Dear Sirs,

A customer has two standby generators set.
Diesel engine data
Make: Cummins
Type VTA 28G5
Serial no. 25226548
Alternator data
Make: Stamford
Type HCI 534F1
Serial no. 075534/01

Up to know they has been used as standby system. Due high energy cost the customer is considering to run them during a complete week. The other three weeks of the month he will connect his installation on the public power grid.

My question is, can the above mentioned engine run for one week constantly? Or are they especially made to serve as standby power?

I want to hear your comments before I advise the customer. Your comments will be appreciated.

Sonny

 

Hello Sonny

Standby generators can be run continuously.
Cummins/Stamford is a great combination.

I have a couple of suggestions.

Test all the engine's shutdown circuits. High water temperature, low oil pressure etc.

Keep up the maintenance. Change the oil, oil filter, air filter and fuel filters at the manufacturer's recommended intervals (make sure the engine hour meter is working).

Install a low water level switch (Murphy gauge) in the radiator to shut down the engine if the water level drops. Without this, you are just relying on the water overtemperature switch which may not work if the water drains quickly through a bad leak. A Murphy gauge also gives you a visual indication of the water level when the engine is running.

Usually the starting batteries sit on the steel frame of the generator. This frame vibrates when the engine runs and this vibration will eventually destroy the battery internally. Lift the batteries off the frame and sit them in a plastic battery box on the floor.

Make sure the fuel tank is big enough and install a low fuel level switch in the tank which activates a loud siren.

Diesels do not like running on light loads for long periods. Make sure there is enough continuous load.

Good luck.
Jamie Downs
New Zealand
[email protected]

 

Dear Sonny,

Whether a given Diesel Engine can run continuously for a week or more, well only the manufacturer can say. But, most large diesel engines will run happily for extended periods of time, provided, proper maintenance procedure is accepted. We have run a Cummins Diesel Generator for 10 days continuously. This was when we lost our mains supply due to a fault on HT incomer.

We run our pipeline pumping using medium speed diesel engines. We alternate engines after 250 hrs of operation. This is a requirement of scheduled maintenance. We have also run them continuously for over 40 days at a time, in exigencies, without any problems.

Endurance of a diesel engine is a matter of design and the
manufacturer should be consulted. Period.

Regards,

Tomy Zacharia

 

Provided they are loaded to the manufacturers specifications that would be quite OK. Check with the manufacturer and find out what % of load is required to stop the engine cylinders from glazing. It si usually about 40% load (horse power) but engine requirements do vary.

 

Should be alright. See this article. http://www.friend.ly.net/GEET/backup.htm

oj

 

If your generators are properly maintained, all alarms work correctly and there is pleanty of fuel, there should be no probelm.. IF your looking for specfic run time limitations of issues, call the rep who services the units or talk with the manufacture. Typically a unit which is loaded appropriately and well maintained can run indefinetly.

Before I would recommend this type of solution, I would look at the respective cost of running the machines vs staying on grid power. There may be cost saving methods available such as turning off non-essential equipment, running heavy demand equipment at night when rates are cheaper, avoided high demand charges by running heavy demand equipment near the beginning of month and keeping it running all month.

A generator has to be maintained, needs fuel and spare parts and if it goes down it can very expensive to repair. Unless the backup system was designed to provide 24/7 extended duty, the associated cost of doing so may not really offset the slightly higher energy cost from the utility provider. You can also look load shedding equipment from the utilit yprovider and other bulk power purchases to meet your demands -many heavy users I deal with purchase a avergae number of KWH's to reduce their overall energy cost, if they use more there is a penalty, if they use less they get a rate reduction or some other form of discount on their energy needs.

MJH