A friend has an off the grid holiday house. He uses a generator to provide 240v for household appliances, and a solar panel charging 12v batteries for lighting.

They have a 240v stove (which has some internal electronics for various functions) that will run OK on the 12v system with a 12v > 240v inverter, however it will not run on the generator.

The mob that sold him the generator say that his stove must be fussy about the sine wave output. I'm aware that the cheaper generators put out more a square wave than sine, which some appliances are sensitive to. He's wondering if there is a commercial device he can put in-line after the generator that will "condition" the generator's sine wave. Any recommendations?

The sine wave may indeed be the problem, but I'm wondering if it could also be the generator not having sufficient capacity to handle the stove's current at switch-on. The generator is 7kVa, but I don't know what the stove draws. He's tried just running the stove without any other 240v appliances connected, without success.

Damien

I guess one should first ask "how smart" a stove it is (Brand / Model).. although it seems a bit dumb if it won't accept almost any reasonable AC waveform. Maybe the supply for the electronics in the smart control circuitry needs a bit more supply filtering (eg more electros to smooth out any voltage changes) if a conventional supply or a wider input range rated SMPS.

The "They have a 240v stove (which has some internal electronics for various functions) that will run OK on the 12v system with a 12v > 240v inverter, however it will not run on the generator. " is an interesting statement in itself.

The in-line filter option doesn't really seem feasible as it would take multiple stages of quite high power level low pass filtering to sine-up a (possibly near) square wave. Then comes the safety concerns about construction of a 240VAC-based device. A commercial filter is likely to cost many $$$$ if available.

The switch-on current should be the same as the run current as they are purely resistive elements in a conventional stove. The specs of the stove should show power consumption values for each element setting.

The best suggestion is to go back to one of the old style stoves that has just heating elements and mechanical power switching. They will work provided that the genny produces around 240V on-load.

In my humble opinion, best to get bottled gas and ditch the 'smart' stove completely. A gas cooktop is not difficult to find; baking is a bit more difficult but not impossible 'off-grid'

Something like this is just perfect and less than $100 raysoutdoors.com.au

just my 20 cents worth

73
Ian

Likewise, I would suggest a re fillable bottled gas type stove which would be quicker to cook on and more economical than running a large 7kva generator.

There are portable type gas stoves with cooking burners, grillers and perhaps even an oven if baking is needed.

There is bound to be something about somewhere that will suit.

Thanks guys.

Yes, the 12v system is normally just for the house lighting, and the gene for everything else (fridge, TV etc.), however the 12v system is now for the stove as well.

He mentioned upgrading the solar at some point to a full off grid system, so either doing that sooner rather than later or getting a basic gas stove as an interim solution are options.

Considering the average electric stove element is about 2000 or so watts your friend must have a mighty powerful DC to AC inverter and a thumping set of batteries. hock:

His best option would be to go gas for cooking, put in extra batteries and solar panels to run the fridge/washing machine etc of the inverter.

Sell the large and expensive to run 7KVA generator and buy a smaller gennie like a Yamaha 3.6KVa or a Honda which give pure sinewave AC.

Such a gennie will run fridges, washing machines with no trouble if needed if and when solar power fails.

A battery charger about 30 Amps capacity so as to recharge the batteries on those cloudy days when there is not any solar charging would be another useful thing.

Good info - ta.

I'll pass this on. Sounds like the best solution.

How about we discuss RF interference issues with generators?

Experiments fixing them.

Brands and models that are OK.

Actual Field Day needs.

JMFD. In previous years, a whole trailer was needed to cart the 5KVA diesel generator
and it's distribution box up the hill!!
Next year, we got by with a 900W 2-Stroke "Dingo" gene. 1/4 the size, 1/8 weight.
Used about 10L of juice - so what.
In my back-yard here I did a trial: Run the gene, float charge a 26AH battery with a 10A switcher p/s.
(p/s is marked Made for RF Industries P/L)
Run my FT-450 and IC910H so we have all bands 160M to 23cm.
Both radios have noise blankers and easily handled the gene ignition noise.

The gene runs smoothly because the p/s is limited in peak amperage.

That'll be my setup this year.

Lighting

Beware, lots of LED light units have VERY NOISY SWITCHER electronics.

Keep smiling

Alan VK2ZIW

Alan said: "Lighting Beware, lots of LED light units have VERY NOISY SWITCHER electronics."

I have to agree. Recently on a JMFD from an extremely quiet RF location we noticed noise on 2 metres when the beams were pointed towards a supposed quality metal encased LED floodlight hanging from a tree and fed from a generator.

It turned out that the light and its connecting cable were radiating noise up to at least 2 metres.

We solved the problem by using a Ryobi 18v LED P720 20 watt Hybrid Work Light which has the double advantage of being able to use either 240volts or its 18 volt battery supply.

Dead quiet and very versatile.

Cheers

Peter VK3QI