Voltage Drop for Robust Telecom Equipment

YouConduit!

YouConduit!

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Location
Midwest
Occupation
Electrical Design
Dealing with a remote location where the 120/240V, 1-phase, 100A distribution panelboard is ~300 feet away from the utility meter. This is a 100A service.

All of the loads are very robust equipment with nominal voltage ranges of 200-250VAC for the 240V loads and 100-130VAC for the 120V loads. Load calcs add up to 8kVA. Typical usage is <1/2 of that.

What size should the service conductors be? Without considering voltage drop, I would say CU #2s. Should the cables be upsized for voltage drop if all of the equipment is manufactured for a broad range of voltages (well below what it should ever see)?
 
Depends on what matters to the users (cost, annoyances, function). My house has a total service drop and service lateral length of close to 200 feet. The wires are minimally sized by the utility (#2 and #1/0 aluminum). When the air conditioner kicks on, you can see all the lights flicker or momentarily dim for about half a second. Everything functions just fine, but will something like that bother anyone? Are any of the loads a substantial motor that has a large locked rotor amp number? That could be a problem if its LRA is in the 150+ amp range and you have a 300' service length (plus its branch circuit).

Code will provide a minimum size, which would be #4 copper for residential or #3 for anything else. You can go as big as the lugs and bending space allow. For me, I kind of like sizing things using the 60C ampacity table when I have concerns for voltage drop on longer runs. You could also use one of the voltage drop calculators and decide what % drop you want to tolerate and see what it says. Future equipment could change, increasing fussiness or total load. Changing 300' of service conductor is probably not easy, so if you have any doubts I'd upsize. I'd maybe go 1/0 copper or 2/0 aluminum, but its not my money paying for it.
 
Appreciate the insight @suemarkp

No motor loads and the service conductors haven't been installed yet. In the process of determining whether the price of extra copper (or aluminum) is worth the peace of mind now and down the road.
 
YouConduit! said:
Dealing with a remote location where the 120/240V, 1-phase, 100A distribution panelboard is ~300 feet away from the utility meter. This is a 100A service.

All of the loads are very robust equipment with nominal voltage ranges of 200-250VAC for the 240V loads and 100-130VAC for the 120V loads. Load calcs add up to 8kVA. Typical usage is <1/2 of that.

What size should the service conductors be? Without considering voltage drop, I would say CU #2s. Should the cables be upsized for voltage drop if all of the equipment is manufactured for a broad range of voltages (well below what it should ever see)?
Click to expand...
Check the specs for the carrier, all telco's have mounds of Technical Publication's it can take eons to dig thru.
I have seen some that require 2.5% voltage drop based on NEC calculated load or 60 amps whichever is greater on the service conductors, but thats going off memory I was not able to find a copy of that spec.
Either way main breaker is irrelevant in VD calcs but If its not economical to achieve this then they can use a Line Voltage Regulator (LVR) or a flow thru UPS, they probably are and you can run with whatever the energy code requires (5% drop based on calculated load here).
I typically would use 3/0 AL for runs 150-350', I noticed you mentioned CU conductors if you think thats a requirement verify that, here they allow AA-8000 alloy and switching to copper when entering the structure that one I have bookmarked;
7.5.2
"Aluminum connectors and lugs are not authorized for use in CenturyLink indoor
installation locations. Copper or tinned copper connectors and lugs shall be used..."
 
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