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3. Installation
For the installation of air heaters in duct systems, see the
individual instructions entitled: Installation Instructions for
Duct Accessories.
The capacity of the air heater with Thermo Guard is inde-
pendent on the direction of airflow through the air heater.
See Fig. 1.
The return pipe must always be connected to the connec-
tion marked Thermo Guard. See figure. 2.
Use a pipe wrench to restrain the pipe connections of the
air heater when tightening the external pipe connections
to avoid damaging the tubes in the air heater.
Always fill the air heater with liquid from the lower con-
nection. Vent the system before you commission it.
The supply flow temperature should be between 55-70°C.
The available pump pressure must not be higher than 25
kPa if the inlet flow temperature is higher than 65°C. If
the inlet flow temperature is between 55°C and 65°C, the
available pump pressure should be between 12–40 kPa.
If the inlet flow pressure substantially exceeds the rec-
ommended pressure, a pressure limiting device, which
reduces the pressure to the recommended level, may be
necessary.
A pressure limiting device should not be installed in venti-
lation systems that utilize hot water supplied from a dis-
trict heating plant, since such a device could contribute to
high recirculated water temperatures.
4. Operation
Thermo Guard frost damage protection
Frost damages in the air heater most often cause the tube
bends to burst.
Research has shown that the tubes in the air stream are
the first ones to freeze. When an ice plug forms inside a
tube, it expands longitudinally along the tube and this
increases the water pressure in the bend causing it to
burst. Hence, it is not the ice itself that causes the bend
to burst, but the high water pressure in the bend brought
about by the ice inside the tube.
Thermo Guard frost-damage-protected air heaters operate
according to the principle that involves relieving abnormal
pressure rise in tube bends by draining water from the
tube bends to the return pipe of the air heater.
This enables the air heater to cope with freezing without
damage. However it is important to note that possible
valves installed in the return pipeline must not be closed
since doing so will put the Thermo Guard function out of
action.
Thermo Guard frost damage protection is the only one of
its kind on the market that offers frost damage protection
in the event of a power failure and similar service disrup-
tions.
2
www.swegon.com
Fig. 1
TBLA connections with Thermo Guard
Fig. 2
Thermo Guard
connection
T piece
Frost guard sensor
Thermo
Guard
Control
Swegon
valve
AB
5. Electrical connections
For particulars of the electrical connections of the valve
actuator and circulation pump, see the separate instruc-
tions for the TBVL/TBVA valve kit.
Swegon reserves the right to alter specifications.
GB.TBLAMT.141001
Shut-off valve (must not be
closed if freezing is likely –
to relieve pressure).
Pressure limiting device,
if required
Heating
water
A
Shut-off valve
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