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svHyLyte · 23-09-2020, 08:08

Friends of ours have a smallish diesel generator on their boat that seems to run well but is not reliably generating 60 Cycle power. Reportedly, its output inexplicably falls to 51 to 55 CPS at times. As I've done the diesel generator battles for several years on our boat he asked me what the adverse effect on his AC equipment might be if he continues using the machine while awaiting repairs/correction (e.g. on his air conditioning system which is vital here in southwest Florida at certain times of the year). Unfortunately, tho' I have worked on the motor, I have very little knowledge of things Electrical and so thought someone on the Forum might have some insight to contribute. (My own counsel was "Don't continue to use the thing", but, what do I know!).

Any knowledgeable comments will be appreciated.

/s/ svHyLyte

capn_billl · 23-09-2020, 08:16

Most electronics don't mind a little frequency dip.

Anything with a clock will run slower.

AC motors will run slower, and draw more current.

Transformers will get hot.

a 5 hertz drift is unlikely to damage anything, Some appliances are designed to run on both 50hertz, and 60 hertz, although most will run better at the designed frequency.

jeff356 · 23-09-2020, 09:00

How does he know his cycle readings or is other equipment just being effected?

Have a 4.2kw diesel generator but only show the A/C voltage...

**tkeithlu** · 23-09-2020, 09:55

The problem comes back to you, svHyLyte, because it is likely to be the throttle governor that is creating it, and you know how to fight with diesel engines. The frequency of the AC output is dependent on the RPMs of the engine, with most being either 1800 or 3600 RPM to produce 60 Hz AC. It's diesel, so assume 1800 until you find otherwise. An optical tachometer and a white mark on the front end of the crankshaft should let you set it, or figure out why it is not stable. Good luck with it.

**a64pilot** · 23-09-2020, 10:49

Or dropping from being overloaded or fuel restricted, it’s how I know to change my generator fuel filter when it droops under high load.

But almost anything will work fine at 50hz that was made for 60Hz, vacuum cleaner etc will run slower etc.

However if the Hz rate is dropping that low, I bet money the voltage is too, I won’t operate things below 110V myself, low voltage will cause problems with airconditioners and the like.

svHyLyte · 23-09-2020, 11:23

Guys--

Thanks for the responses. FWIW he used a Fluke Meter to check the machine when he observed the voltage drop from 120 under no load to 105+/- when the AC was running. Evidently his meter has a setting for CPS when the leads are plugged into an A/C outlet. The fuel filter is new so that's not an issue. At this point I am not well enough acquainted with the motor to fool around with the governor (mechanical). That will take a professional mechanic (which I am not!).

We'll see. Given the voltage drop coupled with the low CPS, it's back to "Don't Use the Device!".

FWIW...

Cadence · 24-09-2020, 09:53

I would guess the cycles fall off when the gen. is experiencing close to to much load?

KBDick · 28-09-2020, 12:51

I am having problems with my 5.5 kw Next Gen not putting out stable cycles when checked with a hand held meter. The meter bounces around showing 200-300 cycles which is obviously wrong. I suspect the meter is not accurate enough to show exact cycles. Voltage is ok and ac, water heater, and other equipment run fine but the Promariner 20 charger will not work. Next Gen was no help and Promariner thinks I need to upgrade to a more sophisticated ProNautic which may handle the Next Gen cycle problem. Tried running water heater as a resistive load but no change. The gen rpms are stable. Sent charger to Promariner for check out and waiting for its return. Any suggestions would be appreciated.

capn_billl · 29-09-2020, 08:26

I've got some bad news for you.

If you are showing 200-300 cycles you have an open/shorted coil in in your generator.

Resistive loads that are low current will be ok.

High current, or the battery charger is a switching supply, is not going to work.

The 200 cycles isn't because your generator is suddenly moving 5 times faster, but is because the voltage is dropping out, which your meter reads as a "cycle".

Check the wiring to the generator rotor, then (with it off), ohm each leg, and go from there.

svHyLyte · 29-09-2020, 08:54

Quote:

Originally Posted by Cadence

I would guess the cycles fall off when the gen. is experiencing close to to much load?

Thanks for the observation Cadence, but the AC load is less than half the reported capacity of the genny. Moreover, the CPS reported is with "no load" on the device. The genny was recently rebuilt- new valves, cylinder, piston, injection pump et al so that may have something to do with the situation. N'any case, a knowledgeable mechanic is coming by the boat next Tuesday AM to adjust the governor and I shall pay close attention to the process.

FWIW...

BlackHeron · 29-09-2020, 09:19

It helps when we talk about AC electrical systems by using the correct terms.

Alternating Current has a "Frequency" and it is measured in "Hertz" which is abbreviated Hz. Speaking of abbreviations, "AC" is alternating current and A/C is typically air-conditioning.

Continuing to use strange non-standard, non-scientific terms doesn't help with gaining a better understanding.

That's all I have to say, since others seem to have eventually figured out your question and given adequate replies.

I'm going out on the rooftop of my floating conveyance now to yank on some strings so the flappy fabric things which hang off of the big long pole quit making so much of a racket.

Cadence · 29-09-2020, 09:33

Quote:

Originally Posted by BlackHeron

It helps when we talk about AC electrical systems by using the correct terms.

Alternating Current has a "Frequency" and it is measured in "Hertz" which is abbreviated Hz. Speaking of abbreviations, "AC" is alternating current and A/C is typically air-conditioning.

Continuing to use strange non-standard, non-scientific terms doesn't help with gaining a better understanding.

That's all I have to say, since others seem to have eventually figured out your question and given adequate replies.

I'm going out on the rooftop of my floating conveyance now to yank on some strings so the flappy fabric things which hang off of the big long pole quit making so much of a racket.

Hz or CPS depends on your manufacture date.