5000W/ 48V water heater dump load element [RE-wrenches]

[Travis Creswell]

Hi Dan,

So you are saying 200 kWh's a month is being lost to regulation?  That
sounds a little low for a Bergey 10 in a "good" wind site.  I'm assume there
are periods (12hr -72hrs?) much windier then others and it's during these
windier periods where most of the regulation happens.

IMHO, I think you really need storage of some sort. Not knowing much about
the exact application I think it could be a control challenge to time the
"dump" elements in the boiler to call for heat only when the turbine is
regulating and still properly charge the batteries.  I don't think you would
get much of the energy lost to regulation back.  What's the heat load of
this place?

In round numbers, 10 kWh's will raise 100 gallons of water 50f.  Yes, you
can easily control a 240v water heater with the properly size contactor.  I
wouldn't even consider doing it on the DC side.

A site built atmospheric tank is easy enough to build but is pretty hard to
do for less then several thousand by the time you get the heat exchangers in
it.  I've built a 1250 gallon atmospheric tank for my Tarm Boiler plus
several other tanks for large solar thermal systems and I can assure you
they are really labor intensive to do right.

If the budget wasn't such a concern the Tarm boiler with atmospheric tank is
clearly the best way go.  I love mine.  It supplies the all the heat for our
radiant system for our 2500ft2 home and 2000ft2 shop plus all of our hot
water.  I build one fire every three days which takes 3-4 armloads of cord
wood.  I also have a Bergey 10 and it will dump excess into the tank once I
get it up.  I also will tie my solar thermal system into it once I get it
going.  Both projects are slated for this year but there never seems to be
enough time.

Best,
Travis Creswell
Ozark Energy Services
Joplin, MO

-----Original Message-----
From: Dan Brown [mailto:Cvsolar2 at aol.com] 
Sent: Tuesday, December 26, 2006 10:42 AM
To: RE-wrenches at topica.com
Subject: Re: 5000W/ 48V water heater dump load element [RE-wrenches]



Thanks for all the input everyone. 
       At this point we're still pretty much in the design phase of this 
project. First off -- yes, the 10K can spend over a third of it's time
regulating, 
(and they already use over 400kwh/mo.)
        the  care taker / main brain of this project is an ex-engineer now 
general contractor. I'm just a lowly system installer.  he's the one pushing
for 
a hot water heater thingy in line with the boiler. I agree, but envision 
something more like a tarn heat storage system with multiple inputs. the
dump load 
from the XL-10 being just one of them. (I'd also like to see them burning 
wood -- they're sitting on like 300 acres of woods, and are totally reliant
on 
propane.) or maybe even a dump load / heating element that fits into their 
existing boiler. right now i have them set up to use two 1200w 110v oil
filled radiant heaters triggered (thru a relay) by an OB aux out. not big 
enough.
        anyway, they say they're considering all options,  and the owner is 
receptive to efficiency, and environmental responsibility issues. but cost
does 
need to be considered.
        the care taker dude was pushing for a conventional 240v hot water 
heater running off the inverters. cheaper --yes. controllable? -- well, we
do 
have two more OB aux outs to use. but running that much freight thru that
much 
circuitry makes me a little edgy. so I'm thinking -- at least keep it on the
DC 
side --yes, i could see setting up multiple hot water heaters, and staging 
element start thresholds. but that conjures up even more control issues
i.e.;  
how is this mess disabled in the eq mode? i would like to keep battery 
maintenance as simple as possible. -- more likely to get done.   
       so, I'm pretty much fishing for  a consensus here -- what do most 
folks do?  what works? what doesn't?  is there a reliable "off the shelf" 
controller / element capable of handling this kind of logic -- at that kind
of 
freight? --( that doesn't require a Ph.D. to operate?)  
        i do value all your insight, and appreciate having this  forum in 
which to air such laundry -- thanks all.
                                                  hope you all have a safe 
and joyous holiday season. dan

--
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