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  #1  
Old 06-30-2007
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Hard-Start Capacitors

Ok, I bought the Yamaha 2400IS generator. As I suspected, it will not start my Marine Airrrrrrr 16,000 BTU air conditioner. So, I'm now educating myself on Hard-Start Capacitors. I don't know much about these devices. I want to get one that will EASILY provide enough kick to get the unit going. (Is it possible to oversize one?) I also want one that won't cause problems down the road. I understand that some are better than others, and I don't mind shelling out the dough for quality and reliability.

Anyone got any advice?
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Old 06-30-2007
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I would recommend that you take the air conditioning unit to a good electric motor repair facility. It is possible that your motor has some wear to it and therefore drawing higher than normal amps, especially on start-up. That type of wear can occur, you guessed it, from inadequate current. I doubt that installation of a larger capacitor in the motor will be sufficient to alleviate the problem alone, although it is possible that your capacitor is weak and replacement may allow it to start. It is also possible that you may be able to install a more lightly wound motor, that will not be so amp hungry, and allow your gen-set to rock it over.

How do you like the Yamaha, otherwise? Is it truly quiet? What is the weight of that one?
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Old 06-30-2007
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hard start caps.

are made now that use a ceramic resistor that takes the start cap out of the circuit when the motor starts. if the unit is still under warrenty call the manufacture about the prob. Have you tried it with shore power?
good luck!
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Old 07-01-2007
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I should have mentioned that the AC is relatively new (only a few years old with minimal use) and works fine on shore power. I think I read on the plate that it draws 60 amps at startup. But, I don't see how this could be true since the breaker is only 50 amps. If there is a start capacitor on the unit, I guess this would explain why the breaker doesn't trip-- but I only see one capacitor on the unit and I assume it is the "run capacitor".

Before I break down and call in a pro, I would at least like to try installing a quality hard-start capacitor.
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Old 07-01-2007
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Quote:
Originally Posted by jr438234606
I should have mentioned that the AC is relatively new (only a few years old with minimal use) and works fine on shore power. I think I read on the plate that it draws 60 amps at startup. But, I don't see how this could be true since the breaker is only 50 amps.
Most circuits can take a very short period of overload before tripping. I doubt that it draws 60 amps for more than a fraction of a second....just enough to get the motor turning, and probably anywhere long near enough to trip the breaker.
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Old 07-01-2007
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You probably are looking at the start capacitor, not the run capacitor. Most motors will draw 3-5 times their running amps at start up, but only for an instant. "Soft start" motors are becoming more common, but are complicated and expensive. The reason you do not blow your breaker is that motor breakers are of the 'time-delay" variety and will tolerate the starting amp draw for an instant. Sustained high amperage will blow the breaker as designed.

If it is any consolation to you, purchasers of house-hold generators are discouraged by the size gen-set they need to rock over their a/c or, more importantly, their water well pump. The fundamental problem lies with the gen-set's inability to speed up, raising it's output, in the timely fashion (read instantaneously) to supply the high amps needed for start-up.

It is possible that running the a/c off a rather large inverter, with the gen-set charging the batteries, could work. This would presuppose a large battery bank. It would also be rather inefficient and shorten the life-span of your battery bank.

A viscous clutch, between motor and compressor, might allow the motor to start in an unloaded condition but the fabrication cost would make the gen-set and a/c set seem cheap.

If the generator has a manual throttle you might attempt revving it and then attempt start-up of the a/c unit-probably a two man operation. I continue to think that a conversation with your local electric motor shop, and there's usually a couple in decent size cities, could shed some light, if not amperage.(g)

Good luck.
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Old 07-01-2007
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The rated current on the Yamaha is 16.7 amps and 20 amps is the maximum. Looking at new 16000 BTU A/C specs it seems like an A/C and pump will put you right at the 15 amp mark. So it appears your Yamaha might be capable of running the units but not handling the startup load.
I have a 16KW unit and it uses about 18 amps when running but the startup load is slightly over 30 for a few seconds.
I know nothing about adding capacitors but if they will store enough energy to supply the extra 1500-2000 watts you need for a few seconds...that may be a viable solution.
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Old 07-01-2007
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Starting Capacitor

A hard start capacitor is basically an oversized start capacitor with a relay that disconects it once the motor has started. I've used these many times with a lot of success. The ones I'm talking about are similar to this.

Typically I've put these on compressors that don't start due to some internal damage. The hard start kit is attached to give some oomph to the motor upon start up. This is typically a life extneder for the compressor and not a perminant fix. The motor / compressor has damage causing the problem in the first place.

In your instance it sounds like the compressor motor won't start, I'm guessing due to low voltage. This capacitor might help. A better solution would be to find and correct the real problem. Being that the A/C starts up on shore power, I'm assuming your generator is undersized.

Having said all theat, If it were mine, I'd give it a try - the low voltage situation will probably only last a second or two until the compressor starts to turn. I'd have an ammeter on it the entire time. I'd also put some kind of delay on the compressor so it doesn't start more than once every 5 minutes (this will allow the system to equalize and recduce the starting load on the compressor motor)
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Old 07-02-2007
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Quote:
Originally Posted by sailaway21
How do you like the Yamaha, otherwise? Is it truly quiet? What is the weight of that one?
It's very quite and smooth running. It weighs only 70Lbs. It cranks with just the slightest tug on the pull-start. Seems very ruggedly built. I would compare it to the Hondas of the same size, and I tend to like Hondas.
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