Underfloor heating from solid fuel

[Anonymous]

We are hoping to run a small area approx 25m2 of underfloor heating from a solid fuel rayburn. Has anyone done this and if so any advice? Thank you.

Kel

 

[Anonymous]

I'm interested in this too - so if anyone has any info it would be good to know!

 

[charlie-ia]

does nobody know?

 

[another_richard]

Tell us, tell us.

 

[NT]

What is it youre asking?


NT

 

[geoff]

I've never tried it or heard of it being done; it might be difficult to get the temperature right - i.e. low enough. Underfloor works on a much lower temperature and I'm not sure the lack of control inherent in a solid fuel boiler - you can't turn the supply on and off like gas or oil - means it would not be possible. Perhaps if the rayburn were connected (only) to a thermal store, this could then be used to blend and circulate the water to the underfloor heating as a sealed system (see Heatweb or Gledhill systems). You would still have the problem of being unable to control the burning though - some sort of heatsink to prevent overheating might be needed.

 

[another_richard]

The Romans could do it, why can't we?

 

[NT]

I've never tried it or heard of it being done; it might be difficult to get the temperature right - i.e. low enough. Underfloor works on a much lower temperature and I'm not sure the lack of control inherent in a solid fuel boiler - you can't turn the supply on and off like gas or oil - means it would not be possible. Perhaps if the rayburn were connected (only) to a thermal store, this could then be used to blend and circulate the water to the underfloor heating as a sealed system (see Heatweb or Gledhill systems). You would still have the problem of being unable to control the burning though - some sort of heatsink to prevent overheating might be needed.

Just use the standard method applied to any UFH run off CH. Ask news:uk.d-i-y or see the central heating articles on
http://wiki.diyfaq.org.uk/index.php?title=Special:Allpages


NT

 

[Aidan]

does nobody know?

FOGB thermal store, 3-port mixing valve with a weather compensated (aka outdoor re-set) controller, modulating flow temperature secondary circuit serving the UFH. Primary circuit to/from the boiler & thermal store.

If you were to use a simple heating circuit direct from the Rayburn, the low return temperature would cause condensation of the water vapour in the flue gases causing corrosion of the boiler. The thermal store is kept at 60 to 80 degC by the Rayburn, flow to the UFH is controlled at a reduced temperature by the 3-port valve. The 3-port valve opening is restricted if the return from the store to the boiler approaches 60 degC. Quite simple really.

 

[Flyfisher]

The Romans could do it, why can't we?

Well, obviously, the underfloor heating goes without saying, but apart from that what have the Romans ever done for us?

 

[Keycare]

I have just installed a DPS heatbank thermal store connected to a Redfyre oil central heating cooker.

The heatbank is capable of being connected to the primary heat source (redfyre) a solar panel and a solid fuel boiler.

The redfyre heats the store directly (no coil). The rads are supplied from the store directly (not from a 3-port or 2 port valve in the boilder flow/return) , the UFH circuit is supplied from the store directly. There are no motorised valves at all, just pumps and blending valves that are controlled by room stats. Also it supplies hot water at mains pressure.

I am hoping that a solar panel will heat the store enough in autumn to pre-heat the UFH circuit.

I may connect the solar circuit to a back boiler connected to my wood burner for really cold spells in winter. I would need a heat leak radiator for this circuit anyway.

 

[Aidan]

the UFH circuit is supplied from the store directly. There are no motorised valves at all, just pumps and blending valves that are controlled by room stats.

Yes, like that. I don't think solar will contribute much to the UFH. You'd need to maintain the store temperature for the hot water supply and the efficiency of the solar system will be reduced.

The blending valves are 3-port mixing valves, but presumably with pre-set thermostatic control, rather than an electric actuator, and with the pump switched by the room thermostat.

Continuous circulation and temperature modulation is reckoned to be a better control system by the manufacturers. The thermal lag of a floor slab can cause a very slow response to room temperature variations. Weather compensation will cause a response from the heating system as soon as the outside temperature drops & heat losses increase, and not wait until the room temperaure has fallen. The electric actuators can also incorporate a control system to maintain the boiler return temperature, if the UFH is causing excessive cooling of the store.

 

[Nemesis]

The Romans could do it, why can't we?

Well, obviously, the underfloor heating goes without saying, but apart from that what have the Romans ever done for us?

Here's another thing the Romans seem to be doing (for charity):

http://www.wallsendorbust.org.uk/index.htm

 

[charlie-ia]

im just learning about ufh.
are there old fashioned ways of doing it?(1960ish perhaps?)

The only time Ive felt underfloor heating was in our maths room at secondary school.Red tiled floor, as hot as a radiator almost, not just background heat.On the third floor I seem to remember.
this seems a lot hotter than "normal" ufh appears to be?

maybe I dont remember right, or it just wasnt supposed to be so hot? you could tell there were hot pipes running through the floor

It was cosy in the winter though, and Ive fancied a floor like that since. Would have loved to lie on it and doze insted of do sums!

 

[Aidan]

im just learning about ufh.
are there old fashioned ways of doing it?(1960ish perhaps?)

Older than that.
The Koreans have had UFH with hypocaust type systems for the past 2,000 years. There's a good article on Wikipedia here.
http://en.wikipedia.org/wiki/Underfloor_heating

Frank Lloyd Wright
( http://en.wikipedia.org/wiki/Frank_Lloyd_Wright ) discovered Korean ondol heating in about 1916 and incorporated the idea into his later buildings, amending it to operate with pipes in the floors. A Google search for Lloyd Wright and Underfloor produces more hits than you can shake a stick at.

There are pre-WW2 UK buildings that had radiant heating systems with steel pipes embedded in the floors, but these systems have mostly been abandoned due to leaks caused by neglect. I also worked on one auditorium that had a working radiant system with steel pipes embedded in a vaulted plastered ceiling. This was also being wrecked by clueless repairs and maintenance; despite being told, the building managers wouldn't listen. By now it has probably got a new radiator system and a new ceiling.

UFH was used in Levittown developments in the US, which were budget housing for demobbed GIs after WW2. There are pictures of Levittown houses under construction in a pdf file here
http://www.heatinghelp.com/library.cfm#Old Radiant Heating Systems.
Also lots of information on other old radiant heating systems.

The Levittown houses had annealed copper tubes embedded in the concrete floor slab that was poured directly onto the sub-soil. No insulation, but oil was cheap!

The metal pipes used in early systems generally fail due to corrosion, erosion or settlement. UFH really only became practical with plastic tubes.

The only time Ive felt underfloor heating was in our maths room at secondary school.Red tiled floor, as hot as a radiator almost, not just background heat.On the third floor I seem to remember.
this seems a lot hotter than "normal" ufh appears to be?

maybe I dont remember right, or it just wasnt supposed to be so hot? you could tell there were hot pipes running through the floor

Probably not. They work much better with a variable temperature system so that the heat emissions are reduced as the building warms up. Many plumbers and "heating engineers" do not understand variable temperature systems or mixing valves. When the mixing valve needs to be repaired, some neanderthal will rip it out and stick in a constant temperature pump. I'd guess that might be what had happened with your school system.

The low water temperatures from UFH can achieve high efficiencies with condensing boilers. However with old systems, using non-condensing boilers, they can cause huge problems with flue gas condensation and corrosion, unless there's a return mixing system to maintain the boiler return temperature. These return mixing systems would get isolated or "repaired" by a moron and the whole UFH system would then self-destruct. Not many old UFH systems survive.