UFH - max slab temp and floor probe location??

[jgtr]

Hi, I have wet UFH in a newbuild 6m x 4m conservatory. Does anyone know what temp the slab (screed) should be ideally? I've only just switched it on so am heating it up slowly, using floor probe mid depth in the screed to raise the temp by 2 degrees per day while slowly increasing the inlet water temp.

Now I am at floor temp of 32 degrees which gives air temp of 19 degree (45 degrees water temp) - does this sound ok as everything I read uses floor surface temp and not actual slab temp.

Where is the best place to measure floor temp, I buried it in screed as I though that it would give better reading but floor surface tends to cool off before slab starts to cool so floor isn't particary warm but room still heats ok.

Thanks

 

[jgtr]

Anyone any ideas??

 

[Agile]

Who designed and installed this?

Why are they not advising you?

Tony

 

[Tipper]

I use an IR thermometer to check the surface temperature. You can get them from Maplin.

Room temperatures are regulated by room thermostats controlling the loop/zone valves.

 

[jgtr]

I installed it myself, company supplying the kit designed it, off the shelf type thing.

It works, just wanted to check what the screed temp should be as everywhere talks about surface temp??

 

[Agile]

The concrete also comes into the equation. As well as the floor finish.

Its normal to use a MAXIMUM flow temperature of about 42 C.

But most would want a surface temp of a maximum of 30 C too.

Depending on the age of the concrete and water content, I would have been increasing the temperature of the flow by only 1 C every day!

Tony

 

[jgtr]

The concrete also comes into the equation. As well as the floor finish.

Its normal to use a MAXIMUM flow temperature of about 42 C.

But most would want a surface temp of a maximum of 30 C too.

Depending on the age of the concrete and water content, I would have been increasing the temperature of the flow by only 1 C every day!

Tony

Thanks Tony

I plan to go upto 50 degrees to condition the slab then drop it back to 40 degrees as this seemed to heat the room fine. Floor surface temp is quite low, I don't think its anywhere near 30 degrees, the probe in the screed is measuring 33 degrees max, floor surface temp would be less than this I think. It all seems to be working fine.

 

[Agile]

Why do you think you need to heat the slab up to 50 C ?

I would have expected that 40 C would have been totally adequate and any higher would be risking cracking!

Tony

 

[Agile]

Why do you think you need to heat the slab up to 50 C ?

I would have expected that 40 C would have been totally adequate and any higher would be risking cracking!

Tony

 

[Agile]

Whilst confirming that I was right I came across this link.

http://www.concreteconstruction.net/concrete-articles/best-curing-temperatures.aspx

Converting the annoying US temperatures to centigrade you will see that curing at too high a temperature seriously degrades the strength.

Whilst your floor is hardly the dam on the Zambesi creating the maximum strength would still be the best option. But the aging concrete on the Kariba dam needs work on it now to prevent any collapse and the subsequent flooding which would occur.

Tony

 

[Dan Robinson]

50 degrees

Your heating a room not firing a flipping kiln.

Screed should be left for a good month or two before putting heat through it and even then 40 - 45 degrees is plenty.

If a wood floor is going on top then the surface temperature mustn't reach more than 27.

 

[jgtr]

50 degrees

No, I said water temp is 50 degrees, and I will then drop it back and run it at 40 degrees.

Slab is running at approx 32 degrees, as measured using a probe laid into the slab (not surface temp) which gives a room temp of 20 degrees, considering it's freezing outside that seemed ok to me.

 

[Agile]

Dont you realise that if the water is at 50 C then the concrete around the pipes is going to get to close to 50 C as well.

Didn't you read the link I posted above?

Tony

 

[jgtr]

Dont you realise that if the water is at 50 C then the concrete around the pipes is going to get to close to 50 C as well.

Didn't you read the link I posted above?

Tony

Haven't read it yet, been busy

UFH is widley stated as working with water temps of 30 to 60 degrees, so screed must be able to withstand this or it would not be the recommended medium for UFH?????????????

I see what you are saying tho, I will read your link.


The other conundrum is what is the difference between curing and drying, as I've been reading alot and the 2 are different it appears. Traditional screed cures to full strength in 21 day, and the major UFH firms all state warming can begin after this time, but drying takes 1 day per mm etc etc and can knacker certain floor coverings if laid before screed is "dry".