Calling all Electrictians - Broken Generator, HELP!!!

[staindsoul]

More accounts. No one runs a utility line to residential home and wires it 120/208 single phase. It's not mathematically possible on a transformer to do so and maintain 120v to the ground reference. You would be dropping the 120 down below the 105v. Not gonna happen.

http://www.doityourself.com/forum/electrical-c-d-c/422430-120-208-single-phase-3-phase.html

http://answers.yahoo.com/question/index?qid=20090809202958AAKJkjf

 

[staindsoul]

Ok dude your so right I've never had a 120/208 single phase hook up! Ya right the majority of services down here that used to be a center grounded wye aka high leg which is where a or c to ground is 120 and b to ground is 208 have all been changed over to a straight 120 208 single phase service where they have deleted the high leg and both hots are fed off of a zig zag ground transformer that is where you delete the center grounded leg and replace a old school 3 phase panel to a single phase panel no more high leg these are real common in areas where you have housing close to older industrial areas. I do these all the time when people buy older industrial shops remodel and repurpose the spaces

:headwallblue: and does his place sound like a industrial shop!

A high leg comes from a delta grounded system, not a wye! See diagrams in post #44

A wye is always grounded in the center with a equal point of reference to all windings. A delta is the only way to ground and obtain a unpoportional reference to ground. Again see post #44

I apologize for saying, bs. It wasn't a great way to approach disagreeing with you. I don't doubt your expierience, but I know that he would do damage with that generator. It wasn't even referencing ground properly for a 120v receptacle.

 

[WillM]

The main breaker does what it's supposed to. The whole house went dark. I just checked the weather channel and it looks like where I'm at might be out of the woods. So, hopefully this will be a non-issue. When I get my tax refund back I'll get an electrician out here to look at this mess and wire it correctly. I have to GFCI a couple of outlets that my tanks are on and add a few more outlets in my basement anyways.

Thanks for everyone's input

 

[staindsoul]

Awesome, will. Roanoke to Richmond 3 hours. I work cheap for beers and a steak. :lol: Unless you got some land for wheeling my jeep, then I work for free, maybe :lol:

 

[Craig pc]

120/208 Single Phase
What is happening is you are providing two legs of a three phase source to a meter that has a neutral potential lug (normally at the 9:00 position) so the customer (normally residential) will have a normal single phase service. The problem is that the two legs are separated by 120 degrees instead of 180 degrees and for water heating, electric ranges, ovens, and electric dryers, he gets 208 volts instead of 240 volts. The meter center gets all three phases and each meter gets different pairs of phases. If a meter center has 12 meters, 4 would have A and B, 4 B and C, and 4 C and A. I hope I haven't muddied the water
Responses based on the 2011 NEC

Here's some more info on 120 208 single phase

 

[Craig pc]

Delta Wye Transformer
Delta-wye transformers are common in commercial, industrial, and high-density residential

 

[staindsoul]

But it is still not a single phase service, and would not be used at a residential home. a strip mall or apartment complex, yes, but not a resi home. Nor did it apply to op, which is why I so addimately disagreed with you, telling him to use that generator was not correct. And slamming me as retarded was way off base, my mother had me tested.

 

[staindsoul]

Delta Wye Transformer
Delta-wye transformers are common in commercial, industrial, and high-density residential

Yes and wire it on line voltage side-delta configuration , load voltage side-wye configuration.

There is no high leg wye configuration, that you referenced.

 

[Craig pc]

Lol and I disagree my whole subdivision is fed like this there is a pad mount xfmr mounted at every third house in the utility easement each house has a meter at the home and is fed from the xfmr it came out 10 times cheaper on the developer to build this way and is all underground nothing overhead except to the substation at the back of the subdivision. Many subdivisions here are doing this for cleaner looks and the developer brings in substation and powers mud district and houses out of it it is a single phase service

 

[dread240]

Staind is absolutely right... I see no way of it being a delta connection at all. In fact... (and I will say honda generators aren't my specialty) but all of them I've come across recently are all inverter units utilizing 3 phase variable excitation (upwards of 300v AC per phase) ends which are rectified to dc voltage and then inverted back to 120/240v ac. Many of our new cummins rv/mobile/commercial sets are doing the same thing now. Even still, I don't put my money on a delta stator setup at all, and sounded like a neutral bonding issue more then anything.

without knowing the exact model of the generator in question though, and having access to literature, I can't condemn the generator itself and is most likely a bad neutral connection. What was the frequency reading like? clean 60-62hz or was it showing 120hz or anything like that? Many times on the new inverter sets they'll use a PMG with a variable speed engine, as load is increased the engine speeds up so that it makes a higher voltage in the 3 phase end, as this voltage is then rectified and inverted it allows for the additional current capacity while maintaining a clean 120v output. This further complicates diagnostics as the inverter at points will do all it can to maintain output, however the stator may have 2 coils shorted together and will cause the unit to go out on over current or give many other issues and can only be tested by isolating the stator and testing it thoroughly.

-Certified Cummins/Onan power gen technician

 

[jimmy frag]

well there you have it folks, someone who agrees with me that it a neutral issue. 2 agains 1

 

[dread240]

as for using delta-wye xformers, I can't say, I leave that up to you silly electricians, I'm only responsible for making the power at my facilities, and I can say that in none of our larger substations is there ANY delta equipment at all, it is all wye stators. Periodically, on some of our mobile units which go overseas, we will do voltage selector switches so that they can utilize any voltage output possible of the unit, but that's the extent of it (lets us run anywhere from 100v single phase 50hz out to 480v 3 phase 60hz on the same generator with the flip of a switch)

I do not handle residential stuff anymore though... I'm all data center, hospitals and military, with systems ranging between 2.7megawatt and 64.8megawatt systems (24 of our 2.7MW medium voltage generators in parallel with utility)

 

[Ciscokid]

Which one would be more protected after an EMP event?

 

[staindsoul]

Dread I put 2-750kw cummins in aquia, va that $4.5 million job i referenced. My tech was Fred, big older guy w/ white hair. Real nice. Long shot you know him?

I wish I had a emp device, Cisco. :lolspin:

 

[dread240]

well there you have it folks, someone who agrees with me that it a neutral issue. 2 agains 1

well realistically, unless it is a commercial unit with a pto output on it 98% of the generators made won't stay running unless they're making the correct power.

Generally our stators have 3-4 sets of windings for system.

t1/t2 windings are your 120v coils, 180 degrees out so you can get 240v l-l or 120v l-n

q windings which are used as a speed reference and feed the voltage regulator to keep the field up on the rotor (without this coil the regulator has no voltage to work with to maintain the dc voltage going through the rotor providing excitation)

b windings are a low voltage ac output that we rectify to dc voltage for control power. Once the start disconnect is engaged the control no longer asks for power from the battery (as it would drain it down and shut down) and utilizes this voltage to keep the unit running.

That is the same on all of our units minus the inverter setups. The inverter setups just rectify the ac output, then diode isolate and step down to control voltage all internally in the inverter system.

 

[staindsoul]

well realistically, unless it is a commercial unit with a pto output on it 98% of the generators made won't stay running unless they're making the correct power.

Generally our stators have 3-4 sets of windings for system.

t1/t2 windings are your 120v coils, 180 degrees out so you can get 240v l-l or 120v l-n

q windings which are used as a speed reference and feed the voltage regulator to keep the field up on the rotor (without this coil the regulator has no voltage to work with to maintain the dc voltage going through the rotor providing excitation)

b windings are a low voltage ac output that we rectify to dc voltage for control power. Once the start disconnect is engaged the control no longer asks for power from the battery (as it would drain it down and shut down) and utilizes this voltage to keep the unit running.

That is the same on all of our units minus the inverter setups. The inverter setups just rectify the ac output, then diode isolate and step down to control voltage all internally in the inverter system.

No problem saying this is over my head. I know the load side of these bad boys. But seriously dread, my previous post, you know Fred? Big ole country boy.

 

[dread240]

Dread I put 2-750kw cummins in aquia, va that $4.5 million job i referenced. My tech was Fred, big older guy w/ white hair. Real nice. Long shot you know him?

I wish I had a emp device, Cisco. :lolspin:

nope, that would have been a cummins atlantic job, just south of our territory. I'm with cummins power systems (a different distributor) and we only really touch northern va, DC, all of MD and Delaware (and our other branches take it from there up)

2 750's would be on the lower end of what I'm normally working with unless there were remote networks and web servers involved too... You can thank me for making sure that the hot lanes they just built around 495 can charge you through even a hurricane, and their guys never even have to get wet to know what they're doing from miles away lol.

We have so many data centers, hospitals and bases in this area that they generally keep me busy on those, and it seems like MC Dean has 90% of those contracts these days

 

[staindsoul]

Come to think of it it was cummins atlantic. Mc dean has a strong hold I'm dc and surrounding area, they are some major players right there.

We stick with waste water and water treatment, company is out of Ashland, va. Northern va is nothing we wanna mess with. Traffic sucks.

 

[dread240]

Come to think of it it was cummins atlantic. Mc dean has a strong hold I'm dc and surrounding area, they are some major players right there.

We stick with waste water and water treatment, company is out of Ashland, va. Northern va is nothing we wanna mess with. Traffic sucks.

yup, that's why I generally start work around 4:30-5am in the morning to beat it going to a site, and then leave earlier so I don't hit it on the way home. I live just northeast of baltimore, so I have to deal with all the corridor traffic.

Hearing our bigger gens fire up and go online is one hell of a sight though isn't it... We've done a couple sites with some ridiculous requirements recently because of people utilizing rotational ups systems. Had 7 1500kw generators in parallel on a common bus with utility. 10 second window to get at least 4 started up, up to speed and pulling full load, and within another 3 seconds the remaining 3 have to be online due to the short timeframe you have with rotational ups systems.

Most people don't realize that what we're doing in essence is actually matching the exact rotation point within a couple degrees of each other when we parallel (otherwise the generator snaps around and is 'motored', sometimes resulting in it jumping off the pad or sometimes even worse and blowing out the diodes on the end). It's tricky but technology has brough it a long ways from watching a synchroscope waiting for the right moment and doing it manually :lolspin:

 

[staindsoul]

to hear your motors start, shoot to feel one is unreal! heart stomping. the 2-750s were fun to put in the building. it was exsisting and we had to roll them in on "skates". i believe they were $250k a piece. i was sweating bullets. got them in and started my buss duct out and then they found the genset was chinese and not british like submitted. engineer blew a gasket. i thought i was gonna have to take them out. they let it go.