Inverter Question

[pappaecho]

Having tossed away my old 8 amp absorption fridge and replaced it with a new (cheap) small table top fridge which is 240 volts, and only 47 watts, I was expecting to be able toi use a 150 watt inverter, which has a maximum pull of 450 watts.
However, reading the Maplin catalogue, it says that a Pure sine wave inverter is needed to power motors, pumps etc,

" ideal for inductive loads such as pumps, fridges etc that cannot be powered by a modified sine wave inverter"

Is this true and why??

Surprisingly Pure sine wave inverters are twice the price!

 

[Bassplayer]

Good modified sinewave inverters will run pretty well anything. On my camper that includes aircon, microwave, tv, fridge, - they want to sell you the expensive inverter no doubt.

 

[sailorman]

Good modified sinewave inverters will run pretty well anything. On my camper that includes aircon, microwave, tv, fridge, - they want to sell you the expensive inverter no doubt.

a Mod sine wave wouldnt run my microwave, the Struder does

 

[jfm]

I'd agree with Bassplayer. A modified (ie not pure) sinewave should generally be fine for a fridge compressor motor. Give it a try!

 

[Gumpy]

The thing you have to be aware of is that the start up draw of a fridge can be 15 times the rated wattage.
MSW inverters work fridges fine, well mine does but then its a 2.5kw one

 

[pappaecho]

Thanks guys, I will give a 300 watt inverter a go with the fridge to see what happens. If this works will see if I can check out a 150 watt from a mate

 

[PCUK]

I bought a 500 watt, max 800 MSW inverter off Ebay (new) for £23 to charge drill batteries in the van. Works fine but at that price got to be worth a try!

 

[Wiggo]

Yup, suck it and see!

 

[oldgit]

Am using a cheapo chinese 1KW jobby which runs everything including my laptop although it does wheeze a bit powering my 500w electric fan heater.

 

[Csail]

Slightly off the subject but my new pure sine wave instructions say put earth connection to negative so why don't they bridge it in the factory?

 

[TrueBlue]

It's very much a matter of suck it and see. Mine runs some power drills well and others not so well. SWMBO had a compact food processor that wouldn't run at all.

Laptop OK, TV ok'ish (bit of a buzz, wavy on some channels).

A fridge ought to run - but some of the better quality units have some form of microprocessor control which might object.

 

[pappaecho]

Am getting the 300 watt inverter of the other boat. Have earthed the shore side of things to the negative side of the house batteries, so this should mean that the inverter is similarly grounded. Wiil report on outcome tomorrow.....

 

[pappaecho]

Put a 300 watt Skytronic "slow start inverter" onto the fridge and it worked perfectly, reducing the voltage on the battery bank by 0.25 volts. So my 47 watt mains fridge seems to be OK on the inverter. I will now try a 150 watt inverter.

A new 12 volt fridge is about £350 - £400. My 240 volt table top fridge cost £75, and the inverter would be another £35, with the advantage that it can be run on shore power when in harbour and batteries linked to solar panels when not. Bargain