Converting kWh/24hr to amps

[ditchcrawler]

The quiescent part is only correct if

 

a he never runs anything else off the inverter all year

b the inverter doesn't drop to low power of standby when not loaded.

[Paul C]

The quiescent part is only correct if

 

a he never runs anything else off the inverter all year

b the inverter doesn't drop to low power of standby when not loaded.

 

a) Yes true. If you evaluate the power consumption of a 230V fridge vs a 12V fridge, you need to do a "partial power audit" based on your own circumstances. For example if you have something else which requires mains power 24/7 (I can't think of anything off the top of my head - can you??) then it could be split out as another item in the power audit completely, ie not taken into account for the comparison. If you had items which saw occasional use, then you could attribute a proportion of quiescent current to the fridge, and a proportion to the other item(s). This is also interesting if doing a cost comparison.

b ) You'd need to know how the inverter behaves. For example, does it drop into low power straight away, or after a time delay? If time delay, then what's the time, and what's the times the fridge is on/off too? You'd have 2 elements to consider then, and the calculations would become more complicated but possible to work out with the right figures. Also, if the inverter has a low power standby mode, does it properly/successfully come out of it when the fridge (compressor) demands power again? If not, then you would need to change the configuration of the inverter to turn it off, negating its advantage.

[Dave_P]

I think I've deduced the answer from all this. When using a 240v appliance through an inverter, you calculate amps based on the 12v of the battery, not the 240v of the appliance. Correct?

[WotEver]

I think I've deduced the answer from all this. When using a 240v appliance through an inverter, you calculate amps based on the 12v of the battery, not the 240v of the appliance. Correct?

Post #4:

Divide by 10. That allows for inefficiencies. It's also erring on the safe side.

[Paul C]

http://www.smartgauge.co.uk/tiny_loads.html

 

Inverter standby load (AKA quiescent current) "counts" as a small load.

[Murflynn]

how do you create a mash-up of confusion on CWDF?

 

................ ask a question about amps, hours and/or volts.

 

 

 

 

 

 

when will they ever learn?

 

 

 

 

 

 

 

 

 

 

 

fact: inverters are very inefficient at providing 240v at low currents.

fact: power requirements can always be related to voltage and current by P=V*i

fact: peak power requirements for appliances involving motors and compressors will always be many times more than the average requirement often quoted by manufacturers over a period of an hour, a day or a year.

Edited February 20, 2016 by Murflynn

[Loafer]

how do you create a mash-up of confusion on CWDF?

 

................ ask a question about amps, hours and/or volts.

 

 

 

 

 

 

when will they ever learn?

 

 

 

 

 

 

 

 

 

 

 

fact: inverters are very inefficient at providing 240v at low currents.

fact: power requirements can always be related to voltage and current by P=V*i

fact: peak power requirements for appliances involving motors and compressors will always be many times more than the average requirement often quoted by manufacturers over a period of an hour, a day or a year.

 

Not in AC terms. Power = VI cos phi (phase angle between the voltage and current).

 

cos phi = power factor. That's why you often see the units 'VA', or volts X amps, but it is only true for DC - or AC into a purely resistive load.

 

It can happen that your generator is thrashing its guts out providing 1000VA, but if the power factor is zero, then (because Power= VI x zero) the power produced is zero and no work is done. This means that you are using petrol to provide NO POWER, at MAX output of your generator!

 

Blimey, eh?

[Murflynn]

 

Not in AC terms. Power = VI cos phi (phase angle between the voltage and current).

 

cos phi = power factor. That's why you often see the units 'VA', or volts X amps, but it is only true for DC - or AC into a purely resistive load.

 

It can happen that your generator is thrashing its guts out providing 1000VA, but if the power factor is zero, then (because Power= VI x zero) the power produced is zero and no work is done. This means that you are using petrol to provide NO POWER, at MAX output of your generator!

 

Blimey, eh?

I was trying to keep it simple.

 

 

 

............. there's always one

[Loafer]

I was trying to keep it simple.

 

 

 

............. there's always one

 

It's always difficult when there's a pendant lurking! I consider it my duty to keep electrical stuff clean and pure! (Well as far as my ageing knowledge allows!)

[Loafer]

just imagine the chaos which would ensue if we allowed today's teenagers to mutilate the electrical language, like they have the parent one!

 

'Ere, Gaz, I got 45 wotsits out of me batteries last week, and I haven't put a single drop of lager in em'

 

'Wot?'

 

No, not Wotts. Them wot says 110 on the side'

 

'Ah them's amps, them...'

 

Scope here for a more comic writer!

Edited February 20, 2016 by Loafer

[Murflynn]

 

It's always difficult when there's a pendant lurking!

they were called chandeliers in my day.

[Loafer]

they were called chandeliers in my day.

 

Good spot! Bleedin predictive text!

[Iain_S]

 

Not in AC terms. Power = VI cos phi (phase angle between the voltage and current).

 

cos phi = power factor. That's why you often see the units 'VA', or volts X amps, but it is only true for DC - or AC into a purely resistive load.

 

It can happen that your generator is thrashing its guts out providing 1000VA, but if the power factor is zero, then (because Power= VI x zero) the power produced is zero and no work is done. This means that you are using petrol to provide NO POWER, at MAX output of your generator!

 

Blimey, eh?

 

And the generator's probably dead.

[ditchcrawler]

 

And the generator's probably dead.

That has to be a greeny

[Loafer]

That has to be a greeny

 

What about ME? All I that I said was TRUE! Ask Nicknorman!

 

And anyway, the generator wouldn't know that it wasn't actually providing any working power up the line, so should still be running.

 

Shouldn't it?

 

Edited for Wadworth's 6X

Edited February 21, 2016 by Loafer

[cuthound]

Reminds me of a standby generator course I once did. Due to lack of space, they gave you the control panel to work with (which had switchable faults on it).

 

I diagnosed all the fault quickly, so the lecturer gave me another.

 

I couldn't find the fault. He pointed out that it was an engine start fault, which didn't show up on the panel.

 

I responded by saying even if I was deaf and blind, I would still have noticed the lack of vibration through my feet if the engine had not of started.

[John V]

That reminds me of when I was doing the practical in my BOT Radar technicians exam.

They used to set 3 faults on a unit and you had a set time to diagnose and fix.

I found my three faults and the damn thing still didn't work properly and I was struggling.

It sort of worked but it was down on gain and not picking up targets that I knew it should.

Eventually (well after everyone else had finished and left) the examiner came over to check what I had done.

I had found all the faults he had put on the set but it had developed one of it's own.

It took the pair of us and a lot more sophisticated test gear than was permitted for the exam over an hour to track it down.

I passed

[Murflynn]

That reminds me of when I was doing the practical in my BOT Radar technicians exam.

They used to set 3 faults on a unit and you had a set time to diagnose and fix.

I found my three faults and the damn thing still didn't work properly and I was struggling.

It sort of worked but it was down on gain and not picking up targets that I knew it should.

Eventually (well after everyone else had finished and left) the examiner came over to check what I had done.

I had found all the faults he had put on the set but it had developed one of it's own.

It took the pair of us and a lot more sophisticated test gear than was permitted for the exam over an hour to track it down.

I passed

what you really mean is that you broke it

[system 4-50]

What a lot of discussion to resolve a simple problem. All you need is one of my Kwh/24hr to Amp converters, £50 each plus p&P. Yes I know it looks very like a bomb detector, but it has these extra wires coming out of one end. Hurry while stocks last.

[Murflynn]

you can find them cheaper on ebay, delivered free from Schenzhen.

[John V]

what you really mean is that you broke it

 

Actually it was a capacitor that was actually only about 10% of the rated value (from memory less than100pF when it should have been 750pF so no. If it had been oc or sc I would have found it. I would love to see you check the gain of one section of a multi valve IF strip armed with only an Avo 8.

 

A Polyscope was required (not allowed in a BOT exam) which was a high frequency combination of an oscilloscope and a wobbulator)

[Murflynn]

look, you lost me as soon as you mentioned radar.

 

but the unit was working before you tried to fix it, so circumstantial evidence is that you broke it.

you'd need the forensic team to prove you didn't - the unit can be the silent witness.

[John V]

Ah..... but the unit was not working "before I attempted to fix it" as you put it.

The examiner was probably not aware that the radar was not working correctly before he put his faults on.

I knew the targets that should show up on the 48 mile range, from that position, with a correctly working 50 Kw radar.

having used several of the radars in that installation and was aware of the respective ranges

When I repaired the "faults" that had been put there for the examination the radar worked, just not with the sensitivity that it should have.

I suspect I could have just said "finished" and still passed as the examiner would probably not be aware that the radar should be picking up the high ground about 20 miles away and wasn't.