wrote:
Daniel,
That sounds like an intriguing technology, much along the lines of an
air
to air heat exchanger. Thanks for the recommendation. These systems
could
keep a lot of CO2 out of the atmosphere if widely used.
Drake
At 10:09 AM 3/19/2018, you wrote:
Content-Type: multipart/alternative;
boundary="----=_NextPart_000_0077_01D3BF6A.5EF88420"
Content-Language: en-us
Drake,
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.
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’d say it’s a home run. (Hopefully though this is not an
all-electric
off-grid building.)
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.
Here are two brand names that I know of.
Vertical mount: renewability
Horizontal mount: ecodrain
I have not used these products, so I cannot endorse any of them, just
though it may be worth consideration.
With Regards,
Daniel Young,
NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90
*From:* RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> *On
Behalf Of *Drake
*Sent:* Thursday, March 15, 2018 1:00 PM
*To:* RE-wrenches <re-wrenches@lists.re-wrenches.org>
*Subject:* Re: [RE-wrenches] Electric Water kWh/ person
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.
Thank you all!
Drake
At 09:21 AM 3/15/2018, you wrote:
Content-Type: multipart/alternative;
boundary="------------EE4E9806B711DEF636076840"
Content-Language: en-US
This is what I came up with:
The calculation is Q = mcp delta T
Water Temp out =Â 120
Water Temp in = ground source Temperature @ 50F?
delta T = 70F
m = mass flow rate. ASHRAE is the source for this. 20gals per
person
per day = 20 gallons x 8.34 lbs/gallon =Â 167lbs/day/person
cp =Â 1 BTU/lb-degree F
Q = 167 x 1 x 70 = 11,676 BTU/day/person
Divide this by the efficiency of the water heating system (I'll assume =
.86)Â =11,676/.86 = 13, 577 BTU/person/day
convert to kWh if necessarym 13,577/3412 = ~4 kWh/person/day, 120
kWh/month
I checked this against one month and it seems reasonable.
Website assuming ~3.5 family size comes up with @ 400kWh per month. They
approached it another way with assuming run times.
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
Chris
On 3/15/2018 8:09 AM, Mike Kocsmiersky wrote:
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.
 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.
Â
Mike Kocsmiersky
Principal
Spirit Solar Inc.
(413) 734-1456
Â
Â
Â
From: Barton Churchill [mailto:bar...@solarips.com
<bar...@solarips.com>]
Sent: Wednesday, March 14, 2018 7:31 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Electric Water kWh/ person
Â
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.Â
On Wednesday, March 14, 2018, < drake.chamber...@redwoodalliance.org>
wrote:
Hello Wrenches,
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.
Does that seem high? There will be a maximum of 2 people per unit.
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.
How can we get a good estimate for a per person energy usage for
electric
hot water? Any other suggestions are welcome.
Thank you,
Drake
--
--Â
Barton Churchill
406.587.5295 <(406)%20587-5295> Â
2430 North 7th Bozeman, MT 59715
www.solarips.com
[image: Image removed by sender.]
Â
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