Alternative Power sources - Re: has anybody compiled a list of rapid return energy saving measures?

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Re: has anybody compiled a list of rapid return energy saving measures?

chrisvillar@hotmail.com

2005-08-17, 2:21 am

Info@_RemoveBetweenSpaces_RedyTemp.com wrote:
> Hot Water Savings
>
> The key to hot water savings... eliminate the waiting.
>
> Every second a person spends waiting for hot water at their faucet /
> shower, your water heater is taking in "cold" city water. In addition
> to the lighting energy used while the person stands there waiting. A
> family of four waiting 1 minute for hot water spends around 97.3 hours
> every year "waiting". (Four people waiting 4 times per day, 365 days
> in a year, divided by 60 for total hrs) Include a lifestyle fudge
> factor and reduce it to 72 hours of "very cold" city water filling up
> your water heater needlessly. Let's pause for a moment and imagine
> having to stand and watch a faucet waste water down the drain for 72
> hrs. . . . Or consider a home which waits only 30 seconds.... that's
> still 36 hours of watching water run down the drain.
>

The only time I wait for hot water is in the morning before I shave.
And I'm not really waiting, the water is running while I'm taking a
leak. And maybe I've wasted 4 gallons? At $0.005 per gallon, that's
$7.30 per year in wasted water. What's my return on investment now?
After the shave, the hot water is 4' away from the shower head. By the
time I turn on the shower and walk around the curtain (2 seconds) to
get in, it is already up to temp. So that is zero wait time for me and
maybe 4 gallons of wasted water.

When I give my infant daughter a bath, I turn the water all the way to
hot and rinse the tub with the cold water from the pipe. I'm done
rinsing before the hot water get there but I close the stopper anyway.
When the hot water finally gets to the tap, I let it run all the way
hot for a few seconds to get the tub temp right and then turn the temp
down and continue to fill. Then I put my daughter in. So no wasted
water at all and no wasted time for my daugther's bath.

Let's say I have two school aged kids. Most likely, they are taking
showers back to back so the second child starts the water with the
pipes already "hot". Same situation if two adults are getting ready
for a work day in a separate bathroom. So suddenly a family of 4 with
4 waits per person per day for a total of 16 "waits" is reduced to 2
"waits".

Actually I love the idea of a tankless water heater but for three very
different reasons. There is basically zero savings from reduced water
useage. It is calculable but negligible as I've described above. The
three great things will be 1) the reduced energy bill because I'm not
continually keeping 40 gallons of water hot (and stupidly using that 40
gallons to heat my Texas house or garage), 2) the reduced space
requirements, and 3) the luxury of instant hot water if it can be
installed close to the tap as a result of #2. What I'd like to do when
I build my house is install the tankless water heater in a closet right
next to the master bath. The kids and guests will have to rough it
like we used to do in the old days and wait a minute for hot water.
I'm the one paying the bills after all

Nick Hull

2005-08-17, 9:21 am

In article <1124269559.704612.135140@z14g2000cwz.googlegroups.com>,
trader4@optonline.net wrote:

> "There is basically zero savings from reduced water
> useage. It is calculable but negligible as I've described above. "
>
> The issue isn't the cost of the water that's wasted, but rather the
> cost of heating the hot water that has to run from the water heater to
> the faucet every time you first need hot water. It takes quite a few
> gallons of water to flush out the cold water in the pipes and get the
> pipes warm. The longer the pipe run, the more energy that is wasted.
> A tankless unit saves that energy loss and it can be considerable.
>

If it takes 'quite a few gallons' to flush out the cold water then you
are using pipes too big, and probably metal pipes as well. If you use
1/2" plastic pipe there is little cold water to flush out and little
thermal mass to heat.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/

Derek Broughton

2005-08-17, 10:21 am

Nick Hull wrote:

> In article <1124269559.704612.135140@z14g2000cwz.googlegroups.com>,
> trader4@optonline.net wrote:
>
>
> If it takes 'quite a few gallons' to flush out the cold water then you
> are using pipes too big, and probably metal pipes as well. If you use
> 1/2" plastic pipe there is little cold water to flush out and little
> thermal mass to heat.

That's exactly what I was thinking as I waited for two gallons of cold water
to flush through my pipes this morning. They're plastic, but embedded in
concrete (and I don't think they're insulated) and 3/4" - obviously, 1/2"
pipe would have wasted less than half the hot water.
--
derek

Dave Hinz

2005-08-17, 11:21 am

On Wed, 17 Aug 2005 11:23:34 GMT, Nick Hull <nhull@access4less.net> wrote:

> If it takes 'quite a few gallons' to flush out the cold water then you
> are using pipes too big, and probably metal pipes as well. If you use
> 1/2" plastic pipe there is little cold water to flush out and little
> thermal mass to heat.

1/2" plastic isn't code around here for source lines unless that changed
very recently, and 1/2" pipe for any length gives you crap for flow
rate. I'll stay with my 3/4" copper, thank you.

nicksanspam@ece.villanova.edu

2005-08-17, 1:21 pm

Dave Hinz <DaveHinz@spamcop.net> wrote:

>1/2" plastic isn't code around here for source lines...

CPVC may be, for hot water.

>and 1/2" pipe for any length gives you crap for flow rate...

The Hazen-XXXXXXXX equation says L' of d" smooth pipe with a G gpm flow has
a P = 0.0004227LG^1.852d^-4.871 psi pressure loss. L = 50' and P = 40 psi
makes G = 9.5 gpm for d = 1/2" pipe.

Nick

Derek Broughton

2005-08-17, 3:21 pm

nicksanspam@ece.villanova.edu wrote:

> Dave Hinz <DaveHinz@spamcop.net> wrote:
>
>
> CPVC may be, for hot water.
>
>
> The Hazen-XXXXXXXX equation says L' of d" smooth pipe with a G gpm flow
> has a P = 0.0004227LG^1.852d^-4.871 psi pressure loss. L = 50' and P = 40
> psi makes G = 9.5 gpm for d = 1/2" pipe.

What's that in English? I _think_ it means I have to have over 40psi in my
pipes to begin. Most well systems run about 40psi.
--
derek

Dave Hinz

2005-08-17, 3:21 pm

On 17 Aug 2005 12:11:59 -0400, nicksanspam@ece.villanova.edu <nicksanspam@ece.villanova.edu> wrote:
> Dave Hinz <DaveHinz@spamcop.net> wrote:
>
>
> CPVC may be, for hot water.

Maybe. But, I really, really don't like off-tastes in my water. I even
have copper for my well piping rather than the (cheaper) plastic option.

>
> The Hazen-XXXXXXXX equation says L' of d" smooth pipe with a G gpm flow has
> a P = 0.0004227LG^1.852d^-4.871 psi pressure loss. L = 50' and P = 40 psi
> makes G = 9.5 gpm for d = 1/2" pipe.

OK, and the "personal observeations" equations show that I'm happy with
my flow with 3/4" pipes until they go into the walls, the water is hot
in a few seconds, and that in houses with bad flow, it's invariably 1/2"
pipe. Since there's only one gallon of volume in 45' of 3/4" pipe, what
problem am I really solving by choking off my flow?

> Nick
>

nicksanspam@ece.villanova.edu

2005-08-17, 4:21 pm

Derek Broughton <news@pointerstop.ca> wrote:

>
>What's that in English?

If your well pressure is 40 psi and you have 50' of 1/2" pipe, the flow
will be 9.5 gpm, enough for about 8 simultaneous 1.25 gpm showers.

Nick

nicksanspam@ece.villanova.edu

2005-08-17, 4:21 pm

Dave Hinz <DaveHinz@spamcop.net> wrote:

>Since there's only one gallon of volume in 45' of 3/4" pipe, what
>problem am I really solving by choking off my flow?

"Choking your flow" to 9.5 gpm can save a little non-recurring cost
and recurring time and water and energy.

Nick

Dave Hinz

2005-08-17, 4:21 pm

On 17 Aug 2005 14:48:50 -0400, nicksanspam@ece.villanova.edu <nicksanspam@ece.villanova.edu> wrote:
> Dave Hinz <DaveHinz@spamcop.net> wrote:
>
>
> "Choking your flow" to 9.5 gpm can save a little non-recurring cost
> and recurring time and water and energy.

Let's try this again. From my water heater to my primary point of hot
water usage, there is 14 feet of pipe. This is not coincidence; I put
the water heater directly under the shower and the washing machine for
that reason. Now, if it takes 45 feet of 3/4" pipe to make one gallon
of volume (someone else's number posted here, which I haven't checked
myself), that means I have just about 1/3 of a gallon of water in those
pipes. Even to the other end of the house, 35' away, there's only a
gallon of water in the pipe between the heater and the faucet. I could
calculate the thermal mass of the copper pipe, I suppose, but I don't
see it making a lot of difference in practical terms.

Yes, you get _decent_ flow with 1/2" pipe. I get _better_ flow with my
3/4" pipe, and given that I never use straight hot water, running a
gallon of cooler water through the hot pipes isn't a loss anyway.
To me, the extra 20 bucks for pipe when I built the house is worth not
having to worry about what else is happening in the house when I want to
take a shower.

daestrom

2005-08-20, 12:21 pm

"Dave Hinz" <DaveHinz@spamcop.net> wrote in message
news:3mhgb1F16p8qrU8@individual.net...
> On 17 Aug 2005 14:48:50 -0400, nicksanspam@ece.villanova.edu
> <nicksanspam@ece.villanova.edu> wrote:
>
> Let's try this again. From my water heater to my primary point of hot
> water usage, there is 14 feet of pipe. This is not coincidence; I put
> the water heater directly under the shower and the washing machine for
> that reason. Now, if it takes 45 feet of 3/4" pipe to make one gallon
> of volume (someone else's number posted here, which I haven't checked
> myself), that means I have just about 1/3 of a gallon of water in those
> pipes. Even to the other end of the house, 35' away, there's only a
> gallon of water in the pipe between the heater and the faucet. I could
> calculate the thermal mass of the copper pipe, I suppose, but I don't
> see it making a lot of difference in practical terms.
>
> Yes, you get _decent_ flow with 1/2" pipe. I get _better_ flow with my
> 3/4" pipe, and given that I never use straight hot water, running a
> gallon of cooler water through the hot pipes isn't a loss anyway.
> To me, the extra 20 bucks for pipe when I built the house is worth not
> having to worry about what else is happening in the house when I want to
> take a shower.
>

You're both assuming that the piping itself is the predominent pressure
drop. In almost all cases, this just isn't so. The straight length of
piping isn't the 'bottleneck'. Keep in mind that an 'average' 90 degree
elbow is about the same flow resistance as a straight length of pipe that is
30 'pipe diameters' long. And a typical globe valve is about the same as
140 'pipe diameters'. So a 14 foot run of 1/2" pipe, with just five
'elbows' and one globe valve under the sink is really equivalent to 14' +
(5*30 + 140)*0.5/12 = 26 feet. If it is 3/4" pipe, then the same number of
elbows and globe valve is equivalent to 14' + (5*30+140)*0.75/12 = 32 feet
of straight pipe.

But in both cases, the majority of the pressure drop is right in the
faucet/spout. If you figure out the pressure drops through the various
portions of a typical lavatory sink run with a flow of about 1.5 gpm and 40
psi source, then replace the piping with a larger 3/4" pipe, the actual flow
change is very little. For a bathroom sink with a flow of 1.5 gpm, an
equivalent 26 ft of 1/2 pipe only has a pressure drop of about 0.7 psi using
nick's formula (Crane TP-410 shows a slightly different number, but pretty
close). The rest of the pressure drop is right in the faucet. Even if you
eliminated the piping completely, the flow would only increase by a factor
of 1.008 (less than 1%).

About the only place 3/4 makes a big difference over 1/2 is if it is feeding
several fixtures that may be used at the same time (e.g. the shower and the
toilet at the same time is a classic), or when the total flow is not
dominated by the faucet (those used to fill a tub comes to mind). So it
does make some sense to run a larger pipe to the general area of the
bathroom and to the fill spout on a large tub, then split off smaller pipe
to individual fixtures.

daestrom

nicksanspam@ece.villanova.edu

2005-08-20, 2:21 pm

daestrom <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:

>...a bathroom sink with a flow of 1.5 gpm...

....might use 0.75 gpm of hot water and 0.75 gpm of cold.

>About the only place 3/4 makes a big difference over 1/2 is if it is feeding
>several fixtures that may be used at the same time (e.g. the shower and the
>toilet at the same time...

And we might close the toilet valve so it takes 5 min vs 30 sec to fill.

Nick

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