Dump Load [RE-wrenches]

[Geoff Greenfield]

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Good point Travis!  With Outback's inverter you can easily relay an AC
dump - very appropriate and easier!  In this case I was using it to hook
into bergey's Xl-1 controller - so I was married to DC (although I probably
could have scratched my head enough and done an AC one based on universal
battery voltage which is what the bergey is looking at - I will ask Todd at
bergey about this).

I did not go through the T-stat and the customer and I agreed that in the
rare case that this  1,500 watt element could take his tank too high his
tempering valve would avoid scalds and the PT valve would blow first
(straight to a drain).  FAR from elegant but I simply do not see this
happening.

For a brighter energy future,

Geoff Greenfield
NABCEP Certified Energy Practitioner

THIRD SUN SOLAR & WIND POWER Ltd.
340 West State Street
Athens, OH 45701

www.third-sun.com
(740) 597-3111


What about an AC dump load?  You can get 1500 w / 120 v water heater
elements from Grainger and I'm sure others.  If you have a 240 AC available
from the inverter system then you could use a 240 volt element.  240 volt
elements as low as 2000 watts are available from Grainger.  A little looking
and you could probably find even smaller ones.

SW's have voltage control relays built in.  I'm thinking the MX60 could be
used to control this also but I'm not sure.  You would still have to use a
relay or contactor that could handle the amps.  The inverter would have to
have the capacity to spare in case there would be other loads on at the same
time.  But then again the reason you've got extra energy is you aren't
running many loads.

Another AC dump load could be a ceramic (or similar) 1500 watt electric
space heater available everywhere for cheap.  But who needs that extra heat
in summer when the PV system would be floating a lot.  Most of them have a
high and a low setting so you could do some tuning to match the needs of the
system.

When folks switch over to DC water heater elements are they using the stat
that came with the water heater, or replacing it or bypassing it?  I would
not think that the built in stat would hold up to that kind of amps for very
long.

Travis Creswell
Ozark Energy Services, Inc.



-----Original Message-----
From: Geoff Greenfield [mailto:Geoff at Third-Sun.Com]
Sent: Thursday, May 19, 2005 10:53 AM
To: RE-wrenches at topica.com
Subject: RE: Dump Load [RE-wrenches]

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I just (yesterday...) did a hot water dump load using a DC element (from
AEE, their 24-48 Volt unit - 60 amps at 24).  PAIN IN THE ASS! (oops I mean
butt).  Factor that into your plan...  Wanting to capture "extra" power from
PV when the batts are full is noble... and as a wind/hydro dump load
sometimes required.  Purchase a specialized wrench for the element - about
$30... we just couldn't get the leaks to stop with channel locks.  Tape and
dope the threads... the rubber washer that tank came with won't seat.  and
then think about clearance/wiring issues.  If they are not using the
electric you may be able to use the internal wiring at the J-box on the top
of the tank... but it is sized for 240 VAC and is (I think) about #12.  I
went with #6 for the DC to the HR and had a Hellacious time with crimped
terminals and very tight clearance at the element terminals... I am not
proud of the somewhat ghetto wiring and would put a $38 box of krispy Kremes
in the other side of the basement if an inspector were to visit... If it
were inspected I prob would have fabed some sort of Jbox onto the removable
cover, or slug busted it, but still - no room there. grrrrrrr.

Thanks all, I feel better now.

For a brighter energy future,

Geoff Greenfield

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