[RE-wrenches] Electric Water kWh/ person
Ray
ray at solarray.com
Tue Mar 20 17:15:09 EDT 2018
Rianai have 3 major issues when used off grid.
1) The phantom load when I checked was over 30 watts continuous. That's
over 700 w-hr/ day.
2) They need pure sine wave, and even have trouble on Trace SW
inverters. (One system I took over has a separate Exeltech on its own
battery and AC charger to run the Rianai, since they have Trace
inverters. Talk about a waste!)
3) They still have the hard well water scaling issues.
Ray
Remote Solar
On 3/20/18 12:03 PM, Dana wrote:
>
> It used to be that “tankless” water heaters were very sensitive to
> stable temperature production as flows from single handle facets shut
> down the hot and opened the cold flows.
>
> I can fully recommend the Rianai heaters of today as we have 2 in
> offgrid and 0 issues. I have family members that have had them in
> residential homes for several years also and 0 issues.
>
> They do require 120 vac & have digital controls. The water temperature
> is very stable & consistent. I have not measured the phantom load but
> could if someone needs to know.
>
> 2 thumbs up for Rianai heaters from MHO.
>
> ----------------------------------------------------------------------------
>
> Dana Orzel Great Solar Works, Inc.
>
> *C - 208.721.7003 dana at solarwork.com*
>
> Idaho Contractor - # 028765 Idaho PV # 028374
>
> NABCEP # 051112-136 www.solarwork.biz <http://www.solarwork.biz>
>
> _"Responsible Technologies for Responsible People since 1988" ___
>
> *P*Please consider the environment before printing this email.
>
> *From:*RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> *On
> Behalf Of *cwarfel
> *Sent:* Tuesday, March 20, 2018 11:48 AM
> *To:* re-wrenches at lists.re-wrenches.org
> *Subject:* Re: [RE-wrenches] Electric Water kWh/ person
>
> What are the issues with tankless water heaters? I have heard them
> described as having "issues", but I haven't read anything that
> describes what they are. They are very popular where I live. Any
> info? Thanks, Chris
>
> On 3/20/2018 1:07 PM, Dave Angelini Offgrid Solar wrote:
>
> And a big maybe for Offgrid where we like multiple ways to
>
> charge/heat/cool and make hot water. The default method is almost always
>
> the most reliable. For a typical home a 50 gallon propane tank water
>
> heater with a zinc change every 7 years is the norm.
>
> An air to water heat pump, an open loop solar water panel or closed loop
>
> if conditions warrant it are great secondary methods. To me heating water
>
> with electricity does not work because of winter and is a last thing to
>
> add.A tankless and their issues are near the end of the list. Ground
>
> source heat pumps are even lower to me with very nice prices on extremely
>
> efficient mini split air source pumps.
>
> I always try and minimize generators but if you need them then it allows
>
> one to have more options.
>
> Dave Angelini Offgrid Solar
>
> "we go where powerlines don't"
>
> http://members.sti.net/offgridsolar/
>
> e-mailoffgridsolar at sti.net <mailto:offgridsolar at sti.net>
>
> text 209 813 0060
>
> Maybe. I designed my own house to incorporate this. The most efficient are
>
> the vertical type, and at 6' the company advertised 20% recovery for about
>
> $1,300 if I remember correctly. This I'm sure is for a new copper pipe,
>
> and
>
> anyone who's ever taken apart a sewer pipe after a few years will know all
>
> pipes get a bacterial mat of a couple mm thick. I suspect this might be a
>
> pretty good insulator. At any rate there is a whole lot of copper involved
>
> and associated inherent environmental challenges. I can't help but think
>
> for the house design challenge to accommodate such a long perfectly
>
> vertical pipe and expense another kW or more of solar would offset more
>
> energy.
>
> On Tue, Mar 20, 2018 at 9:50 AM, Drake
>
> <drake.chamberlin at redwoodalliance.org
> <mailto:drake.chamberlin at redwoodalliance.org>
>
> 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-bounces at lists.re-wrenches.org>
> <mailto:re-wrenches-bounces at lists.re-wrenches.org> *On
>
> Behalf Of *Drake
>
> *Sent:* Thursday, March 15, 2018 1:00 PM
>
> *To:* RE-wrenches<re-wrenches at lists.re-wrenches.org>
> <mailto:re-wrenches at 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.
>
> 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.
>
> Â
>
> Mike Kocsmiersky
>
> Principal
>
> Spirit Solar Inc.
>
> (413) 734-1456
>
> Â
>
> Â
>
> Â
>
> From: Barton Churchill [mailto:barton at solarips.com
>
> <barton at solarips.com> <mailto:barton at 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.chamberlin at redwoodalliance.org
> <mailto:drake.chamberlin at 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 <http://www.solarips.com>
>
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>
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> --
>
> Â Â Â Â Â Â Â Â Christopher Warfel, PE
>
> Â Â Â Â Â Â ENTECH Engineering, Inc.
>
> PO Box 871, Block Island, RI 02807
>
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â (401)466-8978
>
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> --
>
> Barton Churchill
>
> 406.587.5295
>
> 2430 North 7th Bozeman, MT 59715
>
> www.solarips.com <http://www.solarips.com>
>
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> Dave Angelini Offgrid Solar
>
> "we go where powerlines don't"
>
> http://members.sti.net/offgridsolar/
>
> e-mailoffgridsolar at sti.net <mailto:offgridsolar at sti.net>
>
> text 209 813 0060
>
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> Christopher Warfel, PE
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> PO Box 871, Block Island, RI 02807
> (401)466-8978
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