03
WHISPA III
®
5000, 9000 & 12000 RCU
1.0 General Information
2.0 Heating System Design
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This MYSON WHISPA III
®
recessed commercial unit (RCU) is
designed for recessed wall applications where the use of
surface mounted units would not be appropriate. All units
have a one piece low profile front cover.
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WHISPA III
®
RCU fan convectors are designed to be used with
mono-flo Tees from a series loop, on a two pipe system, or as
a stand alone zone.
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WHISPA III
®
RCU fan convectors are available in three sizes,
and before proceeding with the installation the heating
system design must be considered and the unit correctly
selected to meet the heat loss requirement of the room.
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WHISPA III
®
RCU fan convectors are supplied with a fan speed
selector switch mounted on the front of the unit.
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WHISPA III
®
RCU fan convectors are supplied with built in
½" compression shut off valves for both the supply and
return.
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WHISPA III
®
RCU fan convectors are supplied with high
volume purge valve - air vents.
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WHISPA III
®
RCU fan convectors are supplied with an integral
combi - zone control and flow control valve, with a factory
fitted insert set to give 1 GPM. The flow rate through the unit
will not exceed this value, however, other inserts of 2 GPM or
3 GPM can be fitted by the installer to give higher flow rates.
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A low limit thermostat prevents the fan from operating if the
water temperature in the unit is below 110°F
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WHISPA III
®
RCU fan convectors are not designed for use with
steam.
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A 24V room thermostat, On – Off or set back type, can be
wired to this unit to give room temperature control.
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A time control can be wired to WHISPA III RCU fan convectors
to provide occasional coil purging flow through the coil if
considered necessary.
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All waterways are of copper. No lead brazing materials are
used to assemble this unit.
The WHISPA III
®
RCU can be fitted on a series loop with
mono-flo or venturi Tees, on a two pipe system or as a stand
alone zone.
For optimum fan convector performance the system must be
capable of providing sufficient hot water through the heat
exchanger. This means that:
1. Care must be taken in sizing both the pump and piping.
The minimum pipe size from the boiler to the fan convector
must be
1
/
2
" copper tube.
2. Where the WHISPA III
®
RCU is fitted on to a system with other
emitters, mono-flo Tees or diverter Tees should be used to
provide adequate water flow.
3. The system water must be above 110°F for fan to switch on,
and best results the mean water temperature should not be
below 140°F.
4. Optimum performance will require effective balancing of the
whole system.
5. The WHISPA III
®
RCU should not be used to replace a
radiator in an existing system unless an adequate flow of
water can be guaranteed through the unit.
6. The loop must be pumped. WHISPA III
®
RCU fan convectors
are not suitable for gravity circulation systems.
3.0 Selection and Sizing for Heating
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Heat output performance figures for the three sizes of
WHISPA III
®
RCU fan convectors are given in the Technical
Data section of this manual.
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Since WHISPA III
®
RCU fan convectors are supplied with fan
speed control, it is important to size the unit to match the
calculated heat loss requirements of the room with the unit
operating at the low fan speed (I).
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The higher fan speed can then be used for more rapid
heating from cold in extreme conditions.
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When establishing the temperature difference, i.e. entering
water to room temperature, allowance should be made for
temperature drop in the system. It is the water temperature
at the fan convector that dictates the output.
4.0 Location
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The WHISPA III
®
RCU fan convector is designed for recessed
wall applications.
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WHISPA III
®
RCU fan convectors are designed for normal
2" x 4" stud wall framing, with 5/16" thick cover
extending beyond the wall surface once installed.
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The size of the opening required to be cut for installation is
shown in Fig 1.
1.0
2.0
3.0
4.0
22072 Whispa RCU (US) Manual:Layout 1 10/9/09 12:21 Page 4
