Inverters?

Tomgunn:

Happy Easter to all! ?

Can an inverter be run off of the mains'?

Why would you want to?

 So... he want's a 3K washing machine... can an inverter be worked, without lot's of batteries, to run this?

Clearly the way to operate from the mains is to have a hefty battery charger! I suggest that you will need about 5kWhr of batteries, probably operating at more than 12V because more volts gives better efficiency everywhere. Lorries often have a 24V one for the kettle and microwave, so the price is fairly low. 200 Ah of deep discharge batteries, a 30A charger and a 3kVA inverter should do it, along with a 24V alternator added to the engine should see you with a great system, perhaps even some solar panels on the roof to keep everything charged during the unused times should do it, perhaps £3k or so altogether if self installed. An excellent addition to any narrow boat, because you can then use mains voltage LED lighting and an electric fridge too.

If a mains supply is available that can supply 3Kw, then a standard washing machine may be connected to this supply. If the available supply is only just sufficient for the washing machine, then care must be taken to limit other loads until the wash cycle is completed.


If no mains supply is available, or if the mains supply is not sufficient, then an inverter powered by batteries will be needed to work a standard washing machine. I would select at least a 5Kw inverter since washing machines are a challenging load. You may need to connect a lamp or other small and continual load in parallel with the washing machine to stop the inverter from going to sleep when the wash cycle pauses.

Make certain that the battery is big enough. 3Kw at 12 volts is about 300 amps !


Alternatively, look for a low powered washing machine, these have no heater and a reduced spin speed, some are directly 12 volt powered.

Can an inverter be run off of the mains'? 

Is the problem that the mains voltage is low? If so you could have a rectifier-inverter arrangement (basically a UPS without the battery) which would be able to generate an in-spec voltage from a low one (provided enough current can be drawn from the supply). In some countries automatic voltage regulators are popular - but often they're a simpler arrangement - typically a variable autotransformer and a mechanism to vary the taps. If you did want to go down the inverter route a reasonably high power UPS (even with a modest battery) might serve the purpose (but beware of any large starting currents).


I've no experience of boat batteries, but caravan 'leisure' batteries (at least of the usual lead-acid type) usually come with a recommendation generally not to discharge them below 50% otherwise the lifespan can be significantly reduced - hence a 110Ah battery might only give you 55Ah of useful power (e.g. 660W for an hour for 12V battery) - so you might need more lead & acid than a simple calculation suggests if you did go down the battery & inverter route.


Failing that a decent genny.


   - Andy.

Once upon a time washing machines had hot and cold water supply connections, losing the hot connection and becoming cold fill only is something that some people blame on the a European Union, however the hot supply was only used when you set a wash at above sixty degrees as the machines could not blend the supplies to get to say thirty degrees, whereas it’s easy to start from cold and heat the water accurately to thirty degrees.


If there is an adequate hot and cold water supply at a suitable pressure onboard ship and you can supply hot water to the washing machine at a preset temperature of say forty degrees the heater within the washing will not kick in and the current draw will be minimal.


So if there is an instantaneous water heater onboard set the maximum temperature to forty degrees or fit a thermostatic mixing valve then fill the machine with hot water and don’t use the heater within the machine, unless the vessel is hooked up to the shore line.


Best check the appliance manufacturers instructions as to the maximum fill temperature, this was however offered as an installation method for many dishwashers and is an option for installing a dishwasher in a boat or recreational vehicle.


BUT DON’T SHRINK THE CAPTAINS GUERNSEY.


 Andy B.

Not all washing machines are suitable for use from inverter-derived power.


This is because of the way in which the speed control for the motor is achieved for some modern motors without carbon brushes.


Again, need to check the manufacturer's instructions very carefully on this one.

WOW, I didn't expect all of that amazing info / feedback! 


Thanks and I'll pass on all of this to my friend and, maybe, it'll help his neighbours' too up there in narrow boat land!


Lot's here on things I wouldn't have thought about, it's good to read your replies and, thanks again!!!!! ?


regards and have a nice Easter holiday! Tom

Chris Pearson:

Sparkingchip:
Miele dishwasher

Great! So we ignore the consumption of the immersion heater which got the water up to 65 deg C in the first place. ?

 

If the stored hot water is heated by either solar hot water or PV panels on the roof it’s a no-brainer, if the water is heated by gas, a heat source pump or any other type water heating that’s not an immersion heater running on a peak tariff it’s still worth consideration.


On a boat it’s shifting the electrical load of heating the water onto a gas bottle dramatically reducing the size of batteries and inverter required to run washing machines and dishwashers as well as the size of the inverter.


Resistive heaters kill storage batteries.


Andy Betteridge