Savaplug-fact or fiction.

[Johnboy]

Came across this http://www.savaplug.co.uk/productdetails.asp?id=2 and wondered if it can work. Looks like snake oil to me but my engineering experience has been in mechanical things not those strange electron thingies.

John

 

[Chris Knight]

Sounds rather less believable than those emails recommending certain enhancement medications!

 

[SketchUp Guru]

Don't know anything about that unit however I think it probably is electrical snake oil.

The power consumed by a device (what you get charged for) is equal to the supplied voltage multiplied by the current drawn by the device. In simple terms the current drawn is dependent on the resistance of the device.

Of course when a motor starts up current draw is temporarily higher than once the motor is at speed. Power consumed at start up with thus be greater but it naturally falls off to a lower level as the current draw is reduced. If the load increases-think tablesaw cutting through a thick piece of oak--the current drawn will increase and thus so will the power consumed.

This power adjustment happens all by itself without the help of some little magic box. I wonder if they would make the claim that their little box keeps the electrons from falling out on the floor when you unplug the refrigerator from the outlet?

 

[Chris Knight]

. I wonder if they would make the claim that their little box keeps the electrons from falling out on the floor when you unplug the refrigerator from the outlet?

I just hoover mine up and reuse them :wink:

 

[Jake]

I think there is some reality behind it, if you have a old or cheap fridge with inefficient controls. Fridge motors are way oversized to get over the initial torque requirement, and in older models they are then just left running. The savaplug is apparently a PWM motor controller which can knock back the power fed to the motor once the initial surge has been overcome.

That's my vague recollection from discussions on uk.diy who are usually arch-sceptics about such things. Do a google groups search and I'm sure it'll throw up more than you ever needed to know.

 

[DaveL]

I think Jake is correct and if you have a relatively new fridge they are fitted with a control box like this as standard to get the 'A' rating on efficiency.

 

[AndyBoyd]

I think this works in the same way some drill speed controllers work, so in principle it seems to be sound to this physicist.

You can slow a drill down by chopping the sine wave of the AC current (so there is actually sections of the sine wave missing) , and so the motor runs slower .I assume you use less power even allowing for the power to run the circuity. So with a smart way to detect when you can slow the motor down it seems on the surface to be feasible.

As with all these things surely we would have all heard of it, if it works that well? Or is it still new?

What is the price by the way? I did not see that it ,should be less than 3 to 4 years annual savings to make it economically viable

 

[ike]

What is the price by the way?

£19.95

 

[AndyBoyd]

Hmm so 20 quid is just about right pricing, the trouble is how do you know it's working for you,? But hey for 20 quid it's probably worth a punt

 

[Anonymous]

It's snake oil in my opinion. Sure, a motor demands more power at startup but then it runs at lower current by itself as the load is reduced (frictions and inerita) and so your savings are already bult-in.

Fridge motors do not run for long periods and they are not huge in the first place. Also, the load on a fridge compressor is not particulalry great either.

Keep the £20 in the bank.

 

[Alf]

My folks had a couple of these on their fridge and freezer a while back, so I asked the old man what he thought. He came to the conclusion they might have been helpful, but as there's simply no way of knowing he wouldn't say he'd recommend them.

Cheers, Alf

 

[engineer one]

i know the electric supply companies try to confuse us, but surely after any motor has started, it no longer runs at peak amperage, therefore automatically it will save its own power.

would you not think the old formula about volts watts and amp has stayed the same since it was invented. seems to me like adding moly to car oil, it only works with old oil.

anyone really understand how the suppliers work out kwhrs anyway what with all these climate levies and other charges that seem to be there???

what is more interesting is that it wont work with anything with an electronic controller, and a whole list of decent machines.

i reckon its better to spend the 20 quid down the pub :lol: :lol: :lol: :lol:

paul :wink: