Okay, let's break this down. This is a common scenario when dividing up commercial spaces, and it's crucial to get it right for safety, code compliance, and tenant satisfaction.

Key Considerations and Steps


Load Calculation is Paramount

Do NOT assume that because you have a 200A service now, and are going to three 200A services, everything is fine. You must perform a thorough load calculation. This is the foundation of the entire project.

Existing Load

Determine the actual connected load on the existing 200A service. What's being used now? Are there any unusual loads? This gives you a baseline.

Future Load

For each of the three tenant spaces, estimate the maximum possible load. This must include: Lighting (watts per square foot - use the NEC table for office spaces). Receptacles (VA per square foot - again, use the NEC table). Assume that each space may be doing various high-amperage tasks on the outlets, even though it may be 'office use.' HVAC (especially the mini-splits - nameplate amps + a buffer). Are there any electric heaters? Dedicated equipment: computers, printers, servers, etc. Future expansion: Leave room for potential load growth.

Demand Factors

The NEC allows you to apply demand factors to reduce the total calculated load. This is extremely important. Demand factors account for the fact that not everything will be running at its maximum at the same time. You may need to consult with the local AHJ (Authority Having Jurisdiction) about these Demand Factors.

Total Load

Sum up the loads for all three spaces, after applying the appropriate demand factors. This total load determines the size of your main service.2.

4/0 Aluminum Wire Capacity (and Suitability)



Ampacity

4/0 Aluminum wire has an ampacity that depends on the temperature rating of the insulation and the installation method. Typically, for THHN/THWN-2 in conduit at 75°C, 4/0 Aluminum is rated for 180 amps. At 90°C it's higher, but you have to ensure all the terminations (breakers, lugs) are also rated for 90°C.

Derating

If the wire runs in a conduit with other current-carrying conductors, you may need to derate its ampacity. If it's in a hot environment, you may need to derate.

Voltage Drop

You must consider voltage drop, especially over long distances. Voltage drop can cause equipment malfunction and even damage. Use a voltage drop calculator to determine if the 4/0 AL is adequate for the length of the run to your new meter stack.

Suitability

Is the existing 4/0 in good condition? Are the terminations properly made and torqued? Aluminum wire requires proper installation techniques and anti-oxidant paste.3.

Main Service Size



Does the Existing Service Provide Enough Power? This is the big question. Based on your total calculated load, will the existing 4/0 Aluminum (assuming it's good for 180 amps max after derating) be sufficient? If not, you will need to upgrade the service entrance conductors and possibly the meter panel, and possibly the utility company's transformer feeding the building. 3-Stack Meter Panel

A 3-stack meter panel is perfectly acceptable. Choose a panel rated for the calculated load. You will need to coordinate with your utility company about their requirements for metering.

Main Breaker or Fused Disconnect

Consider a main breaker or fused disconnect before the meter stack to provide overcurrent protection for the service entrance conductors. This is often required by code and/or the utility.4.

Subpanel Sizing



Minimum Size

The subpanel size in each tenant space must be large enough to accommodate the calculated load for that space. It's better to oversize them slightly than to undersize.

Ample Space

Choose a subpanel with plenty of extra breaker spaces. Tenants often add equipment, and it's much easier to add a breaker than to replace the whole panel later.

Main Breaker or Lugs Only

You can use a subpanel with a main breaker or a lugs-only subpanel. If you use a lugs-only panel, the feeder breaker in the meter stack acts as the main overcurrent protection.5.

Overcurrent Protection



Feeders

The feeder conductors from the meter stack to each subpanel must be protected by an appropriately sized breaker in the meter stack. The breaker size must match the ampacity of the feeder conductors.

Branch Circuits

Within each subpanel, all branch circuits must be protected by appropriately sized breakers (15A, 20A, etc.).6.

Grounding and Bonding



Proper Grounding Electrode System

Ensure the building has a proper grounding electrode system (ground rods, water pipe ground, etc.) connected to the main service panel.

Bonding

All metallic components (conduit, enclosures, etc.) must be properly bonded to ground. This is critical for safety.

Separated Neutrals and Grounds

In each subpanel, the neutral and ground buses must be kept separate. The neutral should only be bonded to ground at the main service panel.7.

Wiring Methods



Conduit

Commercial installations generally require wiring to be installed in conduit (EMT, rigid, etc.). Check your local codes.

Cable

In some cases, cable (Romex, MC) may be permitted, but it's less common in commercial buildings.8.

Code Compliance



NEC

Adhere to the National Electrical Code (NEC) and any local amendments.

Local AHJ

Consult with the local Authority Having Jurisdiction (AHJ) before starting any work. They can provide guidance on local requirements and interpretations of the code. They will also inspect the work.9.

Permits and Inspections



Permits

Obtain all necessary electrical permits before starting work.

Inspections

Schedule inspections with the AHJ at various stages of the project (rough-in, final).

Specific Answers to Your Questions



Can I use the 4/0 aluminum wire for a 3 stack 200 amps? Maybe. You absolutely must perform a load calculation to determine if the existing service and conductors are adequate. Assuming it's rated for 180 amps, you might be able to get away with it, but don't count on it. What size sub panels would be legal? As large as you need them. It depends on the total amperage of the breakers installed, and must be at least the amperage of the feeder breaker from the 3-gang meter setup.

Important Considerations for Aluminum Wire



Proper Terminations

Aluminum wire requires special connectors and termination techniques. Use connectors listed for use with aluminum conductors.

Anti-Oxidant Paste

Apply anti-oxidant paste (e.g., Noalox) to the aluminum conductors before terminating them. This prevents corrosion.

Torque

Torque all connections to the manufacturer's specifications. Aluminum connections tend to loosen over time due to thermal expansion and contraction.

Regular Inspections

Periodically inspect aluminum connections to ensure they are tight.

Recommendation



Hire a Qualified Electrical Engineer

For a project of this scale and complexity, it's highly recommended to hire a qualified electrical engineer to perform the load calculations, design the electrical system, and create the necessary drawings. This will help ensure code compliance, safety, and optimal performance.

Contact Your Utility Company

Talk to your local utility company about your plans. They may have specific requirements for metering and service connections.

Disclaimer: I am an AI chatbot and cannot provide professional electrical advice. This information is for general guidance only. You must consult with qualified professionals and comply with all applicable codes and regulations. Improper electrical work can be dangerous and illegal. Flag for review