Six Questions to Correctly Size A Generator

When it comes to taking care of the generator fleet, correctly sizing a generator for a customer is critical. You want to make sure they have enough power, but not enough that there will be issues with light loading, inconvenient regions, or lockouts. Here are six basic questions to ask to ensure that the generator recommended to the customer is appropriate for their needs.

1. Is the load going to be a single-phase (10) or three-phase (30)?
   This is one of the most important items to know before starting. Understanding what phase the generator needs to be placed in will address what voltage requirements are needed by the customer to properly operate their onsite equipment.
2. What is the voltage required: 120/240, 120/208, or 277/480?
   Once the phase requirements have been met, then you as the provider can set and lock the appropriate voltage per the generator’s selector switch. This presents an opportunity to fine-tune the generator to the voltage for proper operation of the customer’s equipment. There is a minor voltage adjustment knob (potentiometer) conveniently located on the face of the control unit to do any minor voltage modifications once the unit is on-site.
3. Do you know how many amps are required?
   By knowing what amps are required to run the customer’s piece of equipment, you can properly utilize the correct generator size for the job. Having this information can be vital in the success or failure of the application. Too big of a generator for the appropriate load and you will underutilize the generator’s potential and cause engine issues such as “light loading” or “wet stacking.” Too small of a generator, and the customer’s equipment may not run at all.
4. What is the item you are trying to run? (Motor or pump? What is the horsepower?)
   In all cases, when sizing a generator to a particular application or customer need, knowing what the customer is operating is extremely helpful. By communicating with the customer, you can understand what type of equipment they are running on location and build a “load profile” based on this information. For example, are they using submersible pumps to move liquid products? Then, knowing the horsepower and/or the NEMA code of the pump is critical in choosing the properly sized generator.
5. Is the application standby, prime, or continuous?
   One of the key components of sizing is the time in which the unit will run. The buildup of heat in a generator’s windings can cause a de-rate inability. Altitude and run times can have a dramatic effect on the generator’s performance. In the simplest of terms, consider that mobile diesel generators are rated in Prime Power, operating for eight hours per day in a rental application. The longer the run times at higher loads, the more harm can occur to the generator’s windings. The reverse is also true however. Long run times with
   zero loads on the generator can hurt the engine of the generator.
6. Will multiple items be run at the same time?
   Knowing what types of loads will be running simultaneously is also a determining factor when sizing a generator. The use of multiple voltages on the same generator can create a difference in performance. If renting a single unit to, say, a construction site application, what type of tool will be used at the same time on the generator? This means lighting, pumps, grinders, saws, electric appliances, etc. If the primary voltage being used is three-phase, then only the convenience outlets are available for minor single-phase voltage output. Contrary to that, if the unit’s main output is desired to be a single phase, then three-phase power will not be available. Asking and answering these questions with your customer before a rental can greatly increase their onsite production to ensure a proper quality rental experience. Your customer may not know the answers to all the questions; however, by doing this due diligence and information-gathering, you can ensure that you are giving the absolute best advice possible to properly size the generator to the application. This in turn will keep your fleet in proper working order as well as keep a happy customer base.

Helpful Sizing Formulas:
Converting three-phase rating to single-phase rating for generator output
30 3phase kVA x .58 = 10 Single Phase kW (+ – 5%)
30 3phase kW x .72 = 10 Single Phase kW (+ – 5%)

Single Phase 10 Formulas
kW= (volts x amps x Power Factor) ÷ 1000
kVA= (Volts x Amps) ÷ 1000
Amps= (kW x 1000) ÷ (volts x PF) (use if kW is known)
Amps= (kVA x 1000) ÷ Volts (use if kVA is known)

Three Phase 30 Formulas
kW= (1.732 x volts x amps x PF) ÷ 1000
kVA= (1.732 x volts x amps) ÷ 1000
Amps= (kW x 1000) ÷ (1.732 x volts x PF) If kw is known
Amps= (kVA x 1000) ÷ (1,732 x volts) if kVA is known

Scaffolding Safety Tips and Hints

Scaffolds offer many advantages over ladder-jack assemblies whether you are changing sky-high warehouse light bulbs or replacing windows on a two-story home. Framed scaffolds or pipe scaffolds provide a wider platform working surface, can be moved without disassembly, and feature guardrails to keep you from falling. Here’s how to safely use scaffolds to get things done off the ground.

1. Make sure you are trained properly to set up scaffolding.
2. Check location for ground conditions, overhead wires, obstructions, changes in surface elevation, and tie-in problems.
3. Inspect frames, braces and all other components for damage, bends and excessive rust or wear.
4. Use a safety harness which is tied off to the scaffold, building or lifeline.
5. Assemble frame scaffolds with one other person so that one person is on the scaffold and one is passing materials from the ground.
6. Check for squareness and alignment of all scaffold parts.
7. Remove debris and mud from the setup area, and level the ground before placing the staging legs.
8. Setup the staging legs on a stable, solid base. Use mudsills when scaffolding is erected on soil.
9. Use appropriate mud sills that are continuous under at least two support feet.
10. Nail or screw the base plates to the mudsills.
11. Use jackscrews to eliminate hazards created by temporarily jacking up the erected scaffold to add shims when sections settle or are not level.
12. Inspect locking devices frequently.
13. Make sure all sections of the first level are level and square.
14. Install ladders as the erection proceeds. When scaffolds are to be in place for an extended period, install a stairway. Ladders must extend 1 m (3 ft) above the platform and be tied securely to the staging.
15. Fasten all braces and guardrails securely. Make sure all cross bracing fits and locks onto each post in every section.
16. Install all of the guardrails that are required: top, mid and toe. Requirements will vary depending on the materials used, and on the the legislation that applies in your area.
17. Inspect planks before use. Check the weight the planks will have to carry, including the weight of the crew, tools and materials.
18. Complete platform fully at each working level before assembling the next level.
19. Secure the scaffolding to the adjacent building structure as specified in the legislation that applies in your area.
20. Assemble all equipment according to manufacturer’s specifications or engineer’s design.

Best Practices for Safe Ladder Use

1. Get the Right-Sized Ladder for the Job
   One of the factors in getting the right ladder for the job is length. A good rule of thumb when selecting a ladder is to calculate a person’s maximum reach height, which is approximately 4 feet higher than the height of the ladder. Duty rating is important as well, so be sure to pick the right ladder for your workload and weight.
2. Place Your Ladder on Firm, Level Ground
   Be sure to clear trash, construction materials, and other obstructions away from the base and top of the ladder. The base of the ladder should be safely secured to prevent accidental movement. You can also use a ladder with non-slip feet or add outriggers or levelers to the bottom of an extension ladder to increase the footprint.
3. Take Your Time Climbing Down—Don’t Skip Any Steps
   Exercise caution whether you are climbing down or up a ladder. Always face the ladder when climbing up or down, and be cautious until you’re on the ground.
4. Keep Three Points of Contact When Climbing Up or Down
   To keep your balance, always maintain three points of contact—two hands and a foot or two feet and a hand—while climbing up or down a ladder.
5. Stay Within Your Reach
   When working from a ladder, keep your center of gravity and body between the side rails. If you can’t easily reach the project area once you have ascended the ladder, climb down and move the ladder more closely in alignment.