need 24 volt applinaces [RE-wrenches]

[Phil Undercuffler]

I too am a fan of micro inverters for micro systems, but I urge caution
on using disposable mod-sine inverters.  

If you provide the inverter, be aware that most have instant mortality
overload protection -- meaning if the customer plugs in a lamp with a
loose wire, all the lights go out in a permanent sort of manner.  Ask me
how I know :-(  I figured it out after the second trip and inverter.
Good news was, it was a friend and neighbor so at least I didn't have to
drive far.

If the client provides the disposable inverter, there is a definite
tendency to buy a bigger inverter than required, which can drastically
increase idle current.  After having learned lesson #1 above, I started
sending folks to the big box stores for disposable inverters.  That
ended after a client came back with an 800w doozy with a 35 watt idle,
on the 260 watt PV system.  Hey, it was only $20 more than the 200 watt
inverter! A bargain!

The previous limitation to micro inverters in homes was the ability to
power up the inrush of a CRT television.  Now the costs (and efficiency)
of LCD televisions eliminates that worry.  My acid test for the client
is the desire to run a toaster or microwave oven -- if those are on the
wish list, spend the extra money and get a larger inverter with a
charger.

In my own home, I do run a handful of 24v DC lights.  My first inverter
was a DR2424, and all my lights were CFL.  My wife wanted something that
could be dimmed.  Being a creative type never afraid to void a warranty
on my own house, I bought a bunch of MR16 and G4 type lights from Ikea,
clipped out & threw away the transformer and bought a couple of Zane 24v
dimmers.  24v MR16 and G4 bulbs are available online at same price as
12v bulbs at Home Depot.  Voila:  dimmable lights, sleeping inverter and
no transformer losses.  Happiness!

 
------------------------------------------------------------

Phil Undercuffler
Director, Battery-based and Off-grid
Conergy, Inc.
Our World is Full of Energy
 
1730 Camino Carlos Rey Suite 103
Santa Fe NM 87507 USA
Office | 505.216.3841
Fax | 505.473.3830
www.conergy.us

------------------------------------------------------------ 

-----Original Message-----
From: Drake Chamberlin [mailto:Drake.Chamberlin at redwoodalliance.org] 
Sent: Monday, March 24, 2008 11:34 AM
To: RE-wrenches at topica.com
Subject: Re: need 24 volt applinaces [RE-wrenches]


I've become a believer in using small, portable inverters for cabin 
systems.  If these systems have small loads, such as CF lighting, 
music or a small TV even, a portable type inverter is usually adequate.

The advantage of 120 volts over 12 is huge.  Instead of wiring with 
#10 copper, #14 is adequate.  120 V CF lights are cheap compared to 
12 or 24 VDC.  Longer runs and 3 way switches work fine, without 
dimming of the lights.  Blenders, coffee grinders, weed whips, etc 
are (of course) readily available for 120 VAC.

A system with 5, 13 W CF lights will only pull 65 watts.  If a 250 
watt inverter is used, there is still 175  watts left over for 
whatever.  A small array and a couple of L-16 batteries would not 
support much more for long.

Small inverters may have a low, no load draw, so the inverter can be 
left on.  Lights come on instantly and Nicad loads can be 
charged.  Many Nicad batteries will charge on mod sine ok, or if a 
true sine  Exeltech is used, DeWalts, etc can be charged.   It is 
more appropriate than using a DR Series or equivalent machine which 
costs more, buzzes and uses more power to stay on, and may require 
two lights to be switched on to bring it out of idle.


Drake 


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