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<p><font face="Verdana">I had tho<font face="Verdana">u<font
face="Verdana">ght of this a long time ago for an island
project, but the cost of plumbing cold <font face="Verdana">inlet
water p<font face="Verdana">ast the heat exchanger was too
high. I think th<font face="Verdana">is can work at time
of construction o<font face="Verdana">r easy
renovation. <font face="Verdana">We <font
face="Verdana">do this for large thermal dump
loads for fabric mills for example.</font></font></font></font></font></font></font></font></font><br>
</p>
<br>
<div class="moz-cite-prefix">On 3/19/2018 10:09 AM, Daniel Young
wrote:<br>
</div>
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<p class="MsoNormal">Drake,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Have you or the client looked into the
drainwater heat recovery units? They make both a vertical and
horizontal mounted version. They just help recover the waste
heat from shower water going down the drain.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">My understanding is that economically they
are barely past the breakeven point when considering
offsetting grid power. If using PV costs as the benchmark, the
economics would be better. If somehow this is off grid, then
I\u2019d say it\u2019s a home run. (Hopefully though this is not an
all-electric off-grid building.)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The main benefit, as far as I understand
it, is that you can get by with a smaller unit, with a smaller
heating element to perform the same task, OR you can get much
longer showers from the same sized unit. Depending on the
clients goals, this might be a useful tool to bring into the
situation.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Here are two brand names that I know of.<o:p></o:p></p>
<p class="MsoNormal">Vertical mount: renewability<o:p></o:p></p>
<p class="MsoNormal">Horizontal mount: ecodrain<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have not used these products, so I cannot
endorse any of them, just though it may be worth
consideration.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">With Regards,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Daniel Young, <o:p></o:p></p>
<p class="MsoNormal">NABCEP Certified PV Installation
Professional<sup>TM</sup>: Cert #031508-90<o:p></o:p></p>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>From:</b> RE-wrenches
<a class="moz-txt-link-rfc2396E" href="mailto:re-wrenches-bounces@lists.re-wrenches.org"><re-wrenches-bounces@lists.re-wrenches.org></a> <b>On
Behalf Of </b>Drake<br>
<b>Sent:</b> Thursday, March 15, 2018 1:00 PM<br>
<b>To:</b> RE-wrenches
<a class="moz-txt-link-rfc2396E" href="mailto:re-wrenches@lists.re-wrenches.org"><re-wrenches@lists.re-wrenches.org></a><br>
<b>Subject:</b> Re: [RE-wrenches] Electric Water kWh/
person<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">This discussion has been a great help. The
house is built and the plumbing is in, but could be modified.
Wood stoves are not a likely solution. I think we need a
different water heating strategy.<br>
<br>
Thank you all!<br>
<br>
Drake <br>
<br>
<br>
<br>
At 09:21 AM 3/15/2018, you wrote:<br>
<br>
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">Content-Type: multipart/alternative;<br>
boundary="------------EE4E9806B711DEF636076840"<br>
Content-Language: en-US<br>
<br>
<span style="font-family:"Verdana",sans-serif">This
is what I came up with:<br>
</span><br>
<span style="font-family:"Verdana",sans-serif">The
calculation is Q = mcp delta T<br>
</span><br>
<span style="font-family:"Verdana",sans-serif">Water
Temp out = 120<br>
</span><br>
<span style="font-family:"Verdana",sans-serif">Water
Temp in = ground source Temperature @ 50F?<br>
</span><br>
<span style="font-family:"Verdana",sans-serif">delta
T = 70F<br>
</span><br>
<span style="font-family:"Verdana",sans-serif">m
= mass flow rate. ASHRAE is the source for this.
20gals per person per day = 20 gallons x 8.34 lbs/gallon
= 167lbs/day/person<br>
</span><br>
<span style="font-family:"Verdana",sans-serif">cp
= 1 BTU/lb-degree F<br>
</span><br>
<span style="font-family:"Verdana",sans-serif">Q =
167 x 1 x 70 = 11,676 BTU/day/person<br>
</span><br>
<span style="font-family:"Verdana",sans-serif">Divide
this by the efficiency of the water heating system (I'll
assume = .86) =11,676/.86 = 13, 577 BTU/person/day<br>
</span><br>
<span style="font-family:"Verdana",sans-serif">convert
to kWh if necessarym 13,577/3412 = ~4 kWh/person/day, 120
kWh/month<br>
</span><br>
<span style="font-family:"Verdana",sans-serif">I
checked this against one month and it seems reasonable. <br>
</span><br>
<span style="font-family:"Verdana",sans-serif">Website
assuming ~3.5 family size comes up with @ 400kWh per
month. They approached it another way with assuming run
times.<br>
</span><br>
<span style="font-family:"Verdana",sans-serif"><a
href="https://www.google.com/search?safe=active&source=hp&ei=Z3KqWvXiNsGb5wKJ2Kf4DA&q=electric+water+heater+use+annual+consumption&oq=electric+water+heater+use+annually&gs_l=psy-ab.1.2.33i22i29i30k1l3.279.9222.0.12475.35.19.0.7.7.0.451.2360.0j6j4j0j1.11.0....0...1c.1.64.psy-ab..18.16.1952.0..0j0i67k1j0i131k1j0i22i30k1.0.CiU8wYZigpI"
moz-do-not-send="true">https://www.google.com/search?safe=active&source=hp&ei=Z3KqWvXiNsGb5wKJ2Kf4DA&q=electric+water+heater+use+annual+consumption&oq=electric+water+heater+use+annually&gs_l=psy-ab.1.2.33i22i29i30k1l3.279.9222.0.12475.35.19.0.7.7.0.451.2360.0j6j4j0j1.11.0....0...1c.1.64.psy-ab..18.16.1952.0..0j0i67k1j0i131k1j0i22i30k1.0.CiU8wYZigpI</a>
<br>
</span><br>
<span style="font-family:"Verdana",sans-serif"><br>
Chris<br>
</span><br>
<span style="font-family:"Verdana",sans-serif"><br>
</span><br>
<br>
On 3/15/2018 8:09 AM, Mike Kocsmiersky wrote:<br>
<br>
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal" style="margin-bottom:12.0pt">Barton
makes a good point with regards to the incoming ground
water temperature and the amount of heat required to bring
it up to shower temp. Â My recollection is that ASHRAE
states 20gal/person/day for the first 2 people, then 15gpd
or 12gpd thereafter. However those rates vary wildly
with consumers, from those that never bathe to the high
schooler that needs 3 showers a day. In the northeast
water heating can be up to 19% of the total household
energy load for the year. Also, I would recommend the
air source heat pump water heaters if you have significant
humidity or an on demand unit. Water tanks are typically
under insulated and can lose 2kWh/day in standby losses.<br>
 <br>
Mike Kocsmiersky<br>
Principal<br>
Spirit Solar Inc.<br>
(413) 734-1456<br>
 <br>
 <br>
 <br>
<b>From:</b> Barton Churchill [<a
href="mailto:barton@solarips.com" moz-do-not-send="true">mailto:barton@solarips.com</a>]
<br>
<b>Sent:</b> Wednesday, March 14, 2018 7:31 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Electric Water kWh/
person<br>
 <br>
You first need to know your ground temperature. Then
figure a delta to 100 or so degrees. Most but not all
showerheads flow 2.5gpm and showers are typically 10
minutes. You can then find a calculator online to
calculate how many Btus are required to raise water temp
for your delta per gallon. Convert to kWh, add some
contingency and you should be good. <br>
<br>
On Wednesday, March 14, 2018, <<a
href="mailto:drake.chamberlin@redwoodalliance.org"
moz-do-not-send="true">
drake.chamberlin@redwoodalliance.org</a>> wrote:<br>
Hello Wrenches,<br>
<br>
Is there a good way to estimate the power that will be
consumed for electric water per person per day? We are
estimating the amount of power that will be used by an all
electric duplex, and the water heater amount seems high.
The current model we have claims 3493 kWh/ year per 26
gallon tank will be consumed. With the two units, that
would add up to 6986 kWh / year for hot water, pushing the
system size to humongous for a 1300 ft sq building. <br>
<br>
Does that seem high? There will be a maximum of 2 people
per unit. <br>
<br>
The owner is considering going to 115 V units with a 15
gallon tanks. I think the smaller tank would help, but it
would seem that the amount of hot water consumed would be
the main issue. <br>
<br>
How can we get a good estimate for a per person energy
usage for electric hot water? Any other suggestions are
welcome.<br>
<br>
Thank you,<br>
<br>
Drake<br>
<br>
<br>
<br>
-- <br>
--Â <br>
Barton Churchill<br>
406.587.5295 Â <br>
2430 North 7th Bozeman, MT 59715<br>
<a href="http://www.solarips.com/" moz-do-not-send="true">www.solarips.com</a><br>
<img style="width:1.0416in;height:1.0416in"
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<span style="font-size:10.0pt">Â Â Â Â Â Â Â Â Christopher
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