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Hot Water Heat Pumps 
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A
Hot Water Heat Pump, all the benefits and none of the drawbacks
compared to the best solar systems.
If
you find that hard to believe, consider this - solar hot water will
on average save 50-55% of your hot water costs - a hot water heat
pump will save 65-80% as no backup is ever required, it operates
efficiently even in the dark and cold, and will provide ALL your
hot water at the lowest price possible.
A hot water heat pump will only cost $3000 to $4000 fully installed,
and many families will save more than this amount in under five
years with much lower electricity charges. Get quotes for solar
systems, then give us a call (Christchurch 03 377 8026) for guaranteed
savings, whatever the weather. Every size and type of hot water
cylinder can be fitted with a heat pump, and it can easily be removed
and refitted if you move house.
There
has never been a better time to realize the benefits of a hot water
heat pump.
For
information on approved solar systems click here.
A
National hot water heat pump - only requires plumbing and electrical
work.
No onsite refrigeration.
The Sova HWHP shown requires some onsite refrigeration.
(Cylinder for
illustration purposes only)
Family of five,
October bill - $140
Hot Water
Heat Pumps - information.
If
you use hot water you will save considerable amounts of energy
and money by installing a hot water heat pump, with the present
price of electricity the actual amount saved will be $150 to
$200 per person per year. A family of five will therefore
save over $60 a month, and possibly $1000 a year,
just on heating water.
An outdoor unit, similar to an outdoor unit for heating and air
conditioning, heats water using a fraction of the usual amount
of electricity and at far lower cost than gas, diesel or day/night
electricity, and invariably at a lower cost than solar.
A heat pump does not do any actual heating, it compresses a gas
which makes it hot and this heat can be used to heat water, it
is exactly the same principal that makes a bicycle pump hot when
pumping up a tyre. For this reason a heat pump hot water system
is far more efficient than conventional ways of heating water,
in practice for every unit of electricity paid for you get another
two or three free ones, saving 65-80% of your hot water
costs. And as hot water can be half of your total electricity
bill, this could in turn be reduced by over one third.
Everyone can benefit from this technology, even households who
use gas or diesel to heat their water - (although properties that
don't have a hot water cylinder installed at present would have
to fit one), everyone would save energy and money, and always
have hot water on tap.
Two
person household plus lots of visitors - about $100/month in winter,
$55 in summer.
A hot water
heat pump is available in three different ways:
1.By fitting
to an existing hot water cylinder - by fitting an outdoor
unit, a circulating pump and with some plumbing work this will
provide the lowest priced hot water whatever the weather, from
just $2999 fully installed. Suitable for all water pressures
and cylinders up to 500 litres - click
here.
2. Fitting
with a new hot water cylinder - from just $2395 (plus
installation), (does not include a new cylinder) - click
here.
3.
For commercial or heavy usage with multiple cylinders, includes
circulating water systems.
Motels, hotels, bakeries, restaurants, schools, rest homes,
laundries, dairy farms, hospitals, backpackers, camping grounds.
The potential for money and energy savings with hot water heat
pumps are outstanding for large users. One system alone could
save thousands of dollars a year yet cost less than $3500 to
install
- click
here.
Believed
to be saving $200 a month.
How
much could I save?
The only people
who will not save energy and money with a hot water heat pump
are those who have access to free wood, a log burner and a wetback,
everyone else - including anyone with solar hot water, will
save.
The actual savings obviously depend on the amount of hot water
used. All conventional methods, gas, electric, diesel, day/night
electric cost similar amounts to heat water (but see below for
the comparison with solar). Many people with day/night rate
electricity don't realize they pay a large penalty rate for
day units and may be only saving around 10% of the total bill
(some people actually pay more!).
The total savings will depend on the number of people using
hot water heat pump, on average every person in the house will
save $150-200 a year at the present price of electricity
(about 17c per unit), therefore a five person house could save
$1000 every year. The sooner you have a hot water
heat pump fitted the sooner you start saving.
If you already have an electricity bill under $150 a month,
you may be able to switch to a low user rate for electricity
with a lower daily charge after installation for some extra
savings.
On
the plumbers roof, quick recovery times.
Day/Night electricity.
The principle of charging lower prices for electricity at night
is to spread transmission loadings out over 24 hours. No energy
is saved (in actual fact energy is often wasted with thermostats
set too high) and for many people the actual monetory savings
are quite small (some people end up paying more) - there are
two ways it is provided:
1. Single meter. For the privilege of having cheaper
electricity at night the cost of the day rate is increased substantially.
If you use half day rates and half night rates the savings are
10%. Install a hot water heat pump system, save over 30% and
enjoy the convenience of single rate electricity so you can
use low price hot water any time.
2. Two meters. With two meters the item connected to
the night rate can only be used at night, hence if your hot
water is connected like this and you run out during the day,
it will be a long wait until it's hot again. A hot water heat
pump system will save a lot more money and provide much more
flexibility and convenience.
You can heat your water at night with a heat pump, just remember
it will be less efficient overall as the temperature is lower.
Gas water
heating.
Heating water with gas can be the best way under certain circumstances,
but it cannot compete with the price of hot water from a hot
water heat pump. (A household of one person with sporadic use
of hot water and with indoor space at a premium could be better
with gas).
A 45kg. bottle of gas costs $90, and there are sometimes hire
charges as well. Each kg. of gas costs $2, and this is equivalent
to 14kw/hrs of electricity (about the amount required to heat
a tank of water) - which would cost around $2.40. However a
gas water heater is only about 70% efficient so the actual cost
of using gas is more like $2.85 for 14kw/hrs. Just to complicate
matters even more a cylinder of hot water has standing losses
- these can be minimised with cylinder wraps but will typically
cost around 35c a day, making electricity $2.75. It is probably
safest to say electricity and gas are very similar in price,
even if the electricity is on a night rate.
Use a hot water heat pump and the equivalent cost is about 85c
- and no problems with the storage or delivery of bottles.
For calculations
concerning Rinnai gas efficiency click here
Make a note
of these figures, the suggestions from Rinnai are extremely
biased.
500 litres
a day of hot water is for a large family.
15°C water inlet temperature is correct for the South Island.
Temperature at the shower - 40°C
Cost of (bottled) gas, 15 cents per kWh (includes some bottle
hire costs)
Cost of electricity when using a hot water heat pump - 4 cents
per kWh.
Still want
to install gas?
Fitted
to a very old "Zip" cylinder, quicker recovery than
the 1kW element!
Hot water heat pump efficiency.
The hot water
heat pump collects and compresses heat from the outside air,
even at sub zero temperatures, however the CoP or coefficient
of performance varies with the outdoor temperature. This means
the actual cost of hot water varies with the weather, but over
a complete year the average efficiency will be at least 300%
and could be 500%, ie you will save at least 66% of your water
heating costs and could save 80%. The actual figure achieved
depends on a variety of factors such as the particular outdoor
unit fitted and when hot water is used.
Fitted
to cylinder with wetback connections, saving about one third
of electricity bill.
A
hot water heat pump versus solar.
Solar
hot water is free, so how can a hot water heat pump compete? In
actual fact solar hot water is anything but free, apart from the
cost of supplying and installing the necessary equipment there are
a considerable number of days in the year when backup is required
- unless you like cold showers. For almost any price between $4000
and $10000 solar hot water can be installed, if the property is
suitable and subject to consent from the council (more cost), and
frequently the roof panels can be unsightly. With a hot water heat
pump it doesn't matter what size cylinder you have, it doesn't matter
which way your roof is facing, it doesn't matter when you use hot
water, it doesn't matter how much hot water you use, it mostly doesn't
matter when you heat the water - you will save more money and energy
than with an equivalent solar system.
Over a complete year the savings with solar will be anything from
30 to 80% of hot water costs, the actual figure will depend on various
factors such as the size of collectors, number of users, your lifestyle
and the volume of storage tanks - most people will save around 50-55%
(according to government figures). A hot water heat pump will save
65-80% of hot water costs over a complete year, without any changes
to your lifestyle, and invariably at considerably lower initial
cost than solar. A heat pump system can be half the price
of an equivalent solar system, and for most people a heat pump will
actually save more energy and money.
In
order to qualify for a $500 subsidy the solar system must be approved
and installed for less than a threshold price - this price based
on savings over twenty years. Information about the approved systems
can be found here.
The savings are
quoted as kWhs per year - if you are serious about saving energy
and money study the figures closely. If you can find anything that
is better value than a Hot Water Pump Pump fully installed for around
$3500 please let us know - as we can't.
Six
person household, $117 a month last autumn.
A Hot Water
Heat Pump and solar, a case study.
For the ultimate
in energy savings consider fitting both a hot water heat pump and
solar hot water. As a combined system this would save 80-90% of
hot water costs, the drawback is the total cost which will probably
be around $10,000 for a family home, and there can be problems with
the controls................
John and Fiona
had a Thermocell solar
system fitted in 2002 into an existing property. Six flat panel
collectors (4 square meters) facing north west were put onto the
40 degree pitch roof - as an existing 300 litre mains pressure cylinder
(for six people) was converted to take solar some problems with
control were experienced. None of these was anything to do with
the Thermocell equipment or installation - Standard cylinders have
the elements at the bottom, as hot water is used from the top the
element is switched by the thermostat to heat the cold water fed
into the bottom. In order for solar to work it is therefore necessary
to stop the element switching on during the day, or rather until
there is no more solar gain. At which point the element is required
to do any necessary topping up, on cloudy days or in winter for
example.(Note, solar installers will often want to fit a new cylinder
for more savings - extra cost for little extra gain. A HWHP can
be fitted to any existing cylinder AND it will invariably save more
energy than solar).
However the actual
time for the element to be switched on varies - too early and efficiency
is lost, too late and there won't be hot water when required. A
simple time clock helps, but the only way to get 100% from the solar
was to install another hot water cylinder - which was done in 2005.
(Fitting a solar cylinder would not have helped - these are frequently
supplied with an element half way up, effectively cutting the hot
water available in half in bad weather which would have meant frequently
running out). The original tank is now purely solar preheat, and
the hottest water became the 'cold' feed to the extra cylinder.
The element was left on in this, so there is always a cylinder of
hot water, with the element only topping up the solar. The pipe
between the two cylinders holds no more than 1/2 litre of water
so losses are minimal, and both cylinders and all pipework had extra
lagging as well. The combined system worked extremely well for a
couple of years despite the best efforts of three teenagers and
thirty minute showers.
June 2006, John
discovers that Climate Zone is importing some hot water heat pumps.
He volunteered his testing services, and the first hot water heat
pump was fitted within a couple of days of landing in NZ. With only
the manufacturers claims to go on, and not wanting to disturb tranquil
home life by running out of hot water, another cylinder was fitted,
heated only with a Sova heat pump. This was put between the solar
and standard cylinder - so the solar preheat fed the heat pump cylinder,
which in turn acts as the 'cold' inlet to the finishing cylinder
with the element left on. This was probably the only domestic house
with three hot water cylinders (all in series), with a combined
capacity of 840 litres, enough for even the most determined teenager.
The heat pump
was comissioned on the first really cold evening of winter, and
the water was raised to temperature as quickly as an element would
have done, but using under half the normal amount of electricity
- despite the freezing cold.
Subsequent tests
with a "cent-a-meter" show the element in the final cylinder
rarely came on. Only if the water has cooled standing in the cylinder,
or the teenagers have done their trick and used 500 litres of water.
Solving both these problems without resorting to drastic measures
was the next step.
The original outdoor
unit was rated at 4kw, and experience showed that the recovery times
in cold weather for six people were too long. So.........
Update 1/8/07.
The "heat pump only" cylinder was bypassed - a larger
capacity outdoor unit was installed and fitted directly to a Rheem
280 litre mains pressure cylinder, and the element switched off.
All the water is now heated with a 6kW heat pump with solar providing
preheat. The heat pump is therefore the backup for the solar and
this ensures the lowest cost hot water at all times. Combined savings
are at least 80% compared with a standard element.
With
quicker recovery times five or six people can use the 180 litre
cylinder.
How
long will a Hot Water Heat Pump last?
We anticipate
that the outdoor unit will last fifteen to twenty years, (a
five year guarantee is provided as standard). We suggest a National
type HWHP is installed in preference to the Sova type where
a refrigeration engineer is unavailable. We believe the Nationals
can legally be installed by a houseowner without any qualifications,
as the houseowner can work on their own plumbing systems and
the unit can be plugged in.
Family
of ten, much better hot water availability..
Hot Water
Temperature and Legionella.
The temperature
of a hot shower is around 40°C, heating and storing water
significantly hotter than this and then lowering the temperature
with cold water is simply wasting energy (hotter water will
lose more heat no matter how good the insulation).
………………………………………………
Safe
hot tap water and the risk of scalds and legionella infection
R Hockey
Senior
Data Analyst, Queensland Injury Surveillance Unit, Mater Hospital,
South Brisbane QLD 4101, Australia; rhockey@mater.org.au
The
recent paper in Injury Prevention by Jaye et al on the barriers
to safe hot tap highlights the problem I raised last year regarding
the perception of plumbers of the risk of legionella infection
from hot water systems compared with that of scalds. The paper
reports that half the respondents thought it more important
to control for legionella than to prevent hot tap water burns.
Much of the blame for this perception can be attributed to the
Australian and New Zealand Standard (AS/NZS 3500.4.2:1997) which
sets a minimum temperature of 60°C for hot water storage
systems to protect against legionella.
In
1994 the standard was amended to require that the delivery temperature
be a maximum of 55°C in personal hygiene areas in domestic
installations through the installation of tempering devices.
Several years ago the NSW Heath Department tried, as part of
its "Burns like fire" campaign, to have this minimum
revised down to 50°C and presented compelling evidence supporting
the view that there would be no increased risk from legionella
at this temperature.
This
view is also reinforced by the situation in the US where the
maximum storage temperature is set at 50°C, a measure that
has resulted in a reduction in scalds without any discernible
increase in legionella infections. Unfortunately the Joint Technical
Committee for Plumbing Standards, which not unexpectedly is
dominated by plumbers, dismissed this evidence and we are left
with a confusing, contradictory, and expensive standard when
a simple solution exists. Setting the storage temperature at
50°C, which is also easily implemented in most existing
homes, would also protect children and more particularly elderly
persons from hot water burns in the kitchen and laundry (a not
insignificant problem).
I
would also contend that in a warm country like Australia, where
during the summer months cold water is often delivered at temperatures
exceeding 30°C, it is likely that cold water is a more significant
source of legionella infection (the ideal temperature for the
growth of legionella is 20-43°C).
The
other issue that was touched on in the paper was the reliability
of tempering valves, something which plumbers I have spoken
to have alluded to and needs further investigation.
Both
scalds and legionella are important public health problems,
however, very little is known about the contribution of a domestic
hot water supply to legionella. No one would deny that hot water
systems are a source of infection, with up to 30% of systems
testing positive to the organism, but the one study published
examining domestically acquired legionella failed to show a
relationship between hot water heater temperature and the disease.
On the other hand the evidence of the association between hot
water temperature and scalds is compelling.
I
hope other countries can learn from Australia's experience.
……………………………………………………
However the New Zealand building code states:
Building
Code G12 - 6.14.3
Legionella bacteria
Irrespective of whether a mixing device is installed, the storage
water heater control thermostat shall be set at a temperature
of not less than 60°C to prevent the growth of Legionella
bacteria.
What all this
means.
As with many
government edicts the 60°C water is with the best of intentions
without taking circumstances into account. Legionella bacterium
is naturally occurring in water and is dormant below 20°C.
In this state no hazard is present as the amounts are of no
consequence. The bacterium will multiply between 20°C and
43°C (peaking at 36°), in the presence of nutrients
(i.e. biofilm in pipes) and appears to be killed by copper,
such as pipes or a cylinder. In order to actually infect any
person, quantities of the bacteria have to be inhaled via water
droplets, such as a shower or cooling tower, and invariably
only certain groups can inhale enough to catch the disease (the
young, the elderly and smokers). Laboratory tests have shown
that legionella survives only a matter of hours in 50°C
water, a matter of minutes in 60°C water, and a matter of
seconds in 70°C water. Hence in a domestic situation with
a heat pump as a water heater and a daily turnover of water
in the cylinder, the chances of enough legionella bacteria multiplying
during the short time the water in the cylinder is between 20°C
and 43°C; and it not being killed with a thermostat even
set at 50°C; and enough getting through to a shower and
actually infecting someone who is susceptible, are as close
to zero as makes no difference. There is slightly more chance
of contracting the disease from a solar system, but in reality
the risk is still effectively zero. For these reasons (and because
50°C water is guaranteed never to scald anyone, tempering
valves set at 55°C not being noted for long term reliability)
we recommend the thermostat on a hot water heat pump is set
between 50°C and 55°C, (50°C being the maximum allowed
in the US). It is the safest and most energy efficient temperature
to store hot water in a domestic situation.
From what
we can work out there is no problem of the householder setting
a thermostat to whatever temperature they want - there is no
"offence" or illegal act - and any temperature above
49 (US maximum) is safe from disease. All National units default
to 55 when turned on - we suggest leaving it there.
(A plumber
has told us on a couple of occasions where a tempering valve
has failed without anyone noticing - then the thermostat fails
and boiling water comes out of the tap. A heat pump set at a
non scald temperature is much safer as a heat pump cannot produce
water much above 70 without the unit shutting down)
Perhaps one reason why 60°C
is suggested as the minimum thermostat temperature is because
standard thermostats can be innacurate, perhaps with a spread
of actual temperature plus or minus 5°C. So a thermostat
set at 60 could be storing water anywhere between 55 and 65.
The thermostat fitted to a hot water heat pump is much more
accurate, being within a degree or two of the set temperature.
It is interesting to note that a solar system is likely to spend
considerably longer periods of time between 20°C and 43°C
during a year, especially when backed up by an element used
overnight, and therefore represents a greater legionella threat.
Also some solar systems are specified with an element half way
up the cylinder, which cannot raise all the water to 60°.
In reality the risk of contamination in a domestic house is
still negligible and can be disregarded. Any individual is much
more likely to be killed by lightening or win lotto.
The following
is the Legionella requirements for solar hot water - from the
New Zealand building code.
3.5 Protection from Legionella bacteria
3.5.1 To prevent the growth of Legionella bacteria, solar water
heaters must either:
a) have a continuously energised heating element fitted within
55% of the bottom of the water tank (by volume) and a thermostat
set to 60°C or higher, or
b) be controlled so that the water above the element is heated
to 60°C once a day, and the element is in the bottom 20%
of the water tank (by volume) and no more than 150 mm from the
bottom of the tank, or
c) be controlled so that all of the stored water is heated to
60°C or higher, once a week for not less than 1 hour. The
temperature must be measured by a probe in the bottom 20% of
the water tank (by volume) and no more than 150 mm from the
bottom of the water tank. For open loop systems the stored water
includes the water in the solar collector and water must be
circulated through the
collector during the heating period.
We realize
there can be circumstances where legionella and other bacteria
could present a hazard, most notably in circulating water systems.
There are other alternative solutions apart from keeping water
above 60, most notably:
1. Ultra violet lights. For large domestic and other premises
using up to 3000 litres per day a correctly sized ultra violet
lamp appears to be the most cost effective. Typical price -
$1000.
2. Copper-silver ionizer. Above 3000 litres per day, or where
there could be pipes with static warm water for long periods
of time, a copper/silver ionizer should be specified. The ionizing
effect is long lasting (a few weeks), the only drawback is the
cost at $10,000 to $!5,000.
3. Ozone treatment.
Non toxic and beneficial to health. This could be a reasonably
priced effective solution to water treatment. We are investigating
further.
Day/night
rate electricity discarded, much better hot water availability.
Features
of a Hot Water Heat Pump system.
We have
fully tested the product, visited the manufacturers and can
offer all these features:
Savings
of 65-80% of hot water costs.
Fully complies with all New Zealand building codes.
Low cost hot water all day and every day.
Can easily be lower cost than equivalent solar systems.
Usually saves more energy than solar.
Low cost installation.
Big energy savings.
Operates down to -15°C.
Very quiet outdoor units.
Ozone friendly refrigerant.
Control panel displaying water temperature.
Five year warranty.
Maintenance free.
Quick recovery times
Efficient even at sub zero temperatures.
Zero consent costs.
Can be fitted to any size hot water cylinder.
Operates with low, medium or mains pressure supplies.
Can be combined with solar or wetback.
No unsightly roof panels.
Easily removed and transferred to another property.
Much safer than gas or diesel.
Zero emissions.
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