On-demand water heater


L

l5ducks

Hi all,
am considering buying an 'on demand' water heater. has anyone had
experience with these? do they work well? have you noticed any
energy savings or increase? any recommendations? how difficult is
the install?
thanks for any help,
Greg
 
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H

hallerb

Hi all,
am considering buying an 'on demand' water heater.  has anyone had
experience with these?  do they work well?  have you noticed any
energy savings or increase?  any recommendations?   how difficult is
the install?
thanks for any help,
Greg
Really should make up a FAQ

If its electric you will probably need a 400 amp service upgrade at a
cost of thousands of dollars, 200 amps dedicated to water heating

If its gas you will need large gas lines and possibly a new meter,
since fuel consumption is so high. New flue too, a tankless gas uses
way more gas than a normal furnace

The energy $ saved will never occur in the lifetime of the unit:(

Regular tank 500 bucks installed

Tankless a couple grand

To save any money you must FIRST, save enough to pa that 1500 bucks.
Warrantied lifetime of tankless is never more than 10 years.

Now in the winter the heat lost by a standard tank helps heat your
home, so cut savings by 1/2

Plus there are sizing issues, you need a large enough tankless to
support all fixtures that may be on at same time.

Thats a lot if 2 are showering at same time


In the case of a power failure you have NO hot water at all, with a
standard tank theres still a couple quick showers available:)

If the water system fails for some reason a standard tank is a good
source of drinking water. Terrorism might be the cause:(

Unlimited hot water can lead some to taking endless showers that run
up energy costs:(

Did you know that standard tanks come in high output versioons?

Regular tank 35 to 40K BTU HIGH OUTPUT tank 75,000BTU

Plus you can go from say a 40 gallon tank to a 75 or 100 gallon high
output tank so you will rarely run out of hot water.

The econmic numbers of tankless dont add up:(
 
D

Dean

Hi all,
am considering buying an 'on demand' water heater. has anyone had
experience with these? do they work well? have you noticed any
energy savings or increase? any recommendations? how difficult is
the install?
thanks for any help,
Greg
I have an Energy star AE12 240volt,,it is intended as a point-of-
use unit but is serves My bathroom shower and sink and occasinally the
washer if I do'nt use the cold cycle only..It works well enuff for Me
and handles the changes that Winter brings to incoming water temp,,the
AE9.5 120volt unit did'nt provide this when installed at the same
location.. A gas whole house unit is probably the most powerfull but
with longer runs of pipe then pipe insulation becomes more needed..
I have no expierience with gas tankless..
The smaller units will provide hot water only within a narrower range
of gallons-per-minute use so flow restricting aerators,showerheads and
valves are needed..There are pipe size recommendations also but I have
some copper,some old steel that is as yet uninsulated and it works
well enuff for the estimated 20-30' runs it travels..
The best price I could find for My unit was at designerplumbing
website,,only took 2 days or so to arrive by Fed Ex ground from
Northeast US to Midwest but there was about 2 days to process order so
4 total..
Living alone with lower hot water needs than a family I believe it
saves alot in that there is no tank to keep hot when idle,,I'll guess
that they save in the long-run in most applications if
purchase,installation and changes costs can be controlled..Any
European Members should know more as I think tankless units have been
widely used There for years..
When You find a unit of interest read the specifications carefully
before purchase,,carefully and then some!!
Dean
 
D

Dean

Really should make up a FAQ

If its electric you will probably need a 400 amp service upgrade at a
cost of thousands of dollars, 200 amps dedicated to water heating

If its gas you will need large gas lines and possibly a new meter,
since fuel consumption is so high. New flue too, a tankless gas uses
way more gas than a normal furnace

The energy $ saved will never occur in the lifetime of the unit:(

Regular tank 500 bucks installed

Tankless a couple grand

To save any money you must FIRST, save enough to pa that 1500 bucks.
Warrantied lifetime of tankless is never more than 10 years.

Now in the winter the heat lost by a standard tank helps heat your
home, so cut savings by 1/2

Plus there are sizing issues, you need a large enough tankless to
support all fixtures that may be on at same time.

Thats a lot if 2 are showering at same time

In the case of a power failure you have NO hot water at all, with a
standard tank theres still a couple quick showers available:)

If the water system fails for some reason a standard tank is a good
source of drinking water. Terrorism might be the cause:(

Unlimited hot water can lead some to taking endless showers that run
up energy costs:(

Did you know that standard tanks come in high output versioons?

Regular tank 35 to 40K BTU HIGH OUTPUT tank 75,000BTU

Plus you can go from say a 40 gallon tank to a 75 or 100 gallon high
output tank so you will rarely run out of hot water.

The econmic numbers of tankless dont add up:(
A tanked heater will add some heat to the house in Winter I agree
but does'nt it also add heat in summer wich must be countered if air
con is used wich would negate at least some of the winter savings?
I think if a person thinks it through well enough for their
situation a tankless *might* be the ticket to water/energy
conservation..We have been spoiled for a looong time here in the USA
but do'nt count on it forever,,conservation is and will be a growing
issue..What was it Grandparents used to say? "Waste not want
not"?.....Sorry,,I digress and do'nt intend to be argumentative..
Dean
 
T

terry

On Jan 31, 9:26 am, (e-mail address removed) wrote:> Hi all,

There are lots of tankless WHs here..http://www.designerplumbing.com/store/POWERSTAR7.html
..
Replaced our 40 US gal electric HW tank ourselves recently (in Canada)
for $300 Canadian (about $250 US) including sales tax. That included a
new 'pressure relief valve'. It has individual 3000 watt heaters top
and bottom with the usual flip-flop upper thermostat. Like previuos
ones it is well insulated by foam insulation; not fiberglass batting.
As mentioned elsewhere we turned off the electricity to such a tank
when going on vacation. Returning after two weeks the water was still
tepid! Testament one would think to very little heat loss.
BTW if your breaker and wiring from panel to tank is adequate you can
(by moving one wire) arrange such a tank to operate both heaters
through their own thermostats simultaneously, for quicker recovery.
However only had to do this once when we had a 'whole slew' of
visiting relatives all taking showers!
The 'Tank less water heaters' seem to be popular in for example the
UK. But one reads about them needing to be heavily wired for 40 to 60
amps? At 230 volts that's like 11 to 15 kilowatts while operating!
The cost of electricity in Europe where tankless seem to be more
common is probably somewhat higher than in Canada?
They don't sound very cheap and are often the subject of repair
enquiries on the < uk.d-i-y > news group. So hard to judge how
reliable they are?
While they may save electrical energy???? the economics of 'Tankless
water heaters appears, to us, doubtful at moment?
BTW when people here, well away from major North American population
centres scrap old hot water tanks, the metal recyclers are more than
willing to accept them. So that's partly encouraging?
Comments from those with different mileage welcome?
 
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P

Paul M. Eldridge

Hi Dean,

Personally, I think they make no sense whatsoever. The current draw,
in the case of an electric model, is enormous and even if your home
has a 200-amp service, a tankless water heater could easily push it
beyond its limit (e.g., an 18 kW tankless heater draws between 75 and
80-amps). And if you happen to live in an area, as I do, where winter
inlet temperatures are just a hair or two above freezing, good luck!
Raising the temperature of water some 70 or 75 degrees takes
considerable energy and with two or more simultaneous draws (e.g., a
shower and dishwasher or kitchen tap) there's an excellent chance
someone is going to be left very unhappy.

Likewise, if you're in the habit of shutting off the water when you
lather-up in the shower, you might want to kiss that idea goodbye
unless you don't mind being blasted with ice cold water when you turn
the taps back on (and if you have to leave the water running to ensure
the minimum flow necessary to keep the elements energized, what
happens to all those savings?).

Let's get to the heart of the matter. The average household uses
between 4,000 to 5,000 kWh/year for domestic hot water purposes (we'll
assume 400 kWh/month). If a conventional tank heater has an energy
factor of 0.94, the standby losses work out to be 24 kWh/month or 288
kWh/year. At $0.10 per kWh, we can reasonably assume these losses are
less than $30.00 a year. If a new conventional water heater costs
$300.00 to $400.00 installed and the equivalent tankless unit is
$1,000.00 or more with the necessary wiring upgrade, how long would I
wait to reach break even and is that even realistic?

For a further take on this, see:

http://www.blackhillspower.com/tankless.htm

Lastly, all eight million or so residential households in Ontario are
being converted to time-of-use meters and, in future, I suspect these
meters will be far more commonplace than they are now. How much you
will save (or be penalized) under time-of-use rates will depend on how
much load you can shift to the off-peak periods. Practically
speaking, you can't shift your water heating to off-peak times unless
you have a storage heater. So if your power utility converts you to
time-of-use rates (as in the case of Ontario) or you decide to take
advantage of the potential savings where such rates are available, the
very last thing you'd want to do is install a tankless water heater.

This is the long-winded answer. The short answer is "are you nuts?".
;-)

Cheers,
Paul
 
D

Dean

Hi Dean,

Personally, I think they make no sense whatsoever. The current draw,
in the case of an electric model, is enormous and even if your home
has a 200-amp service, a tankless water heater could easily push it
beyond its limit (e.g., an 18 kW tankless heater draws between 75 and
80-amps). And if you happen to live in an area, as I do, where winter
inlet temperatures are just a hair or two above freezing, good luck!
Raising the temperature of water some 70 or 75 degrees takes
considerable energy and with two or more simultaneous draws (e.g., a
shower and dishwasher or kitchen tap) there's an excellent chance
someone is going to be left very unhappy.

Likewise, if you're in the habit of shutting off the water when you
lather-up in the shower, you might want to kiss that idea goodbye
unless you don't mind being blasted with ice cold water when you turn
the taps back on (and if you have to leave the water running to ensure
the minimum flow necessary to keep the elements energized, what
happens to all those savings?).

Let's get to the heart of the matter. The average household uses
between 4,000 to 5,000 kWh/year for domestic hot water purposes (we'll
assume 400 kWh/month). If a conventional tank heater has an energy
factor of 0.94, the standby losses work out to be 24 kWh/month or 288
kWh/year. At $0.10 per kWh, we can reasonably assume these losses are
less than $30.00 a year. If a new conventional water heater costs
$300.00 to $400.00 installed and the equivalent tankless unit is
$1,000.00 or more with the necessary wiring upgrade, how long would I
wait to reach break even and is that even realistic?

For a further take on this, see:

http://www.blackhillspower.com/tankless.htm

Lastly, all eight million or so residential households in Ontario are
being converted to time-of-use meters and, in future, I suspect these
meters will be far more commonplace than they are now. How much you
will save (or be penalized) under time-of-use rates will depend on how
much load you can shift to the off-peak periods. Practically
speaking, you can't shift your water heating to off-peak times unless
you have a storage heater. So if your power utility converts you to
time-of-use rates (as in the case of Ontario) or you decide to take
advantage of the potential savings where such rates are available, the
very last thing you'd want to do is install a tankless water heater.

This is the long-winded answer. The short answer is "are you nuts?".
;-)

Cheers,
Paul
Paul
Short answer to Your answer/question,,"maybe".. To expand a bit,I
do'nt claim to be the "average bear" in any way,shape or form..Greg
asked,,I answered the best I could without going on forever..I do'nt
have all the details in the world..Just My own modest expierience wich
I can and will impart as I choose..TY..
Dean
 
P

Paul M. Eldridge

Hi Dean,

I have to apologize, I didn't realize it was Greg who had asked this
question and not you, and I certainly didn't mean to imply your
experience or opinions were in any way less valid than my own.

I soured on tankless heaters after spending time with one down in
Atlanta where water supply temperatures are much higher than here in
Canada. Everything I mentioned I had experienced first hand, plus the
fact that the water never got what you might consider truly "hot".
There was one other issue I didn't mention because it was most likely
unique to this home; that is, the central air shut down anytime the
unit turned on (there was a load controller) and so the compressor
constantly cycled on and off anytime someone turned on a tap or the
washer or dishwasher ran through one of its cycles; I suspect that a/c
wasn't long for this world.

Again, my apologies for the oversight.

Cheers,
Paul
 
J

Jim Yanik

(e-mail address removed) wrote in
Hi all,
am considering buying an 'on demand' water heater. has anyone had
experience with these? do they work well? have you noticed any
energy savings or increase? any recommendations? how difficult is
the install?
thanks for any help,
Greg
One thing to remember;if you lose power,a tank water heater still keeps hot
water for some time.
I had warm-enough-to-shower water for 3 days after Hurricane Charlie.

On-demand heaters;NO hot water if the power goes out.
(I doubt gas-fired ones work during elec.outages.)
 
P

Paul M. Eldridge

Hi Jim,

That's a great point. I was without power for about a week after
Hurricane Juan, but my supply of hot water held on for the first two
days, with moderate use (it's a 30-gallon indirect hot water tank tied
to my oil-fired boiler; a larger tank would have likely extended that
another day or so).

If you should wake up one morning to discover the power's gone out,
this could be the difference between heading off to work or school
having showered or not.

Cheers,
Paul
 
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G

Guest

On-demand heaters;NO hot water if the power goes out.
(I doubt gas-fired ones work during elec.outages.)
My gas Takagi draws less than one amp maximum, lower than that most of
the time, so during power failures it can easily run off the pocket-size
inverter I use for my laptop computer in the car. If we had power
failures more often I'd put it on a UPS like our phones and home
network.

With three kids in the house, I'm hooked on the tankless system -- no
matter who has been running what for how long, there's still plenty of
hot water for my shower, even if the power is out.
 
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J

Jim Yanik

My gas Takagi draws less than one amp maximum, lower than that most of
the time,
At 120V that would be over 100 watts,considering startup surge.That's more
than 10A at 12V.(considering conversion losses)
so during power failures it can easily run off the pocket-size
inverter I use for my laptop computer in the car. If we had power
failures more often I'd put it on a UPS like our phones and home
network.
You can "unplug" your on-demand gas water heater's controller/igniter,and
plug it into an inverter or UPS? I thought they were hard-wired.
Have you actually DONE this?

how long do those UPS run with the power out?
Just long enough to shut down the PC? 15 minutes?
With three kids in the house, I'm hooked on the tankless system -- no
matter who has been running what for how long, there's still plenty of
hot water for my shower, even if the power is out.
where's the hot water come from when the power's been out before you begin
the shower?
does your tankless system have some sort of battery backup?
 

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