Before you rent temporary power, you have to know how much you need.
If you have to keep your whole facility operating as it would with utility-supplied power, you need to determine your aggregate electrical load.
The quickest, easiest, and most accurate way to do this is to take ammeter readings of your electrical distribution boxes. Take the reading when your company is normally operating at peak load. You may also be able to obtain peak demand readings from your utility bills.
Aggregate loads are also listed on panels of electrical distribution boxes.
At times, you may want to power only those electrical loads that serve critical functions at your facility. If so, you need to prioritize individual loads.
If you’re not sure what your critical loads are, start by determining the lost profit or other problems that result if your company is without the equipment. Other than life-safety electrical loads powered by your standby generator sets as required by law, examples of critical loads include:
- Heating, ventilating, and air conditioning (HVAC)
- Process Equipment
Prioritizing will help you decide which loads require power immediately during an emergency. This is important since it may take several hours or longer to secure all of the rental equipment you need onsite during a large-scale emergency, such as a natural disaster.
In most buildings, a separate distribution box will feed critical loads. In this case, you may only need enough temporary power for the loads served by that set of circuit breakers.
You can also decide to power specific critical loads served by separate circuit breakers within a distribution box. To do so, take an ammeter reading of the distribution box during the off-hours at your facility with the equipment you don’t need shut off and the critical loads on. The ammeter will tell you how much power you need to serve the critical loads since that is all the distribution box is feeding. However, it’s important that the non-critical loads are shut off and kept off when rental power is hooked up.
If you want to power individual pieces of equipment that use motors, amperage and voltage information is listed on nameplates. You can list this information and all your power needs on the downloadable worksheet on this page.
An additional note: Rental power is often used to back up standby gensets during scheduled and emergency outages. To find out how much temporary power you need for standby service, contact the company that supplied the standby generator or a qualified rental generator set dealership.