Inverter for induction appliances

[Deleted member 5112]

Hi there, I've recently started the research phase for a solar-powered Tiny House and it's all going well so far. However, while looking at the inverters linked below, I came across the following information which has confused me. They state that for inductive appliances (fridge, AC, washer, microwave, etc...) the inverter would require 3-7 times the rated power of the appliance. The second link even mentions that, for fridges, you should have 10 times the rated power! I'm no electrician but this seems astronomical to me and very budget unfriendly. On every post/video that I've come across, it seems as though everyone is ignoring this as they have not sized their systems to allow for 3-10 times the power of their inductive load.

• https://www.amazon.com/Inverter-2000W-Invert-Converter-System/dp/B0827CH3QC?th=1
• https://www.amazon.com/WZRELB2500W-...pure+sine+wave+24v&qid=1580333808&sr=8-3&th=1

I've estimated an average max load of 1700Wh under the scenario where all of the following are on at the same time, which would not occur very often:

• Window AC 714w
• *Fridge [300w always on, but cycles]
• *Security cameras [26w always on]
• Lights (indoor and outdoor)
• TV
• Video game console
• Laptop, Tablet, Phone (charging)
• *Router [7w always on]
• *Modem [7w always on]
• Water pump

*Total always on = 340w when the fridge is active.

I am also considering the following appliances but I would turn off almost everything else when running these for short periods:

• Microwave 1000w
• Toaster 850w
• Blender 500w
• Washer 800w
• Dryer 1500w
• Clothes Iron 1200w

If necessary, I could do without the dryer and the clothes iron. So the extreme example here would be the microwave of 1000w and the fridge of 300w plus the additional 40w of always-on devices. If I take the suggestion of having 10 times the power for the fridge and 3-7 times the power for the microwave then I would need an inverter capable of 6,040-10,040w!

So, my question is, what size inverter would work for my needs? I've decided on a 24V system and so if there are any good inverter recommendations for my system I would greatly appreciate it. Thank you!

 

[svetz]

... while looking at the inverters... They state that for inductive appliances (fridge, AC, washer, microwave, etc...) ... require 3-7 times the rated power of the appliance. The second link even mentions that, for fridges, you should have 10 times the rated power! ...

"Inductive appliances" are things with "motors". The problem is those motors take a very high current to start up, but only for a fraction of a second.
When you look at inverters you'll see they typically have two rates, a continuous rate and peak rate. Continuous is what it can output all day long (and this number is almost always over-stated on cheap inverters) and peak is for the short burst inductive loads. If you have an induction stove (or don't want hum in your TV), you'll also want a pure-sine-wave inverter.

How big of a peak rating do you need? It depends on how many appliances you want to turn on at once (some, like the refrigerator's compressor, will automatically turn themselves on/off).

 

[Deleted member 5112]

"Inductive appliances" are things with "motors". The problem is those motors take a very high current to start up, but only for a fraction of a second.
When you look at inverters you'll see they typically have two rates, a continuous rate and peak rate. Continuous is what it can output all day long (and this number is almost always over-stated on cheap inverters) and peak is for the short burst inductive loads. If you have an induction stove (or don't want hum in your TV), you'll also want a pure-sine-wave inverter.

How big of a peak rating do you need? It depends on how many appliances you want to turn on at once (some, like the refrigerator's compressor, will automatically turn themselves on/off).

The most load the system would possibly see is 1,700-1,800Wh but ONLY VERY RARELY IF EVER. This is excluding those quick bursts of needs by a motor.

If I ever want to run the microwave, toaster, blender, washer, dryer, or clothes iron I will ensure that ONLY ONE is ever in use at a given time and that all other non-always-on appliances are off.

However, if I were to listen to the suggestion of 3-10 times the power, this still leaves me thinking that I need an overkill of 6000-10,000w inverter for the simple fact that my microwave and fridge can both spike for a fraction of a second simultaneously. Am I right about this?

EDIT:
I guess at the very least a continuous 3,000-5,000w inverter with a peak of 6,000-10,000w should work?

Something like this: https://www.amazon.com/WZRELB-5000W...ords=5000w+24v+inverter&qid=1580353368&sr=8-5

My question then would be what would be the disadvantages, if any, of using a 5,000w inverter when 99.9% of the time I would only be using 1,700-1,800w?

 

[oudin_coil]

How about a soft starter for the induction appliances?

 

[nosys70]

i think you will better have to go with a 48V system.
it looks you need a lot of Amps, and with 12 or 24V systems you climb very fast to huge numbers.
The consequence is big batteries, thick cables, everything heating a lot.
3000W on a 24v system is 125A and you can count on 150-180A peak.
the equipement is particularly sensitive to peak when the cabling is not able to provide the kick need for a short periode.
you can go for a 5000W 48V system, so you got some room for adding stuff later and it does not cost a lot more.

 

[Deleted member 5112]

How about a soft starter for the induction appliances?

Would I need one of these for each appliance? These seems as it might work but I think going to 48V with a 5000W inverter would be a better choice.

i think you will better have to go with a 48V system.
it looks you need a lot of Amps, and with 12 or 24V systems you climb very fast to huge numbers.
The consequence is big batteries, thick cables, everything heating a lot.
3000W on a 24v system is 125A and you can count on 150-180A peak.
the equipement is particularly sensitive to peak when the cabling is not able to provide the kick need for a short periode.
you can go for a 5000W 48V system, so you got some room for adding stuff later and it does not cost a lot more.

Thank you, I think this is my best bet. The MPP LV 5048 seems like a good buy but it does not mention what the peak is. Can I assume that since the inverter is 5,000W that the peak would be 10,000W?

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