What is the point of a generator acceptance test on site and commissioning?

The process of a generator acceptance test and commissioning is for the end user to accept that the product delivered is suitable to their requirements and is set up correctly. A diesel generator can have many individual settings for control and monitoring which should be configured to the clients requirements.

The point of commissioning is the point at which any warranty based on the time of delivery is invoked and also the point at which non-warranty visits (for example a change of settings would be chargeable to the end user.)

What should be ready at the point of generator commissioning? 

The generator should be fully installed by the installation company or the end user. For reasons of cost companies and individuals often opt to install a generator themselves or using their own subcontract teams rather than the generator suppliers team. 

This is rarely a good idea, as inexperienced people will make installation mistakes that mean the commissioning cannot be completed and lead to additional commissioning charges for a second visit.

if the company performing the commissioning is not the company doing the installation then aborted or failed commissioning visits will be charged and further charges raised for future visits to site.

In order to perform the commissioning the generator should be fully installed; have a suitable amount of fuel available, have the correct coolant in the radiator and have the correct engine oil in the sump, filled to the correct point on the dip-stick. The batteries should be fully charged and any jacket heating devices should of been wired in and left on to ensure the unit gets to the correct block temperature. 

Which tests are normally performed at commissioning?

At commissioning the generator would normally have a basic function test performed on it, followed by a site load test. At this point, the site will lose power briefly (unless it has a UPS backup) as the load is switched onto the generator. It will also lose power again as the load is switched back to the mains. As this is the first initial run on site of the generator, the first changeover could of course have issues, in which case the power may be down for longer. It is suggested that the test is therefore conducted at an appropriate time.

The length of the test will depend on the clients requirements and the fuel available. it is typically between 1 and 4 hours.

The generator settings should be confirmed with the client also. Settings such as under-voltage, over-voltage, under frequency, over frequency as well as a full array of other generator parameters. The customer should then sign off these parameters to accept the generator.

Why isn't a full load test performed at generator acceptance?

Normally a site is not capable of providing full load, or load stepped in such a way it is practical to do a full load test on site. A full load test could be performed with the aid of a load bank. This would be with prior arrangement of the commissioning engineer. the site will also need to have made allowances for the connection of this load bank.

Load banks are more commonly used at a generator factory acceptance test (FAT).