Category: Technical information associated with S&P Coil Products
Trench Heaters Product Selection Heat Pipes Product Selection Part 1
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Trench Heaters & Heat Pipes - Product Selection - Part 1
MINIB Trench Heaters – Product Selection & Design Guide
Applications
Trench heating is a branch of perimeter heating in which the heaters
themselves are located below floor level. The top of the heater is
formed from a continuous roll-out grille which finishes flush with the
floor level and hence can be walked upon or used as standing area.
Trench units can be installed in false floors or in trenches within the
concrete screed.
Trench heating is typically specified in zones which incorporate full
height wall to floor fenestration. Not only does the window provide a
source of cold draughts but it also prevents the siting of alternative
intrusive heating equipment. When fitted adjacent to the window the
trench heater will convect warm air upwards to prevent the cold down
draught and warm the glazed surface to prevent misting.
Depending on the heat loss and type of trench heater selected, trench
heating can be used in isolation or in conjunction with other forms of
heating. It is particularly useful in providing additional window
protection for spaces whose interior is warmed by underfloor heating
pipes which themselves are incapable of preventing cold draughts.
The addition of the perimeter trench heating system will dramatically
reduce the warm-up period of an underfloor heating system. During
certain times of year the main heating system can be closed down
allowing the trench system alone to maintain the required space
temperature.
Shallow, passive trench heaters should be selected to provide additional
heating. When used as the primary heat source deep trenches should be
specified or the use of fan-assisted heaters considered.
Types of Trench Heater Available
All MINIB trench heaters are manufactured from a stainless steel
trench to protect against corrosion, a feature uncommon in other units
but invaluable in areas where moisture may collect inside the casing.
All trench heaters incorporate a heat exchanger consisting of copper
tubes expanded into aluminium fins and should be c/w flexible
connections on the hot water flow and return pipes, flow-setting and
shut off valves and an air bleed plug. When the heaters are fan-assisted
an electric heating element can be selected instead of hot water.
The top of the trench heater should be formed into an edging frame into
which the aluminium, stainless steel or wooden roll-out grille is laid.
This grille is easily removed in order to gain access to the inside of
the trench for servicing. Grilles are available in a wide range of
materials and decorative styles to match the interior space.
Heat Outputs Available
When selecting the type of trench heater required the first stage is
to calculate the heat output required per linear metre. If the value is
less than 350W then a shallow passive trench can be used (typically
125mm deep). If the value rises to 450W then a deep passive trench will
be available (300mm deep) to provide the output. The effect of depth on
output is due to the stack effect, with a taller stack above the heater
drawing more air through the matrix.
Passive trench heaters are available in a variety of widths with the
wider units providing for greater induced airflows and somewhat higher
outputs; typical widths are 250 to 400mm. Units should always be fitted
with the heat exchanger away from the window in order to optimise the
output.
If heat outputs per linear metre rise above 450W then a fan assisted
trench heater should be considered. Outputs of up to 1500W per linear
metre are achievable with fan assisted trench heaters. In order that the
noise level be minimised and that good coverage of the heat exchanger is
achieved small diameter tangential fans are used.
All MINIB fan assisted trench heaters incorporate fans driven by 12V DC
motors. The energy consumption of these DC motors is 80% less than AC
motors used on competing products. The specific fan power achieved with
these motors is only 0.1W/litre/s and noise levels in typical furnished
spaces are only around 28dBA at medium speed.
Fan assisted trench heaters can also be designed to provide summer
cooling in four pipe or two pipe changeover systems. This can be useful
when summer solar gain through windows is high. Maximum cooling capacity
should be designed around a figure of 300W per linear metre.
The width of fan assisted units can be as low as 100mm and depths of as
little as 50mm are possible though typical dimensions are 250mm wide by
125mm deep.
Control
Passive trench systems can only be controlled on the water side and
this control can be on/off or modulating using mixing or diverting
valves. Fan assisted trench is ideally controlled on the air side
whereby the fan speed can be accurately controlled by thermostats,
occupancy sensors, timers etc.
Technical information associated with:
SPC - S&P Coil Products - Coils, Heat Pipes, Heaters, Exchangers,
Dehumidifiers, Radiant Heating, Warm Air Door Curtains & Fan Convectors
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