Refrigeration Circuit; Plate Heat Exchangers; Remote Condenser - Lennox INNOVA DHADC Series Application Manual

rEFrIGErATION CIrCUIT

The entire refrigerating circuit is assembled in LENNOX proper
workshop, including all pipe work, using only primary brand
for components. The workers involved in the welding and pipe
work process are qualified by a third part according CEE 97/23
PED directive : necessary to underlines that this qualification
for workers was not request, but it was LENNOX's decision
taking care about the quality and_in general_for the customer's
satisfaction. The DX units are present in siingle or double circuit
eexecution and are precharged with dry notrogen for "A", 3D3 or
with R407C refrigerant for "W", "F", "Q", "D" versions. Refrigerant
different from R407C, like R22, R134a, R410A are available on
request and previous check for local rules.
COMPREssORs
On INNOV@ only primary brand scroll compressor [Fig.1] are
installed. Scroll compressors represent for C.C.U. units the
best solution in terms of efficiency and reliability. The internal
compression ratio is very close to the typical operating condition
of C.C.U. giving the maximum in terms of COP and the perfect
balanced pressure at start up gives big advantages to the e-
motor in terms of reliability, mainly in this fields where frequent
start ups can happens.

PLATE HEAT EXCHANGERs

Only AISI 304 BPHE with low carbon steel connections are used.
The special design of the plates gives both an advantage to
increase the turbulences-reducing the fouling and increasing the
efficiency and a reduction of the overall dimensions : this features
allows to install the BPHE behind the compressor compartment,
making more space for piping and the other components
FINNED COILs HEAT EXCHANGER
All coils are made using a 25x21,65 mm geometry in combination
with 9,52 mm copper pipes and 0,10 mm thickness aluminium
fins. The expanding process to ensure perfect contact between
pipes and fins is one of the most critical points and it is 100%
monitored in the whole production process. The design criteria
for R&D department and our laboratories, are summarized in
4 main points :
- Reduction of pressure drops by using a large coil front
surface
- Hydrophilic treatment on the fins to allow a film condensation
in dehumidification operation (typical angle water/al<10°)
- The reduction of the vertical height to avoid thickness in
water film, as a consequence, the possibility to operate with
high air volume and high relative humidity without dragging
out of water (especially in down flow units)
- Special Corrugated Fins increase the heat transfer coefficient
on air side in order improve the SHR.
In chilled water units a special attention was paid for checking
the behaviour of the Reynolds number inside pipes during the
modulation of three way valve : transition between laminar and
turbulent flow may cause big step in heat exchanging efficiency
loosing accuracy in temperature control.
Looking into advantages of spare parts : one same coil is used
for both up and down flow units.

REMOTE CONDENsER

Coils are made using 25 x 21,65 mm geometry in combination
with 9,52 mm copper grooved pipes and 0,10 mm thickness
aluminium louvered fins : the combination of this technology
allows the maximum reduction in internal volume and as a
consequence a reduction of the refrigerant charge amount.
The adopted fans are only with external rotor motor and 4 or
6 poles execution, depending on the selected sound power :
in the catalogue two choices are already available, but special
request can be examined by the R&D department.
[Fig.1]
Panels are made in galvanized precoated steel and special
feet for horizontal installation are available for the whole range
[option]. Looking to the destination of such units, three different
type of condensing controls are available :
- None
- Modulating fan speed control in Standard alone version
installed in the C.C.U. : down to -15°C
- Flooding technology in addition to the fan speed control for
the temperatures below -15°C and down to -30°C. This last
option will be supplied as a kit including liquid receiver, back
pressure valve, safety valve, protection cabinet and needs
to be installed on site next to the condensing unit.
[Fig.2]
Application Guide INNOV@-0907- Page 9