WDH Ground source heat pumps
MTWDHGB REV.072008
9
TECHNICAL CHARACTERISTICS
The WDH ground source heat pump units have been designed to guarantee high heating capacities with excellent efficiencies; units
are suitable either for heating or domestic hot water production. WDH heat pumps have been optimised for applications in
buildings where water temperature demand for space heating is around 50°C. The WDH heat pumps allows to efficiently
produce water temperature up to 60°C during cold winter time. This new technology in space heating and tap water production
allows traditional boilers to be replaced by Heat Pumps in retrofit applications without changing the radiators.
Frame
All WDH units are made from hot-galvanised thick sheet metal, painted with polyurethane powder enamel at 180°C to ensure the
best resistance against the atmospheric agents. The frame is self-supporting with removable panels. All screws and rivets are in
stainless steel. The colour of the units is RAL 7035.
Refrigerant circuit
The refrigerant gases used in these units is R407C. The refrigerant circuit is made by using international primary brands components
and according to ISO 97/23 concerning welding procedures. Each refrigerant circuit is totally independent from the other. Any
incorrect operation of one circuit does not influence the other circuit. The refrigerant circuit includes:
•sight glass,
•filter drier,
•thermal expansion valve with external equalizer,
•Schrader valves form maintenance and control,
•pressure safety device (according to PED regulation).
Compressors
The WDH units are supplied with scroll type compressors, optimized for heating applications with a special scroll design who
allows extreme high efficiencies especially when the heat source temperature is low. Compressors are supplied with
crankcase heater and thermal overload protection by a klixon embedded in the motor winding. The compressors used are all in
tandem execution. This solution allows much higher efficiencies in partial loads compared to the units with independent refrigerant
circuits. In all units the crankcase heaters are always powered when the compressors are in stand-by. The inspection is possible
through the frontal panel of the unit that allows the maintenance of the compressors even if the unit is working.
Source side heat exchangers
The source side heat exchangers are made of AISI 316 stainless steel braze-welded plates type. From size 039 to size 162 they are
single water side circuit, from the size 144 they are double circuit “cross flow” type. The use of these kind of heat exchangers allows
a massive reduction of the refrigerant charge of the unit compared to the traditional shell-in-tube ones and increases the efficiency of
the refrigerant cycle in partial loads. The source heat exchangers are factory insulated with flexible close cell material and are
provided with a temperature sensor as antifreeze protection.
User side heat exchangers
The user side heat exchangers are made of AISI 316 stainless steel braze-welded plates type. From size 039 to size 162 they are
single water side circuit, from the size 144 they are double circuit “cross flow” type. All units are supplied with sub-cooler to enhance
the performance of the refrigerant cycle. The user heat exchangers are factory insulated with flexible close cell material.
Electric enclosure
The electric switch board is made according to electromagnetic compatibility norms CEE 73/23 and 89/336. The accessibility to the
board is possible after removing the front panel of the unit and the OFF positioning of the main switch. The moisture protection
degree is IP55. In all WDH units are installed, standard, the compressors sequence relay who disables the operation of the
compressor in case the power supply phase sequence is not the correct one (scroll compressors in fact, can be damaged if they
rotate reverse wise). The following components are also standard installed: main switch, magnetic-thermal switches as a protection
of compressors and pumps (where present), control circuit automatic breakers, compressor contactors, pump contactors. The
terminal board is supplied with voltage free contacts for remote ON-OFF, Summer / winter change over and general alarm.
Microprocessors
All WDH units are supplied standard with microprocessor controls. The microprocessor controls the following functions: regulation of
the water temperature, antifreeze protection, compressor timing, compressor automatic starting sequence, alarm reset, potential free
contact for remote general alarm, alarms and operation leds. Upon request any microprocessor can be connected to a BMS system
for the remote control and management. The technical department is available to study, together with the customer, different
solutions using MODBUS; LONWORKS; BACNET or TREND protocols.
