Wattage of Refrigerator: Safe to Use This?

[Crossy]

2 hours ago, bankruatsteve said:

Is that for 100m of cable?  Wouldn't it be different for 1m?

 

It makes no difference.

 

The current rating of the cable doesn't change with length. The resistance and thus the volt drop increases with the run length so the voltage at the far end can drop to unacceptable levels but the cable isn't going to be damaged.

 

An example.

0.75mm² copper has a resistance of about 2.6 ohms per 100m, so a 100m run (out and back) will have a resistance of 5.2 ohms.

At its rated 6A that will drop V=IR = 6 * 5.2 = 31V  about 15% @ 220V. Enough to upset some appliances.

[junkofdavid2]

So there you have it.

 

My verdict: I'll try to change the extension if I can to a thicker cable (I dunno how easy it is to do that in Thailand).

 

If they don't let me, I'll just use it as is, since it's rated for it by "Thai industry standards" and just not leave it unattended.

 

Longest I ever use the oven is 30 minutes straight, and never at the maximum temperature of 230 C, probably 220 C at *most*.  (My normal practice for all appliances even my cooking stove is to never use the highest setting) 

 

 

.

[bankruatsteve]

10 minutes ago, Crossy said:

 

It makes no difference.

 

The current rating of the cable doesn't change with length. The resistance and thus the volt drop increases with the run length so the voltage at the far end can drop to unacceptable levels but the cable isn't going to be damaged.

 

An example.

0.75mm² copper has a resistance of about 2.6 ohms per 100m, so a 100m run (out and back) will have a resistance of 5.2 ohms.

At its rated 6A that will drop V=IR = 6 * 5.2 = 31V  about 15% @ 220V. Enough to upset some appliances.

Well, then it does make a difference.  Resistance is what will heat the cable not the voltage.  ????

 

[Crossy]

8 minutes ago, bankruatsteve said:

Well, then it does make a difference.  Resistance is what will heat the cable not the voltage.  ????

 

1m of our cable (0.026 ohms) with 6A flowing will dissipate I²R = 36*.026 = 0.936 Watts.

 

It doesn't matter if that 1m is on its own or part of a 100m run. The 100m will dissipate 93.6 Watts in total, but each metre will still be dissipating 0.936 Watts.

 

 

[Crossy]

21 minutes ago, junkofdavid2 said:

My verdict: I'll try to change the extension if I can to a thicker cable (I dunno how easy it is to do that in Thailand).

 

Look for a lead with a cable marked as "3 x 1.0mm²" which would be a "real" 10A rated cable. Sadly, I'm not sure you'll score.

 

As noted earlier, it will likely be fine, it's only a 15% overload, it will certainly get warm but shouldn't be a significant hazard. 

 

[bankruatsteve]

44 minutes ago, Crossy said:

 

1m of our cable (0.026 ohms) with 6A flowing will dissipate I²R = 36*.026 = 0.936 Watts.

 

It doesn't matter if that 1m is on its own or part of a 100m run. The 100m will dissipate 93.6 Watts in total, but each metre will still be dissipating 0.936 Watts.

 

 

Maybe i am just arguing with dead brain cells and for that I will apologize.  And I can't seem to Google an answer.  But what I recall is that electrical energy to heat energy is a relationship of amps, resistance and time.  To me the resistance would be the total resistance versus an incremental part of the load.  I'm thinking 100m of cable will get hotter over time than 1 m of the same cable.  And I'm sure, in the states anyway, both wire size AND length affected the amp rating of extension cords.

[Crossy]

8 minutes ago, bankruatsteve said:

I'm thinking 100m of cable will get hotter over time than 1 m of the same cable.

 

It will certainly dissipate 100x more power, but that power will be spread over 100 times the length. This is one reason why one shouldn't use your extension whilst coiled, the heat can't get out and things melt (or worse).

 

[sometimewoodworker]

8 minutes ago, bankruatsteve said:

I'm thinking 100m of cable will get hotter over time than 1 m of the same cable.

It also depends on how the 100m of cable is laid out as my mother found out when running about a 1kW or 2kW load without uncoiling the much shorter (maybe about 10m) extension and smelling the unmistakable odour of melting PVC. She lucky found it before it actually caught fire, but not much before. The extension became about a ½m one ???? 

[sometimewoodworker]

5 minutes ago, Crossy said:

 

It will certainly dissipate 100x more power, but that power will be spread over 100 times the length. This is one reason why one shouldn't use your extension whilst coiled, the heat can't get out and things melt (or worse).

 

I think that it’s not only heat from the load but also from the interaction of the magnet field, isn’t it!

[bankruatsteve]

27 minutes ago, bankruatsteve said:

And I'm sure, in the states anyway, both wire size AND length affected the amp rating of extension cords.

An example from Lowes.  And with that, I quit.  ????

[bankruatsteve]

Well, just one more.  I Googled:  "Hence the heating effect produced by an electric current, I through a conductor of resistance, R for a time, t is given by H = I²Rt."

 

Which would be an exponential effect of I not just linear effect of R.

[Crossy]

1 hour ago, bankruatsteve said:

Which would be an exponential effect of I not just linear effect of R.

 

Yup. But for our purposes I is a constant.

 

Why not do some worked examples?

 

The actual current rating of the cable does not change with length. Other important factors (volt drop) do change.

 

[Crossy]

1 hour ago, bankruatsteve said:

An example from Lowes.  And with that, I quit.  ????

 

12 AWG cable is typically rated for 20A or so, right hand unit. (not sure what the connectors are if any)

 

The left hand unit has US 15A connectors which is what is limiting the rating rather than the cable.

 

[bankruatsteve]

21 minutes ago, Crossy said:

 

Yup. But for our purposes I is a constant.

 

Why not do some worked examples?

 

OK. Then using above, 100m of cable would generate 600 times more heat than 1m. ?? I have no idea how cable is rated but suspect it's very conservative and recall (caveat dead brain cells) that short lengths of cable have more capacity due to the issue of overheating. 

[Crossy]

12 minutes ago, bankruatsteve said:

OK. Then using above, 100m of cable would generate 600 times more heat than 1m. ?? I have no idea how cable is rated but suspect it's very conservative and recall (caveat dead brain cells) that short lengths of cable have more capacity due to the issue of overheating. 

 

No, 100m will generate 100 times more heat in total assuming the same current through each (which negates the square law).

 

OK, if you recall that. Better if you can provide a source.

 

Cable is rated in Amps (and Volts for insulation), it is pretty conservative but the rating is for a conductor temperature of 75C.

 

See my signature.

[bankruatsteve]

53 minutes ago, Crossy said:

(which negates the square law).

So, you don't accept H=I²Rt?  My logic (which fails me at times) is:

 

Given I=10, R=0.1, t=10 and R=0.1 per 1m of conduit,  (constant I) then:

 

For 1m: H=100x0.1x10=100 (don't know what the units of H are)

For 2m: H=100x0.2x10=200

For 100m: H=100x10x10=10,000

 

Obviously, t would be limited to the boiling point of the conduit.  And there's probably more physics behind this equation that I don't remember or bother to research.

 

If heat is constant on the conduit, 10,000 versus 100 is a big difference.  If heat is the only (?) factor affecting ampacity rating, then length must make a difference.  I think the "rating" is based on some length (100m?) and some temperature well below the boiling point where the length is not a significant factor but nevertheless is and can be upgraded/downgraded accordingly.

 

This is what I understand and I'll stick by it.

 

 

[Crossy]

10 hours ago, bankruatsteve said:

So, you don't accept H=I²Rt?

 

Of course I accept Ohm's law!!! I does not change, so I² does not change, so the square has no effect on the result. If we have the same t then it too has no effect on the result.

 

Your logic is totally correct. The only thing that I think you may be missing is that 100m of whatever is 100 times longer than 1m of whatever. The heat of 10,000 is 100 times greater than 100. So the per-metre heat generated is exactly the same. Coil it all up in the same space as the 1m and you have significant heat build up.

 

Cables are rated in free-air, the actual current rating (ampacity) is determined by the ability of the heat generated to dissipate without reaching the temperature limits of the materials (a core temp of 75C for general use cables).

 

The unit of H would be Joules, but if we keep t constant then Watts are just fine (a Watt is a Joule per second).

[Jan Dietz]

Think of it like this:

 

If length would matter, how would fuses work? (the ones with a small wire in it, not the resettable ones)

it's only a cm or so, it would never burn.

 

[jastheace]

35 minutes ago, Jan Dietz said:

Think of it like this:

 

If length would matter, how would fuses work? (the ones with a small wire in it, not the resettable ones)

it's only a cm or so, it would never burn.

 

????

[Jan Dietz]

2 hours ago, Jan Dietz said:

Think of it like this:

 

If length would matter, how would fuses work? (the ones with a small wire in it, not the resettable ones)

it's only a cm or so, it would never burn.

 

Wouldn't*

[junkofdavid2]

Changed to very thick 1.5 just in case ????

 

1) To minimize kinks/bends, I stuck it to the wall upside down... (See attached). Any issue with that?

 

2) Is it ok if the coil's extra slack behind fridge touches back of the fridge like compressor, etc?

 

 

[sometimewoodworker]

1 hour ago, junkofdavid2 said:

Changed to very thick 1.5 just in case ????

 

1) To minimize kinks/bends, I stuck it to the wall upside down... (See attached). Any issue with that?

 

2) Is it ok if the coil's extra slack behind fridge touches back of the fridge like compressor, etc?

 

 

Depending on the fridge the compressor can get significantly hot so best to keep it away from that.

[JAS21]

On 11/18/2019 at 5:50 AM, Jan Dietz said:

Wouldn't*

It wouldn’t never burn does not sound quite right either....????

[Metropolitian]

On 11/12/2019 at 8:37 PM, junkofdavid2 said:

Attached is my circuit switch...

Toshino is considered a good brand, but I wouldn't overdo the amp as it says.

The wire diameter is 0.75sqmm/18.5AWG. That wire has short maximum of 16 amp and for DC 3AMP. But I would strongly advice to not exceeding 6 amp for a while.

Also don't go on what the package is saying, it says 10 AMP 250V and 2300W. This doesn't really add exept for the watt rating, its a MAX rating for continuous use.

At 6 amp, on 3 meter you will get a small voltage drop of 0.5 volt and that wouldn't burn the wire.

 

The frigidator is rated at 190 watt, 160 for the cooling power and 0.8 watt for the led lights.

The info gives also 220 volt and 0.9 ampwatt. That is 198 watt.  Another print says 418kWh on one year, that's with moderate use and no leaking.

So to stay on the safe side say your fridge is 200watt max.

 

Your oven. 1300 watt. Together, 1500 watt.

I would say, that 'circuit switch' is ok to use.

 

BUT... Don't plug in out in out the plug too many times, as the contacts will get loose, sparks will make black marks and creating an resistance layer which will heat up and that is where many connections fails.

 

The best solution is replacing the socket on the wall for a 2 gang one. 

 

We don't know if you are owning or renting and is allowed to change or not but then you can just ask the owner.

 

 

 

[Metropolitian]

On 11/12/2019 at 8:57 PM, junkofdavid2 said:

Wow, do fridges really have such low wattage? 

I'm more surprised about the fridge being labelled as just 160 watts max ????

You would be surprised if you know that most bigger, and newer, fridges are rated lower.

Split doors and inverter are generally lower in power usage too.

Mine is  2 meter tall and uses 'only' 70 watt.

 

But the energy consummation here is high with my family which I could offer a seat and a bag of chips when they are standing in front of it with the door all open..for a while.