[VAC] Re: Balsa core flooring

["Dr. Gerald N. Johnson, electrical engineer" <geraldj@xxxxxxxx>]

I think that product would be handy but its not structural, it depends
on there being floor under or wall behind it. E.g. it won't span joists.
The floor we've been talking about would span the joists with no other
support.

5/16" tube raises an interesting possibility useful in the RV. The large
tubing is run all in series or sequence so the tubing diameter needs to
be relatively large to control the pressure drop. But it means that the
tubing closest to the heat source will always be warmer than the tubing
near the other end of the run. In houses, the tubing run is arranged so
that the beginning and end are next to each other and most of the run
is  arranged with hot and cool parallel and adjacent so the average
between them is always the same throughout the run. Going to a much
smaller tubing can let on run a parallel phalanx of tubes from a common
manifold at each end of the space to be heated. With out the meandering
of the single tube system (but with more connections) draining should be
a lot easier. I built an auxiliary radiator for a water cooled boat
engine that once, used 3/4 copper pipe for the manifolds and 1/4" tubing
for the parallel runs (swaged the ends down to make shoulder for support
while soldering).
> 
> > Radiant heating is most effective when it can radiate to the occupants.
> > That's how its efficient. It can't radiate from under the cabinets, and
> > you sure don't need to be adding heat under the refrigerator...
> 
> In a retro-fit (applying radiant floor over existing) I agree with you. I still
> like the idea of some heat going into the cabinets, may be wasteful, but so be
> it. If it make you any happier, you have convinced me not to put as much under
> the cabinets as I would have before we traded posts   :-)
> 
> > I don't know about a heat source. Needs a pump too. I suppose a surflo
> > water pump will handle the temperature. There are versions that handle
> > farm chemicals decently. Looking at the prices for electric tankless
> > water heaters, I'm inclined to use a 2 or 6 gallon water heater tank for
> > that application.

Overnight I looked in the Shoup catalog and see that their surflo
chemical demand pump is rated to operate to 170°F. 1.5 gpm for about
$105. There probably would need to be some revision to disable the
pressure demand switch or to make sure the pressure in the loop didn't
rise enough to shut it off.

> 
> I think that with the small amount of water I would try out the smaller version,
> 2 gal., especially with the 5/16" tubing.

Then one might use an Atwood LP/electric RV heater to allow either fuel
source.

> 
> > 5100 btu (1500 watts) is nearly enough for my Caravel, but something
> > larger would need more to be comfortable.
> 
> I may be able to get away with less BTU's than other with my Excella, I have the
> double insulated glass versions of the windows. I wouldn't think I would need
> more than 10,000 BTU's for the 30' trailer.

Yes, my Caravel windows are single pane. But every Airstream has
aluminum structure between the outside and inside wall. Just seeing a
spray in place foam applied on the tube. I presume a variation on
Icynene. Might be something beneficial to the major Airstream retrofit.
R 6.5 per inch. 40 cents per board foot installed for open foam, 80
cents per board foot installed for closed cell foam. Versus 20 cents a
board foot for fiberglass. They say. Last I checked in Iowa the
difference between the open cell foam and fiberglass was more like 3:1.
The foam can't be installed except by a qualified contractor.

> 
> > The 1500 watt element standard
> > in a 2 or 6 gallon electric water heater could be replaced by something
> > larger. There needs to be an expansion chamber on the heating loop to
> > allow for the changes of water volume when hot.
> 
> I found what looked like about a 1 quart version in a catalog at the
> contractor's today

Should be a standard part of a closed loop water heat system.

> <snip>
> I wonder if two or three air chambers might not work for the expansion just
> throw a pressure pop off in line, and everything would be good to go. The whole
> thing including the electric heating would only take up the space of a small
> suitcase.

You can predict the expansion volume required from the volume of the
system and the air space available in the expansion chamber and the
expansion of water from 33° F (maximum density) up to say 140°F (to
allow for a bit of over heat).