Running a washing machine from an inverter


Postby ericmark » Sat Jun 19, 2010 10:01 pm

Running a washing machine from an inverter, we have encountered a problem. As the washing machine reaches the point, where the heater would turn on the inverter switches off. It has to be manually switched off and on to reset.
I would assume this is some safety system cutting in, however it would seem it is cutting in too early.

The paper work for inverter states the alarm should sound at 10.5v and should switch off at 9.5v. However using a kettle, which draws 8A+, has the battery voltage still at 11.2v and running the washing machine from shore supply it uses 9A maximum and will run on a B6 MCB without tripping it.

Running the washing machine from the inverter we hear the speed drop on central heating pump then it raises again as the inverter trips. (Making us think it has just been loaded up) No alarm sounds on inverter and the watt, ammeter, shows maximum amps of 0.8A the sampling rate it seems is too slow to capture amps at point of tripping.

On cold cycle, and steam cycle, the machine runs A1 through whole cycle on the inverter.

The washing machine is a LG as they were only manufactures who said they see no reason why it should not work on an inverter. And to be fair this seems an inverter problem rather than a washing machine problem. The inverter modified sine wave is rated at 3KVA with 6KVA peak for motor starting etc.

Microwave, Vacuum cleaner, and Kettle all run without a problem. However the washing machine rated at 2.2Kw is the largest item we have tried to run.
Inverter is feed with twin 35mm singles both Pos and Neg chassis return is not used. There are three 140Ah batteries in the bank feeding inverter charged from a 25A step charger and a 70A alternator.

At the moment the only cause we can think of is battery volts and we have in mind two tests.
1) Try a bigger kettle and see if a 2.8Kw kettle trips inverter if it does then likely we are on write track with volt drop.
2) Put jump lead between pos of engine battery and aux battery bank which will then allow two 70A alternators to charge bank when engine running and will increase output from batteries.

We checked water levels in battery and this was OK and we tested in case inverter had inbuilt RCD and this also had no effect.

However we are not perfect and likely we may have missed something. We did note the power factor was not very good but I would not think when the heaters cut in this would have much effect and with an inverter direct drive to drum one can expect this to fox the cheap power meter.

Any ideas? Or any experience of this before? If worse comes to worse we will have to try feeding hot water into cold fill. Machine web site said hot/cold fill but only cold fill. Pity as more hot water then we know what to do with and we have heat sinks on side of boat to get rid of excess heat from both solid fuel stove and engine. We wonder if there would be a problem in feeding it as hot fill only and use a mixer valve to control temperature!

We have given up for night and unlikely we can do anything tomorrow so seemed worth throwing open for ideas.
ericmark
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Postby sparx » Wed Jun 23, 2010 5:35 pm

Hi Ericmark,
I think you are on right track with Pf.
Invertors are rated at near unity Pf, and the 3KvA soon drops dramatically as it changes, which is why they don't rate them in KW's.
Don't be fooled into assuming the heaters are pure resistive cause i bet they ain't!
Some 'Pyro' types are very capacitive & some wound types are inductive.
An oscilloscope on the output would make for interesting viewing!
good luck, may need some 'conditioning' filtering on supply to washing M/c.
Know what you mean about hot fill as we have loads of solar 'free' hot water in summer, but washer/ dishwasher all cold fill then heat up grrrr!
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Postby ericmark » Wed Jun 23, 2010 11:44 pm

I asked LG and they tell me there is no problem as far as the machine goes in filling with hot water.
Seems blood and egg etc on cloths comes off better with cold water rather than hot so dish washers and washing machines need to start with cold water then heat up after wash has started hence cold only fill.
It seems filling with hot may affect the washing but not the machine so using a shower fitting with thermostatic unit should allow a hot fill.
At the moment waiting for news from my son GW7PVD who was going to try with larger kettle and with extra battery but he is a little slow with results.
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Postby speedygonzarlis » Thu Jun 24, 2010 9:48 pm

hi Eric
If you have to go down the route of mixing the water to a hotter temp on filling, go to a plumbers merchant and ask them for a TMV (thermostatic mixing valve) we have to fit them to new build baths now, as people have fallen in baths and scolded themselves, basically it has two 15mm inlets, 1 hot 1 cold and one 15mm outlet with an adjustable temp control on it, a lot smaller and cheaper than a shower mixer! you can then play around with the temp coming in etc,
shame its not an old skool washer you could of changed the stat on the back or linked it out, i presume this will have thermistor now, although i thought most washers now had a cold wash or adjustable temp control on front?
can you not change the heater for a smaller rated one? i used to work as a service engineer for hoover, most are the same fitment but different ratings on different machines, i.e how efficient it was, A rated etc, all they do is reduce the amount of water in the drum so the heater isn't on as long, or the heater rating,
only problem i can foresee with mixing temp on linlet is when it gets to cold rince cycle it will still fill with warm water which does not remove soap suds the same as cold water, also when the clothes are warm and it goes into spin it ruins cloths they tend to stretch, many a time i went to calls for ruined clothes/faulty machines and all it was, was faulty installation, i.e. customer had put hot and cold pipes on wrong way round!!
good luck
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Postby ericmark » Fri Jun 25, 2010 10:34 am

Thank you for info on TMV they will be neater and I think a 30 deg wash and rinse would not be a problem. The steam cycle works OK so good for any crease.
As my son pointed out max of 20 washes per tank full of water so even when all running A1 still not ideal.
As to mods to washer brand new so only LG mods would be considered and they do not do a hot fill and there are no smaller elements available.
It is about the most economic on market and weighs the cloths as first part of cycle so only enough water is used.
It seems it is blood and like which means washers need to gradually increase heat rather than start out hot. So all washers now are cold fill.
Also of course gas is not renewable.
It seems they have forgotten about the people who have to use heat sinks to remove excess heat in their homes. My son has a large tank next to hull and water is cooled by passing it through that tank.
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Postby ericmark » Mon Jul 05, 2010 8:18 am

Up date. Inverter burnt out. All control wiring melted, but no sign of main component failure (Except fuses). Contacted manufactures and they have agreed to repair if I pay postage which is fair enough, however they claim overload damage, and a 2.2Kw washing machine with soft start inverter motor control should not overload a 3Kw inverter with a 6Kw peak capacity.
ericmark
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