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Old 09-09-2012, 09:03 PM   #1
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AC Amp Meter For Genset

It seems that my genset (NextGen Power) wants to overheat if I load it to near capacity. It's only a 3.5KW and I need it to last (i.e. I can't afford a new one right now). I have looked at most of the usual suspects for overheating issues short of pulling off the heat exchanger.

I want to put an amp meter on the generator to monitor the load we put on it. I'd like to have a 2" round gauge to go next to my new battery monitor. Any suggestions?

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Old 09-09-2012, 09:14 PM   #2
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Like this:

AC Digital Meters - PN - Blue Sea Systems

Anyone use this? It looks perfect. Fits in a 2" hole and has high/low alarms. Although, at $250, maybe it doesn't need to be "marine grade" for this internal application.
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Old 09-09-2012, 10:28 PM   #3
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One on eBay.......Blue Sea 8238 AC Digital Ammeter Gauge 0 to 150 Amps Amperage Display 80 - 270 V | eBay
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Old 09-09-2012, 10:29 PM   #4
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There's any number of cheap analog ammeters out there Tom. I bought one last winter and put it on the hot line after the gen/shore power switch. I have it for the opposite reason - my gennie will make more power than I can use but we routinely overload the shoreline. Mine's about as handy a location as hip pockets in long underwear but it was quick and easy to install and it didn't cost anywhere near $250 - $40 if memory serves and that was in a chandlery so I could likely have done better.
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Old 09-10-2012, 06:06 AM   #5
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IF you watch a meter would be fine.

But a cheaper system is known as load shedding .

This is done with a simple relay that prioritizes your loads .

EG the air cond comes on , the HW heater goes off.

In the archives.

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Old 09-10-2012, 07:28 AM   #6
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Originally Posted by GonzoF1 View Post

I want to put an amp meter on the generator to monitor the load we put on it. I'd like to have a 2" round gauge to go next to my new battery monitor. Any suggestions?

Try this: PANEL AC AMMETER 400 Hz 0-50 amp - MODEL 10909 | eBay

With this: 1pc CT Current Transformer Coil YAL-1 AC50A 50/5A 15VA Acc=1% Size=

There may be a slight error because this is a 400Hz meter but it should be insignificant. If you need lab quality readings you may be hard pressed to find a 2 inch round analog meter you can afford.
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Old 09-10-2012, 07:29 AM   #7
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if you like the blue seas one and you don't like square off to the side...you could swap around the other round instruments to put it next to the square panel to the right...may look a bit more natural...

me...
I know what AC loads are on and usually pretty easy to calculate...always factor in around 5 amps for the misc/momentary stuff like electronics chargers, table lamps, etc.

Like FF posted...unless you look at the meter constantly to guess when the water heater kicks on or whatever...then just knowing the system loads will be enough and manage them from overlapping.

I'm sure you know all this or have thought about it....just reinforcing one side to a less than perfect situation for many of us with greater electric demands than supply sources.
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Old 09-10-2012, 08:52 AM   #8
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.................... we routinely overload the shoreline. ............
When I do that, my main circuit breaker trips. Or the one on the dock pedestal.

I agree with the thought of automatic load shedding, but it wouldn't be a simple project. Fixing the genset might be a better plan in the long run.
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Old 09-10-2012, 11:11 AM   #9
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The easiest is to put the high amp items on a timer so you know when the come on/off. the first thing I did was put a time on the water heater, and the electric heaters. If you install a AC amp/volt meter wire it in for shore and the gen set.

A major reason engine get rebuilt is the raw water/exhaust muffle exchange is plugged and/or a hole in the exchange which back fills the engine. The outer tubes of most exchanges become plug so only the middle one are open thus restricting water. I would have the exchange pulled and looked at just for peace of mind.
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Old 09-10-2012, 02:13 PM   #10
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Gonzo

Have you used an IR gun to be certain your genset is indeed overheating? Is it tripping out on high temperature? Are the ususal suspects for overheating OK such as RW pump, impeller and HX?

On many/most setups the amp meter is hooked into the same circuitry as shore power via a directional switch using the same amp meter and breakers as shore power.

Inverter/chargers in the 3000 watt range will easily pull 18 + amps then automatically cutback as the batteries are filled - thus consuming most of a small genset's capacity. Do you have a separate low amp charger you can use in place of the inverter's charger?
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Old 09-10-2012, 03:34 PM   #11
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Have you used an IR gun to be certain your genset is indeed overheating? Is it tripping out on high temperature? Are the ususal suspects for overheating OK such as RW pump, impeller and HX?
Yes. Part of why it overheated last time (A think) is my neglect in managing the load and leaving the hot water heater on. We (the diesle mechanic and myself) have indeed checked all the usual suspects.

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On many/most setups the amp meter is hooked into the same circuitry as shore power via a directional switch using the same amp meter and breakers as shore power.
I believe I will try RickB's inexpensive solution. I saw that Simpson meter at Grainger, but didn't find the coil. For $30, it might be worth a try.

Quote:
Originally Posted by sunchaser View Post
Inverter/chargers in the 3000 watt range will easily pull 18 + amps then automatically cutback as the batteries are filled - thus consuming most of a small genset's capacity. Do you have a separate low amp charger you can use in place of the inverter's charger?
My inverter and charger are already separate devices (Don't you pay attention around here? ) . With an accurate meter, I can easily work on learning what I can and cannot use when running the generator. While not 100%, it's far better than what I am doing now.


On another topic, during the repair process, I am sure I adjusted the full-throttle setting, something the factory indicates is the adjustment for the power frequency (in hertz). Is there a way to easily measure without bumming an o-scope from someone?

**EDIT** Look like I can use a multimeter if mine has the ability. Thought I'd need a scope for sure.

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Old 09-10-2012, 05:27 PM   #12
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... With an accurate meter, I can easily work on learning what I can and cannot use when running the generator. While not 100%, it's far better than what I am doing now...
The amp gauge will also help manage your shore power demands as Sunchaser has said. It's a good tool when your at different marinas and only have 30 amps available.
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Old 09-10-2012, 05:48 PM   #13
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If I have 2 30A 125V shore power cables, if I put the current transformer on neutral, I'll read total current on both legs, correct? Or should I get two for each hot leg and rig a selector switch?
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Old 09-10-2012, 06:02 PM   #14
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.... With an accurate meter, I can easily work on learning what I can and cannot use when running the generator. While not 100%, it's far better than what I am doing now.
It would be just as simple and less expensive to just write down the current draw from the appliance labels. 15 amps for the water heater, 18 amps for the AC, 3 amps for the refrigerator, etc. (I'm pulling these figures out of the blue, you need the real ones for your appliances).

Remember that many appliances, including the examples I listed, are controlled by thermostats so their consumption is intermittent. Many also have a larger current draw each time they start than they do once they are running.

If the genset output is not protected by a circuit breaker to prevent overload, installing one would be a great idea. Draw too much power and the breaker trips rather than the genset being damaged.


Quote:
.............. On another topic, during the repair process, I am sure I adjusted the full-throttle setting, something the factory indicates is the adjustment for the power frequency (in hertz). Is there a way to easily measure without bumming an o-scope from someone? -
An old fashioned electric (synchronous motor, not quartz) clock keeps time by the frequency of the input power. If the clock runs fast or slow, your genset frequency is off.
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Old 09-11-2012, 05:39 AM   #15
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Installing an amp meter is a good idea in its own right...but it seems like an odd response to an overheat-under-load problem. The NextGen is quality gear and should be comfortable running at 85-90% load near-continuous. Is it a problem to re-circulate Rydlyme or BarnacleBuster or diluted pool acid through the HX, if you have checked everything else in the raw water circuit?
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Old 09-11-2012, 07:21 AM   #16
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If I have 2 30A 125V shore power cables, if I put the current transformer on neutral, I'll read total current on both legs, correct? Or should I get two for each hot leg and rig a selector switch?
Tom: You only need one. The generator, inverter (if you have one) and both AC hots, not neutrals, are wired through the coil.
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Old 09-11-2012, 07:43 AM   #17
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Installing an amp meter is a good idea in its own right...but it seems like an odd response to an overheat-under-load problem.
Yes. It is attempting to treat the symptoms, not the problem.
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Old 09-11-2012, 07:46 AM   #18
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Installing an amp meter is a good idea in its own right...but it seems like an odd response to an overheat-under-load problem. The NextGen is quality gear and should be comfortable running at 85-90% load near-continuous. Is it a problem to re-circulate Rydlyme or BarnacleBuster or diluted pool acid through the HX, if you have checked everything else in the raw water circuit?
After discussing my problem with NextGeneration yesterday, I will be doing this very thing. As well as making sure the freshwater coolant is correct. We are suspecting there might be some blockage in the exchanger. Maybe some growth or perhaps impeller scraps. Either way, this is supposed to be a very robust genset. The generator side is the same hardware as the one with twice the KW rating with only a smaller motor. As it was explained to me, as the load nears max, the engine will slow, the voltage will drop (which, of course, cause amperage to sky rocket), and the motor will tank itself and shut off before it overheats. Adding also that this little motor can take temps as high as 250 degrees quite easily and that they set the thermostat at 225 to tip you off that there might be a problem needing attention.

Whatever happens, I still am sure an ammeter on the A/C side of my panel is a good idea for all the reason you guys have mentioned. Most especially because it's a pretty easy project that will pay dividends down the road.
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Old 09-12-2012, 06:20 AM   #19
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"I still am sure an ammeter on the A/C side of my panel is a good idea for all the reason you guys have mentioned. Most especially because it's a pretty easy project that will pay dividends down the road."

Who is going to spend their cruising time observing this?
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Old 09-12-2012, 07:50 AM   #20
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Who is going to spend their cruising time observing this?
Why is this any different than an oil pressure gauge or a tach or a temperature gauge?
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