This is topic Gadget which claims to reduce your fridge's energy consumption by 20% in forum Film-Yak at Film-Tech Forum ARCHIVE.


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Posted by Leo Enticknap (Member # 534) on 08-20-2003, 10:56 AM:
 
Just over a year ago an ecologically-minded relative mentioned that she'd bought a Savaplug. This is a gadget which replaces the mains plug on your fridge, which claims to reduce its energy consumption by up to 20%. Apparently a conventional fridge compressor is very energy-inefficient when running at anything less than 100% speed. The Savaplug therefore allows it to have full power when starting, but thereafter regulates the electricity supply to maintain peak efficiency.

I'm told that a fridge is by far the most power-guzzling appliance in most people's homes, typically drawing 100-200 watts for hours at a time. The Savaplug people claim that over the 10 year guarantee period, it will save you approx. £120 in electricity costs.

Being a gadget-minded sort of person I decided to put their claim to the test and got one. I've just compared my electricity bill for the May-August quarter for last year (the first full quarter in which the Savaplug was running) with the equivalent bill for this year. Typically my electricity bill is highest in this quarter, because all the heating and water heating in the flat is on gas. I guess that the fridge having to work harder in the warm summer must be responsible for that.

Anyhow, the bill this year was £4.32 lower! I can't think of any other variable which has changed (e.g. it's not like I was away for two weeks this year but not last year, and I haven't got rid of any power-hungry things that plug into the wall). So it looks like this thing really does do what it says it does. The only possible drawback I can think of is if this thing does long-term damage to the fridge compressor, but I'm a year down the line with it (and my relative is 2-3 years down the line with hers) and there's no hint of any problem so far.

In the UK you can order one here. They cost £25 including P & P. I don't know if they're available for continental and US power supplies.
 

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Posted by Jack Ondracek (Member # 1466) on 08-20-2003, 11:18 AM:
 
I heard about something like that here in the states... some 4 or 5 years ago... don't recall the name they sold it under.

Technically, just limited the current available to the compressor at the point when it needed it the most... at startup... pretty much like putting a common resistor in the line. You could argue that this would save (some) electricity... but most comments here were against using it. For one, the head pressure (Paul?) would have to drop a lot lower than normal in order to restart a compressor with one of those things in the line.
 

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Posted by Leo Enticknap (Member # 534) on 08-20-2003, 12:09 PM:
 
This thing claims to be more sophisticated than that. It does not limit the current during startup, but kicks in as the current drops off after startup. How it works.
 

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Posted by Paul G. Thompson (Member # 655) on 08-20-2003, 12:15 PM:
 
BAH!
 

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Posted by Michael Brown (Member # 890) on 08-20-2003, 12:19 PM:
 
I should really start switching my TV off rather than putting it in standby. Has anyone see that TV advert?
 

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Posted by Paul G. Thompson (Member # 655) on 08-20-2003, 01:15 PM:
 
Dest way to save power on a TV set is to unplug the damn thing.
 

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Posted by Michael Schaffer (Member # 1204) on 08-20-2003, 01:28 PM:
 
In Germany, you can borrow a power consumption monitoring device from the electricity companies. I saw such a device here just a couple of days ago, I think it was at RadioShack or Fry`s. With that, it should be easy to see if the Savaplug actually saves power.
 

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Posted by Paul Mayer (Member # 355) on 08-20-2003, 01:30 PM:
 
I remember these things being marketed here back in the '70s. They are just a capacitive load that is supposed to bring the power factor for inductive loads like motors back towards unity. Whether that affects how a power meter works provokes some questions: Are we billed for VA or W (reactive power or real power)? Do power meters run true only at unity power factor? Do they run 'fast' under reactive (especially inductive) loads?

My understanding is that most power companies bill residential accounts based on watts, as opposed to industrial accounts which are billed for VAs since industrial loads usually require utility-supplied capacitive correction. If a residence is being billed in watts, I don't see where one of these devices will save anything on the power bill. But if one is being billed in VAs, these devices may help, assuming they last long enough to repay their purchase price.
 

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Posted by Leo Enticknap (Member # 534) on 08-20-2003, 02:05 PM:
 
Michael: what I must do sometime is switch everything else off in the flat while the fridge condenser is running, then look on the meter (a digital one which gives you a readout in watts as to what the whole flat is pulling), then disconnect the Savaplug and see what the fridge condenser runs without it. Next time I switch the thing off to defrost it I'll have a go. But on the evidence of the electricity bill (down from £38 to £32 across equivalent quarters), I'm starting to be convinced that this thing actually works.
 

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Posted by Phil Hill (Member # 371) on 08-20-2003, 06:25 PM:
 
Those devices are basically a glorified light dimmer. A zero-crossing "variable-power", motor control with some intelligence to monitor the load-current and automatically adjust the triac/scr conduction angle...with some power factor correction thrown in if the unit is the "deluxe" model.

Without getting into a big discussion about VA, watts, apparent power, etc., the motors in those appliances consume the same amount or more energy when not fully loaded than when running at full load. Since those appliances motors rarely run at maximum load (but must be capable of supplying the required hp when required), the unused "power" is consumed anyway and thrown away as heat.

By allowing "just" enough power to the motor as dictated by the load, less energy is used.

>>> Phil
 

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Posted by Mark Hajducki (Member # 1732) on 08-20-2003, 08:23 PM:
 
If they work well, do not damage the appliance, why dont the fridge/freezer manufacturers build them in [at a fraction of the cost] and get a better energy efficancy rating,
 

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Posted by Paul G. Thompson (Member # 655) on 08-20-2003, 08:26 PM:
 
Mark, I would guess it is either a scam or the savings are not worth the powder it would take to blow it to hell.
 

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Posted by Phil Hill (Member # 371) on 08-20-2003, 08:36 PM:
 
Actually, in the U.S., many are in use in commercial HVAC systems for BIG ASS Fans.... They do work...especially well for moving fluids.

Whether or not it pays for a private individual to put one on their "ice box", I doubt it. Changing to those fu*cking fluorescent light fixtures is what REALLY saves the bux!

>>> Phil
 

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Posted by Leo Enticknap (Member # 534) on 08-21-2003, 01:38 AM:
 

quote:

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If they work well, do not damage the appliance, why dont the fridge/freezer manufacturers build them in [at a fraction of the cost] and get a better energy efficancy rating,

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The instructions on my plug said not to use it on 'modern fridges which have a digital display and/or electronic circuitry' and to contact the manufacturer if in doubt

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That suggests to me that a regulated DC power supply (which digital electronics need) doesn't react nicely to whatever it is this device does to the AC input to the fridge.
 

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Posted by William Hooper (Member # 71) on 08-22-2003, 01:23 AM:
 
???
Ed Jurich told me that the government deregulated power supplies in 1987!

???
 

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