Well Disco,I have to thank you for your original question.My immediate answer was,stop complaining, you have got the damn frig in the back of your vehicle,just be thankful for that.Then I thought,no,the poor old Duck Person is in strife andis asking for help.I took my do it yourself book from my bookcase and started looking up how to answer your question.I was doing ok until I arrived at the part that started talking about OHMS,what the hell has Her Majesties Service got to do with electricity.Befuddled I then started reading the posts from the Einsteins,Electrical Gurus and other learned people who supply sensible info to their fellow Forumites.Things like wire,fuse,lighter plug socket etc sink in to mynon electrical mind.But when the Amps,Volts,surge protectors,Watts and other highly sensative info starts to flow,then I thought up yours Disco,getabloody esky and some ice bags.Save me a Yummie from your now warming up fridge..........when the power switch is up then the power is off,when it's down the power is on,that is of course unless the powerpoint has been installed upsidedown,then the JPS and the modulators will not let the ohms to pass through the wiring of the plug that is in place in the power point..Cheers.Ibbo.

No prob Ducky if you suspect the frige where the tinnys are is alive, just use the back of your hand to touch the frige handle first to see if its alive. If your hand isntkicked away then it probably safe to open the fridge & down a tinny ( thats how we used to check we wernt earthed when working on live mains when i was an ETSA linesman/ person back in the early 70s). Cheers Daryl

As always I get the real answer from Ibbo. You are a man amongst men, my friend. How would I ever sort my problems out without you razor sharp, computer-verifying brain to help me. Two Yummies for you today!!.......Help yourself from the car fridge.........they are warm anyway. LOL The OHMS on the book is probably because you stole it. Hehehehe Thanks DeBe........works a bit like seeing if Daisy is alive. Rub the hand on the backside and if I don't get kicked away........I'm in with a chance. I just wish she would take off the steel caps........!! I can see why you gave up being a linesman if that's how you test. A short but BRIGHT life. LOL

Frick'ns falls over bloody laughing so bloody hard....hahahahahaha!!!!! Dave

Disco Old Salt.Thank you for the warm yummies.Hey how do you know what Fireflys backside looks like?.OOps better go.The Eagle is Hovering.Cheers.Ibbo.

twobob wrote:

---

OT123

What is being spoken about refers to a standard power formula ... watts=Volts * Amps. All electrical equipment requires so much Power (Watts) to operate. So if you lower the Volts, the Amps must raise to provide the required Watts (power).

So it is correct, lower the volts and the amps rise.

There are ways to lower the volts AND amps, but these are beyond this discussion, and bring in another formula relating to resistance.

---

Sorry twobob but OT123 is on the money with this one.....

A 240 Volt radiator (as in room heater) that is rated at 1200 watts will draw (1200 divided by 240) amps...i.e. 5 amps and the resistance of the heater is 48 ohms i.e 240 divided by 5 (Ohms Law)

If the voltage is reduced to 180 volts the radiator will now draw 180 divided by 48 (the "load" resistance does not change) i.e. 3.75 amps, and the power consumed will be 180 volts times 3.75 amps, i.e. 675 watts. (Not the rated 1200 watts that's based on the 240 volt supply.)

In some more complex devices the "load" resistance (ohms) or its notional equivalent may change with a change in voltage so that the relationship between volts and amps and as a result watts may change due to the change in ohms but the fundamental Watts = Volts * Amps formula does not change.

I've tried to keep this as simple as possible without compromising its accuracy, I hope I've had some success

PS: Pedants please note, I have not introduced "Power factor" into the discussion as it only applies to some AC (not DC) devices such as AC motors and fluorescent lamps etc.

-- Edited by jimricho on Tuesday 1st of December 2009 08:41:25 PM

jimricho wrote:

---

Sorry twobob but OT123 is on the money with this one.....

A 240 Volt radiator (as in room heater) that is rated at 1200 watts will draw (1200 divided by 240) amps...i.e. 5 amps and the resistance of the heater is 48 ohms i.e 240 divided by 5 (Ohms Law)

If the voltage is reduced to 180 volts the radiator will now draw 180 divided by 48 (the "load" resistance does not change) i.e. 3.75 amps, and the power consumed will be 180 volts times 3.75 amps, i.e. 675 watts. (Not the rated 1200 watts that's based on the 240 volt supply.)

In some more complex devices the "load" resistance (ohms) or its notional equivalent may change with a change in voltage so that the relationship between volts and amps and as a result watts may change due to the change in ohms but the fundamental Watts = Volts * Amps formula does not change.
I've tried to keep this as simple as possible without compromising its accuracy, I hope I've had some success

pedants please note, I have not introduced "Power factor" into the discussion as it only applies to some AC (not DC) devices such as AC motors and fluorescent lamps etc.
-- Edited by jimricho on Tuesday 1st of December 2009 08:41:25 PM

---

Hi Jim

I am always suprised to see how much this is misunderstood even by qualified electricians

 I have had some strong discussions on many forums on the subject  some claiming to be "engineers" others telling me how experienced they were.  Been told  "I should teach my mother to suck eggs etc""
Good to have some one back me up for a change .
Yes, best leave PF out of it, although I did have to go there when someone asked why the readings on their new power calculator showed that amps by volts did not equal watts.  

I can't tell you how I know about Firefly's dimples Ibbo..............I'm a gentleman ! I never kiss and tell.

The mind boggles.................Gentleman?I certainly hope so.Nice dimple though.lol.Cheers.Ibbo.

Getting back to Ducky.......Yes Mate.......get the biggest JST you can find..... what you can afford.....you didnt say what draw your fridge took.......but for travelling....use the JST.......and recharge it when needed Dave

Onya Smokey!! Sorry, but my fridge can't draw. It is ONLY a fridge. Do you have one that can?? My My.........they have come a long way haven't they?

"Hey Daisy...............we gotta get us one of them new -fangled updated cooling machines, hell, they can draw purty pictures and all and yep, I think they actually cool your drinks as well. Hot Damn!! Then I can ask the good old boys on the old grey nomad site how to wire it all up"


BRB all!!




(about 5 amps and generally runs about one in 4 hours.   Damned good insulation on them there Trailblazers)

-- Edited by Disco Duck on Wednesday 2nd of December 2009 12:15:09 PM

-- Edited by Disco Duck on Wednesday 2nd of December 2009 02:26:52 PM

Disco Duck wrote:

---

Onya Smokey!! Sorry, but my fridge can't draw. It is ONLY a fridge. Do you have one that can?? My My.........they have come a long way haven't they?

"Hey Daisy...............we gotta get us one of them new -fangled updated cooling machines, hell, they can draw purty pictures and all and yep, I think they actually cool your drinks as well. Hot Damn!! Then I can ask the good old boys on the old grey nomad site how to wire it all up"


BRB all!!




(about 5 amps and generally runs about one in 4 hours.   Damned good insulation on them there Trailblazers)

-- Edited by Disco Duck on Wednesday 2nd of December 2009 12:15:09 PM

-- Edited by Disco Duck on Wednesday 2nd of December 2009 02:26:52 PM

---

         Oooooooooooppppppppssssssssss.....SSSSuuuuuuuugggggaarrrrr

       over done it with the wire ; ;;;;;;;;;;;;;;

       now the b#%&#   drinks are frozen,,,,,,,,,,,,

         BUGGER<,,,,,,,,,,,,,,,,,,,,,,,,,

 

oh bloody hell now James is corrupted!!

Onya Justcruisin.................. LOL LOL You have come over to our side. ALRIGHT!!! We are starting to outnumber you numbats on your side DaveO. Ibbo will be proud!!

Go with dry ice or block ice. Or freeze some 2litre bottles of water and use them in the esky. Last for days if your system is right. I have a Waeco and I run it off the cig lighter in the cruiser. Works a treat, nothing overheats, and everything stays frozen. The power to lighter is only supplied when the ignition or accessory is on. Food stays frozen solid for about 6-8hrs without any power, depending on the climate at the time. I haven't lost anything yet. When I'm on 240 I plug it into the van. You blokes make everything sound so complicated. No wonder Ducky is confused. I'm totally blinded by techno-speak. But then I'm a gerl.

Only a Gerl just wait until after your op..........things may have changed Christopher/Chris.Starting to get carried away a bit aren't we?We being me.Cheers.Ibbo.

What are you saying Ibbo? I'm only having an adrenal gland removed, aren't I? They're not getting any more of my body parts, well, the ones I have left, that is. At this age a girl has so many things to contend with as far as body parts and hormones go. Then we have to worry about car fridges as well? Jeez, it's all too hard! Got any yummies left Ducky? I think I'll just go and wallow in the pool. It's too hot in the shade now the humidity has kicked in.

After checking your pre op notes I see that a great mistake has been averted.All your body parts will be left in place,well most of them.I hope you had a happy wallow in the pool.Cheers.Ibbo.

when camping or travelling we always used an engel fridge, we also carried a spare battery with us and had it hooked to that when it wasout of the car under a tree or in the tent or where ever we were ,it would run for a day or so from memory and then we would swap batteries over and take the car for a run up beach or whereever to recharge the battery we were always on the move realy so it was never a problem ,we had weaco fridges all kinds of fridges, then we purchased an engel from a caravan park in port mcquarie nsw it was being sold from the van it was in, double basket 700 dollars and went for many many years on very rough trips to weipa when the road was just ruts all the way, the motor used to bounce around in the fridge and i was always worried it was going to ruin it but nope. i am now with a different partner as that was over 7 years ago now, we bought an engel from a man in rainbow beach was like new and works a treat only a single basket one but there is only the two of us so its all we need, my hubbys mum had an engel (she passed away last june) and she used hers as a spare freezer so it was never turned off in her carport and its still going to this day, we have inherited it just got to pick it up on central coast next time we venture that way , but i must say after in the old days going thru every fridge we could possibly buy the engel was the way to go .

and in my opinion, still is Della!