Operating Underfloor Heating

[nirish]

@Exedon thanks, I regret having it commissioned through the builder and not arranging it myself. I was given no documentation or calculations or follow up support. I'm going to chase to see if any of this exists.

Can I ask one question, in my picture of the manifolds there is a red toggle at the bottom. It is in the vertical position which matches all the black toggles. The difference is this puts the black ones in the anti-clockwise position and red in the clockwise position which is confusing. Do you know what it does and which way it should be?

 

[winston1]

@winston1 I'm afraid that isn't helpful in any way, after much research it was clear that underfloor heating is the most effective way to heat a high vaulted ceiling room as the radiative effect warms the lower space more than convective heat from radiators which all instantly rises to the ceiling. Clearly mine isn't working efficiently enough to meet the demand which is incredibly infuriating but I don't think ripping it out should be the first port of call.

I'm sorry you disagree. But the fact is underfloor heating suffers from hysteresis, i.e. it takes ages to heat up and cool down. Excellent for a nursing home where it is on 24/7 but hopeless in a house where you want it on for an hour or so before going to work and then a few hours in the evening before going to bed.

 

[Swwils]

I'm sorry you disagree. But the fact is underfloor heating suffers from hysteresis, i.e. it takes ages to heat up and cool down. Excellent for a nursing home where it is on 24/7 but hopeless in a house where you want it on for an hour or so before going to work and then a few hours in the evening before going to bed.

Nothing to say that having a heating system on for an hour is efficient. The bigger emitter is always going to be more efficient.

 

[winston1]

Nothing to say that having a heating system on for an hour is efficient.

The less you have it on the less fuel used. If you have on for an hour and it does not heat it is wasted. If you have it on four hours to get it up to temperature for one hours use I call that 25% efficient.

The bigger emitter is always going to be more efficient.

Can you back that up with calculations?

 

[nirish]

Sorry to try stop the squabbling, but for better or worse I have underfloor heating and would like to get it into a functional state if possible. The pros and cons aren't really helping at this point!

Does anyone know what the red valve does in my picture does and what position it should be in? Vertical which is turned clockwise is where it has been up to now.

 

[nirish]

@Exedon I found these images of the insulation and underfloor pipes being laid. Any thoughts?

 

[Exedon]

I can only assume that valve is some sort of bypass
With the heating on turn off the two valves above it
If the brass tee's below stay hot after a few minutes the red valve is open if they go cool it's off
Its needs to be off.

 

[Exedon]

Pictures very useful pipes look about 250mm apart?
Can you give us room dimensions in metric please! Window / door sizes how much and type of insulation in ceiling and walls sketch showing dimensions to show which are external walls would be good.

 

[nirish]

@Exedon based on number of pipes in the pictures and room length I estimate 200mm apart for the pipes

The room is 5.3x5.65 so about 30msq External on 3sides, 5.65, 5.65 and 5.3
Two windows 2msq each
French doors 4.5msq
Double height vaulted ceiling with ...
Dormer Window 0.6msq
Two Velux 1.3msq each

Ecotherm insulation in all walls and ceiling 70mm thick

 

[Mr Chibs]

I’m curious about how this is installed.
I assumed that it would be pressed into an insulated tray, then your flooring on top.

Looking at yours (clipped on insulation)
I was thinking it was going to be screeded over.

I’m asking the question now, won’t there be large air pockets around the pipe work that will be getting heated up and not passed straight through the floor?
Will this have an effect on efficiency?

I’ve no experience with suspended floors and ufh so would be interested in hearing Exedon’s opinion.

 

[Exedon]

My understanding is that pipework is in a screed #1
Underfloor in Suspended floors is quite common typically involving insulation then a reflector plate with pipework clipped. in.
Hight of vaulted ceiling please!

 

[Nozzle]

Set both loops to maximum flow with the adjustment flow meter. Temperature blender at 45C is enough, as there are limits to how hot the screed should be. Maybe tweak the temperature up a little bit

https://www.underfloorheatingsystems.co.uk/2006/03/05/underfloor-heating-mixing-valve-set-up/

Nozzle

 

[Nozzle]

Can I ask one question, in my picture of the manifolds there is a red toggle at the bottom. It is in the vertical position which matches all the black toggles. The difference is this puts the black ones in the anti-clockwise position and red in the clockwise position which is confusing. Do you know what it does and which way it should be?

Black ones are isolation valves for the manifold, pump and UFH loops away from the rest of your system. The red one looks to be a bypass so, if you wanted to take isolate as above, then you can link the flow directly to the return.. Which is a bit odd as that might have the effect of bypassing any other radiators in the house - OR it could be used as a throttle. Is it multi-turn or just 90 degree full on to full off?

Nozzle

 

[SpecialK]

What boiler do you have? I had a cycling problem with my boiler as it was just bypassing internally. Try opening that red valve half way and see if your boiler cycles less when the UFH is calling.

How is the rest of the floor made up - you mention screed??? or is it just 18mm chipboard, thin layer of levelling then LVT?

I don't know if this will help but here is a graph of mine. This is laid in 55mm liquid screed...heats the slab from 19 to 24 degrees from 17:00 to 22:00. It wasn't running continuously. Im very new to UFH and this is the first time I have it in a property.

Also does the return temp reach the same as the flow temp fairly quickly? That would mean not enough heat is being drawn from the pipes...

 

[nirish]

@Nozzle the flow for both loops is set to maximum, the installer appears to have capped the temperature blender as it only turns to 4.5/6 which translates to about 48degrees on the flow. I've been requesting 21degrees on the room thermostat for days but it has never managed more than 19degrees in the room. The link you sent shows a higher temperature of 55-60 for timber! Over the screed we have 18mm chipboard, plywood (not sure of thickness) and then the karndean vinyl so I don't know if it should be in this higher range due to all the wood.

The red valve is only a quarter turn valve, I'm at a bit of a loss when it comes to reasons for a bypass / throttling etc.

@SpecialK our boiler is a newly installed Worcester Greenstar24ri, I've not looked at how it's behaving when the UFH calls for heat or what a cycling issue is I'm afraid. As mentioned above the screed is cement/sand I believe, then 18mm chipboard, the karndean installer laid ply and vinyl on top. From what I've seen the return temp and flow temp almost always read within a degree of each other which concerns me. I have tried reducing the flow rate to see if that changed anything but it didn't help. How would you normally increase heat drawn from the pipes?