Warehouse Power: Amps, Volts and Three-Phase

Three terms come up on nearly every industrial spec sheet. You do not need to be an electrician to use them, but you should know what each one tells you.

• Volts. The electrical potential. Ameren's Missouri service rules, as one utility's example, list standard single-phase service at 120/240 volts and standard three-phase at 120/208 and 277/480 volts. Your utility's standards may differ.
• Amps. The current the service can carry, such as 400, 800 or 1,200 amps.
• Phase. How power is delivered. As a general matter, single-phase often covers basic lighting and office equipment, while larger motors and much industrial equipment call for three-phase. The equipment's nameplate says what it needs.

A complete description looks like this: 400 amps, 480/277 volts, three-phase. If a listing gives you only one of those numbers, ask for the rest. The choice between 480/277 and 208/120 three-phase service can affect transformer needs, conductor sizing and which equipment you can run, so it is not a small detail.

For a rough comparison of three-phase services, a common formula for apparent power is volts times amps times 1.732, divided by 1,000, which gives kilovolt-amperes (kVA). The following example is hypothetical, for illustration, and not a substitute for an electrician's load calculation.

• 400 amps at 480 volts, three-phase: 480 times 400 times 1.732, divided by 1,000, is about 332.5 kVA.
• 400 amps at 208 volts, three-phase: 208 times 400 times 1.732, divided by 1,000, is about 144.1 kVA.

Both spec sheets say 400 amps, yet one service has more than twice the capacity of the other. Capacity listed on paper also is not the same as what is free for you. Existing loads, panels and how much of the service is shared with other tenants all reduce what you can use.

Do not compare buildings by amps. Ask for voltage, phase and amps, and ask how much is available to your premises after existing loads.

Start with a list of everything you will run, then let a professional size it.

1. List each piece of equipment with its voltage, phase and amperage or horsepower, from the nameplate or manufacturer.
2. Add building loads such as lighting, HVAC, heaters, dock equipment, compressors and any cooling for your product.
3. Add electric forklift chargers. OSHA requires battery charging in designated areas, with provisions for spills, fire protection, protection from trucks and ventilation, so plan the location too.
4. Note which equipment runs at the same time, because demand drives sizing.
5. Include growth, such as added machines, automation or more chargers over the term.
6. Give the list to a licensed electrician or electrical engineer and ask for a load calculation.

Rules of thumb for amps by building type circulate online, and they should only start a conversation. An amp figure with no voltage says little, because, as the example above shows, voltage changes the real capacity a lot. Your equipment list is what matters.

Have an electrician walk the building before you sign, not after. The goal is to know what exists, what is available and what it would take to close any gap.

• ✓What is the actual service size, voltage and phase at the main disconnect and transformer?
• ✓Is the service dedicated to our premises, or shared with other tenants?
• ✓What do the panel schedules show about available capacity?
• ✓What is the condition and age of the switchgear and panels, and are there any visible code concerns?
• ✓Can our equipment run on this voltage, or do we need transformers or converters?
• ✓Is three-phase available at the site at all, and is there capacity for more from the utility?
• ✓Where would new panels, conduit and charging equipment go?
• ✓What permits and inspections would any electrical work need?
• ✓What is a realistic budget and timeline for any upgrade, and what are the long-lead items?

Possible fixes for a mismatch may include a phase converter for limited applications, a transformer for voltage adjustment, or a utility service upgrade. Which works depends on your equipment and on the building, so get the answer from your electrician and, for anything beyond the building, in writing from the utility.

We do not quote an upgrade cost here. It can range from a small panel addition to new switchgear, a transformer and utility work, and it depends on the building, the site and the utility. Only a contractor's quote and the utility's written estimate tell you what your project costs, and the utility's own terms decide what it will charge. Get both before you sign if the building's fit depends on them.

Who pays is a negotiation, and it should not be left to chance. LeasePilot, a lease software company, recommends specifying electrical capacity in amperage and voltage, plus who pays for utility infrastructure improvements and the landlord's approval process for tenant modifications. These are the usual points to work through:

• A landlord contribution, either directly or through a tenant improvement allowance, on the argument that a stronger service stays with the building.
• Approval of the plans at lease signing, so you are not waiting on consent after you commit.
• Who owns the upgrade, and whether the landlord can require removal when you leave. Restoration can add a cost at the end of the term.
• Timing. Make sure that a late utility connection does not start your rent before you can operate, where you can negotiate that.
• Repairs. Law firm LP notes that a typical industrial lease makes a tenant maintain electrical lines serving its premises, so ask who repairs the new equipment.

Tenant Advisory Group represents tenants and buyers. We work to bring power questions into the first round of a search, so you can compare a building that already has the capacity against one where you would be paying for it. We also coordinate with your electrician and attorney on the terms.