Heat Pump Water Heaters
Paul M. Eldridge
boiler. With heating oil currently selling at $1.10 per litre and
with a summer EF rating of 0.60, oil is now 1.6 times more expensive
than electric resistance.
Although the easiest and least costly option would be to install a
conventional electric tank, I've always considered a Nyle heat pump
water heater a better alternative. Unfortunately, I lack sufficient
space in my laundry room for another full size storage tank (it's not
CSA/UL approved for what I have now), an external heat pump and all
the related plumbing. That said, a fully integrated product such as
this GE design could fit if I remove the storage cabinet that sits
next to the washer and dryer.
The video link can be found here:
http://www.geappliances.com/video_launcher.htm?emcid=1144&empid=4923&packageid=0000
Availability is said to be 4th quarter 2009, so I'm going to wait a
bit and see how this pans out.
Cheers,
Paul
Lou
"Paul M. Eldridge" <paul.e...@ns.sympatico.ca> wrote in message
news:krfkv393j0es7ib64...@4ax.com...
A heat pump takes heat from the air and transfers it, in this case, to the
water. In that sense, heat pumps make sense - they can deliver several
times more heat than could be generated by the same energy it takes to power
the pump. But there's a catch - the heat has to come from somewhere.
I can't tell for sure from the cite you give but if the unit is
"self-contained" it's pulling heat from the inside air. And you're heating
that air (in the winter anyway) with your furnace. So, it may help cool the
house somewhat in the summer as heat is taken from the inside air and dumped
in the water tank, but in the winter it'll make the furnace run more (or
you'll have a cooler house). It may use less electricity than a standard
electric water heater, but a standard electric water heater doesn't use any
of your home heating oil.
So the question is not how much electricity does the thing use, but how much
electricity plus heating oil over the course of a year, and is the cost of
that combination less than the cost of running a standard electric water
heater over the course of a year. And if the combination does cost less,
the secondary question becomes is it enough less to make the extra cost of
this combination unit worth it over the lifetime of the appliance.
I suggest you run some numbers using a very sharp pencil. One other thing
to consider - back in 1999 or so GE was saying that by the year 2001 it
would have a residential sized, natural gas powered, fuel cell unit that
would be able to provide a typical home with electricity, space heating, and
hot water. (It was dubbed the HomeGen 7000.) I haven't heard anything about
it since.
Paul M. Eldridge
wrote:
>A heat pump takes heat from the air and transfers it, in this case, to the
>water. In that sense, heat pumps make sense - they can deliver several
>times more heat than could be generated by the same energy it takes to power
>the pump. But there's a catch - the heat has to come from somewhere.
>
>I can't tell for sure from the cite you give but if the unit is
>"self-contained" it's pulling heat from the inside air. And you're heating
>that air (in the winter anyway) with your furnace. So, it may help cool the
>house somewhat in the summer as heat is taken from the inside air and dumped
>in the water tank, but in the winter it'll make the furnace run more (or
>you'll have a cooler house). It may use less electricity than a standard
>electric water heater, but a standard electric water heater doesn't use any
>of your home heating oil.
>
>So the question is not how much electricity does the thing use, but how much
>electricity plus heating oil over the course of a year, and is the cost of
>that combination less than the cost of running a standard electric water
>heater over the course of a year. And if the combination does cost less,
>the secondary question becomes is it enough less to make the extra cost of
>this combination unit worth it over the lifetime of the appliance.
>I suggest you run some numbers using a very sharp pencil.
Hi Lou,
The bulk of my space heating -- some 80 per cent -- is provided by a
ductless heat pump with a seasonal COP of just about 2.5. A heat pump
water heater would allow me to take advantage of this low-cost heat,
whereas I'm currently dependent upon fuel oil for 100 per cent of my
DHW needs. It's only when I'm heating with oil "at the margin" (i.e.,
when any incremental demand is met by my oil-fired boiler) that the
results would be neutral; in my case, the two or three coldest weeks
of the year.
I live in a temperate maritime climate where space heating is required
roughly seven months of the year (i.e., October 1st through April
30th); the other five months I run my dehumidifier virtually non-stop
to prevent issues related to mould and mildew. A heat pump water
heater would effectively provide me with "free" hot water during these
five months because it would eliminate the need to operate my
dehumidifier either in whole or in part (dehumidification being one of
the desirable side benefits).
I consume roughly 450 to 500 litres of fuel oil a year for domestic
hot water purposes; at $1.10 per litre that's $500.00 to $550.00.
Taking into consideration the "free" hot water during the summer
months and my heat pump's seasonal COP of 2.5 during the heating
season, I would peg my net savings over oil at about $400.00 a year.
>One other thing to consider - back in 1999 or so GE was saying that by the year 2001 it
>would have a residential sized, natural gas powered, fuel cell unit that
>would be able to provide a typical home with electricity, space heating, and
>hot water. (It was dubbed the HomeGen 7000.) I haven't heard anything about
>it since.
I remember that too. I'm much more optimistic about this announcement
because the technology has been around for some thirty years and has
proven to be reliable, and because it can be manufactured using "off
the shelf" components (basically a standard refrigerator compressor).
The incremental cost of a HPWH versus a conventional electric water
heater is generally in the range of $400.00 and this particular
product can be installed by a plumber or homeowner. The financial
return, especially in more milder climates, should be pretty solid;
even more so if it should qualify for various utility incentives or
government rebates.
Cheers,
Paul
h
"Lou" <lpogoda...@comcast.net> wrote in message
news:R8mdndsJ2v4RKmfa...@comcast.com...
>
> "Paul M. Eldridge" <paul.e...@ns.sympatico.ca> wrote in message
> news:krfkv393j0es7ib64...@4ax.com...
>> I have an indirect hot water tank that is connected to my oil-fired
>> boiler. With heating oil currently selling at $1.10 per litre and
>> with a summer EF rating of 0.60, oil is now 1.6 times more expensive
>> than electric resistance.
>>
>> Although the easiest and least costly option would be to install a
>> conventional electric tank, I've always considered a Nyle heat pump
>> water heater a better alternative. Unfortunately, I lack sufficient
>> space in my laundry room for another full size storage tank (it's not
>> CSA/UL approved for what I have now), an external heat pump and all
>> the related plumbing. That said, a fully integrated product such as
>> this GE design could fit if I remove the storage cabinet that sits
>> next to the washer and dryer.
Is the water ever really hot with that kind of setup? I have friends in
Massachusetts with that setup, and the only time the water is ever above
body temp is in the dead of winter when the furnace runs almost constantly.
It's ok in the summer, but lukewarm showers in January are not particularly
appealing. They plan to replace with an electric water heater as soon as
they can afford to, but it's their first house and money is very tight.
Jeff
up a few more degrees. You'll still have most of efficiency benefits and
energy is not getting cheaper.
Jeff
Paul M. Eldridge
>Is the water ever really hot with that kind of setup? I have friends in
>Massachusetts with that setup, and the only time the water is ever above
>body temp is in the dead of winter when the furnace runs almost constantly.
>It's ok in the summer, but lukewarm showers in January are not particularly
>appealing. They plan to replace with an electric water heater as soon as
>they can afford to, but it's their first house and money is very tight.
To answer your question, they should provide plenty of hot water and
can heat this water up to 60C/140F (most electric tanks are set to 50C
or less to prevent the risk of scalding). During periods of unusually
high draw when the heat pump can't keep up with the demand, the
electric element(s) inside the tank will kick on and so the water
heater will perform in the same way as a standard electric unit.
Have your friends checked and cleaned/replaced the air filter on their
unit? If not, the condenser could be clogged with dust and lint,
which would severely impact its operating performance and,
potentially, its service life. Have they also checked the tank's
upper element and thermostat? If either has failed (not uncommon on
older tanks) or if the thermostat was turned down too low -- or was
disconnected by the previous owner so that heat pump would operate on
its own, in an attempt to maximize savings -- you could conceivably
run out of hot water during periods of high demand.
Installed correctly and with proper routine maintenance (basically,
nothing more than cleaning or changing the air filter), these products
should provide many years of trouble-free and economical service. I
understand Massachusetts has some of the highest electricity rates in
North America and replacing a water heater with one that could
potentially use twice as much electricity doesn't strike me as a good
solution.
Cheers,
Paul
h
> Installed correctly and with proper routine maintenance (basically,
> nothing more than cleaning or changing the air filter), these products
> should provide many years of trouble-free and economical service. I
> understand Massachusetts has some of the highest electricity rates in
> North America and replacing a water heater with one that could
> potentially use twice as much electricity doesn't strike me as a good
> solution.
>
> Cheers,
> Paul
They've had several "specialists" come out to take a look (boiler guy, water
heater guy, heat pump guy) and the "experts" all say the heater is working
properly, and the settings are correct. At this point, they could have
simply replaced the water heater, since they've spent over $500 on
professionals to tell them that the system is just fine. The water heater
guy told them he had the "same setup", and looked at them funny when they
complained about the water temp. He said, "It's already at 95 degrees (F).
How much hotter would you like it? Sheesh." Maybe it's a local thing (tough
New Englanders), but I think most people want their hot water to be at least
120 degrees F. The guy jacked the thermostat all the way up (grumbling that
they would "scald themselves"), so now the water is at 100 degrees F. Still
way too cold, but it's apparently running "properly". I'm just glad I don't
have to shower in it!
Paul M. Eldridge
Thanks for the additional info. FWIW, a typical heat pump water
heater provides 8,000 to 10,000 BTUs/hr of heating (nominal). That's
the same amount of heat as would be provided by a 2.3 to 2.9 kW
electric element. A standard electric water heater is normally
equipped with either a 3.0 or 3.8 kW element although 4.5 or 5.5 kW
elements are used on some larger capacity models. What this means is
that HPWHs require longer recovery times and, thus, to maximize
potential savings (i.e., to avoid the backup elements from kicking on
to help out), it's best to spread out demand over a wider timeframe
where possible.
That said, if the heat pump cannot keep up with demand, it would
automatically switch over to the backup resistance elements so it
should provide the same level of performance as a conventional
electric unit. If everything were truly working properly and they're
still running out of hot water, they would likewise run out of hot
water with a conventional electric tank.
Clearly, something is not working as it should. Either they're
drawing unusually large amounts of hot water over a short timeframe
and therefore the electric elements cannot keep up, or the thermostat
is not properly set up to facilitate this switch-over to electric
resistance. In any event, anyone claiming that 100F is too hot
frankly doesn't know their ass from a hole in the ground. The tank
thermostat should be set to 120F, or higher if equipped with an
anti-scalding valve. With that, the likelihood of a "run out" qould
be vastly diminished.
Cheers,
Paul
Bob F
<h> wrote in message news:47faf53b$0$6131$4c36...@roadrunner.com...
Do the friends have a heat-pump water heater, or are they just using the
superheat from a heatpump that heats the house to warm the water? If so, I
wouldn't recommend replacing the thing, but just supplementing it.
h
Oh, they never, ever "run out" of hot water. The water is always around body
temperature; never hotter, never colder. Just dreadful, in my opinion.
Paul M. Eldridge
>Oh, they never, ever "run out" of hot water. The water is always around body
>temperature; never hotter, never colder. Just dreadful, in my opinion.
Well, 100F isn't going to provide much reserve capacity, so as cold
water is drawn into the tank, outlet temperatures will start to fall
off rather rapidly. In any event, I would recommend the upper and
lower tank thermostats be set at 120F or 140F if the tank is equipped
with a mixing value to prevent scalding. Given normal line losses,
being set at 100F, the temperature at the shower head may very well be
95F or less -- much too low for my liking.
Cheers,
Paul
Logan Shaw
> "Paul M. Eldridge" <paul.e...@ns.sympatico.ca> wrote in message
> news:mkpmv3tln2v6p7us6...@4ax.com...
>> Installed correctly and with proper routine maintenance (basically,
>> nothing more than cleaning or changing the air filter), these products
>> should provide many years of trouble-free and economical service. I
>> understand Massachusetts has some of the highest electricity rates in
>> North America and replacing a water heater with one that could
>> potentially use twice as much electricity doesn't strike me as a good
>> solution.
> They've had several "specialists" come out to take a look (boiler guy, water
> heater guy, heat pump guy) and the "experts" all say the heater is working
> properly, and the settings are correct. At this point, they could have
> simply replaced the water heater, since they've spent over $500 on
> professionals to tell them that the system is just fine. The water heater
> guy told them he had the "same setup", and looked at them funny when they
> complained about the water temp. He said, "It's already at 95 degrees (F).
> How much hotter would you like it? Sheesh."
Hindsight is not exactly useful, but there was an easy to solution to that
problem: don't pay the "expert". The stated purpose of having him come
out was to get the tap to deliver hotter water. If he's going to do a
bunch of stuff but ultimately refuse to even attempt to accomplish the goal
he was hired for, then he shouldn't be paid, because he hasn't held up his
end of the bargain.
I do wonder about one thing, though, which is whether this heat pump water
heater is drawing in the heat from indoors or outdoors. If it is bringing
the heat in from outdoors, there is usually a maximum temperature difference
that a heat pump can achieve, so if it can boost the temperature by 60F
and it's 32F outside, then heating to 92F is proper operation for the heat
pump portion of the system. If this were the case, then (a) the "emergency"
resistive heating should be kicking in (assuming it exists, which it seems
like it should in a climate like that), and (b) there would be a marked
difference in performance during the summer vs. the winter, but I think you
said it seems to always be about body temperature.
- Logan
Lou
>
> Hi Lou,
>
> The bulk of my space heating -- some 80 per cent -- is provided by a
> ductless heat pump with a seasonal COP of just about 2.5. A heat pump
> water heater would allow me to take advantage of this low-cost heat,
> whereas I'm currently dependent upon fuel oil for 100 per cent of my
> DHW needs. It's only when I'm heating with oil "at the margin" (i.e.,
> when any incremental demand is met by my oil-fired boiler) that the
> results would be neutral; in my case, the two or three coldest weeks
> of the year.
>
> I live in a temperate maritime climate where space heating is required
> roughly seven months of the year (i.e., October 1st through April
> 30th); the other five months I run my dehumidifier virtually non-stop
> to prevent issues related to mould and mildew. A heat pump water
> heater would effectively provide me with "free" hot water during these
> five months because it would eliminate the need to operate my
> dehumidifier either in whole or in part (dehumidification being one of
> the desirable side benefits).
Hi Paul -
I dunno - I have a small dehumidifier in my unfinished basement. I don't
use it much, but when I do, it throws off a lot of heat - enough to make the
space noticeably warmer. Of course, the heat the machine generates and the
latent heat from the condensed water vapor both get thrown off into the
cellar air, and in your case at least some of that would end up in the hot
water. But if I turn it on when the air conditioning is in use, the two
machines seem to end up fighting each other.
> I consume roughly 450 to 500 litres of fuel oil a year for domestic
> hot water purposes; at $1.10 per litre that's $500.00 to $550.00.
> Taking into consideration the "free" hot water during the summer
> months and my heat pump's seasonal COP of 2.5 during the heating
> season, I would peg my net savings over oil at about $400.00 a year.
The question isn't really, or only, about this new type of heater compared
to oil. Just to get some ballpark estimates, I went to the Sears site and
picked the first sizeable electric water heater I stumbled across - it
happened to be a 55 gallon model priced at 309 US dollars - and the
estimated annual electric usage was 4721 kWh/year. The most efficient
model, according to the energy guide label, uses 4600 kWh/year. Oddly
enough, a 30 gallon model had the same estimated energy usage, though the
cost was only $199 US. (I guess that means that standby losses are pretty
minimal, and it takes a certain amount of energy to heat a certain amount of
water whether you do it in a few big batches or a bunch of little ones.)
The question is, how does something like that compare to the estimated cost
of running the heat pump water heater, plus any extra running your space
heating heat pump, plus running your oil burner when you need the extra
heat.
I'll note that if your heat pump is reasonably sized for the space you're
heating and your climate, adding the additional load of heating your
domestic hot water may mean that the oil burner gets more use than it does
at present. On the other hand, you may need to use the dehumidifier and air
conditioning less in the summer. I don't know enough to figure all this
out, but it's why I suggested to use a sharp pencil to calculate the
alternatives.
It's pretty much a given that almost anything new would be cheaper to
operate than your present setup. It's not quite as obvious which
alternative would be the most economical.
> >One other thing to consider - back in 1999 or so GE was saying that by
the year 2001 it
> >would have a residential sized, natural gas powered, fuel cell unit that
> >would be able to provide a typical home with electricity, space heating,
and
> >hot water. (It was dubbed the HomeGen 7000.) I haven't heard anything
about
> >it since.
>
> I remember that too. I'm much more optimistic about this announcement
> because the technology has been around for some thirty years and has
> proven to be reliable, and because it can be manufactured using "off
> the shelf" components (basically a standard refrigerator compressor).
> The incremental cost of a HPWH versus a conventional electric water
> heater is generally in the range of $400.00 and this particular
> product can be installed by a plumber or homeowner. The financial
> return, especially in more milder climates, should be pretty solid;
> even more so if it should qualify for various utility incentives or
> government rebates.
Incentives/rebates can have an effect on your calculations, of a certainty.
I take it from your use of "litres" that you're not in the US, and have no
idea what may be available to you in that line. Which ever way you decide
to go, good luck.
Paul M. Eldridge
wrote:
>"Paul M. Eldridge" <paul.e...@ns.sympatico.ca> wrote in message
>news:60ilv3t7ksu6dgb4i...@4ax.com...
>Hi Paul -
>
>I dunno - I have a small dehumidifier in my unfinished basement. I don't
>use it much, but when I do, it throws off a lot of heat - enough to make the
>space noticeably warmer. Of course, the heat the machine generates and the
>latent heat from the condensed water vapor both get thrown off into the
>cellar air, and in your case at least some of that would end up in the hot
>water. But if I turn it on when the air conditioning is in use, the two
>machines seem to end up fighting each other.
Hi Lou,
I have an Energy Star dehumidifier but, like yours, it dumps a
considerable amount of heat into my home during the time of the year
when it's least welcome. In the case of a heat pump water heater,
most if not all of the waste heat from its operation would be
transferred to the water -- if not on the first pass, then on each
subsequent run.
Being a frugal two-person household we don't use a lot of hot water so
this shouldn't be a problem for us, but I understand excessive cooling
can be an issue in homes with high hot water demand. For example, 100
litres (26.5 gallons) of hot water demand with a temperature lift of
40C (72F) would result in some 15,840 BTUs of cooling. According to
the DOE, a typical U.S. home uses about 240 litres of hot water per
day and if we assume a 40C temperature lift, this translates to be
some 38,000 BTUs of cooling. Great if you live in the southern
states, but perhaps too much of a good thing if you live further
north, as I do.
>The question isn't really, or only, about this new type of heater compared
>to oil. Just to get some ballpark estimates, I went to the Sears site and
>picked the first sizeable electric water heater I stumbled across - it
>happened to be a 55 gallon model priced at 309 US dollars - and the
>estimated annual electric usage was 4721 kWh/year. The most efficient
>model, according to the energy guide label, uses 4600 kWh/year. Oddly
>enough, a 30 gallon model had the same estimated energy usage, though the
>cost was only $199 US. (I guess that means that standby losses are pretty
>minimal, and it takes a certain amount of energy to heat a certain amount of
>water whether you do it in a few big batches or a bunch of little ones.)
>The question is, how does something like that compare to the estimated cost
>of running the heat pump water heater, plus any extra running your space
>heating heat pump, plus running your oil burner when you need the extra
>heat.
>
>I'll note that if your heat pump is reasonably sized for the space you're
>heating and your climate, adding the additional load of heating your
>domestic hot water may mean that the oil burner gets more use than it does
>at present. On the other hand, you may need to use the dehumidifier and air
>conditioning less in the summer. I don't know enough to figure all this
>out, but it's why I suggested to use a sharp pencil to calculate the
>alternatives.
>
>It's pretty much a given that almost anything new would be cheaper to
>operate than your present setup. It's not quite as obvious which
>alternative would be the most economical.
One litre of residential fuel oil contains 36,500 BTUs of energy and
with an estimated summer EF of 0.60, I net 6.42 kWh of useful heat.
During the winter months, my gain is 8.77 kWh per litre based on my
boiler's 82% AFUE rating -- not all of this heat is transferred
directly to the water, but other than what's lost up the stack, the
remaining boiler and tank losses simply offset a portion of my home's
space heating demand. On that basis, at $1.10 per litre, the summer
and winter operating costs are $0.171 and $0.125 per kWh(e)
respectively; again, the lower winter number reflects the economic
benefit of the boiler's standby losses in terms of offsetting a
portion of my home's normal space heating demands.
Electric resistance is currently $0.1067 per kWh and with a seasonal
COP of 2.5, each kWh of heat provided by my heat pump is just $0.043.
So, as long the HPWH is "stealing" heat supplied by my heat pump, the
operating costs of the HPWH are quite low. It's only when the heat
taken away by the HPWH is provided by my oil-fired boiler that the
results are basically neutral. For much of the winter, my ductless
heat pump should have sufficient surplus capacity to meet this
additional load (again, we're not heavy users of DHW); during the
times when the ductless heat pump can't keep up then, obviously, the
oil-fired boiler has to pick-up the slack -- roughly speaking, the two
or three coldest weeks of the year.
In any event, for five of the twelve months, my operating costs are
effectively nil because the HPWH would be powered by the electricity
that would normally be used by my dehumidifier. For another six
months say, virtually all of the heat consumed by the HPWH would be
supplied by my ductless heat pump at an average of 4.3 cents per
kWh(e). For the one remaining month, it's likely the additional HPWH
demand would be met by the boiler, so there would be no net gain
vis-a-vis my current system.
>Incentives/rebates can have an effect on your calculations, of a certainty.
>I take it from your use of "litres" that you're not in the US, and have no
>idea what may be available to you in that line. Which ever way you decide
>to go, good luck.
Thanks. There are no incentives or rebates available at this time,
but that could change as Nova Scotia Power is starting to ramp-up the
DSM efforts and, hopefully, this is something they might like to
promote. As a guess, a conventional electric water heater would save
me about $200.00 a year over oil, so if the installed cost of an
electric unit is $400.00, the simple pay back is two years. A HPWH
might save me upwards of $400.00 a year and assuming the installed
cost is three times that of a conventional water heater, the pay back
is something in the order of three years. However, in terms of their
ten-year NPVs, I would expect the HPWH to be the hands-down winner.
Admittedly, my particular circumstances are better than what one might
normally expect because the bulk of my space heating is no longer met
by oil. But by the same token, those who heat with wood or wood
pellet or some other low-cost alternative would share a similar
advantage over oil (and electricity). As you correctly point out, you
really need to look at the numbers carefully to see if this option
makes sense.
Best regards,
Paul