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What does your 5kva inverter power?


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Hi All

Absolute beginner here with basically zero knowledge of inverters,solar etc. I’m (almost) set on getting a 5kva inverter installed. Brand-wise I’m considering Victron. 
 

2 questions-

1. What does your 5kva inverter power? 

2. This might be a silly question but can I assume that a 5kva inverter will produce 5000 watts? Will the output differ from brand to brand? 
 

Thanks in advance.

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1. You can run a full house on a 5kva. It all depends on how many things you want to switch on and use at the same time. For 99% of the time I run my house of a 3kVA Multiplus II. I have scheduled the big items to try and minimize concurrent use of those, so my geyser (heat pump) switch on at times when the stove and oven would mostly not be used. If it is used it will fall back and add extra power from the grid. 

2. Most of the time 5000VA is not 5000W. There is a power factor at play and if there was no losses in conversions then it would be possible. But not in real life. For instance my Multiplus 3kVA give 2400W, but only 1700W if it is very warm (65 deg). The better the components used, the better the power factor, so don't expect to much from that cheap inverter you buy at that sale.

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4 minutes ago, JK844 said:

1. What does your 5kva inverter power? 

I live in an apartment, so I don't use the solar charge controller.  I just use it as backup when Eskom fails.

My light circuit and a "red plugs" in ever room of the apartment are fed from the inverter.  Been running like that since roughly 2014, I switched to an Axpert King in 2018 (If I recall correctly) for the double conversion, I have a lot of computers and stuff I didn't want damaged by Eskom's sh!tty supply.

I power my TV, router, microwave, kettle, Nespresso, fridge, TV, amplifier for TV, NAS, home office from the Axpert, occasionally things like vacuum if there is load shedding and the place needs cleaning.

The Axpert King runs in inverter mode 24/7 and it has held up well, when I turn on the kettle or microwave the fan speed increases but it is pretty much drowned out by the noise those appliances makes.  Everything else it remains fairly quiet (so not much load).  I rarely go above 3.5kW.

4 minutes ago, JK844 said:

2. This might be a silly question but can I assume that a 5kva inverter will produce 5000 watts? Will the output differ from brand to brand? 

Different brands may have different models.  You can look at the models available here: http://voltronicpower.com/

Voltronic Power makes the actual inverter and then puts the badge on the seller wants.  There are companies that manufacture clone Axpert inverters, meaning they actually copied the design.  They took an already low cost inverter and went cheap on it, so you can guess the end result of that.

My 2c: Buy your inverter here https://www.fullcirclesolar.co.za/

I've bought a few from them, they are the cheapest I could find, respond quickly and they don't sell fakes.

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11 minutes ago, Louisvdw said:

2. Most of the time 5000VA is not 5000W. There is a power factor at play and if there was no losses in conversions then it would be possible. But not in real life. For instance my Multiplus 3kVA give 2400W, but only 1700W if it is very warm (65 deg). The better the components used, the better the power factor, so don't expect to much from that cheap inverter you buy at that sale.

I mean they'll say the kW, for all the newer Axperts, 5kVA = 5kW.  But that said, the power factor does not come into play on the inverter...  Power factor is determined by the devices you power in your home.  So ultimately if you bought good quality stuff your PF is close to unity (1.0) in which case the extra power factor overhead is wasted.  But if you use a lot of things like florescent lamps, motors, very old switch mode power supply, your PF could be around 0.5 or lower in which case having an inverter with a higher kVA rating is sufficient.

That said, if the kVA and kW on an inverter doesn't match, I don't put much faith in it.

EDIT: My point was power factor is not an indication of quality of the inverter.  But I wouldn't buy an inverter based on kVA rating, you look at the KW and decide based on that.  The kVA is just gravy on top.

Edited by Gnome
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I also run my whole house off a single 5kW inverter:

  • Borehole pump
  • Swimming pool motor
  • Oven & hob
  • Geyser element
  • Kettle
  • Wall plugs
  • Lights
  • Panel heaters
  • etc.

Some of them are very high draw items (I'm looking at you, you 3kW oven!) and you may need to ensure that you do not run them at the same time as other high draw items (kettle or geyser element).

It also pays to spread the load...  Our home's base load is around 500 W (3x fridges/freezers, extensive alarm system, three desktop computers, fish tank, etc).  Every morning at 08:30 our automated sprinklers turn the borehole pump on (1.3kW) for 30 minutes.  When they're done at 09:00 the pool motor starts up (750W) and runs until 17:00.  If it's very cloudy the solar geyser's element (2kW) may kick in at 13:00 via a GeyserWise megafter to ensure that the water temperature is at least 65 deg C.  If my wife were to boil a kettle (another 2kW) during this time, my home automation (Nodered & Sonoff) would turn the pool pump off to ensure I stay below 5kW.

If you buy a grid-tied inverter like mine you can get away with peaks over its rated output (it will just supplement the difference from the grid), but I try to remain off-grid as far as possible.

Oh, and I agree that it won't hurt to chat to Paul at FCS when shopping for inverters!

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1 hour ago, ChristoSnake said:

I also run my whole house off a single 5kW inverter:

  • Borehole pump
  • Swimming pool motor
  • Oven & hob
  • Geyser element
  • Kettle
  • Wall plugs
  • Lights
  • Panel heaters
  • etc.

Some of them are very high draw items (I'm looking at you, you 3kW oven!) and you may need to ensure that you do not run them at the same time as other high draw items (kettle or geyser element).

It also pays to spread the load...  Our home's base load is around 500 W (3x fridges/freezers, extensive alarm system, three desktop computers, fish tank, etc).  Every morning at 08:30 our automated sprinklers turn the borehole pump on (1.3kW) for 30 minutes.  When they're done at 09:00 the pool motor starts up (750W) and runs until 17:00.  If it's very cloudy the solar geyser's element (2kW) may kick in at 13:00 via a GeyserWise megafter to ensure that the water temperature is at least 65 deg C.  If my wife were to boil a kettle (another 2kW) during this time, my home automation (Nodered & Sonoff) would turn the pool pump off to ensure I stay below 5kW.

If you buy a grid-tied inverter like mine you can get away with peaks over its rated output (it will just supplement the difference from the grid), but I try to remain off-grid as far as possible.

Oh, and I agree that it won't hurt to chat to Paul at FCS when shopping for inverters!

I understand that this is how a grid tie inverter should function. i.e. you use power as you want to and the grid provides a backstop if demand is too great.

You must have moved most of your load to daylight hours to maximise the use of your solar power? So effectively you are running your house on grid power at night?

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15 hours ago, Louisvdw said:

1. You can run a full house on a 5kva. It all depends on how many things you want to switch on and use at the same time. For 99% of the time I run my house of a 3kVA Multiplus II. I have scheduled the big items to try and minimize concurrent use of those, so my geyser (heat pump) switch on at times when the stove and oven would mostly not be used. If it is used it will fall back and add extra power from the grid. 

2. Most of the time 5000VA is not 5000W. There is a power factor at play and if there was no losses in conversions then it would be possible. But not in real life. For instance my Multiplus 3kVA give 2400W, but only 1700W if it is very warm (65 deg). The better the components used, the better the power factor, so don't expect to much from that cheap inverter you buy at that sale.

Thank you so much! Appreciate your response.

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On 2020/09/28 at 8:18 PM, ChristoSnake said:

I also run my whole house off a single 5kW inverter:

  • Borehole pump
  • Swimming pool motor
  • Oven & hob
  • Geyser element
  • Kettle
  • Wall plugs
  • Lights
  • Panel heaters
  • etc.

Some of them are very high draw items (I'm looking at you, you 3kW oven!) and you may need to ensure that you do not run them at the same time as other high draw items (kettle or geyser element).

It also pays to spread the load...  Our home's base load is around 500 W (3x fridges/freezers, extensive alarm system, three desktop computers, fish tank, etc).  Every morning at 08:30 our automated sprinklers turn the borehole pump on (1.3kW) for 30 minutes.  When they're done at 09:00 the pool motor starts up (750W) and runs until 17:00.  If it's very cloudy the solar geyser's element (2kW) may kick in at 13:00 via a GeyserWise megafter to ensure that the water temperature is at least 65 deg C.  If my wife were to boil a kettle (another 2kW) during this time, my home automation (Nodered & Sonoff) would turn the pool pump off to ensure I stay below 5kW.

If you buy a grid-tied inverter like mine you can get away with peaks over its rated output (it will just supplement the difference from the grid), but I try to remain off-grid as far as possible.

Oh, and I agree that it won't hurt to chat to Paul at FCS when shopping for inverters!

Thanks for the feedback!

Quick follow-up question: I'm assuming you use the inverter throughout the year (i.e. not only during load-shedding. If this is correct, what % reduction have you seen in your electricity bill compared to pre-inverter days?

 

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On 2020/09/28 at 9:25 PM, Richard Mackay said:

You must have moved most of your load to daylight hours to maximise the use of your solar power? So effectively you are running your house on grid power at night?

Indeed, pool motor and borehole pump only runs only during the day, and we only use the oven during the day over weekends for roasts, etc.  Batteries are only charged via solar and we run everything off them at night.  Eskom is there as backup for very cloudy weather that lasts longer than a day.

We've used less than 500 kWh of grid electricity this year:

image.png.65fa6436b3945259352e86742b6e00ff.png

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On 2020/09/29 at 6:24 AM, Stanley said:

I have a 5kVA off-grid inverter, and I have it running my whole house except the geyser and stove.

i.e. All plug and light circuits

 

Yep, running a normal (i.e. non-solar) geyser's element or an oven requires some care.  Both of these can run at 3kW or more, leaving little capacity to spare. We have a solar geyser with a 2kW element (only runs during the day if required courtesy of a Geyserwise switch), and generally only use the oven during the day (so that the sun pays).

I found that our hob (at 500-800 W per plate) is not an issue at all, unless you turn all 4 plates to their maximum setting simultaneously.  Luckily we don't cook that way 😁

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On 2020/09/28 at 6:54 PM, JK844 said:

1. What does your 5kva inverter power? 

It is capable of running your whole house with the proper planning and due diligence by the occupants of the household. I had a 5kVa running for 3 years where we did not even know when the grid power was off most of the time. I did however split my DB into 2 and ran the whole house except for air-con, oven and back-up electric geyser.  The 5kVa can handle  these other loads as well, but the problem arises when you run the appliances concurrently. If you run the oven and the missus switches on the kettle, then the inverter would change over to grid feed.

The funny thing is that I now am running a 3kVa Multiplus and I am getting better effeciency than I did with my 5kVa due to the power assist function. I still have my DB split in 2, but whereas the air-con etc was connected to the grid on the 5kVa it is now the second output on my 3Kva....so during the day when my solar panels are putting out 3600W all the extra power is going to my second output. The multi can quite comfortably give an AC Load of +5000W  during the day, blending all the supplies.

It all comes down to proper planning and due diligence.

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