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'[OT] tankless hot water heaters?'
2011\05\06@102749 by William Couture

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Hi all,

My wife has decided that we should get a tankless hot water heater to save
energy.

They are fairly uncommon in the USA, but fairly common in the rest of the
world.

Does anyone on the list have any experiences they could share with me?

We are looking at the Navien CR-180A (this one includes a small, 1 gallon
holding tank as a buffer) and the Noritz NR83-DVC.  Any personal experience
with either of these?  Also, the Noritz is a new model.  If you have experience
with an older model that would also be helpful.

Thanks!
  Bill

-- Psst...  Hey, you... Buddy...  Want a kitten?  straycatblues.petfinder.org

2011\05\06@103605 by Mark E. Skeels

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Can I add my question also.......can these things operate for extended periods of time (say a couple of hours), or are they only good for, say, the time it takes to fill up a bathtub?

Mark Skeels
Engineer
Competition Electronics, Inc.
TEL: 815-874-8001
FAX: 815-874-8181
http://www.competitionelectronics.com

On 5/6/2011 9:27 AM, William Couture wrote:
{Quote hidden}

2011\05\06@104636 by Michael Watterson

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On 06/05/2011 15:27, William Couture wrote:
> Hi all,
>
> My wife has decided that we should get a tankless hot water heater to save
> energy.
>
> They are fairly uncommon in the USA, but fairly common in the rest of the
> world.
>
> Does anyone on the list have any experiences they could share with me?
>
> We are looking at the Navien CR-180A (this one includes a small, 1 gallon
> holding tank as a buffer) and the Noritz NR83-DVC.  Any personal experience
> with either of these?  Also, the Noritz is a new model.  If you have experience
> with an older model that would also be helpful.
>
> Thanks!
>     Bill
>

Not tankless, but a Willis heater (which really isn't an immersion heater) gives instant hotwater or a bath full.

http://www.willis-renewables.com/immersion-how-it-works.htm

We called "tankless" a Geyser. Gas ones common from pre-WWII to 1980s (typically directly above a sink). Electric ones now available for sink or shower

2011\05\06@104755 by Olin Lathrop

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William Couture wrote:
> My wife has decided that we should get a tankless hot water heater to
> save energy.

I'm not sure they save energy.  I can see some reasons they might take more,
but other reasons they might take less.  The main selling point as I
understand it is that hot water is always available.  You never run out.

> They are fairly uncommon in the USA, but fairly common in the rest of
> the world.

They are fairly popular in new construction around here.  My house came with
such a system, and it was built in 1985.

> Does anyone on the list have any experiences they could share with me?
>
> We are looking at the Navien CR-180A (this one includes a small, 1
> gallon holding tank as a buffer) and the Noritz NR83-DVC.  Any
> personal experience with either of these?  Also, the Noritz is a new
> model.  If you have experience with an older model that would also be
> helpful.

I know nothing about that model.  Our unit is a Wyle McClain, but I don't
know the model off the top of my head.

All I can say is that the system seems to work.

We have pretty acidic water, and at one point added a downflow neutralizer
to the water feed right after the pressure tank.  This is just a tank with a
bed with small limestone gravel in it.  The acid eventually eats away the
limestone, but of course loses some of the corrosiveness in the process.
You periodically add more limestone gravel.

This worked fine for a while, and other things were not being corroded
anymore.  However, solubility of the calcium carbonate goes down as
temperature goes up.  This meant that it came out of solution and got
deposited inside the hot water heating coil.  Eventually it clogged up and
was replaced.

I'm only pointing this out to beware that instant hot water and some kinds
of water treatment might have unexpected side effects.

2011\05\06@105235 by Olin Lathrop

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Mark E. Skeels wrote:
> Can I add my question also.......can these things operate for extended
> periods of time (say a couple of hours), or are they only good for,
> say, the time it takes to fill up a bathtub?

The one I have can operate indefinitely.  The flame is much hotter than the
desired water temperature of course, so when the heater kicks on the water
is quickly heated to well above the eventual temperature, then it turns off
again.  The system then "coats" on the thermal mass in the heating coil, and
eventually kicks on again when it gets to the low end threshold.  Meanwhile
a mixing valve adjusts the amount of cold water blended with the hot from
the heating coil to keep the result roughly constant.

When hot water is used continuosly, the heater goes on and off every few
minutes.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000

2011\05\06@112716 by M.L.

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On Fri, May 6, 2011 at 10:27 AM, William Couture <spam_OUTbcoutureTakeThisOuTspamgmail.com> wrote:
> Hi all,
>
> My wife has decided that we should get a tankless hot water heater to save
> energy.
>

Why do you want to heat hot water? (sorry)

Tankless water heaters come at quite a cost premium over tank units of
equivalent efficiency. If you have gas service, the most efficient and
economical option may be a "condensing" gas fired water heater.

-- Martin K

2011\05\06@115322 by Herbert Graf

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On Fri, 2011-05-06 at 10:48 -0400, Olin Lathrop wrote:
> William Couture wrote:
> > My wife has decided that we should get a tankless hot water heater to
> > save energy.
>
> I'm not sure they save energy.  I can see some reasons they might take more,
> but other reasons they might take less.  The main selling point as I
> understand it is that hot water is always available.  You never run out.

The main theory on "save energy" is that fact that you don't have a tank
of hot water that has to be kept hot all the time.

Considering the efficiencies of modern hot water tanks the difference is
quite small for more, zero for some.

TTYL

2011\05\06@123319 by Richard Pytelewski

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Bill:

Tankless water heaters are fairly common where I live, in South Carolina.
New houses generally opt for these when building.  They cost a little more
to install so some people say "pass".

I am not familiar with the brand you named but depending where you live, if
the winter temperatures go below freezing, get a water heater that ensures
the exterior tank/pipes don't freeze.  This is generally done with a factory
installed electrical heater that, should the unit get to the freeze point,
it just keeps it from freezing.

You didn't say if you had gas, natural or propane, but here, they are
natural gas.  Also, talk with your plumber to ensure placement of the unit
is central to all of your piping; i.e., there are some pipe length
considerations/limits for tankless hot water and if you have long lengths of
pipe, you may find that you may need 2 units in different places in the
house to properly meet your expectations.

They work well, are very reliable. As a summary, for a retrofit, you'll have
gas, electrical, plumbing, exterior siding work so it isn't cheap to get
this done.
I hope this helps in your consideration of this project.

Rich

{Original Message removed}

2011\05\06@124912 by Dave Tweed

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Herbert Graf wrote:
> On Fri, 2011-05-06 at 10:48 -0400, Olin Lathrop wrote:
> > William Couture wrote:
> > > My wife has decided that we should get a tankless hot water heater to
> > > save energy.
> >
> > I'm not sure they save energy. I can see some reasons they might take
> > more, but other reasons they might take less. The main selling point as I
> > understand it is that hot water is always available. You never run out.
>
> The main theory on "save energy" is that fact that you don't have a tank
> of hot water that has to be kept hot all the time.

Even a "tankless" heater keeps some part of itself hot all the time. The
theory is that that part is much smaller than a water tank and therefore
has less surface area through which to lose heat, and it also can be better
insulated.

The fundamental limit on a hot water tank is how much hot water you're likely
to need at once. The fundamental limit on a tankless system is the total rate
(GPM vs. temperature) at which you need hot water.

-- Dave Twee

2011\05\06@133054 by Bob Ammerman

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----- Original Message ----- From: "Mark E. Skeels" <.....mskeelsKILLspamspam@spam@competitionelectronics.com>
To: "Microcontroller discussion list - Public." <piclistspamKILLspammit.edu>
Sent: Friday, May 06, 2011 10:36 AM
Subject: Re: [OT] tankless hot water heaters?


> Can I add my question also.......can these things operate for extended
> periods of time (say a couple of hours), or are they only good for, say,
> the time it takes to fill up a bathtub?
>
> Mark Skeels
> Engineer

We have one at our church building that will run at least long enough to fill our baptistery, which has to be at least 750 gallons. I have no reason to believe that it can't run continuously.

-- Bob Ammerman
RAm Systems

2011\05\06@133817 by Mark E. Skeels

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Really! That is exactly the use I had in mind.

Is it used only for the baptistery? If so, does it fare OK considering the long periods of inactivity between uses?

Mark Skeels
Engineer
Competition Electronics, Inc.
TEL: 815-874-8001
FAX: 815-874-8181
http://www.competitionelectronics.com

On 5/6/2011 12:30 PM, Bob Ammerman wrote:
> {Original Message removed}

2011\05\06@141727 by Olin Lathrop

face picon face
Herbert Graf wrote:
> The main theory on "save energy" is that fact that you don't have a
> tank of hot water that has to be kept hot all the time.

Right, but insulation for that is relatively cheap and easy.  On the flip
side, the heat exchanger coil in the heater also looses heat and eventually
the heater will fire, bring the coil to the maximum temperature, then turn
off again.  I can occasionally hear my heater firing for a minute or so when
I know nothing should have been using hot water and the house heat is not
on.  It's infrequent enough that I suspect it amounts to a very small
fraction of overall oil usage, but it's still due to heat loss like a tank
system.

Of course the whole heater is insulated too, but I would guess that it is
more expensive to do that to get to the same level of power loss.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000

2011\05\06@152859 by Bob Ammerman

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----- Original Message ----- From: "Mark E. Skeels" <.....mskeelsKILLspamspam.....competitionelectronics.com>
To: "Microcontroller discussion list - Public." <EraseMEpiclistspam_OUTspamTakeThisOuTmit.edu>
Sent: Friday, May 06, 2011 1:39 PM
Subject: Re: [OT] tankless hot water heaters?


{Quote hidden}

Mark,

We do use it for hot water in the church kitchen, so it is only inactive about one week at a time.

They actually installed it in the wrong place for our use. They placed it adjacent to the baptistery, which means there is about 100 feet of 1/2" copper pipe to the kitchen. It takes a _long_ time (probably about a minute or two) for the water to get hot in the kitchen. It should have been placed near the kitchen with a long pipe to the baptistery. Then it would take a couple of minutes to get hot at the baptistery, but since it probably takes an hour or two to fill the baptistery that wouldn't be a problem.

-- Bob Ammerman
RAm Systems

2011\05\07@122033 by RussellMc

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You can get electric instant heat water heaters.
I installed a 6 kW unit in our church kitchen many years ago.
Good for eg kitchen sinks  used intermittently.

You can get these with a shower nozzle fitted.
At 6 kW the flow rate at showering temperatures is exceedingly modest.
..Far lower than anyone would normally use.


  Russel

2011\05\07@140204 by Jonathan Hallameyer

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On Fri, May 6, 2011 at 11:26 AM, M.L. <mspamspam_OUTlkeng.net> wrote:
> On Fri, May 6, 2011 at 10:27 AM, William Couture <@spam@bcoutureKILLspamspamgmail.com> wrote:
>> Hi all,
>>
>> My wife has decided that we should get a tankless hot water heater to save
>> energy.
>>
>
> Why do you want to heat hot water? (sorry)
>
> Tankless water heaters come at quite a cost premium over tank units of
> equivalent efficiency. If you have gas service, the most efficient and
> economical option may be a "condensing" gas fired water heater.
>
>
In general from what read, it seems that the ROI for a tankless system
is quite long, or even non existent for a full family, shorter for a
couple, and even shorter for a single person,  I.E. the less hot water
you use the more a tankless system makes sense.   For the original
poster, obviously there is a SWMBO in the picture, if there is kids in
the picture or soon to be, or maybe even just planned, then a
condensing 'tanked' water heater may be the best choice, as mentioned
above.

They even have heat-pump electric water heaters now, using a heat pump
to provide heating for the water, cooling the surrounding area
accordingly.  It'd be interesting to see an absorption refrigeration
style heat pump, gas powered water heater. Obviously not useful in all
climates, but in places where heating requirements are small, it would
seem like a good way to use energy rather then just dumping all those
useful BTU's outside.

-- Jonathan Hallameye

2011\05\07@145912 by M.L.

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On Sat, May 7, 2011 at 2:02 PM, Jonathan Hallameyer <KILLspamjmhtauKILLspamspamgmail.com> wrote:
> They even have heat-pump electric water heaters now, using a heat pump
> to provide heating for the water, cooling the surrounding area
> accordingly.

I was going to mention those, but at the SEER they quote (3), it's not
very economical unless you have no source of burnable fuel.
Electricity is (from my calculations) several times more expensive
than any combustible fuel. I just did a 2 minute search and I may be
wrong about that. It might be closer to parity with oil (electric at a
SEER of 3)

What I wonder is why they can make household A/C units with a SEER of
14 but the water heaters only achieve 3.

The delta-temp for A/C is going to be something like 90F hot to 55F
cold (35 degrees)
For water heating it will be something like 90F to 135F - so the
delta-T isn't that different.

-- Martin K

2011\05\07@153631 by Herbert Graf

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On Sun, 2011-05-08 at 04:19 +1200, RussellMc wrote:
> You can get electric instant heat water heaters.
> I installed a 6 kW unit in our church kitchen many years ago.
> Good for eg kitchen sinks  used intermittently.
>
> You can get these with a shower nozzle fitted.
> At 6 kW the flow rate at showering temperatures is exceedingly modest.
> .Far lower than anyone would normally use.

I once stayed at a very "affordable" hotel in London that had one of
these, had to turn it on, wait a few minutes and then take your shower.

It worked, but the flow rate was pretty low, as one would expect.

TTYL

2011\05\07@164645 by cdb

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:: It worked, but the flow rate was pretty low, as one would expect.

Perhaps I'm thinking of the wrong thing here, but power showers are quite common in the UK, requiring their own 30A connection and breaker, mains water fed (not from a cold water tank in the loft). I used to have one, not only was the heat adjustable, but the pump provided a 'forceful' shower and apart from the 3 or 4 second delay whilst the tank filled and heated worked very well.

Camping in NZ a few years ago two of the campsite had electric showers, no problem with heat or water force.

This is what I'm thinking of.

http://littleurl.info/3dz

Personally I think local instantaneous heating not only saves electrickery but also reduces water used. The only time this would not be so in my opinion is if running a bath was required (will be in next years Olympics as a sport) and where constant high usage hot water is required.

Reasons for assertion:

Only heating the water that you actually use - so as kW's are charged in units of time, 5 minutes is less than the 30 or 40 minutes it takes to heat a large tank.  
Less than 500ml (3/4 pint) of water is 'wasted' between being cold and hot. assuming the system is installed at point of use.

Sadly they don't seem to be legal in OZ, especially now that it is mandated solar or heatpump systems can only be installed in Queensland.

Colin
--
cdb, RemoveMEcolinTakeThisOuTspambtech-online.co.uk on 8/05/2011
Web presence: http://www.btech-online.co.uk   Hosted by:  http://www.justhost.com.au
 "For those who believe, no proof is necessary. For those who don't believe,
no proof is possible." - Stuart Chase

2011\05\08@055348 by Lee Jones

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Martin K. wrote:
>
> The delta-temp for A/C is going to be something like 90F hot
> to 55F cold (35 degrees)

Wow, 55 deg F is a really cold room and way past the guidelines
for energy saving of cooling to 75 deg F.

But here in Southern California (Inland Empire or desert) or
Las Vegas or Phoenix, your 35 deg F delta-T IS correct due to
mid-day summer temperatures that can hit 100 to 110 deg F.  I
have experienced such outdoor temperatures [ and don't mind
them -- just don't touch any exposed metal surfaces :-) ].

> For water heating it will be something like 90F to 135F - so
> the delta-T isn't that different.

I don't know where you get the base temperature of 90 deg F.
Everywhere I ever ran a wet process darkroom the cold water
out of the tap was about 55 deg F.  I don't expect that has
changed in the last few years.  So the delta-T for hot water
(assuming 120 deg F set point) would be about 65 deg F --
almost twice the delta-T compared to air conditioning.

                                               Lee Jone

2011\05\08@085927 by M.L.

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On Sun, May 8, 2011 at 5:58 AM, Lee Jones <spamBeGoneleespamBeGonespamfrumble.claremont.edu> wrote:
> Wow, 55 deg F is a really cold room and way past the guidelines
> for energy saving of cooling to 75 deg F.
>

The heat exchanger which cools your air is not at 75 degrees F. It's
more like 55F.


{Quote hidden}

The delta T I'm talking about is from heat source to heat sink. The
source is the air to refrigerant heat exchanger which might be at 90F.
The sink is the refrigerant/water heat exchanger which might be around
135F.

--
Martin K.

2011\05\09@153917 by Gerhard Fiedler

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cdb wrote:

> Personally I think local instantaneous heating not only saves
> electrickery but also reduces water used. The only time this would
> not be so in my opinion is if running a bath was required (will be in
> next years Olympics as a sport) and where constant high usage hot
> water is required.
>
> Reasons for assertion:
>
> Only heating the water that you actually use - so as kW's are charged
> in units of time, 5 minutes is less than the 30 or 40 minutes it
> takes to heat a large tank.
>
> Less than 500ml (3/4 pint) of water is 'wasted' between being cold
> and hot. assuming the system is installed at point of use.
The downside is that local instantaneous heating basically assumes
heating with electricity. (Using oil or gas for local heating is at
least inconvenient.) Heating with electricity is not only more expensive
in many places, but usually also less efficient (overall).

> Sadly they don't seem to be legal in OZ, especially now that it is
> mandated solar or heatpump systems can only be installed in
> Queensland.

If you factor in the efficiency of a heatpump/solar system, I don't
think that local instantaneous heating saves energy. It still saves
water, though.

There is the possibility of having a small backflow pipe with each hot
water pipe, inside the insulation, and force a small amount of flow at
all times, from the end of the hot water pipe back to the hot water
reservoir. This would of course increase the energy losses, but it would
also reduce the amount of water wasted. Has anybody experience with such
a system?

Gerhar

2011\05\09@160451 by Bob Blick

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On Mon, 09 May 2011 16:39 -0300, "Gerhard Fiedler"  wrote:

> There is the possibility of having a small backflow pipe with each hot
> water pipe, inside the insulation, and force a small amount of flow at
> all times, from the end of the hot water pipe back to the hot water
> reservoir. This would of course increase the energy losses, but it would
> also reduce the amount of water wasted. Has anybody experience with such
> a system?

There are two versions. One runs continuously. Not very popular now that
electricity is no longer unmetered. The second is a demand based
recirculator that pumps fast and furiously for two seconds when it
senses you turning on the hot tap. The return line is full size.

I had a house with the first system, always left it switched off. Since
it was already plumbed for recirculation, I could have added the extra
gizmo to modernize it, but didn't.

Bob

-- http://www.fastmail.fm - Email service worth paying for. Try it for free

2011\05\10@173333 by Peter

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William Couture <bcouture <at> gmail.com> writes:
> Hi all,
>
> My wife has decided that we should get a tankless hot water heater to save
> energy.
>
> They are fairly uncommon in the USA, but fairly common in the rest of the
> world.
>
> Does anyone on the list have any experiences they could share with me?

I have used and am using instant water heaters with and without holding tank,
electrical. I'm in Europe. They work well but they have the caveats brought up
by others. By FAR the best solution I've had was a *gas* fired water heater and
heating (hot water room heating) unit which is basically a gas fired computer
controlled wall mounted thing that contains everything needed to do this, and
exhausts through a 4 inch pipe bored horizontally out through the wall. VERY
popular here. Input is water electricity and gas and output is hot water pipe
(thermostated) and hot water room heating to and from radiators in the room, on
the storey, or in the house. They cost from about 600 Euros up here, (heating)
power is from 15kW up. LPG and natural gas models exist we use natural gas.
Electricity consumption is around 50-80W (circulation pump and
computer+valves+igniter on), and maybe 5W in standby.

A type example is: Junkers CERACLASS MIDI ZW24-2MFA which is a 25kW thermal unit
that provides 11l/min hot water and costs about 800 Euros (plus installation)
here. Many are condensing units and are very efficient (>75%).

-- Peter

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