Automatic transfer switch testing

[cornbread]

NFPA 110 has the following:

8.4 Operational Inspection and Testing.
8.4.1* EPSSs, including all appurtenant components, shall be inspected weekly and exercised under load at least monthly.
8.4.1.1 If the generator set is used for standby power or for peak load shaving, such use shall be recorded and shall be permitted to be substituted for scheduled operations and testing of the generator set, providing the same record as required by 8.3.4.
8.4.6 Transfer switches shall be operated monthly.
8.4.6.1 The monthly test of a transfer switch shall consist of electrically operating the transfer switch from the standard position to the alternate position and then a return to the standard position.


Does any one test ATS monthly? Seems a bit risky to me!

 

[buddhakii]

Yearly is what i normally see.

 

[charlietuna]

there are a lot of moving parts in a transfer switch --you want problems--don't test it ! it should be tested under load weekly if possible. i have maintained buildings in both catigories - it pays to function them ! running a generator with no load is bad for the engine ! remember they also test elevator recall relays and other interlocks ---

 

[joebell]

there are a lot of moving parts in a transfer switch --you want problems--don't test it ! it should be tested under load weekly if possible. i have maintained buildings in both catigories - it pays to function them ! running a generator with no load is bad for the engine ! remember they also test elevator recall relays and other interlocks ---

I don't agree that running the generator without the load is bad for the engine. Most generators have a cool down period to properly shut them down.

I do agree that the generator should be exercised under load. I have seen too many instances where a generator failed during a power outage. when ever I get one of these calls the first question I ask is when was it serviced last and the second is when was the last time it was tested under load?

Preventive maintence I feel is also crucial for proper operation.


Joe

 

[brian john]

We have several sites that refuse to test the ATS and sure enough come an outage and income the calls.

They make a test switch for one reason.

What I do not like is sites that test on off hours with no one on site.

The ATS has moving parts, clearing contacts can come out of adjustment, lubrication can become contaminated, if this is a concern to you regular maintenance should be considered.

 

[LarryFine]

From a purely mechanical point of view, engines break in better under load. The increased cylinder pressure pushes the rings against the cylinder walls better.

 

[brian john]

I don't agree that running the generator without the load is bad for the engine. Most generators have a cool down period to properly shut them down.

This has NOTHING to do with it. Diesel's run under no load do not adequatly burn all fuel, continue operation like this can lead to problems when trying to operate under full load. Not a recommended situation.

 

[mdshunk]

This has NOTHING to do with it. Diesel's run under no load do not adequatly burn all fuel, continue operation like this can lead to problems when trying to operate under full load. Not a recommended situation.

"wet stacking". Literally, everything on the exhaust side gets gunked up with unburned fuel. You might notice black tar running out of the exhaust pipe joints.

 

[charlietuna]

joebell,
standard controls on transfer switches have a timing relay which allows the generator to cool down before engine shutdown. this is adjustable.
engines do not like to be loaded while in a cool condition--thats why most insurance companies require generator engines to be equiped with crankcase heaters--running a diesel engine connected to a generator at no load proves nothing and many controls are never functioned unless a load is applied--full expected load preferably ! and as brian stated--buildings that do not function their emergency systems are the ones calling at every power outage! we had one building that had 46 asco transfer switches and a program where they were tested weekly via the transfer switch's "test switch" and once a year by actually de-enegizing the normal power source. the building across the street had six asco units and had a constant list of problems after every power outage. they never tested weekly nor yearly ?

 

[iwire]

I don't agree that running the generator without the load is bad for the engine.

As the others have mentioned diesels need a load in order to run correctly.

We have installed load banks for over sized generators and we have also received Gensets with built in load banks to load the unit for weekly exercising.

 

[mdshunk]

On a side note, any diesel genset that has only been exercised unloaded for years, and is suddenly pressed into service for real, will put on a fairly dramatic display. The exhaust will look like you're burning coal for a couple hours until all that build-up is burned off.

 

[cornbread]

Appreciate the replies. Most of the ATS's we have are break before make, so I get a power blip during the transfer.

 

[joebell]

Diesel's run under no load do not adequatly burn all fuel, continue operation like this can lead to problems when trying to operate under full load. Not a recommended situation.

I didn't think it could harm the engine but I can see I was wrong. Thanks for setting me straight.

I do however think anytime a generator is exercised it should be under load and it should IMO operate the ATS. This way you know everything is functioning as it should.

Joe

 

[brian john]

I do however think anytime a generator is exercised it should be under load and it should IMO operate the ATS. This way you know everything is functioning as it should.

Joe

I agree 100%

 

[JacksonburgFarmer]

Yepppp....

Yepppp....

Ya, they get tested....We do Agricultural work, and in hog barns, they get tested once a week. If there is no electric to run the fans and pull out the gasses from the manure pit under the barn, the pigs die....quick.....REAL QUICK...So they test once a week at least....Not using something is harder on it than using it...goes for any thing, trucks....tractors....lawn mowers......breakers.....what ever ya got, sitting is worse than using!!!!

 

[ohm]

Before we were allowed to use a new ASCO ATS we had to have the installation approved by them, or loose the warranty. So we paid the big bucks to have a factory guy come. He arrived late while 50 electricians and a plant was waiting to start up. We gave him a hardhat and ignored his tennis shoes. He asked to borrow a megger and a few minutes later told us we needed to dig up 300 ft of direct burried 500 MCM (8/ph).

After everybody calmed down I noticed he had placed the megger un top of the busswork. Well it was a hot humid day and the megger was still in the cardboard shipping container.

After taking it off the bussbars everything tested fine.

He said he didn't need a torque wrench he had done this so many times he could test the bolting with a socket wrench.