Running a washing machine from an inverter

[ericmark]

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.

 

[ricicle]

Can you not use an analogue meter on the battery to look for any drop in voltage as the invertor trips ?

 

[ericmark]

Can you not use an analogue meter on the battery to look for any drop in voltage as the invertor trips ?

All meters on site were digital although some were more expensive than others but the Fluke did have the bar graph. I have an old Avo Mk8 at home but on 25v scale reading the volt drop would not be too easy.

Maybe we need to construct a load bank to find what voltage the inverter trips out at.

However it seemed we should have been within limits and I just wondered if I am missing something?

 

[conny]

Can't help with the tech side of the inverter but if you use a hot fill you would find that on the rinse cycle it wouldn't remove all the soap traces from the clothes and may well shrink some garments such as woolies.
Missus should know more about that side of things though.

 

[SteNova]

i expect it will just be too much short term load, i have the same issue with a 1000w inverter generator, it will run the whole house fine during power cuts, computers/drills/shower pump/fridge/heating pump but if the freezer kicks in then it strains for a second then trips, i'm sure the freezer isn't rated at 1000w+

 

[SteNova]

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!

i'm guessing the heater comes on in the washer then heats till a switch says the water is hot enough then it continues with the cycle, if you could feed in water at the correct temp (maybe using a shower style thermo valve?) then it may work, would also have to check for a level sensor in the tank as you wouldn't want it sucking on the water before the tank is full

infact thinking differently here what would happen if you replaced the heater in the tank with a pipe coil connected to your hot engine water, an electronic valve connected to the heater power feed to open water to the coil when the machine requests the heater being on

 

[big-all]

my washing machine on economy and program 2 only accepts fill water from the hot side and turns the heating off
once its filled i turn it to program 4 a mixed fill program that will then allow cold water in of the water is too hot
so worth checking your machine to see if it has a program that turns the heating element off

 

[ericmark]

Can't help with the tech side of the inverter but if you use a hot fill you would find that on the rinse cycle it wouldn't remove all the soap traces from the clothes and may well shrink some garments such as woolies.
Missus should know more about that side of things though.

Thank you good point it would need change over valve of some sorts. Sure I could program into PLC but I hadn't thought of that.

We had considered something in the line of a shower mixer as domestic hot can get very hot when solid fuel stove is running. However "Conny" has raised a very good point and it may need a more complex method so only first fill is hot.

The web site said the washer was hot / cold fill but on arrival seems cold fill only. Maybe a conversion kit is done but will have to wait until Monday to phone LG to find out.

However seems it was a good idea to ask question on hear as cold rinse was something I had missed.

 

[plugwash]

Can you provide more details on the inverter you are using?

 

[ericmark]

Can you provide more details on the inverter you are using?

Yes
Type/specification(W) 3000
Max power(W)/5 min's 6000
Converting efficiency(%) 90±1
Input voltage (12V/DC) 11-15
No load current (A) <2.5
Euro Output (V/AC) 230
Weight (kg) 8.0
Over temperature protection( °C ) 85±5
N. operating ambient temperature(°C) -20-40
Overload protection yes
Short circuit protection yes
LED display yes
Protection feature of inverter:
Some abnormal conditions occur with RED LED on:
1. battery voltage drops to 9.5V/19V, audible alarm occurs when battery voltage drops to 10.5V/21.0V.
2. battery voltage goes up to 15.5V/31.0V.
3. The power of connected equipment exceeds inverter's rated power range.
4. The surge power of equipment is too large for inverter to start. The surrounding temperature goes up to 165F
About Power Inverters:
Power Inverter, an innovator in portable inverter design, has developed a new line of super-efficient power inverters with the highest surge capability in the industry. These extremely advanced, microprocessor controlled units run cooler and more reliable than any in their class. Their superior surge capability allows them to start even the most difficult loads, including colour televisions, TV/VCR combinations, microwaves, refrigeration units, even small air conditioners! They also sport the highest efficiency available (up to 90%), which translates into longer running time and extended battery life. This Inverter convert 12V/24V low voltage, direct current (DC) to 110V/230V/240V alternating current (AC). According to the special condition of your autos or boats, please choose the corresponding type of power inverter.
Gives part number as PI-3000 but that is about the limit to useful instructions

 

[toasty]

What about wiring a large electrolytic over the supply terminals of the inverter just to absorb the potentially large inrush current when the heater kicks in? Assuming this is taking the voltage momentarily under the allowed threshold, this might just do it...? You could probably achieve the same with a car battery in the same location and good thick leads?

Does the same problem occur regardless of whether the alternator and/or chargers are working at the same time? I would have though that having these going would keep the voltage a fair bit higher.

 

[ricicle]

Is it possibly that the invertor is seeing the motor control switching as very brief short-circuits (similar to other motor control can do on the input sine-wave) and this coupled with the heating load is causing the shut-down ?

 

[JACKC]

Has the inverter got a flc ramp time setting, this may be set to low for when the heater load is applied and tripping the inverter.

 

[ericmark]

Has the inverter got a flc ramp time setting, this may be set to low for when the heater load is applied and tripping the inverter.

There are no user setting on the inverter. Talked to my son yesterday and he has decided not to try using a hot fill. Tonight he is to do some more tests including a jump lead to add extra battery. If that works then is a case of getting another battery carrier welded in and the engine battery will then be moved leaving space for a forth battery for domestic bank.

However this then causes a second problem in that the battery charger a WAECO 925-012TB is designed for a maximum of 300 Ah and to exceed the limit I would think it could over charge the battery?

The charger has three stages:-
1) Flat out 25A until voltage reaches 13.8.
2) When current drops to 20A then the voltage rises to 14.8v (or 14.4v switch-able) also timer starts.
3) Holds output at 14.8v (or 14.4v switch-able) until current drops to 2.5A or the 4 hour (or 8 hour switch-able) limit is reached.
4) Float charge at 13.8v

As far as I can tell the charger needs unplugging to re-start cycle. For the units that connect to alternator there is a lower voltage limit that re-starts cycle but not for shore power charger.

There is a warning "Attention The maximum battery capacity (see Chapter „Technical data“ on page 45) should not be exceeded in order not to influence the functions of the individual charging phases."

We should fit a 945-012TB which gives 45A charge instead of 25A charge but at £400+ not really what we want to do. The idea is of course to re-charge the batteries as quick as possible without damaging the batteries but in real terms for a shore charger this is not required. It is not a case of just connecting for one night to recharge batteries but a continuous supply and batteries take the ups and downs with normal shore supply of just 4A and for items like the vacuum cleaner this has worked and they can with inverter use vacuum cleaner.

To test if washing machine was faulty they borrowed a 6A supply and it worked the washing machine in spite of it drawing 9A however with 4A supply it trips straight away.

The marina has a problem in that the total supply to marina is only around the 200A and the use of such small MCB's on individual supply ensures the 200A is not exceeded so drawing 4A 24/7 is not a problem. It's not how much power they use but what the max power they use is which is important. Hence the charger, battery, and inverter.

So now it is just a case of waiting until my son has completed next set to tests. Thank you all for your input. I will advise on how it all goes.

 

[matt1e]

The inverter modified sine wave is rated at 3KVA with 6KVA peak for motor starting etc.

hi eric
modified sine wave inverter's are no good for washing machines your inverter needs to be pure sine wave
have a google

Matt