Do it Yourself: [DIY] Re: Hot water tank

Posted by: westande@gmail.com

> Heat pump hybrid water heater.
> I'd never heard of them but it has been working great for me.
> No problem with running out of hot water.
> I would seriously consider looking into this option.
> It does seem to outshine the tankless in
> functionality and energy efficiency.
> It is eligible for an energy tax credit as well.

Heat Pump Water Heaters can be an excellent option
I have used them in the last two highly energy efficient
houses that I have designed, and will likely use them in
virtually all from now on. After 2016 all electric water
heaters, over 50gal, that are sold in the US, must be
HPWH. However, they are different from other water
heaters, in where they get the extra heat that makes
them efficient. They get it from the air around them.
So, while they are efficient, they could increase the
amount of energy needed to heat your home. In
Winter, for most houses, the net effect of a HPWH
is the same as a standard electric water heater,
except that if you heat your home with a cheaper
fuel (than electricity) such as natural gas, wood,
or Solar, then you are partially heating your water
with that less costly energy source, as well as the
electricity that the water heater uses. That can give
you significant savings. I suspect that is confusing
some people, so I will explain.

Just as a home heating heat pump takes heat
from the cold air outside the house, and uses it to
produce high enough temperatures to warm a home,
the HPWH take heat from the house air, to produce
hot water. That is wonderful in Summer, because it
not only gives you over twice as much water heating
for the same amount of electric, but you get the bonus
of that much free air conditioning and dehumidifying
at the same time. That makes it the best thing going,
if you live in a warm climate. But, if you live where
it is cold a lot of the time, you are just, as they say;
robbing Peter to pay Paul. You are air conditioning
your house in Winter, to heat your water. So, the
key is in the balance of heating season and cooling
season. Obviously, climate is a major factor in what
makes it a good strategy or not. But, and this is a
big BUT, we have other ways that we can effect
the length of our homes heating season.

However, it can get complicated. For instance,
using highly energy efficient light bulbs, which saves
money, or doing anything else that reduces your house-
-hold electric usage, will lengthen you heating season,
because virtually everything that uses electricity is an
electric resistance heater. We design some houses
now that, over the course of the heating season, end
up getting most of their heat from standard electric
usage, natural sunlight shining in windows, and even
the body heat of the occupants, all which I must
consider when I do my design calculations. The
heating season (in this context, which means when
the furnace runs) can also be shortened or even
eliminated by using a wood stove or Solar heating,
and to an extent by heating the house with a heat
pump, powered by Solar electric.

So, who gains from a HPWH and who does not.
Well, definitely those with a long non-heating season
gain. It does not have to be air conditioning weather,
it just needs to not be furnace weather. However,
even if it is the middle of Winter, and you have gas
or a heat pump for heating the house, a HPWH will
cost less to operate than a standard electric or propane
water heater (though a propane water heater is highly
unlikely in a house with gas home heating) And, while
a HPWH may not save you much (or even cost more
to operate than a gas water heater during Winter)
the Summer saving usually make up for it in most
climates.

As a last note, since this is the DIY group, there are
some clever tricks that we can use Heat Pump Water
Heaters for, so that they can give us very high efficiencies
year round. Basically a heat pump takes low temperature
heat, and virtually compresses it into higher temperature
heat in less mass. So, it can take heat from air, at most
any temperature, and heat water with it. But, it works
more efficiently, the warmer its heat source is. If we
locate our HPWH where it can be heated by a wood
stove, or a simple Solar air heater, it will provide us
with a lot of free water heating.

I designed a system where the HPWH is located in a
closet like space, above where the woodstove sets. There
is a floor/ceiling grate, so that hot air can rise off the wood
stove, into the space around the HPWH. Also, in this little
room/closet, are a lot of two-liter soft drink and juice bottles,
filled with water. They are heated by the rising air, and when
the woodstove is not warming the air around the HPWH,
they do. That way the HPWH will have warm air around
it 24/7 to operate at its highest efficiency. The PET plastic
(mylar really) bottles are excellent for this, since they have
an expected life of hundreds of years, and will not leak,
even if the water in them were to freeze hundreds of times
(I have literally tested them through hundreds of freeze-
-thaw cycles, so I know) This same design strategy can
be used when the heat source is a Solar sun room, or
simple Solar air heaters, which are quite easy for a DIYer
to build, and generally produce enough free heat to save
you as much (in heating costs) as the material cost, just
in the first heating season. And, it will go on giving close
to a 100%, tax free, return on that invest (as sure as
the sun will shine) every year, for decades to come. Try
to find a bank that will give you a 20th of that interest.
And, while being excellent for you wallet, it is also great
for the environment and your local air quality, too. And,
they can heat you whole house, not just your hot water.
It is a lot simpler, and more economical, to have Solar air
heaters warm your house, and a Heat Pump Water Heater
draw its heat from the house (and also air condition it in
Summer) than to have two (or three) separate systems.

So, if that interests anyone, just ask. We can discuss
how simple and effective these things can be. I have
been designing and building them for decades. I used
to have a company that just made them, and my simple
vented soffit design is about the most efficient and
attractive there is. With a Heat Pump Water Heater,
and simple low cost Solar air heaters, you can have
Solar water heating, and Solar home heating, that is
far more simple and low cost than the old panel on
the roof, water pumping type Solar water heaters..

Posted by: "Dale S" dalu@hbcomm.net

> Notice you mention outside walls and heat pumps.

> there is so little latent heat in the atmosphere during hard
> winters that I would be afraid of heat-pumps.

Hi Dale;

That is an irrational fear. The lowest that the efficiency
of the Heat Pump Water Heater can get is the same as a
standard electric water heater. And while a yearly average
will be around 2.33 times as efficient as a 100% efficient
electric resistance water heater, you also get the free air
conditioning and dehumidifying. HPWHs do not draw
heat from outdoors. They draw heat from the air inside
of the home, in the area where it is located. In more
northerly climates that is often the basement, which is
a space that often has issues of too high humidity. A
HPWH supplies free dehumidification. In warmer
climate, houses are less likely to have basements and
the HPWH is located on the main floor, where it air
conditions and dehumidifies.....for free, in addition to
giving over twice as much heat per electricity used,
as an electric resistance water heater.

> Heat pumps have never really caught on in this part
> of the country and those who did go that route were
> not happy with the results.

Do not choose to be ignorant about modern heat pumps.
The ones I use in the homes I design give more heat, for
less cost than natural gas, even at cold temperatures like
minus ten (F) We are installing them in climates like
Massachusetts and Minnesota. These units can be
bought online for as little as $1500. Technology and
prices have gotten to the point where it costs less to
heat a new energy efficient home with a heat pump
while generating the electricity from your own Solar
electric array, than to heat with natural gas, or any
other purchased fuel (unless you have a real cheap
wood supply).

> "Why waste time learning when ignorance is
> instantaneous."

I recommend that you try learning about modern heat pumps.
Knowledge converts well into both profit and cost savings.

-Laren Corie-
Natural Solar Building Design and
Solar Heating/Natural Cooling/Energy
Efficiency Consultation Since 1975
www.ThermalAttic.com (many new
photos and pages, coming soon)

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http://www.dongrays.com/essn/

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