# 500w/600w microwave - how many amps required at switch on?



## tonyt (May 25, 2005)

The lady insists a microwave is the answer  

I've always shied away from getting one as I don't need/want one but I'm told "just go get one!"

I know 500/600w versions are available at a reasonable cost and, on paper, should only use only around 3 amps so should be fine on a 6/8 amp hook-up but I have in my mind that, at start up, a microwave can cause dials to quiver on the National Grid  

Are any of you using a microwave successfully on 6/8 amp sites? (excluding inverters).


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## tonka (Apr 24, 2006)

A microwave will use an additional 50 - 100% on start up..
Unfortunately many manufacturers dont give these figures..
So worst case a 500w could take 1000w.... The time is only short but enough to trip a supply..


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## Rapide561 (Oct 1, 2005)

*Microwave*

Hi

Be a bit careful with low wattage microwaves is my advice.

We have had motorhomes with 800 watt models in but the last one had a 700 watt model. It was a lot slower and things like baked spuds were in there so long, they were "off their best".

We have stayed on many 6 amp sites overseas and have never tripped out as a result of the microwave.

Russell


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## ThursdaysChild (Aug 2, 2008)

Ours is an 800w cheapie which we use regularly. Never tripped a switch by itself on a 4A site supply, but there have been times when I have forgotten it is on and switched on the kettle at the same time ...... oops.
Also remember that if you have a Truma electric water heater, after a journey the water temperature will have dropped and the heater will cut in as soon as you hook up. There's a couple of precious amps gone already. Same if you forgot to turn off the electric space heater when you left your last stop.
So any problem might not be an overload from the microwave, but an aggregate of other power consumers.


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## pippin (Nov 15, 2007)

It is a few years since I left the trade but heavy transformers were gradually being phased out in favour of electronic power supplies.

Panasonic were the leaders in the technology.

memory is fading, but a magnetron (wot produces the waves) takes quite a few amps for its filament and a staggering amount of amps at about 3kV.

A traditional ferrous core + copper windings were the norm.

Very heavy, physically large and a hefty start-up surge.

By contrast a switch-mode EHT power supply is very light and has slow-start capabilities to minimise the switch-on surge.


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## teensvan (May 9, 2005)

Hi 

We have had a few 700/800 watt microwaves and never had a problem on a 6 amp hookup. the 4 amp one may well trip.

steve & ann. ------teensvan


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## listerdiesel (Aug 3, 2012)

We have a Sharp 800W in the trailer, switch-on current is quite high but only for half a cycle or 10mS, so as long as your own MCB's aren't A type, you'll be OK. We've had no problems.

MCB's are graded to suit the expected load, not just in handling current, but of their response to overload.

A types are for purely resistive loads and trip pretty quickly

D types are for reactive loads like transformer which have a high initial surge on start-up.

The overload tripping is thermal or magnetic (current) or a combination of both, depending on the type.

Peter


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## Penquin (Oct 15, 2007)

We have a 600w and have never tripped an EHU using that alone, only when we have forgotten and switched e.g. the kettle / electric hob / water heater on........ (as others have so correctly said.......)

Microwaves are a useful commodity IMO - not just for jacket potatoes. but also for heating food that we have prepared before leaving home on a journey - it means we can be eating e.g. pasta and reheated sauce within a very few minutes without having to heat on the hob.

It's all to do with what HTMBO wants to produce for your delectation.....

Dave


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## tonyt (May 25, 2005)

pippin said:


> It is a few years since I left the trade but heavy transformers were gradually being phased out in favour of electronic power supplies.
> 
> Panasonic were the leaders in the technology.
> 
> ...


Thanks for that - I think


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