(2+2) Furniture Wiring

J

JohnnyPElec

Member
Location
Portsmouth, VA
Occupation
EE
Working on a lot of commercial offices lately it would seem, with many of them having very large Open Office concepts. I keep running into Furniture systems that utilize the (2+2) electrical system, essentially meaning that 2 sets of 2 circuits, where the 2 circuits in each set share a neutral and a ground. My question is, we typically power 4-6 workstation pods with (2) 120V circuits, and have the contractor use a circuit on each of the 2 sets, simple as that. The current contractor is pushing back and saying he's only ever done it to where both circuits HAVE to share the same neutral and ground so they have to both be on the same set, but then wouldn't that mean I'd need a 2P breaker back at the source such that they have the same disconnecting means? And even if so, is there anything wrong with the approach we've been doing? I can't find where it wouldn't be code-compliant to just use one circuit off each set and be done with it

Thanks in advance!
 
So there are 2 sets (2+2) each set has 2 hots/neutral?

Your method: set 1 use one hot and and the neutral. Set 2 use one hot and the neutral.
 
infinity said:
So there are 2 sets (2+2) each set has 2 hots/neutral?

Your method: set 1 use one hot and and the neutral. Set 2 use one hot and the neutral.
Click to expand...
Yes, each set has 2 hots, and a neutral and a ground (neutral and ground intended to be shared)

My method, use one hot, one neutral, and one ground off each set, such that they both have their own neutral and ground.
If 6 workstations, you'd essentially have 3 on each circuit.

Contractor is saying he wants to use exclusively one set and share the neutral and ground.
 
Your method is code compliant and better. For one you don't have a shared neutral and two you won't need a 2 pole circuit breaker or handle ties.
 
Your method's better, and as infinity says, code compliant, but also check the mfr instructions. While remodeling one of our offices, the structured wiring inside the cubicles we chose had this weird three hot, two neutral, one ground thing going on where one set of hots plus neutral went to the desk-level receptacles (where you'd plug in things like a desk lamp, coffee heater, transitory gear being configured), and a second set of hot+neutral went to the floor for the more permanently installed gear (workstations, monitors, printer if you had one).
 
ModbusMan said:
Your method's better, and as infinity says, code compliant, but also check the mfr instructions. While remodeling one of our offices, the structured wiring inside the cubicles we chose had this weird three hot, two neutral, one ground thing going on where one set of hots plus neutral went to the desk-level receptacles (where you'd plug in things like a desk lamp, coffee heater, transitory gear being configured), and a second set of hot+neutral went to the floor for the more permanently installed gear (workstations, monitors, printer if you had one).
Click to expand...
Thanks, the one page cutsheet says the below, so I'm assuming the intent is also to have computers and such equipment that could be deemed sensitive on one (isolated) circuit and other less sensitive equipment on others.

2+2 Electrical System
The Dividends Horizon 2+2 electrical system
is designed for areas where power usage is
significant and sensitive electronic equipment
requiring two isolated circuits are required.
The wiring configuration of the (2+2)
electrical system is (see chart):
• Hot ‘‘A’’ (black)
• Hot ‘‘B’’ (red)
• Shared neutral ‘‘N1’’ (white/black) for circuits #1 and 2
• Shared ground ‘‘G1’’ (green, bare copper) for circuits #1 and 2
• Hot ‘‘Y’’ (tan)
• Hot ‘‘X’’ (pink)
• Isolated Shared Neutral ‘‘N2’’ (white/red) for circuits #4 and 5
• Isolated Shared ground ‘‘G2’’ (green/yellow) for circuits #4 and 5
Circuits 1 and 2 share common neutral and ground. Circuits 4 and 5 share a separate common neutral and ground.
 
JohnnyPElec said:
Circuits 1 and 2 share common neutral and ground. Circuits 4 and 5 share a separate common neutral and ground.
Click to expand...
The neutrals are both the same, one for A&B the other for X&Y. The EGC for A&B is used for all equipment grounding and bonding, the EGC for X&Y is isolated within the furniture system.
 
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