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Old 15-02-2021, 12:29   #1
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Cable heating up in cablemaster drum

Hi, I have a Glendenning Cablemaster system. As the power pedestal is close by, I am using only a short length of cable and there is still at least 30' (10m) inside the drum (maybe 20 coils) . I have noticed that the coil of cable in the drum is considerably hotter than the cable outside. The cable inside the drum is 120F (50c). The part of the cable outside is 75F (25c). The boat is drawing 30amps from 100amp service.
Is there something going on with electricity flowing in a coil of wire that would make it heat up? or is it just the usual heat building up in a confined space?
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Old 15-02-2021, 12:36   #2
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Re: Cable heating up in cablemaster drum

Coils of cable energised with electricity can generate quite powerful magnetic fields. Your alternator works in much the same way. I once was (stupidly) welding using a reeled extension cable that actually melted the plastic shielding and caught fire.
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Old 15-02-2021, 13:14   #3
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Re: Cable heating up in cablemaster drum

Yes! current flowing through a coliled cable generates heat which can't escape. There have been many fires caused by this,

It's a basic safety rule to not leave a cable/extension cord coiled while in use.
https://www.hsa.ie/eng/Safety_Alerts...le_Reel_Alert/
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Old 15-02-2021, 13:16   #4
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Re: Cable heating up in cablemaster drum

The cable will always get slightly warm if there's a good bit of power flowing through it. The coiled cable can't dissipate heat as well, so it will get warmer. In general, I'd suggest letting the cable all the way out and loosely coiling the excess outside the boat where it can get more airflow and will stay cooler.
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Old 16-02-2021, 10:41   #5
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Re: Cable heating up in cablemaster drum

Quote:
Originally Posted by Kerryf View Post
Hi, I have a Glendenning Cablemaster system. As the power pedestal is close by, I am using only a short length of cable and there is still at least 30' (10m) inside the drum (maybe 20 coils) . I have noticed that the coil of cable in the drum is considerably hotter than the cable outside. The cable inside the drum is 120F (50c). The part of the cable outside is 75F (25c). The boat is drawing 30amps from 100amp service.
Is there something going on with electricity flowing in a coil of wire that would make it heat up? or is it just the usual heat building up in a confined space?
125F doesn't sound to bad. Can you vent the drum. I would contact the manufacturer. You are likely to get a lot of BS here. Everyone likes to tout their electrical expertise.
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Old 16-02-2021, 10:52   #6
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Re: Cable heating up in cablemaster drum

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125F doesn't sound to bad. Can you vent the drum. I would contact the manufacturer. You are likely to get a lot of BS here. Everyone likes to tout the electrical expertise.
Why would you do that? I am not an electrical expert but have first-hand experienced what happens when high loads are put through an extension reel. This is a commonly-known condition, it’s a long way from BS.

Instead of proposing to “vent the drum” and “contact the manufacturer”, why don’t you tout your own “electrical expertise” by simply suggesting that some turns be taken off the reel to prevent the heat build up.

And if you have zero electrical expertise or first-hand experience, rather just STFU.
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Old 16-02-2021, 10:57   #7
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Re: Cable heating up in cablemaster drum

You don't say what voltage or type of system, but assuming 120V, single-phase.

At 30A you are using 3600W. If your cable is 10AWG you lose about 1.5% in 60' (depending on whose calculator you believe and exactly what wire you have). You have 30' on the drum, which means 60' of single-phase circuit.

1.5% of 3600W is 54W. That means the cable on your drum is basically a 54W heater inside the drum (it would be a 54W heater outside the drum as well, just more area for air contact to dissipate the heat).

If you have 8AWG cable then the power loss is about one-half the above, still a 27W heater inside your drum.

(examples for demonstration purposes only since I have no knowledge of cable sizes, type, etc.)
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Old 16-02-2021, 11:05   #8
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Re: Cable heating up in cablemaster drum

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Originally Posted by CassidyNZ View Post
Why would you do that? I am not an electrical expert but have first-hand experienced what happens when high loads are put through an extension reel. This is a commonly-known condition, it’s a long way from BS.

Instead of proposing to “vent the drum” and “contact the manufacturer”, why don’t you tout your own “electrical expertise” by simply suggesting that some turns be taken off the reel to prevent the heat build up.

And if you have zero electrical expertise or first-hand experience, rather just STFU.
I'm sorry if you took it personally. It was not directed at you, it was directed at any no of responses he may get. And yes I have a degree in it and worked in the field for 23 years.
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Old 16-02-2021, 11:24   #9
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Re: Cable heating up in cablemaster drum

I have never heard of anyone emptying their cable storage drum every time they plug in. I have a pair of these with 100’ of cable in each and I just imagine the chaos of two hundred feet of cable snaked all over my foredeck every time we hooked up in the summer. If we have guests onboard I use both 50a power cords simultaneously to balance loads.
Corrosion induced resistance can cause cables and particularly connectors to heat up and melt, but it rarely happens mid-cable. I’m going to say this is normal. If you are worried, just call Glenndenning.
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Old 16-02-2021, 11:28   #10
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Re: Cable heating up in cablemaster drum

Thinking about it more, if it's getting to 125*, but not getting warmer than that, it's probably not a big issue. That should still be well below the cable insulation ratings.
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Old 16-02-2021, 11:57   #11
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Re: Cable heating up in cablemaster drum

Take a shorter cable if you have to use it this way often
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Old 16-02-2021, 15:25   #12
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Re: Cable heating up in cablemaster drum

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Originally Posted by Woodland Hills View Post
I have never heard of anyone emptying their cable storage drum every time they plug in. I have a pair of these with 100’ of cable in each and I just imagine the chaos of two hundred feet of cable snaked all over my foredeck every time we hooked up in the summer. If we have guests onboard I use both 50a power cords simultaneously to balance loads.
Corrosion induced resistance can cause cables and particularly connectors to heat up and melt, but it rarely happens mid-cable. I’m going to say this is normal. If you are worried, just call Glenndenning.
So you mitigate the risk by passing load through twice the cable. To me that’s an acknowledgment that you agree with the principle. Of course we don’t empty the reel every time we use it because mostly the loads drawn are light but if you’re going to be drawing high electrical loads through a wound reel of cable, expect it to get hot.

The OP simply asked if this was normal, I believe you agree that it is.
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Old 16-02-2021, 17:34   #13
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Re: Cable heating up in cablemaster drum

If a AC cable is coiled up while running heavy loads , the impedance in the coil can easily equal the resistance , effectively doubling the heat.

Try connecting a heater and a AC voltmeter to the output and put the heater on maximum. Coil up the cable and watch the voltage drop.

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Old 16-02-2021, 19:22   #14
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Re: Cable heating up in cablemaster drum

Quote:
Originally Posted by Kerryf View Post
Hi, I have a Glendenning Cablemaster system. As the power pedestal is close by, I am using only a short length of cable and there is still at least 30' (10m) inside the drum (maybe 20 coils) . I have noticed that the coil of cable in the drum is considerably hotter than the cable outside. The cable inside the drum is 120F (50c). The part of the cable outside is 75F (25c). The boat is drawing 30amps from 100amp service.
Is there something going on with electricity flowing in a coil of wire that would make it heat up? or is it just the usual heat building up in a confined space?
Golden rule is to unwind at least most of the cable from a cable drum. They are all supposed to be labelled to that effect. You might get away with it, but many don't.

With any significant current, a cable heats due to the resistance of the wire dissipating some energy. In an open length you normally don't notice this (with higher currents you do), but rolled up into a coil and that heat builds up quite quickly.

On top of that, you have a coil of wire with AC (alternating current) passing through it. Technically this is termed a choke, and the effect is used everywhere in electronics. That choke also acts like a resistor, so more energy is dissipated, adding to the heating effect.

And on top of all that, the hotter the cable, the higher the resistance, so as it warms up, the resistance increases, and the heating increases, and the resistance increases, and .....

Effectively you are now into what is termed thermal runaway (= smoke and sparks).

We have two 10 metre cables (one for service, one for A/C), that serve well most of the time, and a 30 metre cable for when the power is a distance off.

Perhaps you could keep your roll of cable for such situations, and use a shorter one for regular situations.

We have a couple of zip-up bags for those cables, and it all works very well for us.
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