Ian Timshel wrote:
Ian Timshel squeezed out:

I've been poking around looking for a list or NG to learn a bit more
about radiant floor heat. I have not had a lot of luck.. If anyone
knows where these guys hang, please post or drop me a note.
Thanks for all I learn here..
Cheers! Ian


Thanks guys..
I posted some details to "sci.energy" after seeing some questions
posted there via google. Here is what I posted on "sci.energy"
Again if anyone has any more comments I'd sure like to hear from you.
Cheers! Ian.

==========
Hi all.

Direct questions are listed at the bottom of this post...
"The rambler" eheh

If there are more appropriate forums to be posting these questions
please steer me toward them.

I have "googled" away a fair amount of time today trying to find an
email list or N/G dedicated to this type of question but did not find
my way home..

I hope only a few of these ideas are "goofy stupid" but I am
willing and able to be set straight with the wisdom of the group.. ;^)

I'm looking for some answers regarding radiant floor heat. I've built
a small 200 sq/ft first attempt system and it works well... meaning
that even with cold Canadian winters I have not noticed a significant
boost in my electric bill to keep the building heated this way.

This first attempt runs with a 15 gallon hot water tank and has the
thermostat controlling the pump. Even during the coldest days (minus
40C) the tank does not spend very long heating, but the pump will run
for extended periods of approximately five or six hours. The tank
kicks in once in a while to keep up with the demand. The tank is set
to it's lowest heating setting. The tank has no trouble keeping up
with demand. It spends most of it's time "off". The tank sports a
single 3000k element.

The pump on the first attempt floor is too big for the job so it
rifles the glycol through at a pretty quick rate.

I find the heat to be very attractive and stable. I am very pleased
with the resulting environment. This is my "clean shop" with a lathe
and mill.

The concrete for both floors is eveloped in 1.5" of rigid Styrofoam on
the bottom and sides, to break contact with the ground. The walls and
ceiling are R40 or better.


==============


I'm now attaching another larger floating pad 22' x 22' to extend the
building and wondering how best to heat it. This will be a guest
house with a sitting area and two bedrooms. Walls and ceiling will
be R40 or better.

This new floor will have an independent heating system.

I'm considering an "on-demand" type boiler system 5000k but am leery
of the thermostat controlling the heating elements. The new pad is a
5" thick pad with a 10"x16" footer around three sides.

The new floor will have a pump appropriate for 300 foot loops of .5"
kytek pipe.

The heating pipe will be 6" from the perimeter on 12" centres in two
loops. The first loop is 262' and the other is 229.5' in theory.
That makes for a difference of between 12 and 15 percent depending on
how you go about calculating it (I think!). The loops are staggered
to allow for circulation throughout the building should one loop fail.

questions

Will the "on-demand" set-up be more or less efficient than the small
reserve tank on this size/type of floor?

Will the difference in loop length be too great between the two loops
and adversely effect the flow or some other element of the design?

Is staggering the pipe a waste of time?

/questions

Any comments will be welcomed.
Cheers! Ian.



I would use a water heater with the capability of temperature reset. Keep
the loop temperature as low as possible which will give you a large delta T
across the heat exchanger. If you can program in an optimal start/stop
scheme it would be even more efficient. More tubing in the slab will allow f
or a lower water temperature and more even heat. Match the circulator to the
actual requirements, which in your case is going to be high head and low to
moderate volume- Taco and Grundfos have the charts on their websites.