Frostbite [RE-wrenches]

[Travis Creswell, Ozark Solar]

Hi Joel,

Zero AC kWh without freeze protection until recently. I hooked up an
exterior motion sensor light and the only way to get it work reliably was to
take the SW4024 out of sleep mode.  So that's another 384 DC watt hours per
day used by the inverter.  ~150-200 DC watt hours used by the Sun Danzer
Fridge.  But the place is only occupied a few times a year.

Of course freeze protection just depends on the average outside temperature.
It estimate it be several kWh's per day averaged over a cold week (every
night into the teens) to just a few kwh's for the entire mild week (just a
few nights below freezing).  I do have an AC kWh meter measuring the total
AC output of the system and was considering installing one dedicated just on
the water heater.  With the addition of the HOBO type data logger I'll be
able to tell a lot better what's going on.

Take care,

Travis Creswell
Ozark Energy Services


-----Original Message-----
From: Joel Davidson [mailto:joeldavidson at earthlink.net] 
Sent: Thursday, February 16, 2006 9:38 AM
To: RE-wrenches at topica.com
Subject: RE: Frostbite [RE-wrenches]

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Hello Travis,
What is the unoccupied cabin's daily electric consumption without freeze
protection and what is the daily consumption with freeze protection active?
Joel Davidson

Original Message:
-----------------
From: Travis Creswell, Ozark Solar ozsolar at ipa.net
Date: Wed, 15 Feb 2006 21:43:49 -0600
To: RE-wrenches at topica.com
Subject: RE: Frostbite [RE-wrenches]


Hi Jeff,

I've been tinkering with the diversion load control feature on a MX60.  We
have a customer with a rarely used off grid hunting cabin.  Don't laugh too
hard when I say this but they have a 240v electric water.  At least I
replaced the 4500 watt element with a 1500 watt.  The customer refused any
suggestions of propane and the system was large enough that it can support
it.

You might consider this set up or some variation of it.  The customer
doesn't want to winterize the bathroom so I installed baseboards which are
hooked up the water heater which is in the super insulated bathroom.  I have
a stat set @ 40f for freeze protection.  It's hooked up to circulating pump
that moves water from the water heater through the baseboards.  

I knew I was throwing a bunch of energy away as the system was in float so
long.  So I've paralleled a 2nd stat set @ 65f that is controlled by a time
delay relay that is hooked up the AUX output of the MX60.  So once the MX60
hits the bulk voltage it turns on the time delay relay which is set @ 4 hrs
to allow the batteries to do a full absorption.  After 4 hrs the time delay
relay closes, if it's colder then 65f in the bathroom the pump turns on and
in a few minutes the water heater kicks on.  The battery voltage gets pulled
down then which turns the AUX relay off which then get the array back up to
full output.  This way I'm using a lot more of the energy even if it is just
to keep an unused bathroom warmer.  The trick was the time delay relay.

So far it's working.  I left a temp data logger (similar to a HOBO) up there
so we'll see just what's going on when I get a chance to look at the data.
I'm sure I'll still need to do some playing with the timing and voltage
settings but the concept is sound.


Best,

Travis Creswell
Ozark Energy Services