The higher radiant output of flat-panel wall heaters provides an attractive option to
traditional, much smaller, recessed, high-wattage fan-coil or filament wall heaters.
Recessed installation of any heater within an outside wall can compromise insulation.
An increase in the temperature differential from the inside to the outside of the
insulated wall at the point of installation could result in additional heat loss to the
outside, which should be factored into the design analysis. Surface installation of
shallow-depth ceramic panels has a smaller impact on adjacent wall heat loss (Fig.
2.21). Comparative installed wattage may be reduced in direct proportion to
decreased backloss and radiant versus convection output that is characteristic of
wall surface-mounted flat-panel heaters in comparison to wall fan-coil units.
Higher radiating surface temperatures are achieved with ceramic or glass
graphite-coated elements that are used for out-of-reach cove and grill-protected
recessed wall heaters. With wattage output of approximately 300 W or more per
square foot, the heating element surface temperatures are much too hot to touch
and require protective grills or location 6 ft or more above the floor. Installation
requires clearance from all surfaces. Back enclosures embody a reflective surface to
enhance radiant output and reduce back heat loss.
High-watt-density glass and ceramic elements are made in numerous sizes. The
actual heater casing is only a few inches larger than the element, but the relatively
high material density results in a weight density approximating the 4 lb/ft2 of metal-
encased radiant panels. The various product housings are designed so that the element
is relatively easy to replace.
Element replacement is an attractive feature that extends fixture life and avoids
the costs that are involved in refinishing a wall in the event of fixture removal. Electrical
element life is very long.The ceramic heat element substrate offers structural
stability. Failure is rare for ceramic elements. Most failures are due to glass failure,
not electrical element failure.
Glass elements, when used, should be manufactured to the same standards as
automotive safety glass.The heat-tempering process is intended to ensure that shatter
fragments or shards are within defined safety specifications, should breakage
occur. The 50-year installation history of glass and ceramic heaters provides useful
product life and field performance information.
Higher-watt-density ceramic heaters require less wall space in relation to most
other radiant wall heaters due to the significantly higher wattage output. As with
most heating systems, occupant comfort may be impacted by occupant location in
relation to the heat output source. For someone who longs for the feeling of warmth
associated with sitting near a fireplace, concentrated warmth may be a particularly
attractive feature unique to high-temperature recessed radiant wall heaters. From a
design standpoint, high panel surface temperature requires that radiant asymmetry
relationships be reviewed in relation to design objectives.
Ceramic element cove heaters provide a means of installing high wattage capacity
in a relatively small space. Installation is usually on an exterior wall about a foot
below the ceiling, just above a window.The unobstructed panel element heat transfer
is evenly split between radiant and convection. Interior wall placement is an
option to be considered for buildings that meet current construction and insulation
standards, as defined in ASHRAE Standards 90.1 and 90.2 for commercial and residential
buildings, respectively. Location on an interior wall minimizes panel backloss
to the outside. Interior wall location facing heavily glazed exterior walls is a popular
residential porch application. Ceramic or glass element cove heaters are relatively
heavy, requiring connection to structural building members (Fig. 2.22).
Sizing of ceramic wall and cove heaters is commonly 20 percent less than convection
baseboard. High element temperature makes these heaters especially effective
task heaters. Users report satisfaction with both comfort and operating cost, which
suggest that they are taking advantage of the excellent task-heating performance.
Ceramic and glass heater elements reach full operating temperature quickly.
Determination of the radiant and convective heat transfer split, relative location to
the occupant, setback temperature, and relative sizing in relation to heat loss are
important factors in determining the time period that is required for comfort
restoration.There are many applications where higher-temperature heaters may be
used for problem solving and task heating, as well as primary heating. Popular applications
include nursing homes, retirement homes, hotel and motel applications, public
and elderly housing, and primary and vacation residences.
The higher radiant output of flat-panel wall heaters provides an attractive option to
traditional, much smaller, recessed, high-wattage fan-coil or filament wall heaters.
Recessed installation of any heater within an outside wall can compromise insulation.
An increase in the temperature differential from the inside to the outside of the
insulated wall at the point of installation could result in additional heat loss to the
outside, which should be factored into the design analysis. Surface installation of
shallow-depth ceramic panels has a smaller impact on adjacent wall heat loss (Fig.
2.21). Comparative installed wattage may be reduced in direct proportion to
decreased backloss and radiant versus convection output that is characteristic of
wall surface-mounted flat-panel heaters in comparison to wall fan-coil units.
Higher radiating surface temperatures are achieved with ceramic or glass
graphite-coated elements that are used for out-of-reach cove and grill-protected
recessed wall heaters. With wattage output of approximately 300 W or more per
square foot, the heating element surface temperatures are much too hot to touch
and require protective grills or...
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