Introduction - Mitsubishi Electric ecodan EHPT20Q-VM2EA Operation Manual

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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 efficient 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.
The Mitsubishi Electric Air to Water (ATW) heat pump system con-
sists of the following components; outdoor heat pump unit and indoor
cylinder unit incorporating main controller.
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 efficiency of a heat pump is known as the Coefficient of Perfor-
mance or COP. This is the ratio of heat delivered to power con-
sumed.
Heat pumps are generally most efficient 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 fol-
lowing is a more detailed explanation.
The first phase begins with the refrigerant being cold and low pres-
sure.
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 ex-
changer. Heat from the refrigerant gas is naturally transferred to
the cooler side (water side) of the heat exchanger. As the tem-
perature 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 pres-
sure drops but the refrigerant remains a cold liquid.
4. The final 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 gener-
ate 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).
Electrical energy Heat energy
input output
2.Gas cooler
(water-refrigerant
heat exchanger)
3. Expansion valve
1. Compressor
4. Evaporator
(Outdoor unit air heat exchanger)
2 Introduction
Air source heat pumps can provide both hot water and space heating all year. The system is different to a conven-
tional fossil fuel heating and hot water system. The efficiency of a heat pump is shown by its coefficient of perfor-
mance as explained in the introduction. The following points should be noted to achieve the most efficient and eco-
nomical 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 flow temperatures, heat pump heating systems should be used with large surface area radiators or
under-floor heating. This will provide a steady heat to the room whilst improving efficiency and so lowering running
costs of the system as the heat pump does not have to produce water at very high flow temperatures.
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 heat-
ing 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 efficient when providing low flow
temperature water. The FTC advanced technology enables the
room temperature to be kept at the desired level whilst utilising
the lowest possible flow temperature from the heat pump, i.e.
operate most efficiently.
In room temp. (Auto adaptation) mode the controller uses tem-
perature sensors around the heating system to monitor space
and flow temperatures. This data is regularly updated and com-
pared to previous data by the controller to predict changes in
room temperature and adjust the temperature of water flowing
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 flow temperature being required.
FTC Room temp.
sensor
Ambient temp.
sensor
Flow temp. sensor
Return temp. sensor
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