Install Instructions

25
IM-PR 566442 1114 (Design Manual)
1.8.2 Panel piping
Panel piping is piping that is used within the radiant
panel, whether floor, wall, ceiling or other location.
Viega provides two types of panel piping, ViegaPEX
Barrier and FostaPEX tubing. ViegaPEX Barrier
includes 4 layers. The first layer is the cross-linked,
high-density polyethylene. The second layer is
an adhesive for the third layer, the ethylene vinyl
alcohol layer (EVOH oxygen barrier). The fourth
layer is another very thin layer of polyethylene,
put on the outside to protect the EVOH layer from
damage. EVOH is highly resistant to the passage
of oxygen. ViegaPEX Barrier is recommended for
hydronic radiant heating, cooling and snow melting
systems utilizing water or a water/glycol mix as
the heat or cold transfer media. Tubing may be
installed in concrete, gypsum-based lightweight
concrete, sand, asphalt (in accordance with special
guidelines) in or under wood flooring or behind
wallboard or plaster. ViegaPEX Barrier may also
be used as transfer lines for baseboard heating
systems with a maximum operating temperature of
200°F @ 80 psi.
Viega’s FostaPEX cross-linked polyethylene
tubing provides the benefits of flexibility and
shape retention. The multi-layered construction
of the FostaPEX tubing is made from one full
dimensional inner PEX core with an aluminum and
outer PE layer surrounding it. This construction
allows the inner layer alone to meet all temperature
and pressure requirements of the system. The
aluminum layer allows tubing to be bent into
position and remain in position when released.
FostaPEX tubing is intended and recommended
for use in hot and cold potable water distribution
systems and hydronic radiant heating and cooling
systems. Like ViegaPEX Barrier, which has a barrier
layer that resists the passage of oxygen through the
wall of the tubing, the aluminum layer in FostaPEX
offers even higher resistance to oxygen permeation
in radiant heating applications. FostaPEX tubing
can also be used in water service applications and
is virtually impermeable to any soil contaminants.
Design temperature and pressure ratings for
FostaPEX are 160 psi @ 73°F, 100 psi @ 180°F, and
80 psi @ 200°F. Detailed information on FostaPEX
and ViegaPEX Barrier are provided within Viega’s
Tech Data sheets.
For panel piping, typical tubing spacing ranges
from 6" to 12" on center, depending on the
application. By reducing tubing spacing, you
can increase the heat delivered to a space while
encouraging comfortable, even heating of the
assembly. The tightest spacing (i.e., 6") is generally
for high heat loads or to support floor drying and
occupant comfort in areas where periodic moisture
is expected – areas such as bathrooms and
foyers. Spacing at the high end of the range (i.e.,
12") is typically reserved for areas with low heat
loads, such as well-insulated garages that will be
maintained at low temperatures; well-insulated,
below-grade slabs; or interior zones of large
commercial buildings.
Tubing diameter has a larger impact on system
pressure (head) and circulator selection than it does
on heat delivery to a space. Larger-diameter tubing
results in lower head and the potential to downsize
circulators, which can save pumping energy. For
indoor applications using Viega products, the
most common diameters specified in panel piping
are ½" and
5
∕
16
" diameters (Table 1-6). When very
long circuits are specified (e.g., commercial and
industrial applications with circuits of 500' or
greater), ⅝" or ¾" tubing is common.
The maximum tubing length per circuit should be
limited to keep pumping head within a reasonable
range. Maximum recommended tubing lengths
are based on the circuit’s heating load, fluid
composition, temperature drop and tubing
diameter. Use Table 1-7 for general guidance on
maximum recommended tubing length for common
installation scenarios. For maximum recommended
tubing lengths in snow melt applications, see
Section 5.3.
Managing oxygen (O2)
Left unchecked, the presence of oxygen in
radiant piping systems can cause serious
problems, including corrosion of ferrous
components, damage to circulators, reduction
of heat transfer and system flow rates, and
increase of system pressure and noise. O2
entry points into a radiant piping system include
joints, dissolved O2 in the fluid itself and tubing
without O2 barrier. Options for managing
O2 include completely isolating any ferrous
components (iron and steel) from the rest of the
piping via a heat exchanger, use of only non-
ferrous components in the system, or Viega’s
recommendation – the use of O2 barrier tubing,
such as ViegaPEX Barrier or FostaPEX. The
use of O2 tubing is recommended for its cost
effectiveness, proven track record and higher
system operating efficiency than would otherwise
be achieved through a heat exchanger designed
for this purpose.