Omission of overload protection for fixed loads.

[stuartcourt]

I feel a long novel coming on

 

[electric will]

Did anyone see it before it was edited?

 

[electric will]

Did anyone see it before it was edited?

Oh I see the table has gone, fair enough. But what was in post 17?

 

[spark 68]

Did anyone see it before it was edited?

Yep,

It was your previous post: "are you sure etc." followed by: "are you sure you want want to ask that question on an open forum ?"

I was going to quote it, but by the time I finished typing it had gone. :13:

 

[Outspoken]

Guys, please let me offer my apologies. Thought quick after wine and screwed up...the last part of my posts is correct, but the middle bit was not accurate at all...THANKS WILL...what a stupid error, I was thinking fixed resistance and worked it out on fixed power..DOH!!

I feel rather embarrassed now that I could make such a fundermental cock up...

Now my argument was correct, but i posted it the wrong way round as I just said..this is what the table should have looked like...with a FIXED RESISTIVE LOAD!!

[TABLE="width: 1101"]
[TR]
[TD]Voltage (V)[/TD]
[TD]Load (W)[/TD]
[TD]Fixed resistance[/TD]
[TD]Current (A)[/TD]
[TD]Load (W)[/TD]
[TD]Fixed resistance[/TD]
[TD]Current (A)[/TD]
[TD]Load (W)[/TD]
[TD]Fixed resistance[/TD]
[TD]Current (A)[/TD]
[TD]Load (W)[/TD]
[TD]Fixed resistance[/TD]
[TD]Current (A)[/TD]
[/TR]
[TR]
[TD]260[/TD]
[TD]11,502.47[/TD]
[TD]5.877[/TD]
[TD]44.24[/TD]
[TD]13,418.02[/TD]
[TD]5.038[/TD]
[TD]51.61[/TD]
[TD]15,977.31[/TD]
[TD]4.231[/TD]
[TD]61.45[/TD]
[TD]19,171.87[/TD]
[TD]3.526[/TD]
[TD]73.74[/TD]
[/TR]
[TR]
[TD]255[/TD]
[TD]11,064.32[/TD]
[TD]5.877[/TD]
[TD]43.39[/TD]
[TD]12,906.91[/TD]
[TD]5.038[/TD]
[TD]50.62[/TD]
[TD]15,368.71[/TD]
[TD]4.231[/TD]
[TD]60.27[/TD]
[TD]18,441.58[/TD]
[TD]3.526[/TD]
[TD]72.32[/TD]
[/TR]
[TR]
[TD]250[/TD]
[TD]10,634.68[/TD]
[TD]5.877[/TD]
[TD]42.54[/TD]
[TD]12,405.72[/TD]
[TD]5.038[/TD]
[TD]49.62[/TD]
[TD]14,771.92[/TD]
[TD]4.231[/TD]
[TD]59.09[/TD]
[TD]17,725.47[/TD]
[TD]3.526[/TD]
[TD]70.90[/TD]
[/TR]
[TR]
[TD]245[/TD]
[TD]10,213.54[/TD]
[TD]5.877[/TD]
[TD]41.69[/TD]
[TD]11,914.45[/TD]
[TD]5.038[/TD]
[TD]48.63[/TD]
[TD]14,186.95[/TD]
[TD]4.231[/TD]
[TD]57.91[/TD]
[TD]17,023.54[/TD]
[TD]3.526[/TD]
[TD]69.48[/TD]
[/TR]
[TR]
[TD]240[/TD]
[TD]9,800.92[/TD]
[TD]5.877[/TD]
[TD]40.84[/TD]
[TD]11,433.11[/TD]
[TD]5.038[/TD]
[TD]47.64[/TD]
[TD]13,613.80[/TD]
[TD]4.231[/TD]
[TD]56.72[/TD]
[TD]16,335.79[/TD]
[TD]3.526[/TD]
[TD]68.07[/TD]
[/TR]
[TR]
[TD]235[/TD]
[TD]9,396.80[/TD]
[TD]5.877[/TD]
[TD]39.99[/TD]
[TD]10,961.69[/TD]
[TD]5.038[/TD]
[TD]46.65[/TD]
[TD]13,052.47[/TD]
[TD]4.231[/TD]
[TD]55.54[/TD]
[TD]15,662.22[/TD]
[TD]3.526[/TD]
[TD]66.65[/TD]
[/TR]
[TR]
[TD]230[/TD]
[TD]9,001.19[/TD]
[TD]5.877[/TD]
[TD]39.14[/TD]
[TD]10,500.20[/TD]
[TD]5.038[/TD]
[TD]45.65[/TD]
[TD]12,502.95[/TD]
[TD]4.231[/TD]
[TD]54.36[/TD]
[TD]15,002.84[/TD]
[TD]3.526[/TD]
[TD]65.23[/TD]
[/TR]
[TR]
[TD]225[/TD]
[TD]8,614.09[/TD]
[TD]5.877[/TD]
[TD]38.28[/TD]
[TD]10,048.63[/TD]
[TD]5.038[/TD]
[TD]44.66[/TD]
[TD]11,965.26[/TD]
[TD]4.231[/TD]
[TD]53.18[/TD]
[TD]14,357.63[/TD]
[TD]3.526[/TD]
[TD]63.81[/TD]
[/TR]
[TR]
[TD]220[/TD]
[TD]8,235.49[/TD]
[TD]5.877[/TD]
[TD]37.43[/TD]
[TD]9,606.99[/TD]
[TD]5.038[/TD]
[TD]43.67[/TD]
[TD]11,439.38[/TD]
[TD]4.231[/TD]
[TD]52.00[/TD]
[TD]13,726.60[/TD]
[TD]3.526[/TD]
[TD]62.39[/TD]
[/TR]
[TR]
[TD]215[/TD]
[TD]7,865.41[/TD]
[TD]5.877[/TD]
[TD]36.58[/TD]
[TD]9,175.27[/TD]
[TD]5.038[/TD]
[TD]42.68[/TD]
[TD]10,925.31[/TD]
[TD]4.231[/TD]
[TD]50.82[/TD]
[TD]13,109.76[/TD]
[TD]3.526[/TD]
[TD]60.98[/TD]
[/TR]
[TR]
[TD]210[/TD]
[TD]7,503.83[/TD]
[TD]5.877[/TD]
[TD]35.73[/TD]
[TD]8,753.47[/TD]
[TD]5.038[/TD]
[TD]41.68[/TD]
[TD]10,423.07[/TD]
[TD]4.231[/TD]
[TD]49.63[/TD]
[TD]12,507.09[/TD]
[TD]3.526[/TD]
[TD]59.56[/TD]
[/TR]
[TR]
[TD]205[/TD]
[TD]7,150.76[/TD]
[TD]5.877[/TD]
[TD]34.88[/TD]
[TD]8,341.60[/TD]
[TD]5.038[/TD]
[TD]40.69[/TD]
[TD]9,932.64[/TD]
[TD]4.231[/TD]
[TD]48.45[/TD]
[TD]11,918.60[/TD]
[TD]3.526[/TD]
[TD]58.14[/TD]
[/TR]
[TR]
[TD]200[/TD]
[TD]6,806.19[/TD]
[TD]5.877[/TD]
[TD]34.03[/TD]
[TD]7,939.66[/TD]
[TD]5.038[/TD]
[TD]39.70[/TD]
[TD]9,454.03[/TD]
[TD]4.231[/TD]
[TD]47.27[/TD]
[TD]11,344.30[/TD]
[TD]3.526[/TD]
[TD]56.72[/TD]
[/TR]
[TR]
[TD]190[/TD]
[TD]6,142.59[/TD]
[TD]5.877[/TD]
[TD]32.33[/TD]
[TD]7,165.54[/TD]
[TD]5.038[/TD]
[TD]37.71[/TD]
[TD]8,532.26[/TD]
[TD]4.231[/TD]
[TD]44.91[/TD]
[TD]10,238.23[/TD]
[TD]3.526[/TD]
[TD]53.89[/TD]
[/TR]
[TR]
[TD]180[/TD]
[TD]5,513.02[/TD]
[TD]5.877[/TD]
[TD]30.63[/TD]
[TD]6,431.12[/TD]
[TD]5.038[/TD]
[TD]35.73[/TD]
[TD]7,657.76[/TD]
[TD]4.231[/TD]
[TD]42.54[/TD]
[TD]9,188.88[/TD]
[TD]3.526[/TD]
[TD]51.05[/TD]
[/TR]
[TR]
[TD]170[/TD]
[TD]4,917.47[/TD]
[TD]5.877[/TD]
[TD]28.93[/TD]
[TD]5,736.40[/TD]
[TD]5.038[/TD]
[TD]33.74[/TD]
[TD]6,830.54[/TD]
[TD]4.231[/TD]
[TD]40.18[/TD]
[TD]8,196.26[/TD]
[TD]3.526[/TD]
[TD]48.21[/TD]
[/TR]
[TR]
[TD]160[/TD]
[TD]4,355.96[/TD]
[TD]5.877[/TD]
[TD]27.22[/TD]
[TD]5,081.38[/TD]
[TD]5.038[/TD]
[TD]31.76[/TD]
[TD]6,050.58[/TD]
[TD]4.231[/TD]
[TD]37.82[/TD]
[TD]7,260.35[/TD]
[TD]3.526[/TD]
[TD]45.38[/TD]
[/TR]
[/TABLE]

 

[SimpleSimon]

This is a really good debate, Darkwood has bought up a really good point that I've honestly never thought of in a domestic situation.

Personally I don't think anybody should be using this reg in domestic situations. A shower is a fixed load, same as a water immersion. But along could come Jo blogs and add this on add that on and than a fixed load is a lot larger.

I though will be using this reg to my advantage.
in the airport where I work we see a lot of lighting MCBs tripping out when contactors click over. These circuits serve fixed display stands in shops that never change and nor do the install conditions apsurrounding it.
Where nuisance tripping had occurred on the inrush of florescent tubes even on D16 breakers we than can look at upgrading the breaker to D20/32.

 

[electric will]

So now your meaning if the voltage should rise the current will increase? I agree but do we really need to consider this in our circuit designs?
Looking at your table if the voltage increased from 240 to 250 the current would increase by less that 2 amps.

just to add, I wouldn't depend on this on a new circuit anyway, maybe like others said I'd consider it replacing a shower.

 

[44ALLAN]

No need to apologise..............great info and like Simon says(had to say that lol)....really good debate and info thanks.

 

[Marvo]

Certain supply neutral faults can cause can cause a voltage far above 250v.

I'm not familiar with the UK regs but I agree this is an interesting debate, I hope it can stay on track.

 

[44ALLAN]

So now your meaning if the voltage should rise the current will increase? I agree but do we really need to consider this in our circuit designs?
Looking at your table if the voltage increased from 240 to 250 the current would increase by less that 2 amps.

just to add, I wouldn't depend on this on a new circuit anyway, maybe like others said I'd consider it replacing a shower.

Will.... that was his whole point I think)..............trying to make people understand it can't be a fixed load without any chance of overload if the voltage can increase by such margins.

 

[Silly Sausage]

Oh deary me, what appeared at first to be a serious discussion, with self proclaimed superior engineers, then falls apart mid thread with an elementary electrical theory error...and all the abuse 5WWs get!

You've got to laugh!!!! :ciappa::smilielol5::smilielol5::smilielol5:

 

[Darkwood]

Outspoken ... just to relay a answer to your reply regarding back tracking i read my first post as stating the regs do permit it on a water heater but i also state that i dont believe it should be applied in a domestic environment when in commercial or industrial the environment is usually more controlled and likely to remain as installed, if your playing the voltage change card this could apply to any circuit calculation you make where you enter 230v as nominal voltage, the regulations have tolerances on the caution built in to the tables to allow for these things, we are told to calculate to 230v but im 99% of the time seeing voltage in the mid 230s to mid 240s yet we still use 230v when designing a circuit.

 

[Darkwood]

This is a really good debate, Darkwood has bought up a really good point that I've honestly never thought of in a domestic situation.

Personally I don't think anybody should be using this reg in domestic situations. A shower is a fixed load, same as a water immersion. But along could come Jo blogs and add this on add that on and than a fixed load is a lot larger.

I though will be using this reg to my advantage.
in the airport where I work we see a lot of lighting MCBs tripping out when contactors click over. These circuits serve fixed display stands in shops that never change and nor do the install conditions apsurrounding it.
Where nuisance tripping had occurred on the inrush of florescent tubes even on D16 breakers we than can look at upgrading the breaker to D20/32.

What would happen to your permitted Zs its this that usually limits you from doing this, you still have to meet requirements in the event of a short circuit.
You shouldn't be applying this really because you have designed the circuit wrong and put more fittings than the mcb manufacturers guidance notes, the discussed regulation should only be applied when its impractical to have the mcb lower than the ccc of the cable in which as an example is a motor circuit where trying to keep the mcb high enough to allow for inrush yet ensuring the cable isn't 2 -4 times larger than necessary for the fLC of the motor which has its own O/L protection anyway.

 

[44ALLAN]

He's comatose :rolleyes2::54:

 

[SimpleSimon]

What would happen to your permitted Zs its this that usually limits you from doing this, you still have to meet requirements in the event of a short circuit.

It's exactly as you put it, my Zs would limit me. I could move it from a 16 to a 20 but a you say unless it was 4mm I'd be kinda stuck there, usually these are 4mm because of the volt drop and 16 because of the small load.

 

[spark 68]

Another Possible limitation is if there are any B15,B22,E14,E27 and E40 fittings anywhere on the circuit, as the max OCPD for any of these is 16A.

 

[Darkwood]

It's exactly as you put it, my Zs would limit me. I could move it from a 16 to a 20 but a you say unless it was 4mm I'd be kinda stuck there, usually these are 4mm because of the volt drop and 16 because of the small load.

I edited my last response to you, you be good to get technical tables from your mcb manufacturers as these state the amount of different types of lamps you can have on a given mcb and this is what you have fallen foul off here.

 

[SimpleSimon]

Another Possible limitation is if there are any B15,B22,E14,E27 and E40 fittings anywhere on the circuit, as the max OCPD for any of these is 16A.

Good point, but they are usually LED drivers and tape and fluorescent fittings.

 

[SimpleSimon]

I edited my last response to you, you be good to get technical tables from your mcb manufacturers as these state the amount of different types of lamps you can have on a given mcb and this is what you have fallen foul off here.

Would these include fluorescent fittings and LEDs?

 

[Outspoken]

Oh deary me, what appeared at first to be a serious discussion, with self proclaimed superior engineers, then falls apart mid thread with an elementary electrical theory error...and all the abuse 5WWs get!

You've got to laugh!!!! :ciappa::smilielol5::smilielol5::smilielol5:

Now that is misreading reality if ever there was a case of it Archy, but glad you had a laugh at my expense..