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# Radient floor BTU/hour/ft2

## Radient floor BTU/hour/ft2

#1
02-03-05, 08:02 AM
jhb
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Can anyone tell me what the BTU heat value of the 5/16 hepex is when installed in the quick trac system (7" spacing"). I am just wondering if its worth prusuing in ym application, thanks!

#2
02-03-05, 01:53 PM
RBean
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Heat output

The output from a radiant floor is a nominal 2 Btu/hr/sf * deg F difference between the floor temp and the room temp. So a room designed for 70 deg F and limited to 85 deg F floor temp has a capacity of 30 Btu/hr/sf.

(85 deg F - 70 deg F) * 2 Btu/hr/sf *deg F = 30 Btu/hr/sf.

This tells us that any load greater than 30 Btu/hr/sf is going to need supplemental heat regardless of fluid temperature or tube spacing.

Incidentally most floor coverings make great radiators. The only difference between carpet, tile or plain concrete is the required fluid temperature which is a function of spacing, but all floor coverings operating at the same temperature have the same output.

Pipe diameter influences the hydralics(velocity & pressure loss) more so than heat transfer. example...a 10" pipe having the same water temperature as the room temperature transfer zero Btu's....a 3/8" pipe running 30 deg F higher than the room temp transfers all kinds of Btu's...so diameter is not as important as delta T, because all it takes is a few degree rise in fluid temperature to compensate for smaller diamter pipes...

Spacing influences water temperatures...closer the spacing the lower the water temperature.

We have lots of great information on radiant transfer and fluid principals on our web blog ... unfortunatly DIY.com site rules prevents me from posting the address.

Sorry.

#3
02-03-05, 02:01 PM
RBean
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Heat Transfer 2

Sorry about all the info above...it was cut and pasted from an answer to a simliar question we rec'd from a reader to our blog.

the diameter and spacing will not give you output.

Your missing the floor R value above the tubes plus any back losses which have to ba calculated.

RBean

#4
02-04-05, 08:44 AM
jhb
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No, the information is just waht I was looking for. How can I find this blog?

The R value for the floor is 3/4 pine...

#5
02-04-05, 08:47 AM
jhb
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...and the room has a heat loss of 9240btu.hour

#6
02-04-05, 05:23 PM
RBean
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what is the total square footage and of the 9240 Btu/hr...how much of it is back loss?

Back loss occurs when the room or ground below is cooler than the floor temperature...it’s typically conduction losses...if you don't know...tell me all the details of the floor assembly...

As far as the blog address...I think you'd have to ask DIY.com for my email address...

Sorry...but its their rules...

You can always do some surf and search...

Robert Bean

BTW...I'm away in Florida at a conference...if you don't hear back from me immediately - you now know why
...