Knowledge: Heat pumps
Adjusting to change
John Felgate, Stiebel Eltron UK technical director, focuses on fine tuning heat
pump systems for today’s more exacting customers
T
here has been a
general movement in
recent years to make
the energy that
consumers use more
apparent to them, in the belief
that this awareness will lead to
behavioural change.
It follows that consumers
should therefore be educated to
understand and use their own
heating systems effectively –
particularly when it comes to new
technology such as heat pumps.
I want to go through
some of the basic and more
advanced controls that can be
used to maximise efficiency.
This information can be passed
on to consumers who are
confident with technology and
are interested in their systems
– and alternatively provides an
opportunity for installers to add
value through service contracts
with routine monitoring and
adjustment.
Let’s tackle why you might need
to change initial settings.
1.
It is never possible to exactly
match the performance of a
pump to a property until all
the factors of the immediate
environment, performance
of chosen emitters and
performance of the building
itself have been fully brought
into the equation. This
means essentially that until
you have the data from
a system that has been
running for weeks, months
and even years, you won’t
have a full picture on which
to base decisions.
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2.
Changing lifestyles. As
examples, hot water and
heating consumption rises
dramatically when children
arrive on the scene; in
social housing situations
the residents of properties
may change – a family may
replace an older resident
moving into sheltered
accommodation.
Basic performance tuning for
heat pumps
It is as easy to change the timers
and programme settings on
heat pumps as it is for a boiler.
However, there are a few more
advanced controls to consider
here. We start of course with the
heat pump mantra that: ‘The
lower the temperature of the
water going through the system,
the more efficient it will be’.
The two basic settings on a heat
pump that can be adjusted to
change this balance are:
1.
2.
The heat curve (weather
compensation). This sets
the water temperature for
heating depending on the
outside air temperature.
The room temperature
setting. This raises or lowers
the water temperature
to give you the room
temperature you require.
Lowering the water
temperature by adjusting
the curve and the room
temperatures has a major
impact on efficiency, but at
the cost of heating response
times.
Fine tuning: Educating consumers on the advanced settings of heat pumps
and customising systems for their individual needs can provide installers
with an added value service, says John Felgate, Stiebel Eltron
Additional refinements to
consider include:
Kelvin minutes
This setting looks at the
temperature of the water in your
heating system and compares
the set temperature with the
actual water temperature. If the
temperature is close to the set
temperature it waits a relatively
long time before recalculating. If
the differential is large it waits a
short time before recalculating
and adjusting the effort up or
down.
Summer mode
This setting takes an average
temperature over a given period
of time to decide if the weather
is warm enough to switch off
the heating altogether and
provide only hot water. I would
always advise setting it up to
take advantage of spells of fine
weather in spring and autumn
and avoiding turning it on during
short spells of cooler weather in
summer.
Pump cycles
The pump that circulates the hot
water in the system can simply
run continuously when the
thermostat calls for the heat to
be turned on. However, it is more
efficient to set a pump to ‘pulse’,
running for a few minutes at a
time, a certain number of times
an hour. This both saves energy
and can extend the life of your
system. Gradually testing how
far apart pulses can be timed
without a noticeable impact
on comfort is a key part of an
advanced fine-tune of a heat
pump’s performance.