Discuss Radial Circuit Cable Length in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
I was trying not to mention the War .4mm T&E is undersized for a 32A protective device if it is contained in conduit.
Hi MM - You are correct that if a bigger cable was used then less voltage would be dropped for any given load in accord with Ohm’s Law, but it’s unlikely to be something that affects the use you propose. If you post up an equipment list I’m sure load estimates will be forthcoming.
what yous running up there, a recording studio or a pirate radio station. ?
remember it well. on my old valve radio.long before FM.
There is quite a few pieces up there as this is a full fledged home theatre so here goes.I rather think you are misunderstanding of misreading the amount of MAINS current that the devices require.
A 200 watt audio amplifier at full whack won’t pull much more current than a 60watt light bulb.
Have a look at the rating information on the back of your devices.
The total length of the cable is 35 meters but as you say I would need to be using 32 amps to start running into issues with voltage drop so I now need to now workout what my total load is but as all of you say it is highly unlikely I am going to be anywhere near 32 amps.That will be interesting. I would be surprised if the total load on the circuit (and therefore assumed design current) was anywhere near high enough to exceed max volt drop requirements.
Also how sure are you on the length of circuit? A quick calc shows that even if the design current was 32A you could run approx. 30m in 4mm before exceeding volt drop.
Is it black plastic conduit in 25mm, it looks like this stuff.OP- is it conduit or plastic mini trunking? Haven't looked at the tables so not sure if it makes a difference to derating factor
Thank you for that information, it seems this is my issue rather than voltage drop at this point from all the information I have received here.4mm T&E is undersized for a 32A protective device if it is contained in conduit.
By looking up the manufacturers specifications, but unfortunately they're not always clear.What is the best way to work out what my total load is?
@westward10 Forgot to ask, do you know if the current carrying capacity of the cable is further de-rated due to the two other cables also running in the conduit along with it?
Yes really confusing & misleading when you are trying to work this kind of stuff out.Hi MM - so coool stuff there
Power wise, I just looked at item 3, the Behringer NX6000 Amplifier of which you’ve got 3. I was stunned to see the spec says ea of these has 2 by 3kW amps. Yep 18kW. Aghhh. Then I looked at the power cable, it’s a plug. And it’s labelled 820W each. So probably closer to 2.4kW rather than 12kW + some efficiency factor. But it does seem like you’re going to need some air handling plant up there.
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The Behringer's are powering 6 18" subwoofers each using dual voice coils totaling four ohms each. They so go infrsonic which literally shakes the room which is all part of the experience so its not just about what you can hear but what you can feel.Realistically if you have 6kW sustained power driving speakers up there you are going to be deaf in seconds and/or subject to a police action.
I doubt you will be drawing much more than a couple of kW average and nothing like the limit for a 32A circuit.
Yes I do own an amp clamp & I would love to see what all this gear is pulling when everything is in full force.By looking up the manufacturers specifications, but unfortunately they're not always clear.
My quick sums predict about 16A with everything on and playing. Obviously the current will go up with the volume controls, but I think you would have difficulty exceeding say 25A while in the same room!
The Behringer NX6000 Amplifier spec says the avarage mains power consumption using 4 ohm speakers is typically 620 watts, which equates to approx 2.6A, so for three of them, say 8A with them all running. The other amplifiers are mostly lower power, so allow say 2A each. The projector is 355Watts, which equates to about 1.5A. Items 8 onwards on your list probably don't consume more than an amp all combined.
If you have access to a clamp ammeter it would be interesting to hear the result and see how way out I am!
My personal opinion is that the 4mm cable you've had installed is perfectly adequate for the use you describe. I'll leave it to others to discuss what the derating implications are, if any.
You mention that there is a 2.5mm & 1.0mm cable also in the conduit.
Grouping factor should be looked at, depending on what these cables feed.
"If, due to known operating conditions, a cable is expected to carry not more than 30 % of its grouped rating, it may be ignored for the purpose of obtaining the rating factor for the rest of the group."
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