Are these the sort of tube like duct to be threaded by pulling ropes through (example) the sort of thing you may poke a 10mm SWA through, or the concrete channel kind that you lay the cable in from the top ( example) These tend to be biggeer cables or longer runs..
In either case ‘larger than you think’ makes threading up easier ;-) Usually while you are digging, it is getting the kit there rather than the exact size of the groove that sets costs, and it is the ease of threading or the number of access points that makes or breaks the job.
I suggest that anything more than ⅓ full is under sized, but I cannot point to a standard figure form anywhere to justify that.
Are you grouping cables that are running near the thermal limit, or is it long enough that voltage drop is the limiting factor ?
Are these the sort of tube like duct to be threaded by pulling ropes through (example) the sort of thing you may poke a 10mm SWA through, or the concrete channel kind that you lay the cable in from the top ( example) These tend to be biggeer cables or longer runs..
In either case ‘larger than you think’ makes threading up easier ;-) Usually while you are digging, it is getting the kit there rather than the exact size of the groove that sets costs, and it is the ease of threading or the number of access points that makes or breaks the job.
I suggest that anything more than ⅓ full is under sized, but I cannot point to a standard figure form anywhere to justify that.
Are you grouping cables that are running near the thermal limit, or is it long enough that voltage drop is the limiting factor ?
