# Electrical appliances for a motorhome? 720 watt generator



## Lauro (Jul 11, 2012)

Hello, 
I have a Metofax charging and distribution system in my motorhome and have a 720 watt generator, what I was hoping to find out was which electrical appliances I need to buy to be able to run using both my metofax system and my 720watt generator??.
ie I believe I could use a microwave but it needs to be low voltage and what type of heater would work best?? I also have a water pump fitted and was wondering if I can fit an heater to generate hot water??.
any help greatly appreciated. :lol:


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## Wizzo (Dec 3, 2007)

I am not familiar with your system but I think you will need to give us some more info. Are you wanting to camp without electric hook up? Do you have the usual appliances that run off gas as well? How many habitation batteries do you have on your system?

Basically your 750w genny will not be powerful enough to run a microwave, or any kind of meaningful heater. What it will (or should) do though is charge your 12v batteries.

JohnW


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## listerdiesel (Aug 3, 2012)

It depends on the microwave wattage (not voltage) and how the generator handles inductive loads.

The small cheapo 850W Chinese generators aren't bad, but they struggle with anything over 500W in the way of a microwave, which eliminates almost all of those small units you can buy.

Peter


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## rogerblack (May 1, 2005)

Don't forget that the rated power consumption of a microwave oven is typically 50% higher than the rated output - e.g. if your oven is rated as 800W 'cooking power' then the until will draw around 1200W


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## listerdiesel (Aug 3, 2012)

rogerblack said:


> Don't forget that the rated power consumption of a microwave oven is typically 50% higher than the rated output - e.g. if your oven is rated as 800W 'cooking power' then the until will draw around 1200W


The device must comply with its type label in terms of power consumption, it is only rated for 'cooking power' for advertising and comparison purposes.

Most microwaves are between 60% and 75% efficient, but as they constitute a large inductive load, even with power factor correction built in, they are not handled well by small generators.

(not criticising your comment, Roger, just trying to make it a bit more factual)

Peter


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## Lauro (Jul 11, 2012)

Thanks for the help lads I do have gas and three leisure batteries but only one is connected I was wondering if I should wire then up in series????? sounds like going for the electric hook up is going to save a lot of hastle would I be able to run a microwave off a camp site hook up????.


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## BillCreer (Jan 23, 2010)

listerdiesel said:


> rogerblack said:
> 
> 
> > Don't forget that the rated power consumption of a microwave oven is typically 50% higher than the rated output - e.g. if your oven is rated as 800W 'cooking power' then the until will draw around 1200W
> ...


Sorry Peter but you've confused me.

So are you saying that if a microwave is rated at 800W that the maximum that it will ever draw is 800W? Or are you agreeing with Roger?

(not criticising your comment, Peter, just trying to clarify)


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## listerdiesel (Aug 3, 2012)

BillCreer said:


> Sorry Peter but you've confused me.
> 
> So are you saying that if a microwave is rated at 800W that the maximum that it will ever draw is 800W? Or are you agreeing with Roger?
> 
> (not criticising your comment, Peter, just trying to clarify)


The type label should show the maximum power draw that the appliance can take from the supply, that is the basis of its CE marking.

That is the only information that you should go on, as any other figures like 'cooking power' are meaningless unless heavily qualified by details of the type of food, the container it is in, percentage of water in the food and so on.

800W should mean just that, BUT it will affect small generators adversely as it will have a low Power Factor, so an 800W microwave will 'look' like a 1200W unit, that may have been what Roger was trying to put across.

More modern units will have Power factor correction capacitors fitted, so will be improved over earlier appliances. Our new Sharp that we bought last year is performing like an old appliance.

Peter


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## selstrom (May 23, 2005)

If you connect them in series you will have a 36 volt system if they are 12v batteries.


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## BillCreer (Jan 23, 2010)

If anyone is still confused by Microwave power consumption:-

Microwave ovens are often referred to by their COOKING POWER which, on average, is only 50% if their actual operating power consumption. On top of this, when switching on, the oven needs another 25% power as the capacitor is energised, hence a normal '600 Watt' oven in fact needs 1500 Watts to operate it.

Amps = Wattage divided by Voltage e.g. 1000W (1Kw) / 240V = 4.1 Amps 
Fuse Rating <700 Watts = 3 Amp Fuse <1000 Watts = 5 Amp Fuse > 1000 Watts = 13 Amp Fuse


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