How load affects Power Pack Performance

How load affects Power Pack Performance

Are your reefer loading processes harming your power packs?

How to properly load a Power Pack Generator
In a recent survey we asked the question, ‘What is your typical practice for connecting reefer plugs to your power pack?’ Possible choices included:

  1. We fill the receptacle panel then start the power pack.
  2. We connect one at a time while the power pack is running.
  3. We connect them in groups of 5 or more at a time.

While the number of responses varied between the choices, a significant number selected choice #1, indicating that loading the power pack’s receptacle panel with connections prior to generator start is the preferred choice.

It’s easy to understand, perishable cargo tends to move in large quantities. And with many reefers hitting the docks at any one time, the goal, of course, is to quickly get these refrigerated containers connected to power. But take a moment to consider that this technique may have the potential to cause damage to your equipment which could potentially render your cargo without any electrical power.

Why this is bad.
Loading too many reefer boxes at one time on a power pack can cause the engine to work excessively hard to catch up to the required load. In the meantime, this may result in a drop in generator performance as the engine struggles to maintain sufficient power to meet this sudden demand. The results will be a reduction in hertz or electrical frequency causing potential damage to the generator’s voltage regulator. Loss of frequency can flow downstream to the reefer causing damage to refrigeration compressors. Additionally, there is added stress on the fuel delivery system to maintain engine power.

Either of these scenarios will leave you with a down machine, expensive repairs, and a load of perishable cargo without electrical power to maintain temperature.

How to avoid a problem
A systematic approach to loading Power Packs should be incorporated in order to avoid costly and time delaying damage.

Power Pack Loading Procedure, a Best Practice Approach
Every power pack is different and may have varying engine and generator configurations. It is strongly advised to review and understand all of the manufacturer’s operations manuals prior to beginning any power pack starting procedure.

Once started, here are some guidelines to ensure that you maintain the best performance from your power pack generator.

Applying load
Once power pack is properly started allow the engine to warm up for 5 minutes before loading reefers. Engage Main Breaker to ON Position.
For ESL Power receptacle panels:

  1. Insert a single reefer plug into the panel and secure locking ring by rotating clockwise q.
  2. Depress the plunger to energize receptacle.
  3. Repeat steps 1 and 2 above for each additional receptacle plug added to the panel.

Continue loading reefers until reaching a load of 50%. At this time, check amperage on the generator control panel. This is important to ensure that your generator is managing the load and working within optimal engine performance. Refer to the specifications of your power pack for total amperage information.

If at 50% capacity total amperage is under the specified maximum amperage of your power pack, then continue to load reefers gradually to full capacity, but continue to monitor the ammeter.

If amperage is OVER the maximum amperage STOP LOADING and wait for refrigerated container compressors to cycle before continuing to load more.

Loading too many reefers, especially hot reefers, at any one time may cause the amperage draw to exceed the limitations of your power pack.

Maximum amperages vary depending on the specifications of your power pack. If you are unclear on the maximum amps for your power pack, contact Power Pool Plus for information. Operating a power pack at near max amp rating should be monitored closely to avoid tripping main circuit breaker and losing all connected reefers.

A special note on loading: At minimum, there should always be at least a load of 25% of total panel capacity. In other words, if operating a 40 plug power pack, minimum load will be 10 reefers or 8 for a 30 plug machine. This will protect your power pack in 2 ways:

  1. Avoid the damaging effects of wetstacking – thick black exhaust smoke.
  2. Allow a more efficient use of your power pack. More reefers attached to your power pack means less fuel burn per reefer – which will save you money.

Unexpected shut down while connected to full load of reefers
Should an unexpected engine shut down occur, either through a run-fault event or manual stop, never perform a re-start while connect to a full load of refrigerated containers. Instead, load should be removed from the power pack and brought back on gradually. Best practice would be; de-energize ALL ESL receptacles, ensure that the main breaker is CLOSED, and re-start the power pack. At this time bring reefers back on line following the procedure highlighted above by energizing the ESL receptacles individually until all are successfully back online.

Manually shutting down an operating Power Pack
Often times, out of convenience, bad habits, or simply insufficient operator instruction, emergency stop (E-stop) buttons are routinely used to shut down a running power pack.

Emergency stop buttons should only be used for emergency situations, such as pending harm to personnel or equipment.

Using E-stop buttons as a regular means of power pack shut down can cause damage to the engine and generator components by not allowing a proper disconnection of electrical current to the load and necessary slow cool down of the engine.
Instead, follow this procedure,

  1. Open main generator circuit breaker
  2. Allow engine to cool down for 10 minutes
  3. Press the stop button located on the generator control panel. The generator will then stop.  Some power packs have a built in shut down procedure that initiates upon pressing the stop button on the Control Panel. Check your Owner’s manual for specific information on your power pack design characteristics.

In short, unless it is an actual emergency, use the stop button located on the Control Panel and NOT the Emergency Stop buttons.

Wrapping it up
Each Power Pack is different with unique engine kVA and kW output. But the process for loading them to protect the Power Pack from overloading is the same. Following these quick and easy steps will ensure long lasting performance from your reefer power solution.

Power Pack maintenance doesn’t begin and end with oil changes. It starts with proper machine operation. No matter if your operation handles chilled loads, frozen loads, or pre-trips hot reefer boxes, Power Pack performance can be greatly affected by the way in which load is applied. Following these procedures to ensure that you get the most out of your reefer power system.

For more details on power pack operations read: 7 Best Practices for Every Power Pack Operator.

Have questions?
Please contact us today to learn more.


Power Pool Plus
Purpose Built Power Generation Solutions for Reefer Transport Since 1990
7 Edge Road | Alpha New Jersey 08865 USA
+1-908-454-1124

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