AC and DC in one cable

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Old 04-08-20, 11:24 PM
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AC and DC in one cable

Good day,

I have a 5 core cabtyre cable (flexable lead with 5 insulated cores inside) with 380volt rating. Can I use one core for earth, two cores for dc12v to power LED's and the other two cores to run a 220V AC fridge?

The length of the cable is about 2 meters.


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Last edited by PJmax; 04-09-20 at 09:43 AM.
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Old 04-09-20, 07:03 AM
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It would be helpful to know where you are located?
 
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Old 04-09-20, 09:47 AM
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Welcome to the forums.

You have five conductor rubber service cable and want to use three of the wires for the fridge and two for running LED's.

Are the LED's inside or part of the fridge ?
If not.... how would a five conductor wire even help ?
For the short distance you are talking about it would seem that two cables would be just as easy.

Cabtyre Cable
 
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Old 04-09-20, 09:54 AM
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Bad idea. There is significant capacitive coupling from HV to LV. Most safety regs prohibit sharing a wireway/cable outside of a device.
 
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Old 04-09-20, 11:57 AM
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It will probably work fine, but you are not allowed to run low voltage and line voltage wires in the same raceway. In the same cable will be even worse.
 
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Old 04-13-20, 12:30 AM
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This is for a camping trailer, the ac will power the fridge and the dc will power LED's for lighting in the trailer. I would prefer to have just one plug goiing into the trailer from outside.The cable will go to an inverter outside the trailer where I want to connect to ac and dc.
 
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Old 04-13-20, 11:03 AM
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You'd need a 5 prong plug and receptacle and there is no plug that I know of that will keep the high voltage and low voltage separate.

So all we can tell you is that based on our electrical codes.... you cannot do what you want to do.
 
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Old 04-13-20, 02:22 PM
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Pjmax, I can show you many 5 prong plugs and receptables that is made for 380volts so they will definately work for 12v and 220v. I will just run LED's from the cable, so my question is not about the plug, it is about wheter the 220v will mess up the 12v circuit for just LED's.
 
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Old 04-13-20, 03:27 PM
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LEDís can be quite sensitive. My illuminated switch feeds two led bulbs and both glow at night when the 120v switch is off. U have now two good reasons not to proceed with your proposal.
 
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Old 04-13-20, 04:48 PM
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but you are not allowed to run low voltage and line voltage wires in the same raceway
This is not true. As long as the insulation rating is higher than the voltage of all the conductors, they can be run in the same raceway.

Example: https://www.encorewire.com/products/mc-led.html
 
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Old 04-14-20, 05:45 AM
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Part of my work is doing safety assessments of complex electronic equipment. When you look at close proximity "hazardous voltage" and "accessible low voltage" systems, the isolation needs to be understood. When the LV system is ungrounded the rules become more stringent, usually getting into the space popularly known as "double insulated". Creepage distances and Air clearance distances usually need to double, from where they can be when the LV wiring system is bonded to earth on one end of its power supply.
For the OP's issue, I don't know the RV specs on this, if any. But, the hazard is a wet connector, or some other HV transient event on mains voltage causing some effect on LV. And, what is accessible (touchable) on the LV side? Can a HV event easily transfer its energy to the LV side and cause a hazard?

My other hat is an EMC engineer. This work shows that there is a risk of capacitive coupling, within a cord, from HV to LV systems, unless one of those is contained inside a shield. What is the impedance and sensitivity of the LV control system? Will a mains waveform of a reduced voltage applied to it cause miss-operation?
 
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Old 04-15-20, 02:46 AM
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Thank you telecom guy.
For anyone that is interested, I did the following tests:
I used a 5 m 5core cable, on the one side I connected 220V ac and earth 3 of the cores and 12V dc from a battery to the other 2 cores.
I then connected 5 LED's to the other end of the cable to the 2 dc cores and different AC loads to the 3 AC cores.
I used a motor load (the fridge) and a resistive load (a 2000W kettle, which is the biggest I will ever use) as loads.
There were zero induced Voltage or current on the DC side (I tested down to 20mA and 200mV).
What was interesting was the induced capacitance. I found that with no AC load there was an induced capacitance of 1.95 nan F which went up to 2.95 nanoF with the 2000W AC load.
I am not sure if my DC source is my car battery (Landrover which probably have some sensitve electronics)
wheter that capacitance is enough to mess up anything in my car. If I use an external battery That will obviously be no problem.
I do understand that the safety is a big factor.But I installed everything in the trailer myself and nothing is assessable to humans.The plug is normally used in wine cellars and is water tight.The only place where the ac and dc are in close proximity is in the plug (10mm) and in the cable.


 
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Old 04-15-20, 03:16 PM
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Using your battery directly connected as a low voltage source would keep induced fields down on the DC wiring. Adding extra wiring between that multicore cable and your 12v source may show slightly increased induced voltage.

It sounds like you're in good shape there.
 
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