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Long 32A Power leads

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levyte357 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Topic: Long 32A Power leads
    Posted: 06 February 2009 at 6:38pm
Am I correct in presuming 6mm cable will allow 50M with  negligible power loss?

Edited by levyte357 - 06 February 2009 at 6:40pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote a1dl Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2009 at 7:14pm
in a word, yes.
 
we often run circa 100m and voltage drop is only about 3v


Edited by a1dl - 06 February 2009 at 7:15pm
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levyte357 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2009 at 7:27pm
Originally posted by a1dl a1dl wrote:

in a word, yes.
 
we often run circa 100m and voltage drop is only about 3v


Which is not so bad if you are starting out with 240V; I'm assuming this is the case whenever you are dealing with dedicated 32A feed, as opposed to ring main which could be 220-240V ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ben_Lawrance Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2009 at 7:45pm
Don't forget that volt drop is proportional to current. (ambient temperature plays a small part as well)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2009 at 8:00pm
6mm is sensible cable for long 32A runs.  I use 6mm for all my 32A cables because I think 4mm is a little on the thin side.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 07 February 2009 at 1:37pm
Originally posted by ceharden ceharden wrote:

6mm is sensible cable for long 32A runs.  I use 6mm for all my 32A cables because I think 4mm is a little on the thin side.


What would you consider as the longest suitable length using 4mm H07 3x core ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonminns Quote  Post ReplyReply Direct Link To This Post Posted: 07 February 2009 at 2:40pm
5-10m would be a sensible limit for 4mm providing the duty cycle isn't too high... ie it's an amp rack not drawing full power. If this is for catering or something the maximum length for 4mm doesn't exist and it shouldn't be used.

I'd advise spending a tad extra and going for 6mm.

Jon


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Post Options Post Options   Thanks (0) Thanks(0)   Quote roborg Quote  Post ReplyReply Direct Link To This Post Posted: 07 February 2009 at 8:52pm
If you're running the cable close to 32A you will still loose alot of power with 6mm2, but it will be adequate thermally.  If you want to power lighting or thirsty amps i'd recommend using a 63a cable & distro for long runs.  The lights will be brighter & the amps louder!
  Cable cross sections are specified for safe operating temperature rather than reasonable voltage drop.  I think 5core 32amp H07RN-F needs to be 6mm2 to be 'safe' under all conditions. 
  Bear in mind most safe 63 amp rated cables are 16mm2 per core, so half that and 32 amps would need 8mm2 for the same voltage drop, IE to be relatively as good as a 63amp cable.
this is useful:
Current ratings for H07 RN-F (H07RN-F) for current supply in industrial application 
Operating temperature at conductor +60°C/+140°F, ambient temperature +30°C/+86°F (Air)
Number of Conductors 1-conductor 2-conductor 3-conductor 3-conductor 4-conductor 5-conductor
Number of
loaded conductors
2 loaded 3 loaded 2 loaded 2 loaded 3 loaded 3 loaded 3 loaded
Cross-section in mm2 Current ratings in Ampere
4 34 30 34 35 29 30 30
6 43 38 43 44 36 37 38
10 60 53 60 62 51 52 54
16 79 71 79 82 67 69 71
25 104 94 105 109 89 92 94
35 129 117 - 135 110 114 -
50 162 148 - 169 138 143 -
70 202 185 - 211 172 178 -
95 240 222 - 250 204 210 -
120 280 260 - 292 238 246 -
150 321 300 - 335 273 282 -
185 363 341 - 378 309 319 -
240 433 407 - 447 365 377 -
300 497 468 - 509 415 430 -
400 586 553 - - - - -
500 670 634 - - - - -
630 784 742 - - - - -
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote roborg Quote  Post ReplyReply Direct Link To This Post Posted: 07 February 2009 at 9:22pm
just found an old spread sheet on this:
  
cable losses     current 32 amps        
mm2 length cable resistance (ohms)   cable voltage drop (volts)   cable power loss (watts)
    20C 60C 100C 20C 60C 100C 20C 60C 100C
1.5 5 0.0573 0.0663 0.0752 1.8 2.1 2.4 59 68 77
1.5 10 0.1147 0.1326 0.1504 3.7 4.2 4.8 117 136 154
1.5 20 0.2293 0.2651 0.3009 7.3 8.5 9.6 235 271 308
1.5 50 0.5733 0.6628 0.7522 18.3 21.2 24.1 587 679 770
2.5 5 0.0344 0.0398 0.0451 1.1 1.3 1.4 35 41 46
2.5 10 0.0688 0.0795 0.0903 2.2 2.5 2.9 70 81 92
2.5 20 0.1376 0.1591 0.1805 4.4 5.1 5.8 141 163 185
2.5 50 0.3440 0.3977 0.4513 11.0 12.7 14.4 352 407 462
4 5 0.0215 0.0249 0.0282 0.7 0.8 0.9 22 25 29
4 10 0.0430 0.0497 0.0564 1.4 1.6 1.8 44 51 58
4 20 0.0860 0.0994 0.1128 2.8 3.2 3.6 88 102 116
4 50 0.2150 0.2485 0.2821 6.9 8.0 9.0 220 255 289
6 5 0.0143 0.0166 0.0188 0.5 0.5 0.6 15 17 19
6 10 0.0287 0.0331 0.0376 0.9 1.1 1.2 29 34 39
6 20 0.0573 0.0663 0.0752 1.8 2.1 2.4 59 68 77
6 50 0.1433 0.1657 0.1881 4.6 5.3 6.0 147 170 193
10 5 0.0086 0.0099 0.0113 0.3 0.3 0.4 9 10 12
10 10 0.0172 0.0199 0.0226 0.6 0.6 0.7 18 20 23
10 20 0.0344 0.0398 0.0451 1.1 1.3 1.4 35 41 46
10 50 0.0860 0.0994 0.1128 2.8 3.2 3.6 88 102 116
16 5 0.0054 0.0062 0.0071 0.2 0.2 0.2 6 6 7
16 10 0.0108 0.0124 0.0141 0.3 0.4 0.5 11 13 14
16 20 0.0215 0.0249 0.0282 0.7 0.8 0.9 22 25 29
16 50 0.0538 0.0621 0.0705 1.7 2.0 2.3 55 64 72
25 5 0.0034 0.0040 0.0045 0.1 0.1 0.1 4 4 5
25 10 0.0069 0.0080 0.0090 0.2 0.3 0.3 7 8 9
25 20 0.0138 0.0159 0.0181 0.4 0.5 0.6 14 16 18
25 50 0.0344 0.0398 0.0451 1.1 1.3 1.4 35 41 46
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mk2_ginger_biscuit69 Quote  Post ReplyReply Direct Link To This Post Posted: 10 February 2009 at 3:37pm
must also note these are charts for a certain 'brand' of cable. cheaper cores will often not perform anywhere near as well as a more expensive core. as much as the above table is a useful guide, it is not concrete. every manufactorer of cable should have a table of test results as above available.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shagnasty Quote  Post ReplyReply Direct Link To This Post Posted: 10 February 2009 at 6:03pm
Another thing to remeber, use bootlace furrells when making off ho7 (i use on everything) but particularly on the bigger stuff as over time the screws seem to cut into the strands giving a loose connection which will heat up. I have have a prob with sub-hired cables on heavy load but never one of mine I bootlaced.
 
I never use 1.5 on 16A, 4mm on 32 or 10mm on 63A as I like all my cables to be able to run anything, you know the gigs where you have to join 20 5m cables to make the 100m run to the delay tower no-one mentioned... :-)
 
If you want to easily see what is going on meter between n and E @ the load with a true RMS meter set to AC volts, consider anything more than a couple of % of line voltage here to be un-acceptable, of course check the source end as well so you know the line supply is doing!!!
 
 
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