leogerritsen

Apologies for the delay in responding to posts, but I'm  working flat out, 7 days a week at the moment.

elkangorito, on 2009-11-07 00:44:42, said:

Thank you Elkangorito, your explanation of how to calculate  the surge load for motors typically found in the home is a very useful addition  to the thread. Historically, when L.R.A and F.R.A data-plate info is not  available, I have multiplied the running watts by 3 where small motors of the  type in your example are present, but I am happy to defer to your experience and  electrical knowledge in using a multiple of 4 as you have suggested.        As a rule of thumb, because most homes contain appliances  with motors such as those listed in Elkangorito's example (and because L.R.A  and F.R.A. may not be available on the motor data-plate), I will always post  the Kw (alongside the Kva) rating of a machine, based on a power factor of 0.8,  to enable accurate sizing and generator selection based on your load requirement.

Quote

    This is a very timely post, as you've opened the door on  generator ratings for 'home' use; a subject that I touched on in my original  post, but would like to discuss in more detail now if I may, as it can be a  source of confusion not only for those seeking information about generators,  but also… unfortunately… some who sell them.

        When you're considering the purchase of a generator, the  very least you should expect is good, accurate information to help you select a  generator best suited for your needs, and not just some guy trying to move a  boatload of cheap generators, who has little if any more knowledge about the  product than you. The misapplication of an under sized generator is the most  common problem I see out there and is normally the result of poor advice from  the seller/distributor to a customer, an incorrect load calculation, or no load  calculation at all.

        Let's look at the ISO  8528-1:2005 ratings for generators and then discuss how each rating translates  into home use.  

        There are four  ratings; we are only interested in the first three with respect to 'home' use,  they are;

        ESP – Emergency  Standby Power Rating

    LRP – Limited Time  Running Power (generally referred to as a Standby Rating)

        PRP – Prime Power  Rating


    ESP – Emergency  Standby Power Rating

        Light duty,  portable, single cylinder sets running at 3000rpm; rated to run for a maximum  200hrs a year (that's 3.8hrs a week) with a variable load at the alternators  maximum load rating, no overload permitted.

        LRP – Limited Time  Running Power Rating ('Standby Rating')

        Heavier duty,  normally a permanent installation, multiple cylinder engines, running at  3000rpm or 1500rpm; rated to run for up to 500hrs a year (that's 9.6hrs a  week maximum) with a constant load at the alternators maximum load rating, no  overload permitted.

        PRP – Prime Power  Rating

        Heavy Duty,  permanent installation, multiple cylinder engines, running at 1500rpm; rated to  run for an unlimited period of time with a variable load at the prime rating of  the alternator; typically an overload of 10% in any 12 hour period is  permitted.

        To better understand  why a particular rating is attributed to a generator for home use and more  specifically, why it is important that LRP Standby Ratings should be limited  to a maximum 500hrs operation a year and PRP Prime ratings are not, we need to  look at aspects of the engine and alternator.

        Voltage and Kva  ratings of alternators are dictated by a number of factors; the length and size  of the copper windings, the length of the lamination stack and the amount of  cooling air passing through the alternator etc.

        The class of  insulation material used to protect the copper windings is a key  factor. Resistance of the copper wire making up the alternator windings causes  its temperature to rise as a current is passed through it… the more current,  the more heat; the more heat, the shorter the life expectancy of the insulation  material, with sufficient heat the insulation material will fail and the  alternator will burn out.

        NEMA (The National  Electrical Manufacturers Association) recognizes four classes of insulation  material for use in alternators (A, B, F and H). The difference between each  class being the maximum temperature at which the copper windings can operate  for each of two duty cycles; continuous use and standby use.

        Continuous Use:

        Running 24 hours a  day, 7 days a week, the maximum operating temperature of the copper windings  permitted by the NEMA insulation classes in degrees C are; Class A-100, Class B-120,  Class F-145 and Class H-165.

        Standby Use:

        As standby use involves  less running hours (that's the maximum 500hrs a year for standby use remember),  the NEMA insulation classes allow the alternator windings to operate at up to  25 degrees C hotter; Class A-125, Class B-145, Class F-170 and Class H-190. The  ability of the copper windings to operate up to 25 degrees C hotter for a  limited period, allows the alternator to generate more power, hence the higher  standby rating.

        The maximum operating  temperature of the copper windings is made up of two parts; the ambient environmental  temperature and the temperature rise resulting from the operation of the  alternator. If the ambient temperature is 40 degrees C, then deducting that  figure from the maximum operating temperature for each class, gives us the  temperature rise permitted for each class due to use.

        A 1500rpm engine can  be rated for use as a standby or prime mechanical power source, but a 3000rpm  engine can only ever be used as a standby mechanical power source…these high  revving engines are simply not designed to operate as a prime mechanical power  source; this is concrete,  regardless of what any dealer or distributor tries to tell you…

        So…to simplify and summarize  I will use the example of two Kipor generators, the KDE12STA and KDE16SS.

        The KDE12STA is a  3000rpm, single phase generator. The alternator features class F insulation and  the complete generator (engine  and alternator combination) is rated as an LRP set for Standby Power use only.  It should be operated at its maximum load rating for up to a maximum of 500hrs a year (9.6hrs  a week maximum) and should give you good reliable service over the long  term. However, as we have discussed, if you choose to operate this generator at  or above its maximum load rating for a period exceeding the maximum runtime,  you should fully expect to experience problems with the under rated mechanical  power source (engine), or for the alternator insulation to fail and burn out at any time. It is a false  economy to 'save' money by purchasing a standby generator only to then commit  it to a prime power role. This is misapplication of the generator and you  should fully expect to experience problems.

        Note; if sufficiently rated, this same  alternator driven by a 1500rpm machine could be used as a prime power source, as long as the heat in  the copper windings does not exceed the class F temperature rise for continuous  use. This is achieved by reducing the maximum output of the alternator from the  maximum standby rating to the prime rating stamped on the alternator.

        The KDE16SS is a  1500rpm, single phase generator. The alternator features class H insulation  (the highest of the NEMA insulation classes) and the complete generator (engine and alternator combination) is rated  for use as both a PRP set for Prime Power use and an LRP set for Standby Power use  (13Kva/10.4Kw and 15.5Kva/12.4Kw respectively) according to application. The  KDE16SS may be operated as a Prime Power source, at its Prime Power rating,  continuously, for an unlimited period. However, as with the KDE12STA, if used  as a secondary Standby Power source, it should be operated for up to a maximum 500hrs a  year at its maximum Standby rating, operating this generator at or above its  maximum load rating for a period exceeding the maximum runtime will eventually result  in failure of the class H insulation and subsequent failure of the alternator.

        Regardless of  whether you are considering a generator for a Prime Power or Standby  application, I would strongly recommend you follow my earlier suggestion that  your generator be sized so that your maximum load requirement falls between 70 and  80% of the alternators rated output (70 to 80% of the Prime rating for Prime Power applications and/or 70 to 80% of the Standby rating for Standby  Power applications). Among the benefits of sizing a generator in this way, are a reduction in the amount of fuel used, reduced strain on the engine, reduced thermal stress on the alternator insulation and a reduction in noise pollution; it also allows capacity for growth in your electrical needs.

My motivation for discussing this now, other than to offer advice to readers, is the result of a recent blizzard of emails between myself, the manufacturer and the distributor in Thailand, regarding the rating for the SS (ultra silent) range of Kipor machines. The manufacturer had initially represented their posted rating as being for Standby use (language and terminology issues), but I now have the accurate ratings sorted out and have amended my earlier posts to reflect the change.

I hope I haven't muddied  the waters with this explanation; these are important points regarding  generator sizing and selection, if you found it a little confusing please try giving it  another read through.

Genset

haveaniceday, on 2012-02-16 11:01:38, said:

There really is no answer to that

Seriously, never seen any sort of security fixings here. Why not go for the poor man's fix? Use normal crosspoint screws and apply your drill to the recess once tightened. You did say you don't want them to come out

leogerritsen, on 2012-03-18 10:18:01, said:

If you get the green switch drop me a PM and I'll tell you how to modify it to use as a transfer switch. NOTE only the 60A version can be modified.

Pics to come in all its glory when finished....any day now.

looking at the  flaps of skin it looks like a young flying squirrel

I haven't a clue what it is, but if it fell out of a palm tree, perhaps it's vegetarian.  You could try offering it some ripe fruit and see what happens.