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3. TECHNICAL CHARACTERISTICS
3.1 Unit description
The LZT series of high efficiency heat pumps has been specifically designed for use with radiant floor heating systems or those applications
where it is necessary to have maximum efficiency when heating.
They have been optimized on heating mode, are able to produce water up to 65°C and can operate down to -20°C ambient temperature.
All versions are supplied with reverse cycle valve used for winter defrost; the HH version is suitable for use in those countries that have
support schemes for use of heat pump technology for heating. The RV versions are also able to produce cold water. The HH heating only
versions is factory set and locked to operate only in heating mode whilst. The noise in XL and NN versions is extremely low thanks to the
use of a special floating vibration damping system which allows a noise reduction of about 10-12 dB(A).
3.1.1 Frame
All units are made from hot-galvanised sheet steel, painted with polyurethane powder enamel and stoved at 180°C to provide maximum
protection against corrosion. The frame is self-supporting with removable panels. All screws and rivets used are made from stainless steel.
The standard colour of the units is RAL9018.
3.1.2 Refrigerant circuit
The refrigerant utilised is R410A. The refrigerant circuit is assembled using internationally recognised brand name components with all
brazing and welding being performed in accordance with ISO 97/23. The refrigerant circuit includes: sight glass, filter drier, two thermal
expansion valves (one for cooling mode, one for heating mode) with external equalizer, 4 way reversing valve, check valves, liquid receiver,
Schrader valves for maintenance and control, pressure safety device (for compliance with PED regulations). The circuit also includes an
AISI316 stainless steel heat exchanger that is used as an economizer plus an additional expansion valve for refrigerant vapour injection.
3.1.3 Compressors
Units use scroll compressors that are equipped with E.V.I. technology, a versatile method of improving system capacity and efficiency. EVI
stands for "Enhanced Vapour Injection." The technology involves injecting refrigerant vapour into the middle of the compression process, a
procedure that significantly boosts capacity and efficiency. Each scroll compressor used in these units is similar to a two-stage compressor
with built-in inter-stage cooling. The process begins when a portion of the condenser liquid is extracted and expanded through an expan-
sion valve. The low temperature liquid/gas mixture produced is injected into a heat exchanger that operates as a sub cooler. Any liquid is
evaporated and the vapour produced is superheated. The superheated vapour is then injected into an intermediate port in the scroll com-
pressor. This cold vapour reduces the temperature of the compressed gas thus enabling the compressor to raise the pressure to levels (and
temperatures) beyond that possible with a single stage scroll. The additional sub cooling of the main volume of liquid refrigerant increases
the evaporator capacity. This compressor technology generates a larger pressure ratio between condensing and evaporating pressures,
with significant performance improvement. In all units the compressors are connected in tandem. The compressors are all supplied with a
crankcase heater and thermal overload protection by a klixon embedded in the motor winding. They are mounted in a separate enclosure
in order to be separated from the air stream thus enabling them to be maintained even if the unit is operating. Access to this enclosure is
by the front panel of the unit. The crankcase heater is always powered when the compressor is in stand-by.
3.1.4 Source heat exchanger
The source heat exchanger is made from 3/8" copper pipes and 0,1mm thick aluminium fins with the tubes being mechanically expanded
into the aluminium fins in order to maximise heat transfer. Furthermore, the design guarantees a low air side pressure drop thus enabling
the use of low rotation speed (and hence low noise) fans. All heat exchangers are supplied standard with fins hydrophilic coating.
3.1.5 Fans
The fans are direct drive axial type with aluminium aerofoil blades, are statically and dynamically balanced and are supplied complete with
a safety fan guard complying with the requirements of EN 60335. They are fixed to the unit frame via rubber antivibration mountings.In the
LS versions the fans are 6 poles type (approx 900 rpm), in the XL versions the fans are 8 poles type (approx 600 rpm), in the NN versions
the fans are 12 poles type (approx 450 rpm). The motors are fitted with integrated thermal overload protection and have a moisture protec-
tion rating of IP 54.
3.1.6 User heat exchangers
The user heat exchanger is a braze welded, plate type heat exchanger, manufactured from AISI 316 stainless steel. The use of this type of
exchanger results in a massive reduction of the refrigerant charge of the unit compared to a traditional shell-in-tube type. A further advan-
tage is a reduction in the overall dimensions of the unit. The exchangers are factory insulated with flexible close cell material and can be
fitted with an antifreeze heater (accessory). Each exchanger is fitted with a temperature sensor on the discharge water side for antifreeze
protection.
Rev. A 11-2020
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