Building Services Engineering 5th Edition Handbook

Heating 91
4.7 Balanced-flue terminal.
Insulated sheet steel case
Electric resistance heating elements
Concrete or cast iron storage blocks
4.8 Off-peak electric storage heater.
obtained with more concentrated forms of heat emission and a uniform distribution of comfort
is produced. An example is shown in Fig. 4.9.
Soft copper pipes are laid in position on the concrete floor slab and held by clips, and the ends
are connected to header pipes in service ducts. Joints are avoided for the under floor sections.
Steel or plastic pipes may be used in some situations. Thermal expansion and contraction of the
pipework must be accommodated and the floor surface temperature is limited to avoid damage
to the structure, surface finishes or occupants. This is done by enclosing the pipe in a hard
asbestos sleeve on water pipes operating at 85 ◦ C or by controlling water temperature to 45 ◦ C
with a mixing valve system. Pipes are buried in the floor screed. Heating elements are evenly
distributed to provide uniform radiation and convection to the occupants.
Electric ceiling heating can consist of buried cables or a flexible conducting mat fixed between
the ceiling joists and plasterboard, as shown in Fig. 4.10. The mat is electrically insulated
from the structure and connected to 240 V 50 Hz supplies to rise to a surface temperature
of 40 ◦ C.