Bryant 50YEW Design Manual page 29

When a door is opened, the stored heat is released to the space
immediately. The larger the temperature difference between the
air in the space and the fl oor, the quicker the fl oor releases its heat
to the space.
Maintenance garages benefi t from radiant fl oor heating systems.
Cold vehicles brought into the garage are warmed from
underneath. The snow melts off the vehicle and dries much more
quickly than when heated from above. In addition, mechanics who
work on the vehicles will be more productive, especially when
their work requires them to lie on the fl oor.
Health care centers and child care centers can benefi t greatly
from radiant heating. Since children play on the fl oor frequently,
the benefi ts of a warm fl oor will keep children from getting chilled
while playing.
Figure 2-11: Radiant Floor Zone Manifold
In residential applications occupants in a space feel comfortable
with lower air temperatures if their feet are warm. Typically the
space will feel comfortable with air temperatures as low as 65°F
[18°C]. Since the heat loss of a building is directly related to
the temperature difference between inside and outside, a lower
temperature difference also means the heat loss is lower.
Some of the factors affecting the heating capacity
of a fl oor heating system are:
• Spacing of the pipe – tighter spacing increases heating capacity.
• Water fl ow through the pipe – more water fl ow increases
capacity (high fl ow rates, however, increase pressure drop and
may result in larger pumps).
• Temperature of the supply water – higher temperature
increases heating capacity of the fl oor.
• Sub-fl oor material (wood, concrete or light-weight poured
concrete) – concrete is best.
• Floor covering (ceramic tile, carpet, wood, etc.) – be careful
with carpeting, which is an insulator, and may require hotter
water and/or tighter pipe spacing depending upon pad type,
carpet type, and thickness.
• Insulation value under the fl oor – make sure that the system is not
heating the ground underneath instead of the conditioned space.
Bryant Geothermal Heat Pump Systems
Part II: Load Side Design / Distribution Design
• Piping layout – always consult the piping manufacturer's
literature for the best layout.
The spacing of the pipe in residential applications can vary from 4"
to 12" [10 to 30 cm]. If the spacing is too great, the temperature
of the fl oor can vary noticeably. The design of the radiant
fl oor piping system is beyond the scope of this manual. Most
distributors of radiant fl oor piping and accessories offer some
design assistance to heating and cooling contractors.
Once the load calculations have been fi nished, the water-to-water
equipment [and loop if applicable] has been sized, and the buffer
tank has been designed, the radiant fl oor piping system can be
designed based upon the water temperature in the buffer tank
(i.e. aqua-stat set point or maximum water temperature at design
conditions if using outdoor reset).
BASEBOARD RADIATION
In existing systems, baseboard radiation is typically designed to
operate with 160-200°F [71-93°C] water or steam. Baseboard
radiators are usually constructed of copper tube with closely
spaced aluminum fi ns attached to provide more surface area
to dissipate heat, as shown in fi gure 2-12. Some of the factors
affecting the amount of heat given off by fi n tube radiators are the
water temperature, water fl ow, air temperature, pipe size and fi n
size/spacing. A decorative cover is normally fi tted over the fi n tube.
In some cases, water-to-water heat pumps can replace a boiler
that was used to generate hot water for baseboard radiation. For
example, if an existing home has had weatherization and insulation
upgrades, it is possible that the heat loss of the home has decreased
enough to allow lower water temperatures. Manufacturer's data
on the baseboard convector should be consulted to determine
the Btuh/ft. of radiation [W/m] at lower water temperatures. The
50YEW series can provide up to 145°F [63°C] for baseboard
radiation. Higher water temperatures, however, lower the C.O.P. of
the heat pump, so lower water temperatures are better if possible.
Another alternative for baseboard radiation is double-stack convection,
where there are two rows of fi n/tubes within the enclosure. This
denser design allows for the use of cooler water temperatures.
Figure 2-12: Baseboard Radiation
Water-to-Water System Design Guide
Aluminum Fins
Copper Tube
Enclosure
Copper Tube
Aluminum Fins
Floor
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