Air Conditioning Malfunction with Genny Power

[Angela]

I’m not sure what the problem is, but I’m going to look to the genny first. Recently, we began having difficulty running the newest air conditioning system (the one in the salon/galley which is now almost a year old) when we’re on genny power and wasn’t sure where to start looking. The problem began about 4 to 6 weeks ago and is persisting, so with time, we are starting to get a clue, or so we think.

This particular AC system is the only thing on the boat, that I can think of, that has electronic controls. It works fine on shore power, but gives me grief on genny power. When trying to fire up even just the fan motor, I often get a terrible noise that sounds like golf balls in a dryer. It’s worse on the bigger of the two blowers that work together. The vibration can be felt through the floor when standing next to the blower unit, and eventually a faint odor comes with it - sort of a burning smell, but not really - hard to describe - an “electrical” smell for lack of a better description. There is no air flow when this happens. This happens even when in fan only mode, so it does not appear to be compressor-related. Then, sometimes it will run fine.

Yesterday, after swapping over to genny power, still in the slip, it misbehaved. I immediately turned off the fan motor, turned it right back on, and it ran fine for about 4 hours before giving me grief again. I leave the fan at a constant speed, so it’s not an issue of starting/stopping. I turned it off for a while, and later, after a few tries, it came back on and ran fine all the way back to the dock. It has never done this while on shore power. I did start watching Hertz readings when this began. She normally runs between 60 and 62 hertz on the meter (it’s an odd looking meter with little tablets, or teeth, in it that appear to roll over on a horizontal scale). Yesterday when it misbehaved, I went to the hertz meter and noticed that it was running at something below 60, in the 56-58 range. Later, when I saw the meter come back up to 60, I started the AC fan motor and it ran fine. Not sure if that was a coincidence or not. When I first started monitoring hertz with the behavior of that fan motor, my recollection is that it was hovering at 61 at times when the fan motor would act up, but I can’t be sure of that since I didn’t have the awareness of the troubleshooting that I do now.

I understand that some of these electronically controlled things are very sensitive fluctuations in power. I seem to recall some people having problems running new refrigerators with electronic controls (or was that during an inverter power discussion?).

Nothing else gives me a problem with running on genny power. So, it could be something in the AC system itself, but because I can only replicate the problem on genny power, I’m thinking it’s a genny issue. The genny, itself, does not struggle or give me any physical symptoms that I can see. She’s a Westerbeke with about 800 or 900 hours on her. What do you guys think?

[yachtsmanbill]

That freq meter is a tuning fork type... for the lack of a better term... on my Roamer, at 56Hz I am at about 85 volts. Thats not good, and my fridge and window shaker really rattle! You are smelling HOT components from a voltage sag and an amp surge. You may have a regulator or governor/fuel situation on that generator.
That meter is at about 61 Hz which gives me about 115 volts for decent clean power, plus a tad of reserve in case anything needs to start while loaded. The ammeter is showing about 3 amps with the window shaker at full bore on shore power ws

[REBrueckner]

What manufacturer is that air conditioning system? Maybe someone else will recognize a sensitivity to cycles per second (frequency) and or voltage.

One or two cycles variation is not normally a concern; Bill's 85 volt experience at 56 cycles seems atypical....but 50 cycle European vs 60 cycle US Definitely can cause issues in some equipment. Typically inductive or capacitive loads, that is electric motors, might well be affected.

Another ploy (which relates to Bill's post and could reflect a governor related issue): when that one troublesome air conditioner acts up, unload the genny from OTHER loads...and/or make note when that one air conditioner acts up if the genny is heavily loaded.

Prior discussions here HAVE noted that some stuff does not work well on modified sine wave...from inverters. A dstorted wave can also result from a genny and I don't know how well a frequency meter registeres such distortions.

If no one has a specific solution, you can always try increasing your genny frequency.... via adjusting the governor control.... a few cycles and see if that eliminates the problem. But if the genny is already a few cycles over 60 at light loads, as you post, that may not the best way to begin.

[MikeP]

I concur with Bill's comments. I found that to have the genny providing good, solid 60HZ power/correct voltage under load - like running ac units - I had to set the frequency at around 62 HZ at no load. Actually, what I did was to have the genny on and then turn on everything I could find - all ac units, stove, oven, washer, etc. Then I set the frequency at 60 HZ.

I am no expert at all re this particular aspect but my understanding is that optimum performance for frequency-controlled items (like motors) using US standard power is 60HZ +/- .5%. That means that the frequency shouldn't be more than 60.3 or less than 59.7. BUT, most of the gennys we commonly have are mechanically governed and they can't maintain that sort of accuracy with transient loads. Further, I understand that it is more harmful to have the frequency too low than too high.

AND, as Reb said, some electronic items do not work properly if they are not receiving true sine-wave power. On our previous boat, which had a modified sine wave inverter, the microwave didn't work properly on the inverter though it was OK on the genny (true sine wave) or shore power. I assumed that all our marine generators deliver true sine wave power but maybe they don't...

I agree that the issue is definitely the generator but hopefully a simple speed adjustment (and therefore frequency/voltage) will correct the problem.

[Pascal]

Isn't that the same AC that was giving you similar symptoms on shore power a few months ago?

56 to 58 is a little low, what kind of voltage are you getting?

Before messing with the genny i would try to duplicate the problem on shore power. How many times have you actually run on the genny since it started? 2 or 3? Even if it happened everytime it s still a small statistical sample.

So while on shore power , shut it down and then restart it. Do this few times then start transferring back n worth to the genny

You have a fluke meter, don't you? Use that to measure actual voltage and Freq it should be more precise than the 30 year old analogs

Make notes and see if you find a pattern

Usually rpm is set to produce 61 to 62 Hz with no load so that it stays around 60 under load.

I can see Freq dipping when your compressor stars but the genny should recover immediately

[MarioG]

Angela time to change the fuel filters on the genny. this happened to me a few days before I left to No Name a few weeks ago. I fired up the genny in the slip to inspect under load. My genny ran smoothly but a slower rpm, I didn't really notice it until I put a load on it. i turned on the old salon ac (another future topic) and noticed the load meter fall way below 115v to about 95v (red arc). the ac and the generator really complained. No problems on shore power. The easyest/ quickest check/fix was to change both primary and secondary fuel filters. Purred like a kitten and no problems since then...

[MikeP]

Just a comment about starting/stopping/restarting the ac unit. If you shut it off and just wait a few seconds and then turn it back on, the start load (amp draw) will be quite high because the pressure in the unit hasn't equalized. I've been told by a local ac guy that it can take several minutes for that to occur but Spcoolin advised me that it only takes around 30 seconds. In any case, be aware of that so you don't draw the wrong conclusions if you perform rapid successive shutdowns/restarts.

[davidwigler]

I don't know how to help diagnose the problem but this little device is very accurate and makes it easy to check the hz every time you start or add loads to the generator:

http://www.amazon.com/P3-Internation.../dp/B00009MDBU

[ThirdHatt]

It does sound like the hz is getting too low Angela, especially for todays electronics. This is probably just due to slightly lower RPM's under load so I think the first thing, as Mario suggested is to replace the racor AND the on-engine fuel filter for the genny. The on-engine filter is all too often forgotten when changing filters but what we forget is that the Racor elements most commonly used are 30 micron (or 10 micron) but the on engine (last chance) filters are usually about 5-6 micron. This means that anything above 6 microns up to whatever Racor element you are using stays in the on-engine filter.

It's interesting to me that although most boats tend to have a vacuum guage on the racors for the main engines, not many have one for the genset fuel filters. I wonder why not? Gensets suffer from the exact same fuel starvation issues that mains do and they usually have more run time than mains. A quick glance at a vacuum guage would identify or eliminate fuel starvation as a problem.

[Canuck Dennis]

If the hertz is going low on fan start only, with low loads on the rest of the genny, you may have a bearing going down in the fan that's drawing down the hertz, as it seems directly involved with generator only.

I understand that when fuel pumps are rebuilt for gensets they are set for +-3% of hertz, if that is the case and and your fan acts up at that reading of 58 hertz I would suspect the fan motor or accessory .

There may be a connection between the control system needing true sine wave vs modified sine wave which the gen may produce at lower hertz??

Good luck on sourcing that gremlin.....getting too hot down there for poor ac performance..