Technical data

BWR MTD2
BWR_MTD2_0011_0121_201110_EN HFC 410A
3
Brine-to-Water heat pump
The MTD heat pumps, optimised for geothermal systems, are
reverse-cycle units that operate in heating, cooling and domes-
tic hot water production modes, using a three way valve (acces-
sory) installed outside of the unit.
The MTD heat pumps can be combined with traditional or radi-
ant systems.
The latter, by working at lower water temperatures, ensure high-
er overall efficiency and are a very popular solution for new low
energy consumption constructions and systems that exploit
renewable energy sources.
Installation is very simple: integration of the hydronic unit on the
system and source circuits means the unit only needs to be
connected to hydronic system and power supply before starting
operation.
Ground source solutions
Ground source heat pumps exploit the energy accumulated by
the ground, a vast source of heat.
The temperature just a few metres underneath the surface
remains constant throughout the year, without the same fluctua-
tions as air temperature.
This means heat can be drawn from the ground in winter so as
to supply a heating system at an efficiency of around 400% or
higher, or give heat back in summer for cooling, maintaining
high efficiency that remains constant all year round.
The same principle can be exploited for domestic hot water pro-
duction.
Heat is exchanged with the ground via polyethylene pipes that
are either laid horizontally in the ground a few metres under the
surface, or vertically if there is limited space around the building.
This is a closed loop with heat carrier fluid made up of water
and glycol, to prevent the liquid from freezing.
Vertical loop
A vertical geothermal loop allows the heat pump to draw energy
from a source at a virtually constant temperature all year round,
with considerable benefits in terms of reducing running costs.
This solution requires a small piece of land.
The yield per linear metre of loop in the ground is 50 W/m; this
value is used as the reference for standard ground, as
described in standard VDI4640. A geologist should always be
contacted to verify ground conditions.
Drilling depth is usually around 100 metres (this keeps pumping
power down, increasing system efficiency, while deeper bore
holes depend on the equipment available locally).
The loops used are double U-bend pipes, PE 100, diameter
DN25, DN32 (most common) and DN40.
Depending on heating or cooling capacity required and capacity
of the ground, a series of geothermal loops may be used,
always leaving a space of 8-10 metres between loops to avoid
thermal interference.
The heat yield of the loop and good operation significantly
depend on the type of grout used.
Once the PE pipe has been placed in the bore hole, the hole
must be filled from the bottom up using a product that guaran-
tees high thermal conductivity and low hydraulic conductivity.
Grout generally consists of mixes of cement and bentonite,
where necessary added with silica or quartz sand to increase
thermal conductivity, or commercially-available premixed prod-
ucts. This also prevents any interference with underground
aquifers that the loop/loops may cross.
Horizontal loop
This solution requires a relatively large piece of land, however
costs significantly less than a vertical loop.
Horizontal systems can be made by excavating a field where
the plastic pipes will be laid to a depth of around 1-1.5 metres.
Excavation is however costly due to the considerable amount of
soil handled. To reduce costs, rather than excavating the loop
field, trenches can be dug for laying the heat exchange pipes.
In this case, the geothermal loop will be long and narrow.
Currently the most widespread trench systems are slinky loops,
either 2-pipe or 4-pipe circuits, laid at a depth of around 2.5-3
metres. In this case, as the loop is laid near the surface, PE 80
pipes can be used, diameter DN25 or DN32.
The amount of heat that can be drawn using these types of
solutions ranges from 10 to 15 W/m2, and even higher if there
is surface water.
These values are however also affected by variations in air tem-
perature. On average, the geothermal field should be two to
three times larger than the surface area being heated.
COMPOSITION OF STANDARD UNIT
Structure
Load-bearing base and structure made from suitably thick hot
galvanised steel plate. All parts painted with polyester power
coat.
Panelling
External casing made from suitably thick hot galvanised steel
plate, painted with polyester power coat, designed to allow total
access to inside components. All the panels are covered with
high density soundproofing material. Soundproof panelling made
from special open-cell cone-shaped sandwich panels on the out-
side with filler material on the inside, total thickness 35 mm.
Compressors
Hermetic rotary scroll compressors, complete with sump heater,
electronic thermal overload protection with centralised manual
reset, and two-pole electric motor.
High density rubber soundproof covering.
Utility-side and Source-side heat exchanger
Braze welded AISI 316 steel plate heat exchanger. The heat
exchangers are lined on the outside with a layer of closed-cell
neoprene to prevent condensation. When the unit is not operat-
ing, the heat exchangers are protected against no flow condi-
tions by a water differential pressure switch. The unit is also
ready to operate using non-freezing mixes and with an electric
heater for frost protection.
Refrigerant circuit
Main components in the refrigerant circuit:
- refrigerant R410A
- dewatering filter,
- liquid flow indicator with moisture signal,
- thermostatic valve with external equaliser,
- high and low safety pressure switches,
- liquid receiver,
- 4-way reversing valve.
System water circuit
Main components in the system water circuit:
- circulating pump
- water differential pressure switch
- expansion vessel
- system vent
- drain valves
- safety valve
- threaded male fittings
1. DESCRIPTION OF THE UNIT