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PTO Generators Observations
In the town where I have some rental houses, when PECO (Philadelphia Electric Co.) shuts off your power, they come out, pull the meter and install near paper thin clear plastic sleeves on the meter legs and re-install it. A few days later when they can finally fit you in, they come out and remove the little sleeves. Not all houses here can be shut off at the pole and I guess they don't want to keep track of loose meters. I wish I had put in a disconnect before the meter too. I am wondering if there is an easy way to install a beeper or something before the generator transfer switch to let me know when power comes back on. If I had to guess, I'd say code just doesn't allow such a convenience.
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PTO Generators Observations
Some transfer switches available up here feature a small bulb like those found on circuit testers which lights up to indicate when there is power available from the grid. Other more expensive systems on permanent generator installations are switched electrically, when the electricity is off form 5 seconds, the switch disconnects the service and starts the generator, when the power comes back on, the switch turns off the generator and returns the service to the grid connection.
Our electrical safety code requires a main switch and fuses or breakers rated for the full capacity of the service panel.
In other words, we have the meter, then (usually, the present minimum) a 100 amp switch, then a pair of 50 amp fusible links, then the service panel itself.
This is the problem, it is too easy to merely flip the main service switch and plug a genset into a dryer or welder recepticle.
Best of luck.
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PTO Generators Observations
Hi Murf, and of course others following this thread.
Quoting Murf:
"What I was trying to get across was that there is a very real danger in leaving the neutral connected back to 'the grid'"
I am going to have to respectfully disagree with you on this statement. How does leaving the neutral connected back to 'the grid' pose a danger, the neutral is grounded at the transformer (and at the service entrance) and voltage is not transformed on this leg. In many instances (as described in my post above on internal wiring of the generator) this connection is required by code (up to and including the 2005 NEC). Take a look at my pictures 2 and 3, they describe the problem nicely. Now if the generator has neutral bonded to the frame then a transfer switch that switches neutral would be required to prevent parallel current flow on the EGC and neutral. This is the real danger here, not "backfeeding" the neutral on the grid. Perhaps we have some folk on this forum who are familiar with the code and wiring these units who could comment?
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PTO Generators Observations
Interested members:
Here is the reason for my post above, Murf with all due respect (and I have great respect for your opinion) your advice is potentially hazardous in this case. It's a very good article I urge interested folk to read it.
http://members.rennlist.org/warren/Gen_Panels_Appl_Note_EN.pdf
Link:
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PTO Generators Observations
Electricicty will ALWAYS take the path of least resistance. Nobody will argue that.
What most people fail to realize though is that it will rarely take ONE SINGLE path.
When you power a house by putting 220v. from a genset into the service panel, then power 110v. loads by 'splitting' the 220v. using the neutral and one leg of the 200v. you now have converted the neutral into a current carrying conductor.
Period.
The part most people cant get their head around is a concept known as "neutral-to-earth voltage". Do a little research on it, the answers you will be find are astounding to most people.
Best of luck.
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PTO Generators Observations
Murf (and of course others still reading this thread),
Neutral IS a current carrying conductor, always has been. It's bonded to ground to provide a zero volt potential difference between the neutral conductor and ground. This ensures that each of the "hot" lines will always be a maximum of 110v potential difference from ground. Only one connection/bond to ground is permitted and its at the service entrance, this ensures that the equipment ground conductor (bare ground wire or EGC) does not behave as a parallel current conductor for neutral current.
On a floating neutral generator:
If, as you suggest you employ a transfer switch that opens the neutral (as well as the supply side L1 and L2) you have disconnected the generator neutral from its ground reference and L1 or L2 could float to 220v (say between L1 and ground) while the other leg could be at 0v (between L2 and ground). By this action you have created the "earth to neutral voltage" you spoke of. The neutral is REQUIRED to remain bonded to ground in this configuration, opening the neutral at the transfer switch breaks the connection. See diagram 8 in the web link I posted. An excerpt of their explanation is pasted below, BTW its a Canadian company, read their narritive and take a look at the diagrams.
IF on the other hand you have a bonded neutral generator you are required to open the neutral conductor at the transfer switch. The bottom line is that in order to be code compliant the type of generator determines the type of transfer switch.
Excerpt form article:
These Diagrams (7 and 8) show that a 3-pole transfer
mechanism switching Line 1, Line 2 and the
neutral conductors would result in a circuit that
does not comply with the rules of the CEC. In
stand-by power mode, a circuit exists in which
the system voltage from the generator could
float on each phase. In the most extreme case
240Vac would appear on one phase and 0Vac
on the second phase, potentially resulting in
damage to any 120Vac equipment operated in
the home.
Link:
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PTO Generators Observations
Two things from the peanut gallery:
1) You guys left me in the dust back on page one.
2) Boy am I glad I hired a professional to install my transfer switch!!!
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PTO Generators Observations
I have to agree with DRankin - you guys have have left me in the dust - not quite on page 1 but, pretty darn close. I'm a Mech. Engineer, consider myself fairly intellegent, but not too smart for my own good if you know what I mean. I have worked around elecrical systems and electronics quite a bit but this stuff is over my head, Some of this, especially the discussion and confusion about "neutral-to-earth voltage", is what I refer to as FM - F___ing Magic. Electricity, like many other sciences or parts of sciences is very unpredictable. As soon as we think we have our hands around it it changes course. Physics is not an exact science no matter what they say. So expect the worst case and try to prepare for it.
I didn't hire a professional to install my transfer switch but I did buy what I believe to be a good quality unit and I followed all the instructions to the best of my ability.
Maybe I'll gather all my spec data and take some pictures and have you guys tell if I've done something wrong and what I can do to correct it. You've got me thinking that I'll burn my house down or kill some poor linesman. Neither one is acceptable.
Maybe I'll hire a professional but, I bet if I hire 12 highly qualified licensed electricians I'll get six of one answer and a half a dozen of another. ;o)
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PTO Generators Observations
The over load of the flux capacitor due to interdimensional wormhole fluctuation caused by the premature discharge of the nucleonic planet buster coil is what you have to be really careful of. ;O) It shorts out the bovine nutrient residue detector grid everytime!!!
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NO, NO, NO, 2ndHandLion it's the plutonic planet buster coil, not the nucleonic planet buster coil, recall that there are two of them (in series) - gosh get it right next time will ya! Well it doesn't look like anyone is loosing any sleep over this so that's good - that's mainly because no one could get their generator running (to code) and so just decided to go to bed - well that's what I usually do in an outage, wake up next morning - guess the power came on sometime in the night.
Seriously, what's concerning is the HUGE amount of discussion there is on this subject at Mike Holt's National Electric Code forum, and these are the "professionals" that install the switches. I lurk there sometimes due to work requirements (PC data control and remote sensing). Don't know which is more dangerous running the generator or burning 6483678 candles for light during an outage.
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02-03-2005, 17:27 
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