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Old 08-11-2008, 04:36 PM   #1
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Post Load Bank Generator Testing vs. Using Building Load to test generators.

Hi All,
I have a question on Load Bank Generator Testing vs. Using Building Load to test generators. According to NFPA 110:8.4.2 that states Exercised at least once monthly, for a minimum of 30 minutes at not less than 30% of the EPS nameplate and then there is another part if the maintenance plan does not meet this, NFPA states that if this requirement is not met, you need to test up to 75% load for two hours annually. (8.4.2.3).

I have a total of 8, 12.47KV, 2-MW Gensets. Each set of 4, connected to their own paralleling switchgear which severs a section of the building. We conduct an annual shut down our utility feeds thus conducting a simulation of a utility failure allowing the buildings full load to automatically switch to our generators. This also tests the ATS and switchgear operation.

Now, my question is... Since I am putting the full load of the building on these generators, am I fulfilling my obligations in meeting this code and not need to load bank the genets monthly? Mind you, we do exercise the generators monthly but under No-Load. Iím just trying to conserve energy (Fuel) and kill two or more birds with one stone. Thanks in advance for any input.

Mr. MAB

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Old 08-11-2008, 07:35 PM   #2
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Default paralled gensets testing

do not listen to me , just a thought how many do it correctly who follows the nfpa ?most plants or data comm maintance is less than needed or i feel bad news for the generators.what i have learned ,no load test each month for 30 min short starts is called wet stacking meaning deposits build up chambers clog diesel when needed it will not start. next a good test is a bad test. meaning at full load bank each time you do it your taking away the life out of that generator ,most say 75% running timed test thats normally done , but if you need to save money then dont ask me about testing a generator iam from the old navy school of testing generators . if ya load test with building load dont flip it over on transfer 100 percent thats only in a emergency case its not good for gensets.but most plant people do it, its not a good thing. slow step up to load is correct , switch banking is normally done by factory testing ,that is the correct way .if you test parralled gens, you need sync phase matching load percent of voltage change during transfer to cycle time , no one does it no one ever in commercial work , how about speed deviation timed at 75 % or response %time,ect ect ect ,save a dollar and spend 100k to fix it i worked on 400 cycle power generators once and was school the correct way , rule one never run a generator without a load minum 35% take time do it correctly flush out the fluids do it on a off day when no ones home test it the correct way get it ready for a power outage. ya that data center will be happy when they need it to start up.i have never agree with nfpa or most electrical contractors on testing generators , and thats any k voltage or mw ask your generators manufacture about this i may be incorrect and out of line best to ya take care .


Last edited by nick; 08-11-2008 at 08:37 PM. Reason: spelling problem i cant spoell
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Old 08-13-2008, 09:41 PM   #3
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Sites I work with exercise weekly ( three weeks - no load and one week with building load ) done in the maintenance window (1-5 AM). Weekly PM by the facility operator. Quarterly PM by contractor. Remote annunciators are tied into a monitoring system which is networked to a 24/7 network operation center. There are always facility personel on site when the units excercise with load and UPS / DC plant status ( batteries ) are checked prior to transfer.

Running diesel gensets continuosly without load can cause " wetstacking" which over time cause engine / performance problems requiring (additional?) engine maintenance.

We loadbank gensets once per year (contractor with a big portable load bank)

The other catch to never transferring load is not ensuring ATS operation.

Which side of the ATS do you connect your load bank???
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Old 08-13-2008, 10:59 PM   #4
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Default generator testing

when we say loadbank we undue the buss or conductors from main breaker or breakers in genset itself and hook up a load bank , just the generator.the heat coils are switch one at a time and all this is 15 minute switching each load to up load to full bank .this takes all day ,when we say transfer load test each transfer switch is tested but the dist panel or panels are shut down and loads are switched in min to maxuim load order not to stress out the genset full on or bogg engine , for only a test, and its a 8 hr run test at 100% once a year ,and each week monday 4am 30 minute with load at 35% not full load with 20 minute noload cool down , pararelling gets more into sync phasen ,voltage unload to load % speed to freq % to each genset and then when transfer is made the same is recorded and logged into a spread sheet for safe keeping , we also take now samples of oil send to lab to be tested most genset come with vac pump and a mailer to send samples to be tested ,even in florida we use engine heaters keeps oil warm ,i feel the engine is main reason for a generator which fails to start but i maybe out of line on this just what i have seen .
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Old 08-13-2008, 11:22 PM   #5
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I was being fasicious. My point being connecting the load bank at the genset doesn't verify ATS operation.

Neither does opening the main disconnect feeding the line side of the ATS. I've seen three phase ATS's fail to transfer upon loss of a single phase on more than one occasion.
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Old 08-14-2008, 05:35 PM   #6
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Default generator bank test

iam not very good at explaining just doing , we test genset alone once a year with load bank full on then reconnect buss connection to genset . next we test transfer switches but up load insteps meaning we shut off loads and turn on loads one at a time but we are testing transfer with loads also ,yes as you said we have seen a ats blow on transfer and i have seen it not complete a full transfer thats lots of fun half way not closed . and you step back a little. the worst ive seen is two parrelled out of phase and online it didnt last long. we are real safe when it comes to testing generators anything above 15kv gets my full attention .its just a way of good safety and less stress on the equipment that is not needed to be done , but thats our thinking hope we did not offend anyone guess we all do things differently out there best to ya take care .
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Old 08-14-2008, 06:07 PM   #7
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Several issues here.

How often do you have utility outages requiring the units to operate.

Running the generators regularly unloaded, is not the best situation, as unburned fuel can result in poor performance when and if the time arise you need the units.

When you do you yearly site load test what percentage of load do the units see?

The ATS should be operated regularly and IMO cycled monthly some one month other next month.

Additionally the ATS needs service / preventative maintenance.

When you run the units unloaded do you allow them to come up and parallel?

Personally IMO a site like this should do a full load bank test yearly and site maintenance yearly maybe six months apart.

You have a lot of money invested in these units your want them to perform at their best should the need arise.
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Old 08-14-2008, 07:39 PM   #8
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Default generator diesel

no one looks at the diesel , we test the electrical but i feel we mistreat the engine part completely , a 8 hour once a year is fine but 100% full load bank meaning 75% of kw , you get injectors blown clean , rings get to rotate meaning not set in one spot to score up the cylinder walls, water beads and acid in oil pan gets to boil out ,carbon built up blows out , oil lub pressure gets to parts when short 30 minute runs dont , seats and heads settle in hot , even the insulation in roto stator gets dried up from dampness just waitng to short it out , we dont load a generator max when in just a transfer at least what i have seen just looking at that amp meter but i think most jobs the larger ones have over sized the gensets dont get me wrong transfer is most important i know just had to give a little to the engine which with out it well ya not getting power at all. i was told you always size no less than kw needed but just 25% more any comments ?

Last edited by nick; 08-14-2008 at 07:49 PM.
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Old 08-14-2008, 07:53 PM   #9
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Quote:
Originally Posted by nick View Post
no one looks at the diesel ,
We look at them all the time you sign a contract and I'll send a tech to service yours.

Quote:
over sized the gensets i was told you always size no less than kw needed but just 25% more any comments ?
Not sure what you are saying?

Do you mean size for load and add 25%? Not sure if this is an engineering standard. Generally the unit is sized for full load capacity, allowing for motor starting (whether simultaneously or step started) and some growth.
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Old 08-14-2008, 08:32 PM   #10
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Default generator testing

ya brian john ,were just talkin generally about the maintance done by commercial or plants in house stuff or call out for a electrical contractor that justs runs a transfer test and thats it ,not a testing outfit .you sound like your specialty is testing mostly is that correct ?we mostly do the install meaning new jobs ground up new construction ,which includes generators ats switchboards , we test these for the owner once at end of the job ,we leave ,it never gets a real test again thats what we are getting at . yes i was asking what is the normal on kw is it 100% load with 25% or what is the standard way they find the size of a generator to load ? iam not into testing for my company but do test our work at the end of construction turn over to the owners we have to test each job generators transfer switches and switchboards but what happens when were done is another issue .we here it from our service dept people , who do test and tell us about some of the jobs not getting a load bank test just running a transfer and walking out , that the owner does not want to pay the bill for a real test or waste the fuel .

Last edited by nick; 08-14-2008 at 09:06 PM. Reason: spelling
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Old 08-14-2008, 09:20 PM   #11
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Hey Nick, understand you guys do the install & intial test and turnup.

I think Brian is stressing the need for routine exercising of both the gensets and transfer switches as well as a scheduled PM program by both the operator and a qualified contract service company ( assuming it is outsourced ) Correct me if I'm wrong Brian.

PM of the facility power system is so critical and often overlooked especially during difficult financial times. As companies look to reduce expenses ( typically this work is not a capitalized cost ) sometimes these type services are cut back as a cost savings measure often times at a catastrophic cost in lost production, service availability, etc.

sorry guys - I'm off my soap box.
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Old 08-14-2008, 09:47 PM   #12
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ya thanks ohmontherange and brain for your info i like to learn and get interested in just about everything i work on , theres another trade to testing from what we do in commercial or industrial work meaning electrical construction , but if you dont take interest in it or ask youll never learn anything not one to stop asking or get into a subject of interest . just to add for you guys for a laugh, my last post when them two paralled generators one running one coming online out of phase it sheared the shaft on the generator coming up when they switched it online no one got hurt but it sounded like the whole building blew up, factory said when its out of phase it will motor or go in opposite direction from diesel running direction the one online rules it split it apart ,take care best to ya

Last edited by nick; 08-16-2008 at 12:08 PM. Reason: for laughs
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Old 12-24-2008, 12:25 PM   #13
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Question Testing

Not sure of the type of facility but you would have to look at NFPA, JACO, and other standards you might have to comply with, on systems, the probelm with reyling on the building load is load factor and devirsity, can you gaurantee to meet 75% of the load for the full test?
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Old 12-25-2008, 10:34 AM   #14
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Quote:
Originally Posted by ohmontherange View Post

Which side of the ATS do you connect your load bank???
Directly to the Gen Set...........No reason to use the ATS. We Load bank 1 generator at a time, And, Hook a Portable gen Set To The Leads at gen set being load banked, along with the 2 Auto start Wires For temporary Service to the A.T.S. Of Coarse Thats a Hospital
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Old 03-16-2009, 04:53 PM   #15
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I am months late to this post, but I have a question.

These companies that do not want to "waste" fuel...how long can the fuel sit/last? What about the diesel Microorganisms (bugs), such as hum-bug?

Has this portion of the problem been conquered? I know there are additives, how long can those be added? How does this affect the gaskets, o-rings, hoses, tank linings, etc...
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Old 03-16-2009, 06:37 PM   #16
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We treat fuel with different products and also have subcontractors come in and do a fuel filter pump down. Basically they run a hose in the tank at high pressure to stir up the fuel and pump it through a special treatment. Other firms have a full time re-circulator that filters the fuel at regular times.

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