wrote:
I see a lot of "Radiant Floor Heating" with a rubbery tubing stapled under
the floor. SInce I tend to be in horror of any kind of leaks, I wonder why
they don't use some compresses gas instead?

Nothing has a greater heat capacity than water (per pound). You would
need to run a *lot* of air through the system, that's why forced air
systems have large ducts and run hotter.

Even mini duct systems need to run the same *volume* of air as their
larger brethren. Now think of running several hundred cfm through even a
1" tube. Daunting and a lot of loss both in pumping and line loss.
Completely impractical.

Leaks really aren't a problem in underfloor staple up systems. The
runs tend to be in one piece for each room.

I believe the better underfloor systems use not "rubber" hoses but
PEX (cross linked polyethelene with oxygen barriers) with heat spreaders.

The only problem I've heard of with that (PEX) has been rodents.

Jeff


Mind you, I have even had experience with central venting "leaking": I
haven't used a/c since my folks died but my uncle's a/c duct sweats onto my
ceiling. That's the price for freeloading (hot air rises) off his a/c.

Jeff writes:


Leaks really aren't a problem in underfloor staple up systems. The
runs tend to be in one piece for each room.

I believe the better underfloor systems use not "rubber" hoses but
PEX (cross linked polyethelene with oxygen barriers) with heat spreaders.

Actually, the better installations I've seen have 2 interleaved runs
for a room. The idea is: if in fact one leaks, the other still handles
the room...
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"David Lesher" wrote in message ...
Jeff writes:


Leaks really aren't a problem in underfloor staple up systems. The
runs tend to be in one piece for each room.

I believe the better underfloor systems use not "rubber" hoses but
PEX (cross linked polyethelene with oxygen barriers) with heat spreaders.

Leaks in hydronic (water-based) floor heating systems used to be a big problem :
In the 60's, many hydronic floorheating systems were installed using copper pipes inside concrete slabs.
It took 30 years but most of these systems eventually start leaking at the pipe joints inside the concrete causing very tricky
leaks.
Leaks in piping in concrete is hard to locate (use helium gas detection method), you need to rip up your flooring, and jackhammer
into the concrete and fix the broken joint.
Very expensive leaks indeed.

Luckily, life got a lot easier with PEX (cross-linked Poly Ethylene).
Apart from being probably the future for all residential plumbing in general (replacing expensive copper plumbing), PEX is almost
ideal for hydronic floor heating systems.

PEX is very, very stable (corrosion free; lasts longer than your home), can handle high pressure if that may occur has flexibility
but is not 'floppy', so it is easy to install and it is much cheaper than copper too. Typically hydronic systems have a continuous
PEX loops, so that there are NO joints in the tubing that is under the floor. This again reduces chances of leaks, since leaks
typically occur at joints.

Basically the only way to get a leak in a correctly installed PEX hydronic system is if you drill into the floor (and into the PEX
tubing) or jam a nail through it. PEX is sturdy, but it cannot handle nails and drillbits.

Once you have a leak, it really depends on how accessible the tubing is if it is costly to fix or not.
If the tubing is inside a poured concrete slab, then fixing it is difficult and expensive.
If the tubing is 'staple-up' underneith an existing wood sub floor, then there is access to the tubing, and fix is easy.
If the tubing is in a 'sandwitch' on top of a sub floor, then of course you need to remove flooring to fix it, so it is difficult.

I have installed a hydronic floor heating system (with PEX tubing) in a sandwich on top of an existing concrete slab sub floor.
Installed 2 years ago.
It's working great, and the PEX tubing was not a problem at all to install.
Risk of leaks is only there when people start drilling into the flooring.

Pictures below


Actually, the better installations I've seen have 2 interleaved runs
for a room. The idea is: if in fact one leaks, the other still handles
the room...

Actually, the interleaved runs are called 'counterflow' loops.
Counterflow loops minimize temperature differences on the floor, by placing inlet and outlet of a loop next to each other.
Multiple loops in a room are needed for pretty much any reasonable sized room, since the temperature drop limits the length of the
loops to about 250 feet.

I've never heard about installing loops so that one still works if the other is leaking. If anything leaks in the system, you want
to fix that before continuing. Unless you want to risk wrecking your hardwood (or whatever else you have installed on top of the
floor heating).

Here are pictures of my (PEX in a sandwich configuration) system under construction.
Some pictures also show counterflow loops with

http://viper.verific.com/WebSites/RadiantFloor

Regards

Rob

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"Rob Dekker" writes:



PEX is very, very stable (corrosion free; lasts longer than your home),
.....
Basically the only way to get a leak in a correctly installed PEX
hydronic system is if you drill into the floor (and into the PEX tubing)
or jam a nail through it. PEX is sturdy, but it cannot handle nails and
drillbits.

Or if it does not last as long as the venders claim it will. Obviously,
we don't have 50 years of experience with it.

I know it has temperature limits. If using a boiler, better have a
hi-temp monitor/safety.

Actually, the better installations I've seen have 2 interleaved runs
for a room. The idea is: if in fact one leaks, the other still handles
the room...

Actually, the interleaved runs are called 'counterflow' loops.
Counterflow loops minimize temperature differences on the floor, by
placing inlet and outlet of a loop next to each other. Multiple loops
in a room are needed for pretty much any reasonable sized room, since
the temperature drop limits the length of the loops to about 250 feet.

Interesting; I thought they always started at the outside wall side
of the room, and returned from the inside. But I didn't lay the floor,
just designed the GSHP controls and installed them.

I've never heard about installing loops so that one still works if the
other is leaking. If anything leaks in the system, you want to fix that
before continuing. Unless you want to risk wrecking your hardwood (or
whatever else you have installed on top of the floor heating).

The idea was you can disconnect that one loop and use the other{s}.

http://viper.verific.com/WebSites/RadiantFloor

The house I refer to had them cast in ?3-6"? of Gunite, with random slate
as the surface.


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"Rob Dekker" writes:


PEX comes in various ratings, but typically can handle close-to-boiling
water under pressure easily.

My system is a closed-loop system driven from the water heater, and
can't get any hotter than 130 F and low pressure (12 psi PT relief
valve on the loop). But even if all safety measures would fail, the my
(cheap) PEX can handle 100 psi at 180 F, so I feel pretty secure that
something else will blow out first.

I'm talking degradation, not sudden pressure failures...I'll let you find
out if it's true...your tubing is easy to replace.

But I didn't lay the floor, just designed the GSHP controls and
installed them.

Cool. I did not go that far. How much piping went into the ground ? ?
How deep did you have to go What were the economics calculations of ?
such a ground-heat system versus other heat sources What was the water ?
temperature requirement for the floor heating system ? How did that ?
affect your GSHP specs I wonder how that system looks like. Have any ?
pics ?

Well, it was that or propane; and the 10 years since have proven
the wells a wise choice.. but it was lots of capital. [3 wells,
~250 ft deep.]

I don't have any pictures. I think there are 12 floor zones and
6 FCU's used for AC as well.

I currently use my water heater as a heat source, but are now planning
to hook that up to DHW solar panels to get some heat from the sun.

We installed a spare 40 gal in case of a GSHP failure or lengthy power
outage. My SWAG showed it would keep the house about freezing. It's never
been used; when occupied & fed, the 2 wood stoves can drive you out onto the
porch in a blizzard, if fueled with pine.

The desuperheater feeds the domestic HW tempering tank.

The idea was you can disconnect that one loop and use the other{s}.

OK. Makes sense, especially in emergency situations. But often a leak
did already do water damage to the flooring before we find it out, so I
would think that it requires fixing either way.

Hard to damage concrete with a little water.


I think that's called a insulated sandwich slab-on-slab. Great system !

Over existing slab, put 1 inch (or more) insulation, lay out rebar and
PEX tubes, and poor a couple of inches of concrete over it for the
new floor.

This IS slab; installed at construction. Yes, it is slow response.

Downsides are that the system is pretty thick (4 inch minimum) and that
water temps need to be relatively high (140 F and up).

No way. I have to think but I recall our upper limit is 30C. With
a GSHP, it costs exponentially more to raise the loop temp.


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433