Date: Sun, 18 Sep 2011 07:27:56 -0700
Reply-To: Vanagon <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Vanagon <camping.elliott@GMAIL.COM>
Subject: Re: Vitrifrigo/Truck Fridge power usage
In-Reply-To: <BAY152-ds12DAAE5C827B56757DFADA0080@phx.gbl>
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Right, but here's my question.
If low current setting + longer runtime = high current setting + shorter runtime . . . in other words, if there is no overall effect on longterm power consumption . . . then why does Vitrifrigo even bother giving the option of three different levels of current consumption?
One thought is that the Marketing department insisted on being able to claim low current operation. I have measured the current in the medium and low settings and neither draw as little current as the advertising claims, even the low setting.
But low consumption might be a major selling point in the truck fridge market, so maybe Vitrifrigo feels pressure to 1. Make a claim they cannot achieve, 2. If a customer says, "Hey, wait a minute! This thing draws more than you say," they can suggest he set it to the low current mode (which still draws more than claimed in the advertising bumf), and 3. Dodge any further questions, as they have with my inquiries.
So why do they ship it set to the medium setting, why not to the low?
I'm going to go out on a limb here and make a couple guesses (puts on arborist's climbing gear):
First, the longer run time necessitated by the low setting might mean that the compressor would never shut off in very hot conditions. Two weeks ago we were camped in 100F + weather and during the day, I'd say the duty cycle of the thing was 90% on, 10% off. If it was inside a closed vehicle sitting under the sun in someplace horrible like, say, Yuma, temps could go as high as 130F (I've measured them) and the thing would never shut off, not having enough current to move the heat out of the cabinet.
Second, maybe there is an overall efficiency gain at the higher currents. The relationship might not be as simple as
low current setting + longer runtime = high current setting + shorter runtime.
Only testing could answer this latter supposition. Or getting some straight poop from the manufacturer. Anyone here know someone in Italy who could call them and pry some useful information outta dem guys?
Sent from my smartphone with tiny screen & even tinier keypad.
On Sep 18, 2011, at 7:07 AM, Dennis Haynes <d23haynes57@hotmail.com> wrote:
> As efficient as these units are the "rated" power consumption is not always
> the same as actual. Mechanical refrigeration (compressors) will be effected
> by loading conditions especially condenser temperature. Considering physics
> that lower power setting probably means the compressor has to run longer.
>
> Dennis
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Vanagon
> Sent: Friday, September 16, 2011 5:52 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Vitrifrigo/Truck Fridge power usage
>
> I have the Vitrifrigo refrigerator in Mellow Yellow.
>
> My ammeter showed me that it draws more current that specified: 3.6A instead
> of the less-than-3A claimed. There is a resistor/jumper thing on the back
> that lets one set it to draw less, or more current. It's unclear to me what
> the advantage or disadvantage is by changing this, but it's presently set to
> the low-current mode, and draws about 2.8 amps.
>
> Last week, Mrs Squirrel and I camped for several days at East Park Reservoir
> in northern California. Daytime temps exceeded 100F, and the reefer ran
> almost continuously. But I had a solar panel array to keep it powered.
> Nighttime temps didn't drop below 80, and after a full night of operation,
> the house battery was down about 28 amp-hours.
>
> Right now I am camping in central Oregon, on the Wickiup Reservoir. Highs
> are around 70, last night's low was below freezing -- it was 35 in the van
> when I got up.* The battery was drawn down 15 A/h.
>
> ======
> * But thanks to my brand-new Mr. Heater Buddy, the van warmed up quickly!
>
> Sent from my smartphone with tiny screen & even tinier keypad.
>
