AC will not run off generator

[twistedtree]

I think you need to do some good old fashion diagnosing rather than guessing. It worked before and now it doesn't, so something is broken or gone wrong. You just need to figure out where between the gen and AC this has happened. The fundamentals are that either the AC is now drawing more current that before, with a number of possible causes. Or the gen is unable to deliver the same power that it could before, with another set of possible causes. All your 108V measurement tells you is that there is inadequate power at the AC to start it. Duh! The trick is to figure out if the problem is on the deliver or consumption side. I like the idea of trying with another load to see if that drags down the voltage too. That will start to narrow down where the problem is and you can proceed from there.

[hellosailor]

" The fundamentals are that either the AC is now drawing more current that before,"
A good point! All AC systems eventually leak, and when they leak they tend to suck more power trying to compress what is left. I don't think that would affect the starting draw but that's something the pros would know.

[rwidman]

The AC used to work powered by the genset. It still works powered from Shorepower. I don't think anything would need to be added to the AC.

Some fault has occurred between the time it worked and the time it didn't. Find the fault, correct it, and all will be fine. Nothing needs to be added or modified.

[Dennis.G]

FYI: i had a comprssor go out in my home regrigerator. Would fail to start. Installed a hard start kit (special capacitor) and got another year out of it. When failed was drawing huge inrush amps. A hard start cap results in high current demand so likely not compatibe with generator as source of power.

[um saudade]

Twisted Tree has a good logical take on this.
Many of us who can trouble shoot this have trouble explaining how to do it to someone who has a limited grasp of theory and experience with other situations of a similar nature.
Yes, it comes down to a couple of basics when a system that worked and supposedly was correctly engineered in the first place now fails to perform. Is it the load or is it the supply? Or the delivery system? The presumption would be the supply as the other source of power appears to operate the device just fine.
But if the device has degraded enough, then the genset supply might no longer be sufficient, while the shore power remains adequate to start the AC.
I would troubleshoot this as follows, assuming nothing:
Test the start and run capacitors in the AC.
Test for the presence of and record the line voltage from the dock power at the load.
Record the run current on the AC. Does this compare favorably with the nameplate rating? If the run current is a lot higher than the rated current you just found the problem.
Using a min/max recording meter, record the minimum voltage at the load when starting.
NOTE: Let the pressures equalize when doing these repetitive tests. No compressor starts well against high head pressures!
This is going to be your baseline voltage/current. I would make the assumption that this is about the minimum voltage you can have at the AC on inrush and still have it start.
As a rule, I would say that there is far more issues with the shore power not working as well as the genset because of the long wire runs involved; thus the shore power voltage is often very low while the genset is usually adjusted to put out a little on the high side to help with inrush issues and the wiring runs are very short.
Run the genset at high idle (no load) and record the line voltage at the genset.
Compare the genset/ dock power voltages. If the genset line voltage is low, you found the problem. Genset should be 120volts or even a bit higher. Check the genset frequency to insure 60 Hz. If it runs slowly at high idle it won’t start much of anything. Adjust output voltage and freq to be spot on.


Visually inspect all connections on the genset to AC wiring. The wiring you need look at is between the genset and the tie in, where the shore power and gen power meet. Doubtful the issues are in the wiring that is common to both.
Since the genset does not want to successfully start the AC, the following testing will need to be done with judicious use of the AC disconnect/breaker:
Set one multimeter with min/max recording capability on the line of the genset, as close to the generator as possible. Set another min/max at the load, same place as you measured the dock power at the load. Attempt a start. If the AC refuses to kick over, trip the breaker at a long second, no more.
Now compare the load voltage meter with the line voltage meter at the minimum numbers. There should be almost no difference or a couple of volts. If there is a big disparity there is a bad connection.
If there is no difference between the line/load numbers then compare the min voltage at the load with the two different power sources. There will be a big disparity in the two numbers and we need to raise this voltage up where it is comparable to the dock power voltage.
This now breaks down into two troubleshooting sections: Genset mechanical or genset electrical? So far we have figured out that the genset puts out just fine at high idle but is not able to handle the inrush to start the AC
At this point you can set up some load boxes and check the genset output and it may be helpful. But going back to what I said in my earlier post: Does the genset even try? Does it sound like it woks really hard? This tells you a lot. If the genset bogs down far more than it should the line voltage goes way down and the freq goes down and the combination is doubly bad for a good start.
If it does not try to go to wide open throttle at all, then I suspect the control in the genset and troubleshooting of that is beyond this venue but you can now go to the Westerbeke folks with real information. I checked the Westerbeke website and I can’t find anything that resembles that model so I can’t look at the genset schematics.
However if it tries but can’t start it, then I would look for mechanical reasons that it can’t produce good power.
Now put on the load box and ramp up the load. Does it produce full rated power or close to it if the load is added slowly? If it does put out good amps but does not handle the inrush then look to engine issues that would prevent fast acceleration. If it does not seem to produce full power it could be more generic engine issues.
Either way this becomes simple diesel troubleshooting. Engine governor working ok? Compression ok? Fuel supply adequate, intake air restricted, exhaust restricted? Does it run hotter than it used to?
I am sure I skipped a few points and you may discover something else along the way but this should give you some answers.

Good luck and keep us posted.

[Dflatimer]

Sorry for not replying sooner. I had to work my day job. Back on the boat tomorrow and will be doing these diagnostics the best I can. I do feel its worth mentioning though that I did have the start/Run caps tested by an AC technician and they showed normal readings. He then sold me a hard-start. Sounds like it would work, but when I installed it, it made the problem even worse. In fact, it wouldn't even start off of shore power once a hard start was added. It seems to me that the capacitors don't have enough time to "Juice up" before the relay is closed to start the compressor. Now, i have researched all of this enough to know that capacitors are not batteries and that capacitors in an AC circuit act differently than those in a DC circuit. It just seems odd that an additional capacitor would aggravate the problem. For now, I believe I try running a new wire directly between the genet and the unit and running the diagnostics that UM Saudade posted. Thanks again, Ill post when I have more info.

[rockDAWG]

Originally Posted by boat_alexandra

very few people have AC on their boats. There is no reason you should. You can achieve the exact same thing using far less energy, much more reliable and simple.

1. wind sock
2. electric fan
3. Put tarps above deck to prevent direct sunlight from hitting the deck.
4. salt/fresh/salt spray incoming air in a duct, to dry/cool/dry it
5. pump cool deep water (5-10 meters) up hose through heat exchanger in boat.
6. Insulate boat properly and have very large tanks of water which circulate through radiators outside to cool at night, and keep the boat very cool all day. Also you can drip water onto radiators to make them cooler. Same system can be adapted to keep the boat warm in winter.
7. Drink ice water
8. Sweat

I can think of many more, but maybe you can try some of those or come up with your own.

You forgot to mention: Imagining you were in Buffalo in the middle of winter. It is so damn cold, I couldn't find my penis and balls.

[Dflatimer]

So today, I ran dedicated,new, temporary wires from the genset to the ac unit and had no change in the symptom. However, out of frustration, I decided to adjust the bolt on the governor and crank the voltage way up. I did get the ac unit to start up one time but only that one single time. How long should I leave the unit off inbetween repetitive attempts? Also, I am noticing that my voltage is not very stable. I can crank it up to 130 volts but by the time I add in everything except the ac unit the voltage will drop to the 116 range. It also seems to fluctuate continuously causing the voltage to vary by about 4 volts. Shouldn't the governor (or voltage regulator) keep the voltage at whatever it is set at and rev up the motor to compensate for the load? This very well may be the issue. By the way my generator is a westerbeke 4.5bcg. Thanks again in advance.

By the way I really wanted to do the above diagnostic but was not able to acquire a min/max meter for it.

[Sailmonkey]

The voltage should be relatively stable around 120, the frequency should be 60hz. Anything from 58-63hz should be acceptable. The engine governor controls the frequency, and it should be stable, ie the engine does not rev up when a load is applied, rather more fuel is delivered to maintain a constant speed.
The AC can take up to 5 minutes to be re-start able from the generator.

[goboatingnow]

I suspect magic smoke release isn't far away here

I'd say this is all to do with power factor.

Dave

[skipmac]

Originally Posted by goboatingnow

I suspect magic smoke release isn't far away here

From the symptoms I suspect some magic smoke has already leaked out of the system. Since the OP didn't capture all the smoke to put it back then repairs are probably in order.

[captainjay]

So the air conditioner runs on shore but not generator? While on shore take a clamp meter and determine how many amps the unit is pulling at start up and running. Measure the incoming line voltage from shore before start up and measure it after start up. If these number stay pretty normal, 8 to 12 amps running 15 to 20 start up and the voltage stays pretty flat there is nothing wrong with your air conditioner, this becomes a my generator won't maintain voltage and amperage under load thread with a whole other set of tests.
Jay

[goboatingnow]

Originally Posted by captainjay

So the air conditioner runs on shore but not generator? While on shore take a clamp meter and determine how many amps the unit is pulling at start up and running. Measure the incoming line voltage from shore before start up and measure it after start up. If these number stay pretty normal, 8 to 12 amps running 15 to 20 start up and the voltage stays pretty flat there is nothing wrong with your air conditioner, this becomes a my generator won't maintain voltage and amperage under load thread with a whole other set of tests.
Jay

Well it could easily be a power factor issue rather then an out and out power issue

Dave

[um saudade]

"Well it could easily be a power factor issue rather then an out and out power issue"

Could you explain this a little?

I went looking for the model and read the manual. I had before assumed this was a diesel genset but it is gasoline operated. Actually makes troubleshooting easier.

Can't do too much if the OP won't follow, or can't follow a logical trouble routine but here goes anyway.

This little genset is pretty stupid simple: Flywheel governor and self regulating exciter.

First I would check the exciter capacitors in the genset. This cap goes bad and the genset can't self regulate.

The cap being bad could make the governor hunt as is described but I doubt it. Sounds more like just a bad running engine situation.

DON'T adjust the governor to get the voltage up!!!

If the voltage is low at 1800 rpm fix genset don't try to counter the problem with more rpm!

[sailorchic34]

One other possibility. Some generators have brushes, some are brushless. The 4 volt bouncing tends to make me say your genny might have brushes that are worn down and need replacing.