peak utility readings vs actual loads

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Since you do not seem to want to explain your statements then I'll have a look for myself:

These items are not addressed in your paper but are addressed in sources like the paper I referenced discussing things like motor starts and other short-time loads and generator protection schemes.


And we have:


And we have:


And we have:


I should also add load-shedding in addition to load banks and parallel generating units.

If you make statements but can't or won't explain then we have communis interruptus. It's really up to you but if you don't want to communicate then what is your function?

Sorry if you don't see the contradiction.

Incidentally I haven't seen you posting any external links to substantiate your quantitive statements, such as the 300% inrush, etc. Could have missed it though.

What I posted was a defineite interpretation of one manufacturer compilation of various ISO rules for genset rating determination. Manufacturers play around with the different ratings, but ALL generators are mechanically capable of delivering ANY of those ratings at the appropriaate penalty. The electronic governors and regulators will impose restrictions not as much to protect the generators and the engine from destruction, but rather to keep it within the manufacturers warranty limits.
 
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Haji

Banned
Location
India
The same diesel or gas gen set may be used at any rating: stand by, prime, continuous etc., other than what its manufacturer specified. It just causes premature wear of the gen set, when used that way.
 

kwired

Electron manager
Location
NE Nebraska
How about asking POCO just what exactly their readings are?

Just because most people agree it should be the peak average over a 15 min period, doesn't necessarily mean it is.
 

topgone

Senior Member
The same diesel or gas gen set may be used at any rating: stand by, prime, continuous etc., other than what its manufacturer specified. It just causes premature wear of the gen set, when used that way.

Correct, and I agree. It's a prime mover problem not a generator problem, IMO. With so many sales people selling these things, it's no wonder things get muddled. Add to that the warranties involved and you'll get the shorter end of the rod if you don't follow what the vendors say you should.
 

iwire

Moderator
Staff member
Location
Massachusetts
The same diesel or gas gen set may be used at any rating: stand by, prime, continuous etc., other than what its manufacturer specified. It just causes premature wear of the gen set, when used that way.


An AHJ would be within their authority to fail a job that installs a standby generator as a prime or continuous based on NEC 110.3(B).
 

Haji

Banned
Location
India
An AHJ would be within their authority to fail a job that installs a standby generator as a prime or continuous based on NEC 110.3(B).
It is not a matter of installation but a matter of abuse of a given gen set in an installation.
 

mivey

Senior Member
Sorry if you don't see the contradiction.
Sorry if you don't see the lack of contradiction.

Incidentally I haven't seen you posting any external links to substantiate your quantitive statements, such as the 300% inrush, etc. Could have missed it though.
Your wish is my command. See figure 3 on page 6 of : http://hslautomation.com/downloads/tech_notes/motor_starting_notes.pdf

What I posted was a defineite interpretation of one manufacturer compilation of various ISO rules for genset rating determination. Manufacturers play around with the different ratings, but ALL generators are mechanically capable of delivering ANY of those ratings at the appropriaate penalty. The electronic governors and regulators will impose restrictions not as much to protect the generators and the engine from destruction, but rather to keep it within the manufacturers warranty limits.
Sure they have multiple ratings, but nothing you posted allows a design beyond the standby rating, which is what you sugested was OK for the OP to do since they "are also capable to handle overload for short periods". Again: there is no overload capacity for the standby rating.
 

mivey

Senior Member
How about asking POCO just what exactly their readings are?

Just because most people agree it should be the peak average over a 15 min period, doesn't necessarily mean it is.
That is the definition of Demand Charges.
Not if you mean 15 minutes. Or even if you mean the metered interval demand.

Demand charges can be based on metered interval demand or some percentage or average thereof, or connected load, or even contracted load, or some combinations of the previous. As for metered demands, I have seen 15 minute, 30 minute and 60 minute. As for the demand that appears on the bill, it could be many things, included the actual interval demand for the month, some percentage of the monthly demand, demands from prior months, etc.

The best bet is to ask the POCO to be sure.
 
Sorry if you don't see the lack of contradiction.

Your wish is my command. See figure 3 on page 6 of : http://hslautomation.com/downloads/tech_notes/motor_starting_notes.pdf

Sure they have multiple ratings, but nothing you posted allows a design beyond the standby rating, which is what you sugested was OK for the OP to do since they "are also capable to handle overload for short periods". Again: there is no overload capacity for the standby rating.

Published in 1997? New standards and a lot more global coordinations between those had changed the rules. That paper is obsolete.

My referenced paper had clearly stated that gensets CAN BE operated at their prime rating with the life penalties outlined therein. Apperently more than one readers and contributors to this posting seems to read it the saem way or had the same understanding.
 

mivey

Senior Member
FERC, NERC and the individual State Utility Commissions provide the necessary coordination and uniformity. Always had and always will.
Not even close. So completely off the mark that you are not even in the right ballpark.
 
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