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Old 19-07-2019, 16:46   #1
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Portable Gen sets

Having read the thread "WOW- Induction Cooktop! " I am exploring the possibility of replacing the gas cook-top with an induction cook-top but I'm not sure of the logistics.

What size portable inverter gen set would I need:
  • given that just one induction hotplate is 2000W? (Realistically I think I would need two)
  • Do I charge the batteries with the gen set and then power the hotplate with the 3000/6000W inverter?
  • Apparently the continuous RPM of these small inverter gen sets is 5000 rpm! How long could I expect the unit to last at that rate?
I would appreciate any "rule of thumb" advice to set me on the right track.
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Old 19-07-2019, 17:07   #2
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Re: Portable Gen sets

Realistically, I think you'd need at least a 2.2kVA but preferably a 3kVA for a single burner although you don't need to run them on full power all the time, obviously. We have been using a single induction hotplate at home for about 2 years now, and have never switched the 4 hotplate resistive element unit back on since, so it's pretty easy to adapt to cooking with a single hotplate. Sometimes you need to swap over pans to reheat, but due to the efficiency of the things, this isn't that big a deal.



With a portable generator, I'd go with inverter for cooking and use the genset to charge at leisure. Your anchor neighbours will also appreciate you not firing the thing up at breakfast and dinner times. You'd also not have to eat cold baked beans for a week if the generator crapped out on a trip.


5000 rpm is nothing for a small engine. Besides, it won't need to run flat out all the time. Just keep it serviced and choose a decent brand.
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Old 19-07-2019, 17:30   #3
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Re: Portable Gen sets

Reefmagnet

QUOTE "We have been using a single induction hotplate at home for about 2 years now, and have never switched the 4 hotplate resistive element unit back on since, so it's pretty easy to adapt to cooking with a single hotplate"

I agree! I rarely use more than one hot-plate at home at the same time. I have a microwave at home as well as on the yacht so I don't see it as a problem. (I often wonder why some yachts have 3/4 hotplates although I notice Bavaria/HalbergRassy/Bavaria generally only boast two in their sales brochures)

I have a single induction hot-plate on the way so we'll see how we go at home.

My "re-cycled" gen-sets have always needed to be run a set RPM but I take it that with Inverter gen-sets that is not a requirement?
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Old 19-07-2019, 18:30   #4
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Re: Portable Gen sets

Non inverter gensets have to run at fixed rpm in order to maintain the correct AC frequency therefore a two pole AC genset will run at 3000 rpm for 50Hz AC output. Output regulation is usually done by adjusting current flow to the magnetic field coils.
An inverter is different in that it generates DC and uses and inverter to provide AC frequency and regulation with the added feature of including engine speed regulation for the latter when in "Eco" modes.


And yes, the microwave is a good accessory for a single hotplate. Only problem is the darn things are extremely inefficient from the perspective of running from a generator or inverter thanks to surge currents and power factor ratios. This means you can run the microwave or hotplate, but probably not both at the same time and you shouldn't be surprised if a portable genset struggles to run even a small microwave.
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Old 19-07-2019, 18:43   #5
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Re: Portable Gen sets

But the microwave is only on for a short time just to cook (or reheat) the vegs while you are serving up from the induction saucepan.
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Old 19-07-2019, 18:56   #6
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Re: Portable Gen sets

It's not the duration of running time, it's the instantaneous VA demand of the unit when running. I've tried a couple and found that this is about twice the cooking output rating.


Check out this link for a bit of an explanation why there is a difference between Volt-Amps and Watts...


https://www.apc.com/salestools/SADE-...NQYF_R1_EN.pdf
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Old 19-07-2019, 19:31   #7
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Re: Portable Gen sets

Yes I was aware there was a difference between kVA and KW and it is due to the PF (Power Factor) which I have always assumed was about 80%. But here

In other words, volt-amps x power factor = watts. Similarly, KVA*PF = KW, Or kilovolt-amps times power factor equals kilowatts. When you want to know how much the electricity is costing you, you use watts. When you are specifying equipment loads, fuses, and wiring sizes you use the VA, or the rms voltage and rms amperage. This is because VA considers the peak of both current and voltage, without taking into account if they happen at the same time or not.

They then go on to to say "the power factor is usually over 90%".

But I never push things to the limit so it is something I just keep in the back of my mind. I am very much aware I will have to manage the loads on the gen -set or battery bank but I don't see that as a problem.

Thanks for your help: I have a better idea now.
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Old 19-07-2019, 20:23   #8
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Re: Portable Gen sets

Well this makes it soooo simple!

One of the great benefits of inverter generators is that they can produce current at any rpm; the engine does not have to operate at 3,600 rpm to produce 60 cycle current. The inverter electronically converts the current to 60 hertz 120 volt power. So, for instance, if you plugged in a 200-watt tool battery charger, the generator might only need to run a little faster than idle speed to produce the electricity needed; the engine rpm is adjusted to produce only the power needed by the power demand. This saves a significant amount of fuel, reduces noise, and significantly increases engine life.

https://www.forconstructionpros.com/...ter-generators
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Old 20-07-2019, 09:42   #9
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Re: Portable Gen sets

carbon monoxide is very dangerous
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Old 20-07-2019, 15:45   #10
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Re: Portable Gen sets

Quote:
Originally Posted by john61ct View Post
carbon monoxide is very dangerous

The LPG locker is sealed off from the rest of the yacht.

To run the gen set you'd have to lift the hatch lid otherwise you would have to punch holes in the side of the hull for exhaust, air intake for the motor and air intake for cooling. (Not on....)
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Old 20-07-2019, 17:19   #11
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Portable Gen sets

Storing in a locker may be OK, or may cause corrosion.
However these things are started with pull cords, which may be hard in a locker. Even if you can make it work, you need to take it out to fuel it.
I believe the cooling and the removal of exhaust to be the long pole, exhaust of course is depleted of O2 to some extent, and is hotter than Hell so for both of those reasons it needs to go.
My little Honda lives in the cockpit with me, under a cover. If I want to use it I lift it and put it out of the cockpit, itís not that hard.
I prefer the Companion model as I can plug the shore power plug directly into it. An EU 2000 is all over the max limit of a 15 amp plug, and Iíd suspect a 2200 is really pushing how much power a single regular plug can handle, there are 20 amp models top of course, but I feel better with the shore power cord that twist locks.

I donít believe I would consider a 2000 now if they are still sold. I believe the 2200 has significant advantages over it, the extra 200W is just one.
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Old 20-07-2019, 17:28   #12
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Re: Portable Gen sets

Quote:
Originally Posted by john61ct View Post
carbon monoxide is very dangerous


It is, but it can be managed by you taking care and detectors etc.
Our use is at anchor where we are usually, but not always into the wind. Boat is opened up as much as possible as we are warm weather cruisers and I have a detector.

However when I first tried a Honda before I put in a Diesel built it, I had two Hondaís and I have a very sensitive CO detector that I used to certify new aircraft with. And I would always get small but detectable amount of CO. Only way I got zero CO was to put the Honda or Hondaís in the Dinghy floating behind the boat.

Now that I have the Diesel built in, I have bought another Honda, partially as a back up, and partially because I just donít need all the power the Diesel can make and the Honda is cheaper to run with amortization figured in, and a whole lot easier to service.
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