Extension lead on compressor

Submitted: Thursday, May 28, 2020 at 19:57
ThreadID: 140080 Views:2491 Replies:11 FollowUps:30
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I need to extend the reach of my compressor to air-up trailer tyres. I would prefer to extend the power lead by 5 metres rather than add-on extra hose. The compressor info states it is 45 Amp.
Can someone please advise me if 6mm 50A twin sheath cable is OK for this task.
Thank you
Ian
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Reply By: Frank P (NSW) - Thursday, May 28, 2020 at 20:19

Thursday, May 28, 2020 at 20:19
There would be a big voltage drop with 6mm twin cable and your compressor may run slow. Better to add extra hose.

If you must use an electrical extension, use 8AWG twin sheath. That may work.
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Follow Up By: Gronk - Thursday, May 28, 2020 at 20:51

Thursday, May 28, 2020 at 20:51
I would be using 5 AWG......stupid USA standard ........or in "proper" size, 16mm2 cable.
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Follow Up By: Frank P (NSW) - Thursday, May 28, 2020 at 22:03

Thursday, May 28, 2020 at 22:03
How about 8 (or 5) Gauge - no nationalism there. Or Browne & Sharpe (B&S)? That's a British standard.

Agree, neither is better than mm2. Do the Yanks do mm2?

And none is as stupid as auto cable sizes in mm diameter, as used widely in Australia, where the cable size includes the plastic insulation. Yep, a hair of copper in a thick plastic tube = 6mm. It's BS, and that's quite different from B&S. LOL
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Follow Up By: Blown4by - Thursday, May 28, 2020 at 22:52

Thursday, May 28, 2020 at 22:52
I always thought B&S stood for Battery & Starter.
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Follow Up By: ian - Thursday, May 28, 2020 at 23:58

Thursday, May 28, 2020 at 23:58
Thanks for your advice Frank
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Follow Up By: Frank P (NSW) - Friday, May 29, 2020 at 11:04

Friday, May 29, 2020 at 11:04
"Or Browne & Sharpe (B&S)? That's a British standard."

Apologies, Gronk, that's quite wrong.

Brown & Sharpe, an American company, developed their wire gauge in the mid 19th century. It subsequently became AWG. Link

The Brits had a number of standards through the ages, culminating in their own Standard Wire Gauge (SWG) in 1964. According to the same link, that was withdrawn and replaced in 1986 by the metric standard.

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Follow Up By: Zippo - Friday, May 29, 2020 at 12:52

Friday, May 29, 2020 at 12:52
Frank, the yanks don't even do mm let alone mm2.
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Reply By: Peter_n_Margaret - Thursday, May 28, 2020 at 20:56

Thursday, May 28, 2020 at 20:56
Air hose extension will be lighter and MUCH cheaper.
Cheers,
Peter
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Follow Up By: ian - Thursday, May 28, 2020 at 23:59

Thursday, May 28, 2020 at 23:59
Thanks Peter
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Follow Up By: Member - nickb "boab" - Friday, May 29, 2020 at 20:06

Friday, May 29, 2020 at 20:06
agree : I made up an extension air hose recently .. just used the regular hardware hose 100 psi as its not under huge pressure . In this case i would go for a larger diameter hose for the extension from the pump & then the existing hose . after all how often is it going to be used ??
Cheers Nick b
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Reply By: Mark C9 - Thursday, May 28, 2020 at 20:57

Thursday, May 28, 2020 at 20:57
yes you will get a big voltage drop. Have you thought about running a permanent air line from the compressor to the rear of the tow
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Follow Up By: ian - Friday, May 29, 2020 at 00:00

Friday, May 29, 2020 at 00:00
Thanks Mark
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Reply By: bellony - Thursday, May 28, 2020 at 22:17

Thursday, May 28, 2020 at 22:17
If you have a trailer do you have an anderson plug at the rear of the car?
If yes, convert the compressor to an anderson plug and problem solved.
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Follow Up By: ian - Friday, May 29, 2020 at 00:02

Friday, May 29, 2020 at 00:02
Thanks bellony.
That seems like a good move
Ian
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Follow Up By: Member - peter_mcc - Friday, May 29, 2020 at 10:57

Friday, May 29, 2020 at 10:57
Came here to say the same thing - cut the compressor lead 30cms from the end and add in 2 Anderson plugs. Then you can plug it into the back of the car or use the current clips.
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Follow Up By: rumpig - Friday, May 29, 2020 at 21:51

Friday, May 29, 2020 at 21:51
Make lead long enough for the compressor to sit on the ground atleast
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Follow Up By: Member - Trevor_H - Saturday, May 30, 2020 at 20:03

Saturday, May 30, 2020 at 20:03
I also split the compressor leads and added 2 Anderson plugs. Don't forget to leave the car motor running when the compressor is. You don't need to have inflated trailer tyres at the expense of a flat starter battery.
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Follow Up By: Macquarie - Tuesday, Jun 02, 2020 at 11:04

Tuesday, Jun 02, 2020 at 11:04
If you are about to fit an Anderson plug at the rear of the vehicle just ensure that the wiring from the battery in the engine bay to the Anderson plug is of sufficient size to carry the load. Some portable compressors such as the ARB twin motor one have 50 amp fuses, anywhere near that level of current could overwhelm light wiring to an Anderson plug.
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Reply By: RMD - Friday, May 29, 2020 at 07:43

Friday, May 29, 2020 at 07:43
I use an Anderson plug at vehicle rear and suitable length of hose to tyres. If remote, I use a 38ah battery which usually is Anderson plug connected to the vehicle aux batt. Disconnect it and take compressor and battery to the trailer, which may be metres away or even next door.
You have the compressor, you have the hose, the multi use battery will almost be cheaper than the cable which doesn't give a high degree of flexibility.
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Follow Up By: Mark C9 - Friday, May 29, 2020 at 08:11

Friday, May 29, 2020 at 08:11
When pumping water from creeks etc, I used to run a 50m lead from the car to the pump but the voltage drop was massive.
Now I just take a lightweight 50a/h lithium batt down to the creek and use that to power the pump.
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Follow Up By: ian - Friday, May 29, 2020 at 12:01

Friday, May 29, 2020 at 12:01
thanks RMD
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Reply By: Phil G - Friday, May 29, 2020 at 09:57

Friday, May 29, 2020 at 09:57
I also have a 45A compressor and yes you'll need 8B&S for an extended cable.
I mount the compressor in the back of the vehicle. That way the hose doesn't need to be overly long to reach all caravan and car tyres.
But as someone suggested above, you could hook up to the anderson plug. Even with the standard 6B&S to your anderson plug, voltage drop can slow the compressor and be compensated by running your motor.
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Follow Up By: ian - Friday, May 29, 2020 at 11:59

Friday, May 29, 2020 at 11:59
thanks Phil
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Follow Up By: Allan B (Sunshine Coast) - Friday, May 29, 2020 at 18:47

Friday, May 29, 2020 at 18:47
.
C'mon Phil, stop with the "B&S". Just always use the metric "mm2" which is sensible and universal to the rest of the world. Leave those Yanks to just stew in their own parochial dogma.
Cheers
Allan

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Follow Up By: Phil G - Saturday, May 30, 2020 at 15:48

Saturday, May 30, 2020 at 15:48
Gday Allan,
Cable size is very hard to express on forums!!

It is impossible to type "millimetre squared" in an abbreviated form because this forum doesn't allow superscript.
Some people type mm2 which is not correct.
Others type mmsq which is a bit better.
Others think mm2 or mmsq is the same as mm and think 6mm auto is the same as 6 B&S
Others think 6mm auto cable is the diameter including the insulation - its not - because 6mm auto measures 4.5mm diameter and is about 4.5mmsq.
In any case the stuff I use is not 8mmsq, it is either 7.91 mmsq or 7.7mmsq!

Buy the cable from Jaycar and it will be 8AWG or 8Ga
Narva use 8B&S
Tycab use 8B&S
Lugs will be 8B&S
Tinned cable from Whitworths is 8B&S.

So when answering in forums, I use the measurement that is the least confusing to a general audience and which the shops use which is 8B&S!!

Cheers
Phil
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Follow Up By: Allan B (Sunshine Coast) - Saturday, May 30, 2020 at 16:45

Saturday, May 30, 2020 at 16:45
.
Yeah Phil, I know, I know, I know! Have you had chat with mate Donald lately? lol
I grew up with "inch" cable specs. e.g. '7/.029' meant 7 strands each 0.029 inches diameter.
Then Australia thankfully metricated and I converted to metric cable as "4mm2" e.g. Of course as superscript is not accepted here (and in any case, my keyboard does not offer it) I write mm2 which, rather surprisingly, everyone seems to understand as an alternate to the superscript.

Now, in any case, as I don't care what Narva, Tycab et al call it as I don't buy from them I continue to use the nomenclature standard of the Australian electrical industry which is "mm squared' and write "mm2".
And incidentally, Jaycar generally use "AWG" not "B&S". Sometimes adding "mm2 cross sectional area".

If I really must acquiesce to avoid serious confusion I may reluctantly specify "B&S", but I will never say "gauge" or some "auto size".
But if you say "B&S" I will understand what you intend even though I may be a pig-headed pedantic.

While we are at it, I say "kilo-metres", not "kill-LOM-eters" as I am following the official Australian standard.
Yes, there is one for metric pronunciation.... Google it.
I don't know where "kill-LOM-eters" came from as no-one says "kill-LOG-rams" or "kill-LODGE-ools" do they?
It's "kilo" dammit..... "KEELOH-metres"..... It means a thousand whatevers.





Cheers
Allan

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Follow Up By: Phil G - Saturday, May 30, 2020 at 17:02

Saturday, May 30, 2020 at 17:02
Nah, Donald ain't my mate - geeze he's got it all wrong lately! I'm guessing if you asked him what B&S stood for, he'd suggest something entirely different :-)
And we both agree that Jaycar uses AWG!
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Follow Up By: Allan B (Sunshine Coast) - Sunday, May 31, 2020 at 10:07

Sunday, May 31, 2020 at 10:07
.
Sorry Phil, I expressed that badly. I was not intending to infer that you had affinity to that bloke. I meant it in the same way as "Uncle Sam"....... USA.

And I guess that we are stuck (for the foreseeable future) with using American cable terminology simply because all the cable suppliers use that terminology. That AWG/B&S terminology is pretty stupid as not only is it "inverted" (increasing number = decreasing size) but also the numerical value is not even proportional. The Yanks have done some stupid things over the years!

So OK, I'll compromise. For public expression I will express it as "mm2" followed by "B&S" in parenthesis.( )

Cheers
Allan

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Follow Up By: qldcamper - Sunday, May 31, 2020 at 16:42

Sunday, May 31, 2020 at 16:42
Ahhhh, the age old wire size debate.
Being an auto sparky I tend to think in probably the worst size format but you get used to what you use. BRAND becomes important because different brands lable different cross sectional size watever it comes close to, usually the one above if it falls between, so being familair with what you use is important.

Insulation heat rating is another thing that does not have to be displayed on automotive cable.

The most important difference is the amount of strands, more strands of a finer size makes it more flexable and lessens the diameter of the cable although it has the same crossectional size. An example is comparing common battery cable to weldflex, the same diameter cable excluding insulation will have a much higher crossectional rating and have a much higher throughput due to there being less air gaps between the strands so Alans old school sizing is probably the best.

Flexability is very important in anything that moves.
I worked on a site recently that used Exane cable and its 2B&S cable was only 3/4the overall diameter of what I was used to and took smaller lugs but performed just as well and was so easy to work with.

And just for those of you that are thinking jeez this is getting boring, 1 more thing.

When looking up specs to work out VD and stuff, be sure to use the tables from the correct manufacturer, there are many things that affect the resistance of copper cable. Much of it has been made from copper that has been recycled many times and cheap cable is cheap for a reason, dont compare it to a quality brand.
How do you know a good brand from a bad one? Ask someone that uses a lot of cable not someone that sells a lot. Does a sparts retailer know a good quality cable when they mainly sell short lengths to people that rarely ever use it, or would they be more likley to know which brand has the highest profit margin?
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Follow Up By: John Baas - Wednesday, Jun 03, 2020 at 01:21

Wednesday, Jun 03, 2020 at 01:21
Only Boomers would get antsy about 'kill-LOM-eters'.

Or worse even, probably pre Boomers...
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Reply By: kgarn - Friday, May 29, 2020 at 11:07

Friday, May 29, 2020 at 11:07
I assume the 6mm cable you originally proposed was similar to this one ;


This cable has a resistance of approx 0.0039 ohm/m so that a total run of 2x5m at 45A would lead to a voltage drop of 1.76V.
In addition there would also be voltage drop across the length of the original cable.
In total the voltage drop would probably be at least 3V. Not insignificent.

8 B&S would give a voltage drop of around 0.9V and 6 B&S around 0.6V (at 45A).

I have seen 6 B&S (twin) 5m offered for around $60 on eBay.
Compressor air hose (4m) is available for around $25 at Kings .


Ken







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Follow Up By: ian - Friday, May 29, 2020 at 11:56

Friday, May 29, 2020 at 11:56
yes.
Thanks Ken
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Follow Up By: RMD - Friday, May 29, 2020 at 12:55

Friday, May 29, 2020 at 12:55
Is the rating on that cross section copper really for 50 amps or is it able to carry 50A ( with lots of voltage drop) and not quite catch fire? or maybe it will!
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Follow Up By: Frank P (NSW) - Friday, May 29, 2020 at 13:19

Friday, May 29, 2020 at 13:19
On the money, RMD.

Here's a great link to a useful discussion on cable sizing.

Toward the bottom it discusses the folly of amperage ratings for cables.
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Follow Up By: qldcamper - Monday, Jun 01, 2020 at 12:49

Monday, Jun 01, 2020 at 12:49
Ken,
Tycab rate their 6mm twin at 38 amps which sounds more like a reasonable rating.

Assuming your data is close to correct then at that voltage drop and current there would be just over 79 watts of heat being generated over the 5 metres.

Given that the compressor will only draw that much when close to its max pressure which wouldnt be long, it would probably serve the purpose for the average 6 tyres at 40 psi.

But this is a clasic example of how retailers take the piss.

The aus standard on the packaging refers to the insulation and has nothing to do with the electrical characteristics of the cable itself.

As RMD indicated earlier if this cable was pushed to 50 amps it would become dangerously hot in minutes and easily exceed the temp rating of its insulation in a short time after that.
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Reply By: Member - Cuppa - Friday, May 29, 2020 at 11:21

Friday, May 29, 2020 at 11:21
As already said, air hose would be lighter & cheaper. It would also be less faffing around than moving the entire compressor around.
I have a compressor mounted inside the vehicle (away from most of the sand & dust), with an outlet on each side of the vehicle. One hose long enough to reach the car's front wheel, & the van wheel on each side suffices.
See 'My Profile' (below) for link to our Aussie travel blog, now in it's 4th year

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Follow Up By: ian - Friday, May 29, 2020 at 11:57

Friday, May 29, 2020 at 11:57
thanks Cuppa
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Follow Up By: qldcamper - Monday, Jun 01, 2020 at 10:14

Monday, Jun 01, 2020 at 10:14
On the lighter side,
How come if someone mentions wire size it always triggers a several day long debate.
Air hose has been mentioned but is there a myriad of posts about sizing, capacity, brands and all the other properties of air hose that is just as relivant as wire but not bothered about?
Use too small an hose will force a wiring upgrade lol.
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Reply By: Kazza055 - Friday, May 29, 2020 at 12:33

Friday, May 29, 2020 at 12:33
I was going to head down this track as well but when my compressor arrive I found it had a cutout switch so once you shut off the airflow, the motor stops about a second later.

Su I now leave the compressor clipped onto the starter battery and use extension hose with digital gauge. While not pumping, the compressor is stopped, release the trigger and it starts up again.

Much easier than dragging a heavy cable behind you.
AnswerID: 631846

Reply By: qldcamper - Tuesday, Jun 02, 2020 at 07:24

Tuesday, Jun 02, 2020 at 07:24
The only advantage I can think of by having an electrical extention is that it would have multiple uses such as an extra lead for portable solar panels or as I use one for to connect the car to the camper so the fridge can draw off both acc batteries over night.

But do yourself a favour and go to an auto electrical wholesaler and you will get a 30 metre roll of 6mm T/S for that price or a little over, and a pack of 10 Anderson compatible plugs off ebay, make 3 of them and share the cost with 2 mates, then you will have a spare half a roll.

Being very familair with the Narva brand you can bet it would be made from the cheapest cable they could find anywhere in the world.
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Reply By: qldcamper - Wednesday, Jun 03, 2020 at 12:10

Wednesday, Jun 03, 2020 at 12:10
Just as an excersize i hooked up my compressor that is claimed to need a 45 amp circuit to see what it actually draws.
The cheap clips and relatively small cables it has lends itself to say it is nowhere near 45 amps.

The tyre was at 35.5 psi when i turned the compressor on and the initial draw was 22.7 amps.
Expecting the current to increase with the pressure. The current remained stable for a while and after a while went up to 22.8 amps. The voltage stayed at 13.8 because of the 24 amps coming from my AC charger.
Shut it down at 22.8 amps and found a pressure of 51.5psi in the tyre.
Maybe the motor windings warming up might explain the current remaining relativly stable?

Never the less I have proved that Tycabs 6mm automotive cable would indeed cope as a 5 metre extention being rated by the manufacturer at 38 amp capacity.(at least with my compressor)
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