[RE-wrenches] DC, or not DC, Dat is Da question (Two Load Questions)

[Ray Walters]

I'd do the comparison against one of the much cheaper energy star rated 
AC models.  In my comparisons,On  the slight edge in efficiency isn't 
worth the extra cost of the DC units.  I've also had premature failures 
of DC fridges due to low voltage.  Finally using the inverter's built in 
low voltage disco keeps the batteries from getting ruined if the charge 
system is down, but loads stay on.
I lived for years with a DC fridge, and my family has no desire to go back.

Ray Walters

12/11/2012 12:54 PM, Jason Lerner wrote:
> Hello Larry,
>
> I still install DC fridge/freezers in off grid systems for efficiency, 
>  but also so that when the owners leave for the weekend/week/month 
> they can turn off the inverter and all the associated phantom AC 
> loads,  but the DC freezer is still on. When they come back, the meat 
> in the freezer is still frozen.
>
> Recently for a new off grid cabin we compared a Subzero 23 Cu. ft. 
> fridge/freezer to a Sundanzer chest freezer and Sunfrost all fridge 
> which is 51 cu ft.combined.  Using nameplate yearly KWH's, retail 
> price tags and putting the freezer in an outbuilding we found the 
> sunfrost/sundanzer has 2.22 times more cu ft at 60% of the subzero's 
> energy consumption....at 66% of the cost of the Subzero.
>
> Adding additional PV/wiring/CC/racking to run the Subzero was going to 
> cost an additional $2500.  The contractor building the cabin brought 
> up the point that the Sunfrost does stick out farther into the kitchen 
> then an "average" fridge and there was going to be a cost associated 
> with custom cabinets to match that depth,  possibly the same amount as 
> adding extra PV's...
>
> Best,
>
> Jason Lerner
> Waldron Power and Light Co.
>
>
>
> On Dec 11, 2012, at 10:55 AM, Larry Crutcher, Starlight Solar Power 
> Systems wrote:
>
>> Why would one specify DC voltage appliances or lighting for off grid 
>> systems today when we have sub-buck-a-Watt PV solar power?  If you 
>> have space, you can make the added power that conventional AC 
>> appliances draw for very low cost. It could even be argued that the 
>> cost for DC items, wiring, distribution gear and labor will cost much 
>> more than simply adding more PV solar and staying all AC.
>>
>> I don't like wasting resources and I understand old school thinking 
>> when PV modules were very expensive, but with high efficiency AC 
>> appliances and low cost inverters and PV modules, does it still make 
>> any sense? Shine some light on my thinking.
>>
>> Larry Crutcher
>> Starlight Solar Power Systems
>>
>>
>>
>>
>>
>> On Dec 10, 2012, at 9:12 PM, Allan Sindelar wrote:
>>
>> Wrenches,
>> We still try to encourage prospective off grid customers to do a full 
>> load analysis as an initial step in the system design process. To the 
>> point:
>>
>> 1) What is a good watt-hours/day figure to use for a typical, modern, 
>> new, carefully chosen, fairly large conventional AC chest freezer, if 
>> kept in a heated indoor location? Assume 65 degrees and seldom opened.
>>
>> I will encourage that the freezer be located in a shaded, protected 
>> outdoor location, in order to greatly reduce winter energy 
>> consumption, but I need a good base figure to work with.
>>
>> The proposed system will most likely be 48Vnom, so a Sundanzer or 
>> similar DC freezer is out.
>>
>> 2) Same question for a ceiling fan, for general slow circulation of 
>> winter heat. The energystar.gov <http://energystar.gov/> list gives 
>> relative cfm efficiency but not wattages. Is 55W still a good figure 
>> to use as a default?
>>
>>
>> I have attached a condensed energystar.gov <http://energystar.gov/> 
>> list for the freezers, but wonder what other off grid Wrenches 
>> typically use. Also, I'm not sure that Wrenches posts allow 
>> attachments, so this may not appear with my message.
>>
>> Thank you,
>> Allan
>> -- 
>> *Allan Sindelar*
>> _Allan at positiveenergysolar.com_ <mailto:Allan at positiveenergysolar.com>
>> NABCEP Certified Photovoltaic Installer
>> NABCEP Certified Technical Sales Professional
>> New Mexico EE98J Journeyman Electrician
>> Founder and Chief Technology Officer
>> *Positive Energy, Inc.*
>> 3209 Richards Lane (note new address)
>> Santa Fe, New Mexico 87507
>> *505 424-1112*
>> _www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
>>
>> *
>> *
>>
>>
>> <Freezers Product 
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