My gen set (120 kva) is only loaded to 20 KW since loads were split. 1

[Farang50]

Good morning from Thailand.

I have a cummings diesel generator set that use to run 3 houses as a stand-by power source.

Due to local problems the load was split and now only supplies 1 house , the maximum load is 35KW with everything on.
the generator is still set to run 10 minutes a day every day, with no load transfer.What kind of dammage is being caused to the engins?, and what suggestions does anyone have to solve this potential problem.

Thanks
Farang in Thailand

 

[FreddyNurk]

Ideally you'd want to load the generator every so often in order to prevent the usual issues with running the set lightly loaded.

Exactly how much load and how often is probably up for debate, waross & catserveng are two members here who would have the most coverage on what would be appropriate loading.

Other factors may include whether there's an engine powered battery charger which needs the engine to run every so often to charge the cranking batteries, or whether the battery charging arrangement is separate. I would have thought once a week would be more appropriate, unless there's a significant draw on the batteries from a generator control system.

EDMS Australia

 

[itsmoked]

I'd change that up for once a month and run it into a load until it reaches full temperature ~30 minutes probably.

Better yet, find a static transfer switch and load it with the house for that 30 minutes without blinking the lights.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Being a complete zero-knower, I have had my thoughts about this during the harsh winters that we have. Sometimes I need to rest for an hour or two while driving long distances and I need some heat so I don't wake up frozen to death.
My thoughts then are; does it hurt a diesel (it's a van with a 125 HP Engine) if it runs idle for a few hours?

I think I understand from the once every week or month recommendations above that a few hours shouldn't be a problem. Did I get it right? Or are there other issues? Not thinking CO or NOx - just Engine Health.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[FreddyNurk]

Skogs, the main issue as I understand it, is various things happen due to lack of appropriate engine heat. A diesel will run in less than ideal conditions, but is far more prone to damage when under loaded. If the rings don't seal properly due to less than adequate combustion temperatures, then oil can build up on the bores, or get pushed out the exhaust (I believe the term is wet stacking, or slobbering).

Automotive engines are designed to operate over a wide speed range and varying load, which most of the time means that less than ideal conditions don't persist long enough to be of any consequence. Since its also possible to reverse some issues due to low loading by loading a generator up and running it at high load for a period, there's generally very little issue in idling for a while and then driving off again.

EDMS Australia

 

[itsmoked]

Not a vehicle problem Gunnar unless taken to extremes. Couple of hours - no problem.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

10 minutes a day unloaded is excessive. It will probably do more long term damage than not running at all.
How often do you have a power failure?
If you have a power failure about once a month or more often, that should be enough exercise.
Some codes require that generators for critical loads be exercised on a regular basis.
As a standby generator for a home, exercise is not generally needed.

Batteries:
One issue with infrequent running is battery state of charge.
A genset for a critical load in a major North American city may not be see a power failure for several years. Even the best battery may not dependably start a set after sitting unused and uncharged for several years. Monthly exercise will show a failing or faulty battery which may be changed out before it is needed for a real event.
An often used option is a trickle charger but that is a two edged sword.

Without the battery charger, eventually the battery will fail. You will get a call from the home owner;
"The power failed and my set didn't start."
Install a new battery and the set is good to go for another three to five years.

With the battery charger, eventually the battery will fail. You will get a call from the home owner;
"The power failed, the was an explosion and my set didn't start."
On the way to the site stop in at a grocery store and buy some baking soda.
Use the baking soda to clean up as best you can the sulfuric acid spread around by the exploding battery.
Disconnect the battery charger.
Install a new battery and the set is good to go for another three to five years.

Many sets have a trickle charger built in to the control panel.
Unless there is a code reason or direct instructions to use the charger, I disabble the charger.
For residential installations I always disconnect the charger.
I never had an injury from an exploding battery, but many of the sets were in fairly exposed locations and an injury was possible.


Standby generators and Wet Stacking or Slobbering;
A standby set engine has a rough life.
Typically it is called upon to start cold and within seconds is hit with a significant overload.
After the initial start it may run for extended periods at 10% to 25% load.
My sizing criteria for residential sets was in part starting air conditioning loads. Without fail, if there was enough capacity to start the A/C there was more capacity than needed to run the normal loads.
Wet stacking brings to mind a set that has a few tens of thousands of hours of run time and is well past the reasonable point of rebuild.
However I have seen this issue with brand new sets.
Occasionally the rings will not be well seated in a new set. I have seen a couple of new sets that blew most of their lube oil out past their rings the first time that they ran in service.
The solution was to load bank the set for three to five days.
I have not yet seen wet stacking in a mature set. It is mostly an issue for brand new sets and end of service life sets.

Cold idling;
It happens. Cold operation is not good for a diesel engine. With the new particulate filters and exhaust gas treatments on the newer truck engines it is even more of an issue.
That said, truckers have historically left their engines running when the vehicle is stopped for up to several hours in cold weather.
When you pull over to warm up, Gunnar, the slight possible damage, or more likely a slight lessening of the life of the engine is insignificant compared to the possible issues should you stop the engine and be unable to restart it.
Your well being may be more important than the engine's well being.
Add to that the possible damage or accelerated wear to the engine of getting an assisted start under the condition of extreme cold.
While cold idling may tend to load up the exhaust filters, highway running under load tends to clean the filters.
Fuel consumption: A generator engine running at light load at minus 20 C will be burning a lot of fuel just keeping the engine warm.
I was in the position of running a home on a genset in minus 20 C to minus 30 C. I restricted the air flow through the radiator to about 10% and the reduction in fuel consumption was noticeable.

Recommendations.
Home standby set:
No exercise. No battery charger.

Gunnar. Keep on keeping warm. I may do exactly the same as you.
On the other hand, on long cold night drives and with a petrol engine, I may turn the engine off and sleep until the cold woke me. If I were still sleepy, I would repeat 10 miles farther down the road.
With a diesel engine, I would do exactly as you do.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

By the way, you may be able to pick up the lost loads with additional transfer switches.
I did a couple of projects with more than one transfer switch. I one case to pick up two widely separated loads in the other case to supply standby power to four residences on four different revenue meters. One generator and a transfer switch for each load.
And by the way, it is often much cheaper to build a transfer switch with off the shelf components than to buy one from the set supplier.
If you buy a transfer switch as a package with the generator you can't beat the price.
If you buy a standalone transfer switch, the price may be insane.
Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Skogsgurra]

Thanks all! We are now in summer - but there will be Winters again.
If there is wind, I position the exhaust pipe away from air intake. Hmm... I mean I position the car.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.