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."
Many thanks for the confirmation, I did ask him to put a 20 amp MCB in instead but he was adamant that there was nothing wrong with using a 32 amp MCB & when asked about the cable running in conduit he said those are guidelines only & not rules.No it shouldn't be on a 32A protective device.
He is incorrect.Many thanks for the confirmation, I did ask him to put a 20 amp MCB in instead be he was adamant that there was nothing wrong with using a 32 amp MCB & when asked about the cable running in conduit he said those are guidelines only & not rules.
Also because not all of the run was in conduit these "guidelines" do not apply.
Am I correct in saying that this is not the case?
He is incorrect. We cannot pick and choose which regulations we want to comply with or not. The cable rating for 4mm2 in conduit is at best 30 amps. If grouping is also a factor then it's even less.He is incorrect.
He is incorrect.
He is incorrect. We cannot pick and choose which regulations we want to comply with or not. The cable rating for 4mm2 in conduit is at best 30 amps. If grouping is also a factor then it's even less.
So a 20 or 25 amp MCB is needed.
Reply to the thread, titled "Radial Circuit Cable Length" which is posted in Electrical Wiring, Theories and Regulations on Electricians Forums.