Electro Frying Forum - Long 32A Power leads

Long 32A Power leads

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Category: General
Forum Name: Electro Frying Forum
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URL: https://forum.speakerplans.com/forum_posts.asp?TID=23741
Printed Date: 07 December 2023 at 5:51am
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Topic: Long 32A Power leads

Posted By: levyte357
Subject: Long 32A Power leads
Date Posted: 06 February 2009 at 6:38pm

Am I correct in presuming 6mm cable will allow 50M with negligible power loss?

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"Who am I? I'm the guy who does his job.. You must be the other guy".

Replies:

Posted By: a1dl
Date Posted: 06 February 2009 at 7:14pm

in a word, yes.

we often run circa 100m and voltage drop is only about 3v

Posted By: levyte357
Date Posted: 06 February 2009 at 7:27pm

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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"Who am I? I'm the guy who does his job.. You must be the other guy".

Posted By: Ben_Lawrance
Date 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)

Posted By: ceharden
Date 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.

Posted By: levyte357
Date Posted: 07 February 2009 at 1:37pm

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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"Who am I? I'm the guy who does his job.. You must be the other guy".

Posted By: jonminns
Date 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

Posted By: roborg
Date 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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What I cannot create, I do not understand

Posted By: roborg
Date 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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What I cannot create, I do not understand

Posted By: mk2_ginger_biscuit69
Date 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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''Remember that the object of a subwoofer is to enhance the output of your main speakers, not overpower it''

''Dubstep - an elongated electronic fart''

Posted By: shagnasty
Date 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!!!