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[genset]

Quote

thanks, amazing! based on that i am considering a "preventive" installation within the coming months.

The amazing thing is that when I eventually begin selling these generators directly, I will be able to knock another 15% off the price...

Genset

Edited by genset, 2009-11-09 15:17:02.

[Naam]

genset, on 2009-11-08 20:24:26, said:

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:

If I may, I'd like to present an example of calculating generator size. If I have left anything out, I hope that Genset will correct me.
Again, this is merely an example.

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.

Honourable Experts Elkangorito et Genset, Esqs.,  

may i humbly add actual (measured in my presence) starting amps?

Daikin "13,000" manufacturers figures:
cooling capacity 3,200 kcal/h = 12,690 btu/h
compressor/condenser running watts 1,105 watt, running amps = 5.17
measured starting amps 8.5

Daikin "24,000"
cooling capacity 5,680 kcal/h =  22,500 btu/h
compressor/condenser running = 1,970 watts, running amps = 9.10
measured starting amps 22.5

Daikin "36,000"
cooling capacity 8,900 kcal/h = 35,300 btu/h
compressor/condenser running = 4,060 watts, running amps = 19.5
starting amps not measured!

the big'un is used to heat my pool water and at the same time cool the pool area but there is no need to add it to a load calculation.

Attached Files

•  GENSET.JPG   55.94K   24 downloads

[genset]

Naam, on 2009-11-12 12:20:01, said:

Honourable Experts Elkangorito et Genset, Esqs.,  

may i humbly add actual (measured in my presence) starting amps?

Hi Naam,

If you measured the current drawn by these circuits directly through the use of a tong tester or the like, I see no reason to question them.

My area of expertise... is the manufacture and installation of generators and not, unfortunately, the specific characteristics of AC motors (why some are more efficient than others).

When calculating the load requirement for a home or business, my preference (if on site), would be to use a tong tester to accurately measure the current drawn by motors such as these on startup. If I am offering advice by email, I am looking for the house/business owner to provide me with as much information as possible, the locked rotor amps (startup) or full load amps (running) if available; and if not, the watt rating stamped on the data plate. If the latter is the only information available, I would normally mulitiply this figure by 3 to give me an approximate startup requirement. For the type of small motors typically found in the home, this general rule of thumb allows me to ensure that the generator selected, is of a sufficient size to handle their power requirements on startup (even if oversized a tad) and is not undersized in relation to your overall load requirement (the less desirable of the two options).

Having said that, I am happy to see that your AC motors are so efficient, aside from saving you money when running on the utility supply; should you choose to purchase a generator, they will place less stress on the engine and alternator when running on the generator supply.

Genset

Edited by genset, 2009-11-13 06:45:06.

[Naam]

genset, on 2009-11-13 05:28:28, said:

Naam, on 2009-11-12 12:20:01, said:

Honourable Experts Elkangorito et Genset, Esqs.,  
may i humbly add actual (measured in my presence) starting amps?

Hi Naam,
If you measured the current drawn by these circuits directly through the use of a tong tester or the like, I see no reason to question them.

that's exactly how it was measured and i was surprised with the results and have no explanation for the rather low values. in olden times we always used "factor 3" but then we were dealing with piston and not with rotary compressors. what i am trying to find out is the reason and i will of course measure again.

going back in history. in ancient times (Nigeria 1982-1983) a 70kva single phase generator was my primary energy source for 1½ years which served 4 houses. if i recall correctly the total number of 1ton aircons was 12 plus 4 2ton units. these were the old rattlers built in the wall, had piston compressors, were drawing more than double the wattage of modern units and ran 24 hours seven days a week. a rough calculation results in a total load 45 kilowatts (~200 amps). engine oil of the generator, plus whatever my chief engineer deemed necessary was checked every day; the service lasted about 10 minutes and then the set was started again. these 10 minutes did definitely exceed the time of the relays which prevents an aircon compressor to start before pressure in suction and pressure pipe was equal.

my question is "how could the diesel and the generator cope with starting amps of 600 (using factor 3)?"  

[Marvo]

Naam, on 2009-11-12 11:20:01, said:

Daikin "13,000" manufacturers figures:
cooling capacity 3,200 kcal/h = 12,690 btu/h
compressor/condenser running watts 1,105 watt, running amps = 5.17
measured starting amps 8.5

Wow, those 13,000 Daikins have a REALLY low start-up ampage! Less than 2x.

[david96]

Marvo, on 2009-11-13 09:06:41, said:

Naam, on 2009-11-12 11:20:01, said:

Daikin "13,000" manufacturers figures:
cooling capacity 3,200 kcal/h = 12,690 btu/h
compressor/condenser running watts 1,105 watt, running amps = 5.17
measured starting amps 8.5

Wow, those 13,000 Daikins have a REALLY low start-up ampage! Less than 2x.

Here are the specs for 5 models of Daikin airconditioners available in Thailand.
They use inverter technology, in other words they have a variable speed drive
and thus reduced voltage starting.

KW 2.5 / BTU   8500 Run amps   4.0 Power consumption   700W.
KW 3.5 / BTU 11900 Run amps   5.0 Power consumption  1035W.
KW 5.0 / BTU 17100 Run amps   6.5 Power consumption  1400W.
KW 6.0 / BTU 20500 Run amps   8.2 Power consumption  1780W.
KW 7.1 / BTU 24200 Run amps 10.8 Power consumption  2360W.

Reduced voltage starting currents are a lot less than DOL starting.
This will explain the lower starting currents.

[InterestedObserver]

Naam, on 2009-11-13 07:31:17, said:

genset, on 2009-11-13 05:28:28, said:

Naam, on 2009-11-12 12:20:01, said:

Honourable Experts Elkangorito et Genset, Esqs.,  
may i humbly add actual (measured in my presence) starting amps?

Hi Naam,
If you measured the current drawn by these circuits directly through the use of a tong tester or the like, I see no reason to question them.

that's exactly how it was measured and i was surprised with the results and have no explanation for the rather low values.

I assume this tong tester (clamp-on ammeter) had a maximum save function for recording starting current. If not, them you may have observed an artificially low current reading. Just a comment for those interested, not questioning anybodies technical ability.

Edited by InterestedObserver, 2009-11-13 10:09:43.

[elkangorito]

Another thing that has a big affect on motor starting current is the nominal speed of the motor. The higher the nominal speed, the higher the starting current.

[InterestedObserver]

Quote

Here are the specs for 5 models of Daikin airconditioners available in Thailand.
They use inverter technology, in other words they have a variable speed drive
and thus reduced voltage starting

That would necessitate the use of a True RMS tong tester (clamp-on ammeter) with maximum hold function to get a really good starting current reading.

[Crossy]

InterestedObserver, on 2009-11-13 11:46:46, said:

Quote

Here are the specs for 5 models of Daikin airconditioners available in Thailand.
They use inverter technology, in other words they have a variable speed drive
and thus reduced voltage starting

That would necessitate the use of a True RMS tong tester (clamp-on ammeter) with maximum hold function to get a really good starting current reading.

I'm wondering what the interesting VI waveforms produced by these VVVF drives will do to the AVR on the Genset. Ref our conversation on UPSs and PC PSUs with active PF correction.

Any A/C load will likely be a significant percentage of the overall consumption along with CFL lighting and switching PSUs.

[Naam]

Crossy, on 2009-11-13 11:50:34, said:

InterestedObserver, on 2009-11-13 11:46:46, said:

Quote

Here are the specs for 5 models of Daikin airconditioners available in Thailand. They use inverter technology, in other words they have a variable speed drive and thus reduced voltage starting

That would necessitate the use of a True RMS tong tester (clamp-on ammeter) with maximum hold function to get a really good starting current reading.

I'm wondering what the interesting VI waveforms produced by these VVVF drives will do to the AVR on the Genset. Ref our conversation on UPSs and PC PSUs with active PF correction.
Any A/C load will likely be a significant percentage of the overall consumption along with CFL lighting and switching PSUs.

nope Gentlemen! none of my units have variable speed compressors. when we built the house 4 years ago i opted for straight ac/ac compressors as we had ongoing problems with inverter units installed in an apartment the Mrs. owns in another country. they were installed in 2002 (?) when the technology was rather new and the technicians of the supplier were rather helpless  

by the way, i called a friend in Germany, he very much doubts that the amp readings i posted here are correct and suggested, no matter what the new readings are, that "Genset" installs for each unit individual "delay relays", each with a time difference of one minute.

i also hope, when the time has come, that ElKangorito makes his expert knowledge available. he does not live far away and has been a guest in my house.

as far as cranes and lifting a ton or more are concerned i shamefully admit that i did not see the forest because of all the trees    when discussing the problem with Mrs. Naam she cooly said "males create or see too often problems where there are none!" and then pointed out with a few words how a crane can place the generator without lifting it over any building. lesson learned: having a wife who has a Ph.D. in anthropology (and one in another breadless art) helps to solve technical problems.  

[genset]

.
I'd like to begin this post by thanking all those who have contributed to this thread.

In addition to offering fundamental advice and promoting a specific line of generators, my goal here, has been to prove that a market exists within the expatriate community for the services I intend to offer. I have received a flood of emails that I am slowly working my way through and significant interest does indeed appear to exist; interest which in large part seems to have been ignited by this thread.

Another reason for my posting in a sub-forum occupied by a knowledgable collection of individuals, was the hope that I could draw on your collective experience and highlight any potential issues specific to the use of generators in Thailand, in anticipation of rolling out a comprehensive service in 2011.

As discussed earlier in the thread, one such issue that has been raised, may be the propensity for expatriate homes to house numerous UPS systems, variable speed motors (in the case of the Daikin AC units cited by Naam) and other rectifier based, non-linear loads.

Crossy, on 2009-11-13 12:50:34, said:

I'm wondering what the interesting VI waveforms produced by these VVVF drives will do to the AVR on the Genset. Ref our conversation on UPSs and PC PSUs with active PF correction.

Any A/C load will likely be a significant percentage of the overall consumption along with CFL lighting and switching PSUs.

After consulting with my tech mates at Mecc Alte, their opinion on the most likely effect of the 'interesting VI waveforms' on the AVR, is one of voltage oscillation and frequency instability; a condition which will further serve to exacerbate the problem.

Their recommendations included:

• Derating (oversizing) the generator where the load is predominantly non-linear.
  
• The possible addition of a small linear load (a load bank sized for approx 10% of the alternators rating for example) where a load is predominantly non-linear so that some resistive load is on the generator as the non-linear loads begins the ramp on process. This should aid in stabilizing the system somewhat.
  
• The use of a single phase or three phase, true RMS sensing AVR. This should provide reliable voltage regulation for generator sets serving non-linear loads. They will sense voltage level more accurately, regardless of the distortion of the voltage waveform.(the SR7 AVR from Mecc Alte is one such AVR, circa 500 sterling).
  
• The use of an alternator featuring Class H insulation. This provides additional thermal protection to offset alternator over-heating caused by non-linear loads.

I dont want to overstate the problem, there are thousands of generators operating satisfactorily, in prime and standby applications throughout Thailand; but in the event that a load is comprised totally, or in large part of non-linear loads, the only way to know for sure how a generator will perform (regardless of whether the machine is worth 200k or 2m baht...) is to get on site and 'test' the generators ability to operate satisfactorily with the proposed load prior to purchase and installation.

I will contact the distributor next week and discuss the possibility of providing a generator specifically for the purposes of testing the ability of the generator to operate with predominantly non-linear loads, where a potential expatriate customer has shown interest in a purchase.

I welcome and look forward to your opinions and comments on this issue; particularly those of InterestedObserver, who has a lengthy and comprehensive experience in generator operation and control.

Genset

[genset]

Naam, on 2009-11-15 04:59:03, said:

nope Gentlemen! none of my units have variable speed compressors. when we built the house 4 years ago i opted for straight ac/ac compressors as we had ongoing problems with inverter units installed in an apartment the Mrs. owns in another country. they were installed in 2002 (?) when the technology was rather new and the technicians of the supplier were rather helpless  

by the way, i called a friend in Germany, he very much doubts that the amp readings i posted here are correct and suggested, no matter what the new readings are, that "Genset" installs for each unit individual "delay relays", each with a time difference of one minute.

Hi Naam,

You beat me to my reply to Crossy, but my previous post is still relevant with regard to homes where predominantly non-linear loads are present. The news that your AC units do not feature inverter technology (given the percentage of your load taken up by AC units), is great from an operational viewpoint. You would, of course, still need to nail down your load requirement. If you dont already own a tong tester (clamp on ammeter), you may wish to pick one up, if you do, try and get a true RMS version with peak hold function as suggested by InterestedObserver, they're relatively cheap and worth having.

Genset

Edited by genset, 2009-11-15 06:51:18.

[Naam]

genset, on 2009-11-15 06:46:40, said:

The news that your AC units do not feature inverter technology (given the percentage of your load taken up by AC units), is great from an operational viewpoint. You would, of course, still need to nail down your load requirement. If you dont already own a tong tester (clamp on ammeter), you may wish to pick one up, if you do, try and get a true RMS version with peak hold function as suggested by InterestedObserver, they're relatively cheap and worth having.

i own one but can't find it Mrs. Naam who knows where to find things flew today to Singapore   most probably i will own an additional one tomorrow or day after tomorrow. but i don't understand why a peak hold function is necessary because i will not select an overkill unit which can deal with all the starting amps and waste a few hundred thousand Baht. my initial idea (switch on aircons manually one after the other) is of course stone age Cheap Charly technology but can be translated into modern technology as my german friend (see "adjustable delay relays" above) suggested.

as mentioned in my e-mail yesterday i am willing to go for "the whole -not 9- but 8½ yards" by selecting the "KDE45SS3" which would handle all my needs (Rated power kW/(r/min) 41.6/1500) but NOT all starting amps.

question to all interested experts: "is there any reason why "adjustable delay relays" would not work?"

[elkangorito]

Naam, on 2009-11-15 03:59:03, said:

i also hope, when the time has come, that ElKangorito makes his expert knowledge available. he does not live far away and has been a guest in my house.

I'm still here doc

genset, on 2009-11-15 06:32:08, said:

Their recommendations included:

• Derating (oversizing) the generator where the load is predominantly non-linear.
  
• The possible addition of a small linear load (a load bank sized for approx 10% of the alternators rating for example) where a load is predominantly non-linear so that some resistive load is on the generator as the non-linear loads begins the ramp on process. This should aid in stabilizing the system somewhat.
  
• The use of a single phase or three phase, true RMS sensing AVR. This should provide reliable voltage regulation for generator sets serving non-linear loads. They will sense voltage level more accurately, regardless of the distortion of the voltage waveform.(the SR7 AVR from Mecc Alte is one such AVR, circa 500 sterling).
  
• The use of an alternator featuring Class H insulation. This provides additional thermal protection to offset alternator over-heating caused by non-linear loads.

Genset, just out of curiosity, what is the "standard" insulation class of generator windings?
An "inverter class" motor has a minimum Class F insulation. There are other Class "combinations" that can be effective, which depends upon the design of the machine. Please be aware that I'm talking about induction motors.

Also...an apology. I made some minor mistakes in my "generator sizing" calculations. By the time I realised my mistakes, I could not edit the post. Regardless, the methodology is correct.

[Naam]

# Derating (oversizing) the generator where the load is predominantly non-linear.
# The possible addition of a small linear load (a load bank sized for approx 10% of the alternators rating for example) where a load is predominantly non-linear so that some resistive load is on the generator as the non-linear loads begins the ramp on process. This should aid in stabilizing the system somewhat.
# The use of a single phase or three phase, true RMS sensing AVR. This should provide reliable voltage regulation for generator sets serving non-linear loads. They will sense voltage level more accurately, regardless of the distortion of the voltage waveform.(the SR7 AVR from Mecc Alte is one such AVR, circa 500 sterling).
# The use of an alternator featuring Class H insulation. This provides additional thermal protection to offset alternator over-heating caused by non-linear loads.

AAARRRGGGHHHH...  

[elkangorito]

Naam, on 2009-11-15 03:59:03, said:

by the way, i called a friend in Germany, he very much doubts that the amp readings i posted here are correct and suggested, no matter what the new readings are, that "Genset" installs for each unit individual "delay relays", each with a time difference of one minute.

This will be a tad complicated as each timer would need to rely upon the status of each other. Example, if you had individual start timers on each a/c unit, there would still be nothing to stop 2 or more a/c units starting simultaneously. Therefore, the timers need to "talk to each other". I'll see if I can dream up a control schematic for this situation.

[InterestedObserver]

Naam, on 2009-11-15 12:24:36, said:

but i don't understand why a peak hold function is necessary because i will not select an overkill unit which can deal with all the starting amps and waste a few hundred thousand Baht.

question to all interested experts: "is there any reason why "adjustable delay relays" would not work?"

1. The discussion has been about motor starting current, or the peak current drawn by the motor. For that you need a peak hold function. If you are not going the deal with all the starting amps, then you don't need to know what they are.
2. Adjustable delay relays would work just fine, stone age technology still works.

[Crossy]

elkangorito, on 2009-11-15 12:49:57, said:

Naam, on 2009-11-15 03:59:03, said:

by the way, i called a friend in Germany, he very much doubts that the amp readings i posted here are correct and suggested, no matter what the new readings are, that "Genset" installs for each unit individual "delay relays", each with a time difference of one minute.

This will be a tad complicated as each timer would need to rely upon the status of each other. Example, if you had individual start timers on each a/c unit, there would still be nothing to stop 2 or more a/c units starting simultaneously. Therefore, the timers need to "talk to each other". I'll see if I can dream up a control schematic for this situation.

How about a quick-and-dirty, just use different delays, 1min, 2 min, 3 min etc

[Naam]

elkangorito, on 2009-11-15 12:49:57, said:

Naam, on 2009-11-15 03:59:03, said:

by the way, i called a friend in Germany, he very much doubts that the amp readings i posted here are correct and suggested, no matter what the new readings are, that "Genset" installs for each unit individual "delay relays", each with a time difference of one minute.

This will be a tad complicated as each timer would need to rely upon the status of each other. Example, if you had individual start timers on each a/c unit, there would still be nothing to stop 2 or more a/c units starting simultaneously. Therefore, the timers need to "talk to each other". I'll see if I can dream up a control schematic for this situation.

i am not talking about timers at the ac units but at their breakers. i have a similar setup for the three phases where each phase can be programmed for different times.  

anyway... Señor Kangorito, no me dé problemas. ¡déme soluciones y nada mas!

[Naam]

Crossy, on 2009-11-15 13:23:04, said:

elkangorito, on 2009-11-15 12:49:57, said:

Naam, on 2009-11-15 03:59:03, said:

by the way, i called a friend in Germany, he very much doubts that the amp readings i posted here are correct and suggested, no matter what the new readings are, that "Genset" installs for each unit individual "delay relays", each with a time difference of one minute.

This will be a tad complicated as each timer would need to rely upon the status of each other. Example, if you had individual start timers on each a/c unit, there would still be nothing to stop 2 or more a/c units starting simultaneously. Therefore, the timers need to "talk to each other". I'll see if I can dream up a control schematic for this situation.

How about a quick-and-dirty, just use different delays, 1min, 2 min, 3 min etc

ah thinks... WE HAVE A WINNER!  

Edited by Naam, 2009-11-15 19:10:29.

[Naam]

InterestedObserver, on 2009-11-15 13:19:57, said:

Naam, on 2009-11-15 12:24:36, said:

but i don't understand why a peak hold function is necessary because i will not select an overkill unit which can deal with all the starting amps and waste a few hundred thousand Baht.

question to all interested experts: "is there any reason why "adjustable delay relays" would not work?"

1. The discussion has been about motor starting current, or the peak current drawn by the motor. For that you need a peak hold function. If you are not going the deal with all the starting amps, then you don't need to know what they are.
2. Adjustable delay relays would work just fine, stone age technology still works.

unfortunately not with autostart  

[elkangorito]

If individual & independent timers are used in each a/c unit, it will not prevent the chance that all or some of the a/c units could start at the same time. This is so because the thermostat controls the start of each a/c unit (the precise starting time for each a/c unit is unpredictable). It may be a small chance that more than one a/c unit could start simultaneously & since this is the case, there is no need for timers at all due to the unpredictability of the start time(s).

If simultaneous starting of multiple a/c units is to be prevented, the a/c units must be linked together via control wiring. Ideally, the whole system would be controlled by one control cubicle & control wiring must be run from each a/c unit to the control cubicle.

I have attached a control schematic, which will allow only one a/c unit to start at a time (while one is starting, all other units are prevented from starting). I'm pretty sure there are no problems with how it functions. If someone finds a problem, please let me know.

 aircon_start_delay_circuit.pdf   67.02K   12 downloads

[genset]

Quote

Genset, just out of curiosity, what is the "standard" insulation class of generator windings?
An "inverter class" motor has a minimum Class F insulation. There are other Class "combinations" that can be effective, which depends upon the design of the machine. Please be aware that I'm talking about induction motors.

Hi Elkangorito,

Synchronous alternator windings are manufactured using all four classes of insulation. The most common for standby and prime power applications being Class F and Class H. It really is incumbent on the generator distributor to give the best advice (regarding the most appropriate insulation class) to a client, based on the proposed application of the generator. The Kipor SS (ultra silent) range feature Class H insulation.

Genset

[genset]

Naam, on 2009-11-15 13:32:57, said:

# Derating (oversizing) the generator where the load is predominantly non-linear.
# The possible addition of a small linear load (a load bank sized for approx 10% of the alternators rating for example) where a load is predominantly non-linear so that some resistive load is on the generator as the non-linear loads begins the ramp on process. This should aid in stabilizing the system somewhat.
# The use of a single phase or three phase, true RMS sensing AVR. This should provide reliable voltage regulation for generator sets serving non-linear loads. They will sense voltage level more accurately, regardless of the distortion of the voltage waveform.(the SR7 AVR from Mecc Alte is one such AVR, circa 500 sterling).
# The use of an alternator featuring Class H insulation. This provides additional thermal protection to offset alternator over-heating caused by non-linear loads.

AAARRRGGGHHHH...  

...apologies Naam...

These recommendations were posted as an example of steps which may be taken, if/when it becomes apparent that a predominantly non-linear load is affecting generator/avr operation.

As you have now clearly stated that your AC units do not feature non-linear/variable speed motors, this should not apply to your prospective project and should be read in the context of the posts which preceeded it.

Genset