel inclined.

Just put the ufh onto its own control circuit.

 

[Agile]

Robin take care with wood floor coverings.

Firstly that they can take the heat and secondly that they will transmit enough heat.

You can reduce the heat output of any UFH loop by reducing the flow through it.

Tony

 

[DP]

Son had his house extended. Extension comprised kitchen and shower room

Installed U/F as two loops in the extension.
Rest of the house is radiators
Kitchen s engineered timber flooring
Shower room is tiled floor
System is split with mid position motorised valve
Underfloor off manfold with its own pump and own room stat

Boiler is a Netaheat GA combi

The installation has been time tested and nothing lacking
In fact son is contemplating getting another house and old man will have to trundle down the well worn road to repeat the process

 

[Richardthe3rd]

Thanks for the replies.

Maybe i should have gone into more detail in the opening post.

We are having an extension built at the rear and side of the property. The whole interior has been removed, including electrics and plumbing, and it will be brought up to at least modern building regs.

There are only a few hours a day that no-one is home. Most of the house will be in use and tbh with the size of the property/ rooms and our inability to keep bedroom doors closed, it seemed inefficient and expensive to have separate zones.

I have done several heat loss calculations and taken an average. The only rooms that im unsure ufh will be enough in, are the 2 spare bedrooms and the bathroom. The 2 spare bedrooms are just over 8m2 and require 85w/m2 at a room temp of 20c and outside temp -3c. Do you think there is enough floor spare to give adequate heating with only ufh?

I have spoken to a few local ufh companies but they all seem to want to sell me way too many things with thermostats for every room, which i cant see the sense in. The next ufh company i speak to is also a veissmann trained installer. Thats why im asking here so that i can get a better idea of what i want/need before speaking to him.

Bathrooms are generally supplemented with a towel rail., with the rails straight of the floor loop, OK so they're only 30-50C, but they're covered in towels!! I've close banded pipes around rooms before to get the watts/M2 jagged up a bit.

Who told you a Bedroom should be 20C, bloody el!! With radiant heat from UFH & little air flow/drafts 17 is equal to 20C.

UFH companies make no money from pipe or fittings, the only way they make money is from selling you controls. Golden Rule KISS.

The index floor loop would need to be sized to establish if one circulator would be addiquid for the whole system. In my experience, no.

Most companies selling UFH kits would do you a design.

For that size of house I wouldn't spend a fortune on an expensive Gerry boiler, complete waste of money, more knobs, bells & whistles to go wrong!!

Oh you can get 100watt/M2 outta screed concrete floor - with tiles, as Danny boy has stated. But it's verging on the uncomfortable & more difficult to control on our 'four seasons in one day' British climate!!

Spend loads of money on insulation, get the best U values you can. It'll save on heating installation costs & more importantly, long term running cost.
HTH

 

[Agile]

Richard, what UFH pipe diameter makes up the most common in your area?

Tony