Mitsubishi Electric ECODAN EHPT20Q-VM2EA Operation Manual page 3

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Introduction
The purpose of this Operational Manual is to inform users how their air source heat pump heating system works, how
to run the system at its most effi cient and how to change settings on the main controller.
This should be kept safe with the unit or in an accessible place for future reference.
Overview of the System
The Mitsubishi Electric Air to Water (ATW) heat pump system
consists of the following components; outdoor heat pump unit and
indoor cylinder unit incorporating main controller.
How the Heat Pump Works
Space heating and DHW
Heat pumps take electric energy and low grade heat energy from the
outdoor air to heat refrigerant which in turn heats water for domestic
use and space heating.
The effi ciency of a heat pump is known as the Coeffi cient of
Performance or COP. This is the ratio of heat delivered to power
consumed.
Heat pumps are generally most effi cient when providing water at
lower temperatures and when temperature difference between inlet
and outlet of the outdoor unit is large.
The operation of a heat pump is similar to a refrigerator in reverse.
This process is known as the vapour-compression cycle and the
following is a more detailed explanation.
The fi rst phase begins with the refrigerant being cold and low
pressure.
1. The refrigerant within the circuit is compressed as it passes
through the compressor. It then becomes a hot highly pressurised
gas. The temperature also rises typically to 90°C.
2. The hot refrigerant gas then passes across one side of a heat
exchanger. Heat from the refrigerant gas is naturally transferred
to the cooler side (water side) of the heat exchanger. As the
temperature of the refrigerant decreases, it naturally changes state
from a gas to a liquid.
3. Now as a cold liquid it still has a high pressure. To reduce the
pressure the liquid passes through an expansion valve. The
pressure drops but the refrigerant remains a cold liquid.
4. The fi nal stage of the cycle is when the refrigerant passes into the
evaporator and evaporates. It is at this point when some of the
free heat energy in the outside air is absorbed by the refrigerant
and it returns to its original gas state.
It is only the refrigerant that passes through this cycle; the water is
heated as it travels through the heat exchanger (Gas cooler). The
heat energy from the refrigerant passes through the heat exchanger
to the cooler water which increases in temperature. This heated
water forms the primary circuit and is circulated and used to serve
the space heating system and the thermal store tank.
The hot water stored within the tank is subsequently used to generate
domestic hot water. (The tank water is NOT the actual hot water that
is typically used for shower or sink appliances.)
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Schematic of packaged cylinder system
Low temperature renewable
heat energy taken from the
environment (i.e. fresh air).
2 kW
Electrical energy Heat energy
input output
1 kW 3 kW
2.Gas cooler
(water-refrigerant
heat exchanger)
3. Expansion valve
1. Compressor
4. Evaporator
(Outdoor unit air heat exchanger)
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Introduction
Economical Best Practice
Air source heat pumps can provide both hot water and space heating all year. The system is different to a conventional
fossil fuel heating and hot water system. The effi ciency of a heat pump is shown by its coeffi cient of performance
as explained in the introduction. The following points should be noted to achieve the most effi cient and economical
operation of your heating system.
Important points about heat pump systems
● The hot water produced by the heat pump is typically at a lower temperature than a fossil fuel boiler.
Implications
● If the heat pump is being used for DHW the time at which tank heat up occurs should be scheduled using the
SCHEDULE function (see page 12). Ideally this should be during the night time when normally, less space heating is
required and economy electricity tariffs can be taken advantage of (see page 10).
● In most situations space heating is best performed using the room temperature mode. This enables the heat pump
to analyse current room temperature and react to changes in a controlled manner utilising the specialised Mitsubishi
Electric controls.
● Using the SCHEDULE and HOLIDAY functions prevent unnecessary Space or DHW heating when the property is
known to be unoccupied, for instance during the working day.
● Due to lower fl ow temperatures, heat pump heating systems should be used with large surface area radiators or
under-fl oor heating. This will provide a steady heat to the room whilst improving effi ciency and so lowering running
costs of the system as the heat pump does not have to produce water at very high fl ow temperatures.
Overview of Controls
Built into the cylinder unit is the Flow Temperature
Controller(FTC).This device controls the function of both the
outdoor heat pump unit and the cylinder unit. The advanced
technology means that by using an FTC controlled heat pump
you can not only make savings compared to traditional fossil
fuel type heating systems but also compared to many other
heat pumps on the market.
As explained in the earlier section, 'How the Heat Pump
Works,' heat pumps are most effi cient when providing low fl ow
temperature water. The FTC advanced technology enables the
room temperature to be kept at the desired level whilst utilising
the lowest possible fl ow temperature from the heat pump, i.e.
operate most effi ciently.
In room temp. (Auto adaptation) mode the controller uses
temperature sensors around the heating system to monitor
space and fl ow temperatures. This data is regularly updated
and compared to previous data by the controller to predict
changes in room temperature and adjust the temperature
of water fl owing to the space heating circuit accordingly.
By monitoring not only the outdoor ambient, but the room
and heating circuit water temperatures, the heating is more
consistent and sudden spikes in required heat output are
reduced. This results in a lower overall fl ow temperature being
required.
Room temp.
FTC
Ambient temp. sensor
sensor
Flow temp. sensor
Return temp. sensor
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