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Heat Pump System Overview
6
The Ecodan
air source heat pump extracts thermal energy from the outside air and transfers this into a property in
®
the form of hot water as a conventional heating system does.
The system works on a hot water priority basis and the pipework configuration is that of a standard S-plan layout.
Hot water mode can be controlled either by the timeclock built into the main controller or can be started and
stopped when a certain drop in cylinder temperature is detected by THW5. It is up to the installer to choose the
setup that best suits their customer's needs, for example if hot water usage was predictable and small then a timed
schedule would be most suitable. If however, hot water use was unpredictable and large quantities were required
then auto reheat would adapt to the requirements and there would always be plenty of hot water available.
Heating can be controlled in a number of different ways using FTC4, there is the option for either timed or
constantly on. When running in timed mode it is possible to program setback periods throughout the course of the
day. Either the main controller, a Mitsubishi Electric wireless controller or a Mitsubishi Electric hard wired sensor can
be installed. Multiple sensors can be used on a single system with the 'master' sensor being rotated at set times
throughout the day. There is also an input on FTC4 to accept third party non voltage thermostats or signals from
underfloor heating wiring centres.
In terms of how the heating water temperatures are controlled there are three options. Option 1 is traditional
weather compensation, the installer will input the correct flow temperatures at specific outdoor conditions directly
into the main controller, the FTC4 will then follow these settings. Option 2 is to run the system at a fixed flow
temperature. This is not recommended as it is the least efficient method of providing space heating. There are
instances whereby it is a useful feature, for example when commissioning a system. Option 3 is known as room
compensation and is only available when using a Mitsubishi Electric thermostat. In this mode the FTC4 will
calculate the optimum flow temperature.
Each of the three Ecodan
models require sufficient primary flow rate for adequate operation. Due to the large
®
resistances caused by the plate heat exchanger in the Ecodan
, the Mitsubishi Electric Package Cylinder has two
®
circulating pumps in series to produce the required flow rates. When in hot water mode only one pump will operate,
whereas due to the higher resistances of the heating circuit when the system is in heating mode both pumps will
operate. These pumps must be set to the same speed or damage to the system may occur.
A flow setter valve is supplied with each system to give an indication of the actual flow rate achieved. It should be
installed in the common flow or return pipe work to the Ecodan
.
®
Automatic air vents must be installed at the highest point of the primary system. The slightest amount of air in the
system can reduce efficiencies and even cause the Ecodan
®
to fault.
The primary loop must contain a 20 - 25% antifreeze concentration (or as recommended by the manufacturer) to
avoid possible freezing during periods when the appliance is not being operated. It is recommended that a mono-
propylene glycol with biocide is used such as Fernox HP-5C or Fernox HP-15C. The hardness of the mains water
(>200ppm) should be checked by the installer and if necessary an in-line scale reducer should be recommended.
To optimise running costs it is advisable to seek the cheapest possible electricity tariff. Although electricity prices
are higher than gas or oil, the efficiency of the system means that it requires less energy to supply the same heating
demands, thus producing cheaper energy bills. Compared to regular electricity bills it will look higher than usual, but
the homeowner should be aware that this bill incorporates heating that is usually achieved through gas or oil.
FTC4 Installation Manual
9
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