Generator engine stalling under load.

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  #1  
Old 08-01-13, 05:38 AM
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Generator engine stalling under load.

I recently acquired a Powercraft PC2800LR/08 generator. It had been laid up for a few years and wouldn't start when I went to inspect it. The then owner was a mechanic and said he'd fix it, which he did by thoroughly cleaning the carb.

Since then I've used it on a number of occasions to power CFL lighting which it has done without issue. I've also used it to power an 1100W SDS breaker/drill.

Yesterday, I wanted to power a 1.5HP 1100W blower motor which I believe to be a capacitor start/run type. As soon as I connected the blower motor, the generator immediately stalled. The circuit breaker did not trip. I know the blower motor will have a fairly high start current but I have used it on lesser rated generators without issue so I believe this generator to still be at fault.

Any ideas as to where I should start to look? I've removed the carb and visually inspected it and it does appear to be spotlessly clean. The generator is 5 years old but has only had approx 20 run hours. The voltage system in my country is 230V 50Hz.

All ideas will be most appreciated.
 
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Old 08-02-13, 08:05 AM
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I've done some additional tests today. The generator is rated at 2500W continuous and 2800W maximum. I connected a SDS breaker drill rated at 1100W and then a circular saw rated at 1800W (2900W total) and it handled both with no problems.

As soon as I connected the blower unit (on its own), the engine stalled. The manufacturers of the blower unit say that I need a 3KVA generator to run the 1100W 1.5HP blower so it's touch and go if this genset has enough power. However, other websites state that I will need at least a 5.5KVA set to overcome the starting loads.

Strangely, I have seen the blower unit work today quite happily on another generator rated at 2.5KVA, so now I'm really confused as to what the issue actually is.

I really could do with some advice!
 
  #3  
Old 08-02-13, 08:53 AM
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Is this one of those $300 China imports? I have a Champion 3500/4000W import that I chose specifically because it has 2X the output needed (nameplate rating) to power my well pump during a power outage. When hooked up to the house with all loads disconnected except the well, the gen stalls like I shoved a crowbar in it.

My conclusion is these china gennies do not have the mass/inertia of better quality generators of the same rating. You need that inertia to keep the flywheel spinning past the huge inrush current required to start a capacitor-start motor (or a submerged well pump).
 
  #4  
Old 08-02-13, 12:15 PM
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It certainly looks like a Chinese copy of a Honda GX160-200 series. Maybe that's the problem.

I only paid 100 (about $132 US Greenbacks) for it as a used/mint item - I thought it was a bargain!

BUT, it will power resistive loads up to 3KVA without a fuss. Inductive loads seem to be the problem.

A few months ago a pal of mine and I tried the blower unit on a equivalent rated Chinese copy and it powered up just fine. Why so?

The genset originally came from a vendor called Aldi - they are the European equivalent of Wallmart - stack it high, sell it cheap, so it could be bad kit, but these companies only survive by pleasing the masses with stuff that works.

I'm wondering now if the start capacitor on the blower unit is about to fail. I can easily change that, but the blower works just fine on grid supply.

Just why would the blower unit cause such an instant (and hard) stall of the generator engine?
 
  #5  
Old 08-02-13, 06:37 PM
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The blower appears as a dead short to the generator.

Also.... another problem could be that the carb can't deliver gas to engine quick enough or maybe the mixture is set slightly too lean.

Snowblowers have the same problem when you flood them with snow if the carb is set too lean.
 
  #6  
Old 08-11-13, 10:47 AM
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Thanks PJmax

I now know that an inductive load presents huge start currents. To help things along, I took the blower unit apart (32 pop-rivets drilled and popped out) and replaced the start capacitor. The blower does fire up more quickly now on grid power than it did before so I suspect the cap change was useful. However, the blower unit still stalls the genset.

I am now completely confused - other websites say that this 1.5HP motor will never power from a 2.8kVA genset while the blower manufacturers state that it will with a 3.0kVA genset. I've seen this blower running on a 2.8kVA genset so I believe, still, that it should work.

If a genset that has a 6.7HP motor can't start a mere 1.5HP load, what are the internal losses? 6.7 horses to drag 1.5? Surely it's do-able.

I admitted defeat this week and sent the genset to a 'specialist'. I don't speak Greek and he doesn't speak English, so things were problematic. After messing me around for at least four days he finally looked at the genset and told me it was fine. It's not fine - it hunts a tad at idle.

I plugged in the blower unit, showed him the stall and he scratched his head. He plugged in a 3kVA angle grinder and it stalled. He scratched his head. He told me that a 2.8kVA set would not power a 3.0kVA load and took the 3kVA angle grinder to a 5.5kVA set to show that a more powerful generator would. It stalled and he scratched his head again.

He then blamed the blower unit, but couldn't explain why it would happily start on grid power. He then called me a 'malaka' (look it up on Google) and motioned that I should leave. Which I did, without payment.

So, my questions are:

What's the point of a genset having a breaker if an overload will instantly cause a stall condition? Surely one or the other will suffice?

How can I make this EPA carb run a little richer? I'm currently convinced that it's lean-running and stalls out when a heavy load is applied.

Why does an equivalent rated (Chinese copy) run this blower unit while this Chinese copy will stall?

Why am I having so many problems this month?

I am looking forward to your input guys. Help me out, if you can.
 
  #7  
Old 08-11-13, 06:37 PM
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My conclusion is these china gennies do not have the mass/inertia of better quality generators of the same rating. You need that inertia to keep the flywheel spinning past the huge inrush current required to start a capacitor-start motor (or a submerged well pump).
Guy48065 posted this back in the third post. It makes a lot of sense.

I don't know how you can richen that carb. Many have caps over the adjustments so that they can't be changed.
 
  #8  
Old 08-11-13, 06:51 PM
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Modern carbs can't be adjusted like the old ones. You can thank the EPA for that, and the ethanol fuel that ruins them too. I think Guy48065 gives the only plausible explanation. I have no better explanation.
 
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