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Posted By Topic: Calculating volt drop in existing installation

Feb 11 2020 16:35

Just wondering if anyone could offer some advice or guidance on what they do or what they believe is the easiest way to calculate volt drop in an existing situation

For example if I wanted to add to a final subcircuit or to say a distribution board that already runs off a submain what's the easiest way to know what percentage the volt drop is already at to ensure you don't exceed it by adding something on

Hope that makes sense

Feb 11 2020 18:03

Too many variables for it to be simple
Which may be why most don't bother; they just hope.

There are a number of recognised ways of coming up with figure for current (maximum demand), and you also need the cable size and the route lengths. both can be guesstimated; but would be really nice to find the installer had recorded these details for each switchboard.

Feb 11 2020 18:15

Ah, yeah I just thought there may be an easier way but that's basically what I'd been trying to do but it becomes rather difficult due to the variables like you said

I thought of measuring voltage at PoS and then at the point to add to and working out the difference but doesn't really help because it'll fluctuate with load