Household Heat Pump Hot Water System Sizing
Sizing a heat pump hot water system is a much simpler task than sizing a
roof mounted solar hot water system.
This is because a Siddons or Stiebel Eltron heat pump hot water system:
-
does not require
direct sunshine, so the availability of a suitable roof area is
not an issue that will affect performance and sizing
-
is
able to produce 1200 to 1600 litres of solar hot water per day
-
is able to
produce solar hot water 24 hours per day - rain hail or shine, and generally
heats faster than a conventional electric hot water system.
This means that the required storage capacity is much easier to
determine.
-
does not
require a booster element, so boosting does not affect heating costs in the same
way that it does with a roof mounted solar hot water system.
This means that a heat pump does not required as much
storage capacity as a roof mounted solar hot water system.
Some Things to Consider
- Usage Pattern.
- When is your hot water being consumed?
- Is hot water mainly used in the evening or morning, or is it spread between the
morning and evening?
- Is there a large amount of water usage at the
times that a mid-rate tariff is switched off, that is, there is no power to
generate more hot water?
- Do you have a spa bath (if so, add 1 to 2
people, depending on spa bath usage)?
-
Water Flow Rate. Hold a bucket under your shower, turn on the
hot water, and time how long it takes to fill the bucket. This will
give you an idea of how many litres per minute flow through the
shower. You should be able to roughly calculate the litres of hot
water required during your peak usage time.
-
Consider the Future. Do you have children who will soon be
teenagers? Are you planning to renovate and will be installing a spa
bath? If your children will soon be teenagers, increase their current
water usage by 1.5 to 2. It is not uncommon for teenagers to spend 20
minutes in the shower. Some simply stay in until all the hot water has
gone, nomatter how big the system. Time for AAA shower roses!
-
Power Tariff. Is the system to be connected to standard (24
hour) tariff, a mid-rate tariff or night rate? The sizing will depend on your
usage pattern.
When we go to your home to do an obligation free inspection and quotation
we will ask you some questions to help us to determine the best system type and
size for your needs.
Please note that the sizing criteria can be very different for other brands of
heat pump. For example, when sizing a heat pump with a lower recovery rate
a larger cylinder capacity should be considered. Also, the performance of
some heat pumps falls significantly on a winter's night. Some heat pumps
are
actually fitted with an element to help to overcome this!
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