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Electric tankless water heater
|
|
| boustephane@hotmail.com 2008-01-11, 9:25 pm |
| Hi,
I have to change my old water heater and plan to buy an electric
tankless water heater (I don't want to use gaz).
We are 5 persons with "normal" needs and we are living in Canada (near
US frontiers). I plan to buy something like "Titan" brand
( www.titanheater.com ) or something else. Maybe I need to combine two
heaters in parallel to raise the capacity ?
I don't need excesive heat. I hesitate to make the change but very
interested by the reduction of electricity consumption.
Does anyone have experience or comment about this product ?
Thank you !
S.B.
| |
| Paul M. Eldridge 2008-01-12, 9:25 am |
| Hi S.B.,
If you live in Ontario, I wouldn't recommend it. The reason? All
residential consumers will be shifted to time of use rates, so their
operation during peak times will be especially expensive (i.e., after
7:00 am) -- about three times more costly, in fact. Secondly, two of
these little puppies would have a combined draw of anywhere from 150
to 180 amps, so unless you have a 400 amp service, it's lights-out,
literally!
As an alternative, I might recommend one (or if need be, two) 60
Imperial gallon conventional DHW tanks controlled by a timer so that
they recharge during off-peak hours [if you find yourself routinely
running out of hot water, you could adjust the timer so that they also
recharge during mid-peak]. In addition, if you can minimize your
overall hot water usage (e.g., front load washer, low-flow shower
heads, etc.) or shift a portion of your consumption to off-peak hours
(e.g., run your dishwasher overnight or do more of your laundry on the
weekends), your potential savings will be greater and you'll less
likely run out of hot water during the more expensive peak times.
Cheers,
Paul
On Fri, 11 Jan 2008 19:23:37 -0800 (PST), boustephane@hotmail.com
wrote:
>Hi,
>
>I have to change my old water heater and plan to buy an electric
>tankless water heater (I don't want to use gaz).
>
>We are 5 persons with "normal" needs and we are living in Canada (near
>US frontiers). I plan to buy something like "Titan" brand
>( www.titanheater.com ) or something else. Maybe I need to combine two
>heaters in parallel to raise the capacity ?
>
>I don't need excesive heat. I hesitate to make the change but very
>interested by the reduction of electricity consumption.
>
>Does anyone have experience or comment about this product ?
>
>Thank you !
>
>S.B.
| |
| daestrom 2008-01-12, 9:25 am |
|
<boustephane@hotmail.com> wrote in message
news:d321901a-06cd-4ef6-a00d-5218d30c0f33@e23g2000prf.googlegroups.com...
> Hi,
>
> I have to change my old water heater and plan to buy an electric
> tankless water heater (I don't want to use gaz).
>
> We are 5 persons with "normal" needs and we are living in Canada (near
> US frontiers). I plan to buy something like "Titan" brand
> ( www.titanheater.com ) or something else. Maybe I need to combine two
> heaters in parallel to raise the capacity ?
>
> I don't need excesive heat. I hesitate to make the change but very
> interested by the reduction of electricity consumption.
>
> Does anyone have experience or comment about this product ?
>
I've heard that electric tankless heater installations often need an upgrade
to the electric service. Some of them draw quite a few kW (on the order of
68 amps @ 220VAC). Two of them would *really* be a heavy load.
The link you provided says a Titan N-120 draws 11.8 kW @ 54 amps. With a 2
gpm shower head flow, it will raise the temperature of the water 48 degF.
So if your area is like central NY (south shore of Lake Ontario),
winter-time inlet water temperature for me runs about 40 degF. That would
be a pretty cool shower at only 88 degF. Two N-85's splitting the 2 gpm
between them would give you 71 degF rise for a shower of 111 degF (pretty
nice). But that's 17 kW for a total of 76 amps.
If you got large service like electric heating, you're probably okay. But
if you have gas heating and a smaller electric service panel, you might want
to check on the size of your electric service before going too far.
daestrom
| |
| Neon John 2008-01-12, 1:25 pm |
| Electric on-demand heaters are pretty much a lost cause unless you can live with a
trickle of lukewarm water. Simple physics. If you could use the entire 200 amp
capacity of your 240 volt service to heat water, that would only be 48 kilowatts or
163,000 BTU/hr.
To put that in perspective, I use a Paloma PH24 gas fired tankless heater
http://www.discounttankless.net/Mer...as&Store_Code=1
At 178,000 BTU/hr input, it does fine in the summer but just skimps by in the winter
when the incoming water is closer to freezing. It is good for a shower but not
anything else at the same time. I used to have the smaller PH12 but I found it
inadequate even with a water saving shower head.
Note that the Paloma has a higher heat input rate than an electric one could have
even if it used your entire service entrance's capacity. The ones that you're
looking at are barely half that, even if you use two in parallel. They discuss that
fairly well here
http://www.titanheater.com/tankless...er_northern.php
Although they tend to downplay the limitations by recommending ultra-low flow
showerheads. Personally, when I take a shower, I want a deluge and not just a
misting!
If you must use electric, here's something you might do. Put a "tempering tank" in
front of the on-demand heater. This tank would be an ordinary electric water heater
with the thermostat set to around room temperature. Say, 70 or 80 degrees. This
would bring the incoming water temperature up to something the on-demand heater could
work with.
The tempering tank would use little to no energy except during and after water use.
There would be essentially no standby losses. The energy input during water use
isn't wasted - it has to be input to the water anyway to raise the water to the
desired temperature - it simply smoothes out the power demand by spreading it over
time. You might could use your old heater as the tempering tank if it is still in
sound physical condition.
For the sinks around the house I've gone to point-of-use heaters. These are smaller
and much cheaper (about $100) versions of the heater you're interested in. These
mount under the sinks and draw about 40 amps at 240 volts. The advantage here is
that there is hot water available practically instantly plus I don't waste the water
nor the heat of flowing hot water through long pipes.
The temperature rise isn't outstanding but it's good enough for washing hands and
dishes.
John
On Fri, 11 Jan 2008 19:23:37 -0800 (PST), boustephane@hotmail.com wrote:
>Hi,
>
>I have to change my old water heater and plan to buy an electric
>tankless water heater (I don't want to use gaz).
>
>We are 5 persons with "normal" needs and we are living in Canada (near
>US frontiers). I plan to buy something like "Titan" brand
>( www.titanheater.com ) or something else. Maybe I need to combine two
>heaters in parallel to raise the capacity ?
>
>I don't need excesive heat. I hesitate to make the change but very
>interested by the reduction of electricity consumption.
>
>Does anyone have experience or comment about this product ?
>
>Thank you !
>
>S.B.
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
I'm going crazy. Wanna come along?
| |
| boustephane@hotmail.com 2008-01-12, 5:25 pm |
| Hi Paul,
Thank you for your answer. I live in Quebec (near Montreal) and the
rate for electricity is the same all the day. I have a 200 amps
service so I think I have to call an electrician before any move.
Stephane B.
| |
| boustephane@hotmail.com 2008-01-12, 5:25 pm |
| Hi daestrom,
I have two problems: Water incoming is cold (particularly in winter)
and my electric panel needs to be checked by an electrician. So I will
continue to think about it for a while before make a choice.
Thank you
Stephane B.
| |
| boustephane@hotmail.com 2008-01-12, 5:25 pm |
| Hi John,
Thank you for your suggestion but is it not dangerous for bacteria
development to keep water at 70-80 F ?
Regards
Stephane B.
> (...)
> If you must use electric, here's something you might do. =A0Put a "temperi=
ng tank" in
> front of the on-demand heater. =A0This tank would be an ordinary electric =
water heater
> with the thermostat set to around room temperature. =A0Say, 70 or 80 degre=
es. =A0This
> would bring the incoming water temperature up to something the on-demand h=
eater could
> work with. =A0
> (...)
> John =A0
>
| |
|
| There is a thread here from Nick Sans a year or so ago where we
calculated the amount of energy used to maintain the hot water in the
tank. The ONLY advantage of the tankless heater is it doesnt have to
provide this small maintenance usage. Both types heat the cold water
up to the selected final temp. You could measure the maintain-the-heat
usage with your water heater now. Put a lamp on the element so you can
tell its on. Heat the tank up. Dont use any hot water for 12 hours.
Note amount of time element is on. Its miniscule. Minutes every couple
hours. Pennies. The cost is heating the water in the first place, and
both tank and tankless heaters are identical in this regard.
| |
| Paul M. Eldridge 2008-01-12, 8:25 pm |
| Hi Stephane,
My pleasure, indeed. BobG makes a good point with regards to standby
losses. In the case of a new, well-insulated hot water tank, these
losses typically fall in the range of 1.5 kWh/day, which works out to
be about 550 kWh/year.
Hydro-Québec currently charges 5.29 cents per kWh for the first 30 kWh
consumed each day and 7.03 cents for any additional energy consumed
thereafter. If we were to blend these two rates together with the
assumption that your summer demand falls below 30 kWh/day, whereas
your winter demand is generally higher (i.e., your home is
electrically heated), your out-of-pocket expenses would average less
than $3.00 per month.
However, if your hot water tank is located within a conditioned space
and your heating season more or less spans October 1st through April
30th, the true cost could be as little as $12.00 per year.
5 months x 30.5 days/month x 1.5 kWh/day = 228.75 kWh/year
228.75 kWh @ $0.0529/kWh = $12.10
Here, we used the lower, first tier rate because the losses occur
outside the normal heating season when presumably your demand falls
below 30 kWh/day. Again, assuming your tank is located inside a
conditioned space, your standby losses during the heating season (and
in Québec I take it that's seven months of year, if not more) simply
offset a portion of your normal space heating requirements -- so your
net cost during these winter months is effectively zero.
With respect to potential issues with legionella bacteria, see:
http://www.hydroquebec.com/advice_hot_water/index.html
Best regards,
Paul
On Sat, 12 Jan 2008 11:38:58 -0800 (PST), boustephane@hotmail.com
wrote:
>Hi Paul,
>
>Thank you for your answer. I live in Quebec (near Montreal) and the
>rate for electricity is the same all the day. I have a 200 amps
>service so I think I have to call an electrician before any move.
>
>Stephane B.
| |
| Anthony Matonak 2008-01-12, 8:25 pm |
| BobG wrote:
> There is a thread here from Nick Sans a year or so ago where we
> calculated the amount of energy used to maintain the hot water in the
> tank. The ONLY advantage of the tankless heater is it doesnt have to
> provide this small maintenance usage.
The second major advantage of a tankless water heater is that you
never run out of hot water. A typical water heater takes half an
hour or more to recover.
Anthony
| |
| Neon John 2008-01-12, 8:25 pm |
| On Sat, 12 Jan 2008 12:14:35 -0800 (PST), boustephane@hotmail.com wrote:
>Hi John,
>
>Thank you for your suggestion but is it not dangerous for bacteria
>development to keep water at 70-80 F ?
I sure hope not, or I'm screwed :-) My well pump's tank is located in conditioned
spaces so the water there reaches room temperature. The water in my motorhome is at
whatever the outside temperature is. With a translucent tank, the combination of
heat and reflected sunlight occasionally makes green slime grow. It's not harmful
but it tastes and looks bad. I now know to address the problem with the addition of
enough bleach to bring the chlorination up to city water standards.
If your water is potable coming into the house (chlorinated or in the case of a well,
tested to be free of pathogens) then it'll be fine sitting in a tank.
John
[color=darkred]
>
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Alcohol, Tobacco & Firearms should be a convenience store, not a government agency.
| |
| Neon John 2008-01-12, 8:25 pm |
| On Sat, 12 Jan 2008 14:14:39 -0800 (PST), BobG <bobgardner@aol.com> wrote:
>There is a thread here from Nick Sans a year or so ago where we
>calculated the amount of energy used to maintain the hot water in the
>tank. The ONLY advantage of the tankless heater is it doesnt have to
>provide this small maintenance usage.
Lots more advantages than that. The main one being that one never runs out of hot
water. When I was married, wifey and I could take hour-long hot soakers back to back
and not run out. I can connect my pressure washer to the hot water faucet and have
almost a steam cleaner. I can wash my cars with warm water even in the winter. I
can thaw ice from my walk with hot water. All kinds of opportunities arise when one
has an unlimited supply of hot water.
>Both types heat the cold water
>up to the selected final temp. You could measure the maintain-the-heat
>usage with your water heater now. Put a lamp on the element so you can
>tell its on. Heat the tank up. Dont use any hot water for 12 hours.
>Note amount of time element is on. Its miniscule. Minutes every couple
>hours. Pennies. The cost is heating the water in the first place, and
>both tank and tankless heaters are identical in this regard.
I've measured the actual energy used by inserting a watt-hour meter in the circuit. I
don't recall the numbers at the moment but it was enough to take note. Especially
when most/all hot water is used during just one daypart.
I wouldn't go out and buy a kilobuck on-demand heater just to save the standby energy
loss but saving that standby loss is a collateral benefit. Especially if the heater
is in conditioned spaces in the summer.
BTW, there's a lots easier way of measuring on-time than with a lightbulb. Just
connect a line-operated analog clock between one heater terminal and neutral. Set
the clock to 12:00. The clock runs when the element is energized. The hours and
minutes racked up is the run time. Divide that by the elapsed time to get duty
cycle.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
I didn't claw my way to the top of the food chain to eat vegetables!
| |
| Paul M. Eldridge 2008-01-12, 9:25 pm |
| Hi John,
An article published in the Le Journal canadien des maladies
infectieuses et de la microbiologie médicale not long ago found that
40 per cent of the electric hot water tanks tested in Québec were
contaminated with high counts of legionella bacteria. As you can
imagine, anyone with a compromised immune system would be subject to
significant risk if they were to inhale this bacteria while showering
(although men over 50 who are heavy smokers and drinkers are said to
be at greatest risk, those with chronic obstructive pulmonary disease,
cancer and diabetes should also exercise due caution).
In addition, standard chlorination treatments are generally
ineffective because this bacteria is shielded by a protective biofilm
cover (slime-forming microorganisms) and since chlorine/bleach doesn't
break down this biofilm, a legionella colony can quickly re-establish
itself. [Chlorine dioxide is a far more effective option.]
Cheers,
Paul
On Sat, 12 Jan 2008 20:27:13 -0500, Neon John <no@never.com> wrote:
>On Sat, 12 Jan 2008 12:14:35 -0800 (PST), boustephane@hotmail.com wrote:
>I sure hope not, or I'm screwed :-) My well pump's tank is located in conditioned
>spaces so the water there reaches room temperature. The water in my motorhome is at
>whatever the outside temperature is. With a translucent tank, the combination of
>heat and reflected sunlight occasionally makes green slime grow. It's not harmful
>but it tastes and looks bad. I now know to address the problem with the addition of
>enough bleach to bring the chlorination up to city water standards.
>
>If your water is potable coming into the house (chlorinated or in the case of a well,
>tested to be free of pathogens) then it'll be fine sitting in a tank.
>
>John
| |
| Neon John 2008-01-13, 3:25 am |
| I treat that report like I do all the other "the sky might be falling" scare du jour.
I pop my head up out of my hole and asks myself, "Self, are there people dropping
dead right and left from legionella?" If the answer is no then I tuck that tidbit
away in the part of my memory space that holds other useless trivia and otherwise
forget about it.
This is the same category with "a flushing toilet spews a mist of bacteria 20 feet
into the air" and "high school student cultures more bacteria from kitchen counter
than toilet seat". And of course, my all-time favorite "that fart you smell just
came from inside someone's butt" :-)
If you ever happen to be around when they crack open a big water main, marvel at the
flora and many times fauna growing inside.
On Sat, 12 Jan 2008 22:45:42 -0400, Paul M. Eldridge <paul.eldridge@ns.sympatico.ca>
wrote:
[color=darkred]
>Hi John,
>
>An article published in the Le Journal canadien des maladies
>infectieuses et de la microbiologie médicale not long ago found that
>40 per cent of the electric hot water tanks tested in Québec were
>contaminated with high counts of legionella bacteria. As you can
>imagine, anyone with a compromised immune system would be subject to
>significant risk if they were to inhale this bacteria while showering
>(although men over 50 who are heavy smokers and drinkers are said to
>be at greatest risk, those with chronic obstructive pulmonary disease,
>cancer and diabetes should also exercise due caution).
>
>In addition, standard chlorination treatments are generally
>ineffective because this bacteria is shielded by a protective biofilm
>cover (slime-forming microorganisms) and since chlorine/bleach doesn't
>break down this biofilm, a legionella colony can quickly re-establish
>itself. [Chlorine dioxide is a far more effective option.]
>
>Cheers,
>Paul
>
>On Sat, 12 Jan 2008 20:27:13 -0500, Neon John <no@never.com> wrote:
>
>
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
WARNING: Do not use this hair dryer in the shower!
| |
| Paul M. Eldridge 2008-01-13, 3:25 am |
| Hi John,
If you're in relatively good health, the chances of contacting serious
illness is quite low. But not everyone is blessed with good health,
e.g., those battling opportunistic infections related to AIDS/HIV,
individuals taking anti-rejection drugs, cancer patients undergoing
chemotherapy/radiation, the elderly and infirm -- those are the ones
who need to judge their own risk and tolerance for the same.
And even good health offers no guarantees. An outbreak of
Legionnaires' disease at a Toronto nursing home in October 2005 left
23 patients dead and another 112 individuals ill, 79 of which had to
be hospitalized for treatment -- that number included 39 staff
members, 21 visitors and 5 individuals from a neighbouring complex.
I'm guessing those fortunate enough to survive this ordeal wouldn't
dismiss their own experience so lightly.
Cheers,
Paul
On Sat, 12 Jan 2008 22:49:20 -0500, Neon John <no@never.com> wrote:
>I treat that report like I do all the other "the sky might be falling" scare du jour.
>I pop my head up out of my hole and asks myself, "Self, are there people dropping
>dead right and left from legionella?" If the answer is no then I tuck that tidbit
>away in the part of my memory space that holds other useless trivia and otherwise
>forget about it.
>
>This is the same category with "a flushing toilet spews a mist of bacteria 20 feet
>into the air" and "high school student cultures more bacteria from kitchen counter
>than toilet seat". And of course, my all-time favorite "that fart you smell just
>came from inside someone's butt" :-)
>
>If you ever happen to be around when they crack open a big water main, marvel at the
>flora and many times fauna growing inside.
| |
| Vaughn Simon 2008-01-13, 9:25 am |
|
"Paul M. Eldridge" <paul.eldridge@ns.sympatico.ca> wrote in message
news:7u2jo31osmj28temin5gomen6vlio0o95c@4ax.com...
> An outbreak of
> Legionnaires' disease at a Toronto nursing home in October 2005 left
> 23 patients dead and another 112 individuals ill, 79 of which had to
> be hospitalized for treatment -- that number included 39 staff
> members, 21 visitors and 5 individuals from a neighbouring complex.
> I'm guessing those fortunate enough to survive this ordeal wouldn't
> dismiss their own experience so lightly.
Yes, but did that outbreak have anything to do with a contaminated hot
water heater? After all, our discussion had drifted to the dangers of storing
drinking water, not to the seriousness of Legionnaires' disease.
That said, I have also mused about what I am breathing when I take a
shower, especially with these newer low-flow shower heads which seem to cause an
intense misting effect. For example, (for your showering pleasure) did you know
that there are still miles of aesbestos water mains in use? A bit of aesbestos
in your drinking water is probably no big deal, that same stuff lodged in your
lungs is a whole 'nuther matter.
Vaughn
| |
| Paul M. Eldridge 2008-01-13, 1:26 pm |
| Hi Vaughn,
There's been some thread drift, for sure, but the main point is that
legionella bacteria is a serious concern to those with compromised
immune systems and inhalation while showering is one of the main
vectors for transmission.
As stated in the Hydro-Québec link provided earlier, roughly one
hundred Québecers are hospitalized each year for pneumonia caused by
contaminated electric water heaters and I wouldn't be surprised if the
number of unreported cases is considerably higher.
Cheers,
Paul
On Sun, 13 Jan 2008 14:22:07 GMT, "Vaughn Simon"
<vaughnsimonHATESSPAM@att.FAKE.net> wrote:
>
>"Paul M. Eldridge" <paul.eldridge@ns.sympatico.ca> wrote in message
>news:7u2jo31osmj28temin5gomen6vlio0o95c@4ax.com...
>
> Yes, but did that outbreak have anything to do with a contaminated hot
>water heater? After all, our discussion had drifted to the dangers of storing
>drinking water, not to the seriousness of Legionnaires' disease.
>
> That said, I have also mused about what I am breathing when I take a
>shower, especially with these newer low-flow shower heads which seem to cause an
>intense misting effect. For example, (for your showering pleasure) did you know
>that there are still miles of aesbestos water mains in use? A bit of aesbestos
>in your drinking water is probably no big deal, that same stuff lodged in your
>lungs is a whole 'nuther matter.
>
>Vaughn
| |
| Richard P. 2008-01-15, 3:25 am |
| That's just air flowing over poo..
"Neon John" <no@never.com> wrote
> And of course, my all-time favorite "that fart you smell just
> came from inside someone's butt" :-)
| |
| Mike Payne 2008-01-16, 5:25 pm |
| I have a 75 gallon traditional gas water heater. I don't believe you could
run it out of hot water if you tried. It seems to regenerate faster than I
can ever use it.
A con to the tankless water heater is it can only heat water so fast. Pull
the water faster than that and it gets colder.
mike
"Anthony Matonak" <anthonym40@nothing.like.socal.rr.com> wrote in message
news:47894f82$0$30708$4c368faf@roadrunner.com...
> BobG wrote:
>
> The second major advantage of a tankless water heater is that you
> never run out of hot water. A typical water heater takes half an
> hour or more to recover.
>
> Anthony
| |
| Neon John 2008-01-16, 5:25 pm |
| On Wed, 16 Jan 2008 14:51:15 -0500, "Mike Payne" <payne@gru.net> wrote:
>I have a 75 gallon traditional gas water heater. I don't believe you could
>run it out of hot water if you tried. It seems to regenerate faster than I
>can ever use it.
You weren't married to my ex :-)
If I didn't have a tankless heater I'd have a gas-fired tank heater. They do, as a
general rule, recover much faster than electrics. The disadvantage, at least for the
regular big-box store units without electromechanical baffles is that the standby
losses are significantly larger than electric. The reason is the flue that runs
through the center of the tank. When the burner is off, that flue generates a draft
that carries away a significant amount of heat. Fancier ones have electronic
controls and a damper that shuts down the draft when the burner is off but they're
more expensive.
>
>A con to the tankless water heater is it can only heat water so fast. Pull
>the water faster than that and it gets colder.
That may be true of some heaters but it isn't of the Paloma. It contains a rather
fancy hydromechanical control valve that proportionally meters gas according to the
water flow AND limits flow to what it can heat. With a large enough burner, that
flow is more than you'd normally use.
I used my -2400 Paloma in my restaurant for a decade. We hand-washed dishes and had
a huge 3 compartment sink that held 60 gallons in each compartment. The wash and
sanitize water got changed very often. I'd have needed one of the largest tank
heaters available ($$$$) to keep up with that load. That Paloma just kept on
truckin'.
The only problem I ever had with the Paloma was concerning the rubber diaphragm in
the control valve. Cleveland put so much chlorine in the water that it ate the
diaphragm out every few years. Paloma supposedly has a teflon one for such
conditions but I never got one. Not a problem now on well water :-)
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Ever stop to think, and forget to start again?
| |
| nicksanspam@ece.villanova.edu 2008-01-17, 3:25 am |
| Paul M. Eldridge <paul.eldridge@ns.sympatico.ca> wrote:
>... In the case of a new, well-insulated hot water tank, these
>losses typically fall in the range of 1.5 kWh/day
That number seems low to me, because I seem to recall that a really well-
insulated tank might have an energy factor (useful hot water output energy
divided by total input energy) of 0.97, which would make the hot water
consumption 1.5/0.03 = 50 kWh/day. IIRC, 50K Btu/day is more typical
for water heating.
And some of the tankless heaters do have small standby losses. They still
keep a small part of themselves warm.
Nick
| |
| nicksanspam@ece.villanova.edu 2008-01-17, 9:25 am |
| Neon John <no@never.com> wrote:
>If you must use electric, here's something you might do. Put a "tempering
>tank" in front of the on-demand heater. This tank would be an ordinary
>electric water heater with the thermostat set to around room temperature...
On one of his TV shows, Charlie Wing made a tempering tank with an 8"x20'
PVC pipe tucked up between basement ceiling rafters.
Nick
| |
| Solar Flare 2008-01-17, 9:25 am |
| "tankless" is a lie. There is always a tank. May be small, but it is a
tank.
<nicksanspam@ece.villanova.edu> wrote in message
news:fmmro3$c7o@acadia.ece.villanova.edu...
> Paul M. Eldridge <paul.eldridge@ns.sympatico.ca> wrote:
>
>
> That number seems low to me, because I seem to recall that a really
> well-
> insulated tank might have an energy factor (useful hot water output
> energy
> divided by total input energy) of 0.97, which would make the hot
> water
> consumption 1.5/0.03 = 50 kWh/day. IIRC, 50K Btu/day is more typical
> for water heating.
>
> And some of the tankless heaters do have small standby losses. They
> still
> keep a small part of themselves warm.
>
> Nick
>
| |
| Paul M. Eldridge 2008-01-17, 1:26 pm |
| Hi Nick,
From what I understand, the energy factor or "EF" of a new, energy
efficient electric water heater falls in the range of 0.92 to 0.95
depending upon, in part, the size of the tank (larger capacity tanks,
as you would expect, have proportionately greater conductive losses).
The current minimum standard for a 50 U.S. gallon model is an EF of
0.90.
This EF value is calculated in accordance to the US DOE's "Uniform
Test Method for Measuring the Energy Consumption of Water Heaters"
testing procedures and is based on a specific pattern of hot water
usage over a 24-hour period (i.e., a total of 64.3 gallons of hot
water/day, an inlet temperature of 58F, a nominal outlet temperature
of 135F, and an ambient air temperature of 67.5). This is said to be
representative of the hot water consumption of a "typical" U.S.
household, although some might argue it could be a little on the high
side given the growing penetration of more efficient clothes washers
and dishwashers; the widespread adoption of reduced-flow shower heads
and other water saving devices; behaviour changes in response to
higher energy prices; etc.
In any event, based on these standardized tests, a 50 gallon electric
hot water tank that meets the minimum standard consumes 4,879
kWh/year. A similar size tank with an EF of 0.93 would use 4,721
kWh/year and, at the upper end, one with an EF of 0.95 would be rated
at 4,622 kWh/year. If my math is correct, that puts the standby
losses for each of these tanks at 488, 330 and 231 kWh/year
respectively. By comparison, my estimated 1.5 kWh/day (548 kWh/year)
seems overly generous.
This is a minor point but, strictly speaking, a hot water tank's EF
rating is based on several performance factors, the appliance's
standby heat loss coefficient or "UA" being just one of them [albeit,
a major one at that]. And although I can offer no evidence to support
this, I have the general impression that many folks keep their hot
water tanks at a lower temperature so to reduce the risk of scalding
and lower their operating costs -- if that's the case, the "real
world" numbers could be even slightly better.
Cheers,
Paul
On 17 Jan 2008 01:14:27 -0500, nicksanspam@ece.villanova.edu wrote:
>Paul M. Eldridge <paul.eldridge@ns.sympatico.ca> wrote:
>
>
>That number seems low to me, because I seem to recall that a really well-
>insulated tank might have an energy factor (useful hot water output energy
>divided by total input energy) of 0.97, which would make the hot water
>consumption 1.5/0.03 = 50 kWh/day. IIRC, 50K Btu/day is more typical
>for water heating.
>
>And some of the tankless heaters do have small standby losses. They still
>keep a small part of themselves warm.
>
>Nick
| |
| nicksanspam@ece.villanova.edu 2008-01-17, 5:25 pm |
| Paul M. Eldridge <paul.eldridge@ns.sympatico.ca> wrote:
>From what I understand, the energy factor or "EF" of a new, energy
>efficient electric water heater falls in the range of 0.92 to 0.95...
Whirlpool's 12-year 50 gallon 0.95 EF "energy-smart" electric tank heater
adapts the water temp to the usage, as low as 115 F. A blanket could still
raise the EF.
>This EF value is calculated in accordance to the US DOE's "Uniform
>Test Method for Measuring the Energy Consumption of Water Heaters"
>testing procedures and is based on a specific pattern of hot water
>usage over a 24-hour period (i.e., a total of 64.3 gallons of hot
>water/day, an inlet temperature of 58F, a nominal outlet temperature
>of 135F, and an ambient air temperature of 67.5). This is said to be
>representative of the hot water consumption of a "typical" U.S. household,
>although some might argue it could be a little on the high side...
.... 135 seems high. At 115, the loss might be (115-58)/(135-58) = 74% of
the 135 loss, with an EF = 1-(1-0.95)0.74 = 0.963.
>In any event, based on these standardized tests, a 50 gallon electric
>hot water tank that meets the minimum standard consumes 4,879
>kWh/year. A similar size tank with an EF of 0.93 would use 4,721
>kWh/year and, at the upper end, one with an EF of 0.95 would be rated
>at 4,622 kWh/year. If my math is correct, that puts the standby
>losses for each of these tanks at 488, 330 and 231 kWh/year
>respectively. By comparison, my estimated 1.5 kWh/day (548 kWh/year)
>seems overly generous.
Agreed, esp with an EF = 0.963 and a 64.3x8.33(135-58)(1-0.963)/3412
= 0.45 kWh/day standby loss.
>This is a minor point but, strictly speaking, a hot water tank's EF
>rating is based on several performance factors, the appliance's
>standby heat loss coefficient or "UA" being just one of them...
IIRC, it's the only one, for electric tanks, using that standard.
Nick
| |
| Paul M. Eldridge 2008-01-17, 8:25 pm |
| Hi Nick,
On 17 Jan 2008 15:12:49 -0500, nicksanspam@ece.villanova.edu wrote:
>Paul M. Eldridge <paul.eldridge@ns.sympatico.ca> wrote:
>
>
>Whirlpool's 12-year 50 gallon 0.95 EF "energy-smart" electric tank heater
>adapts the water temp to the usage, as low as 115 F. A blanket could still
>raise the EF.
Whilst it's certainly possible to further reduce standby losses by way
of additional insulation and/or other external modifications, I was
limiting our scope to commercially available products that can be
purchased "off the shelf". Also, it bears mentioning that improper
installation of thermal blankets may result in excessive heat build up
that can cause internal components such as thermostats to fail
prematurely -- in fact, some water heaters come with warning labels
that explicitly state the installation of such blankets will void the
manufacturer's warranty.
>
>... 135 seems high. At 115, the loss might be (115-58)/(135-58) = 74% of
>the 135 loss, with an EF = 1-(1-0.95)0.74 = 0.963.
It may seem high to some of us, but that's the temperature specified
by this testing standard. I suspect the standard was developed at a
time when many residential dishwashers were not equipped with internal
boosters. It may also have something to do with health concerns
related to growth of legionella bacteria [and, forgive me, for once
again I don my "scaremonger" chapeau].
For a Canadian perspective on this, see:
http://www.ciph.com/press_releases/...emperatures.pdf
>
>Agreed, esp with an EF = 0.963 and a 64.3x8.33(135-58)(1-0.963)/3412
>= 0.45 kWh/day standby loss.
Here in Canada, where the OP lives, electric water heaters are
certified in accordance to the CSA-C191-00 standard. The current
minimum standard for new water heaters 50 and 270 litres in size, with
bottom inlet supplies, is based on the following formula:
standby losses (in watts) = 35 + (0.20 x volume in litres)
For example, the maximum standby losses of a 175 litre tank would be
70-watts and in the case of a 270 litre storage cylinder, 89-watts
(1.68 and 2.14 kWh/day respectively). Generally speaking, these tanks
would be equipped with either 2.0 or 2.5 inches of foam insulation.
For water heaters with top-inlet supplies, the formula is:
standby losses (in watts) = 40 + (0.20 x volume in litres)
For more information related to these standards, see:
http://canadagazette.gc.ca/partI/20...l/regle1-e.html
Interesting to note that this document claims some 880,000 new water
heaters are sold each year in Canada and the majority of these have
efficiency ratings "close to the minimum requirements of existing
regulations." It seems we Canadians need to be beaten with a bigger
stick when it comes to using energy more efficiently.
>
>IIRC, it's the only one, for electric tanks, using that standard.
Well, as noted above, testing standards here in Canada provide for an
additional 5-watt allowance for water heaters equipped with top-inlet
supplies (0.12 kWh/day) due to higher thermal leakage.
Cheers,
Paul
| |
| Paul M. Eldridge 2008-01-17, 9:25 pm |
| Hi Nick,
I didn't properly address this last point. What I meant to say is
that other factors can potentially impact the energy performance of
electric water heaters, including something as simple as the placement
of the cold water inlet.
Other variables might include the sensitivity of the thermostats --
water heaters with larger dead bands would presumably have lower
standby loses because water temperatures would be allowed to fall
further before the elements cycle back on. Likewise, a tank equipped
with higher wattage elements would have a faster recovery, so outlet
temperatures may not deteriorate as quickly under heavy draws and the
tank would return to its set temperature more quickly (again, higher
maintained temperatures over longer durations equals greater heat
loss). A taller tank would also encourage greater thermal
stratification which could conceivably reduce the losses that occur at
the base and along the lower portion of the side walls. By the same
token, tanks that have been specifically designed to minimize this
stratification so to increase storage capacity, or that do so
indirectly due to other design goals (e.g., tanks that employ curved
dip tubes to swirl the water around upon entry in an effort to
minimize sediment build-up) would presumably have higher standby
losses as well.
I guess my main point is that a tank's conductive losses can be
indirectly influenced by a number of factors, such as the ones I've
described above.
Cheers,
Paul
>
>Well, as noted above, testing standards here in Canada provide for an
>additional 5-watt allowance for water heaters equipped with top-inlet
>supplies (0.12 kWh/day) due to higher thermal leakage.
>
| |
| ateliving 2008-03-17, 9:25 pm |
| Hi everyone,
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Website: http://www.ateliving.com
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