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Domestic Hot Water Immersion Heater; Legionnaires Disease; Faq's - Mitsubishi Electric Ecodan PUHZ-W50VHA-BS Homeowner's Manual

Air source heat pump
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Domestic Hot Water Immersion Heater

As the Ecodan® ASHP can heat domestic hot water cylinder to 55°C. Pasteurization should be carried out by an
immersion heater situated in the body of the hot water cylinder. The heater should be timed to operate after
the Ecodan has completed a hot water cycle thus completing the lowest temperate rise possible (from 55°C to
60°C). Please note the larger the temperature rise completed by the immersion heater the less efficient the sys-
tem becomes.
To determine the ON time of the immersion heater the
recovery period taken during the commissioning stage
should be used. The ON time from the immersion heater
should be the ON time of the Ecodan® hotwater heating +
the recovery period taken during the commissioning stage.
This heat up times have been based upon using a 3kW
Immersion heater.
Legionnaire's Disease
The immersion heater should be time clocked to take the cylinder up to 60°C shortly after the heat pump has
heated the cylinder up to 55°C set out in the current building regulations concerning control of Legionella bacte-
ria. Immersion heater cylinder pasteurization (60°C) should be controlled in accordance with BS6700.


Q) Why is the exhaust air from the outdoor unit cold?
A) The heat pump boiler is working in reverse to a refrigerator therefore has removed the heat in the air and
put it onto the water.
Q) How long will the defrost cycle last for?
A) A complete cycle will take less than 3 minutes.
Q) How often do I need to clean the outdoor unit?
A) Visual checks should be carried out every 6 months and also an annual service by an approved Ecodan in-
Q) My electricity bill is too high, how can reduce this?
A) Well insulated houses have lower heating loads, also reducing the flow temperatures through the PAR-
W21MAA controller. Always ensure Eco mode is selected for central heating. Eco-mode flow temperatures
should be set as commission stage and suit the property type. Lower flow temperatures lead to lower operating
Q) How does Ecodan help reduce carbon emissions?
A) Because Ecodan®'s output efficiencies are in the seasonal order of 3 to 3.5 (i.e. 300% to 350%), the actual
amount of electrical energy consumed from the national grid is dramatically reduced. So even taking in to ac-
count the reduced CO
/kWh for gas (0.19) against CO
than even the highest efficiency condensing gas boiler.
Q) Are air source heat pumps classed as a renewable technology?
A) Within the Climate Change and Sustainable Energy Act (Sources of Energy and Technologies), yes. Here air
source heat pumps are defined as a microgeneration technology. However, there is still debate as to whether air
source heat pumps can be truly classed as a renewable technology if the primary power (the electricity) does not
come from a renewable source.
Immersion Heater (boosting from 55°C—60°C
Tank Size
/kWh for electricity (0.43) Ecodan emits far less CO2
Heat up times

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