High frequency verses low frequency inverters

[fafrd]

I thought sol-ark was supposed to be super nice and all? Did he fib on any of that video?

No, those are extreme loads. If building a true off-grid system where all home loads are being powered by a single inverter with no access to grid power, LF is almost certainly the better choice than HF.

If only powering a modest CL panel with known loads of modest consumption, different use-case entirely.

On my case, I’m only trying to take my fridges/freezers off-grid. As long as I have an HF inverter with sufficient surge capacity to start each fridge/freezer while all others are running, I should be fine.

The compressor had an 11X locked rotor current, which is the highest I’ve ever heard of.

Average load for all 5 of my fridges and freezers is 400W and the largest one has locked rotor power of less than 11 x 200W = 2200W.

So a 2600W HF inverter should probably handle my CLs just fine.

I’ve got a 3000W WZRELB inverter currently and am toying with the idea of getting a 5+5kW split-phase model.

But part of the rationale of getting a higher-powered split phase inverter was to have the freedom to move other frequent loads such as the toaster oven and coffee maker off-grid, and that was a good video for bringing the importance of power-budgeting home.

5kW per leg gets chewed up awfully quickly at 1800W per bite…

 

[fafrd]

Well that depends. The main problem has to do with how do you know it will never be driven past 50% of its rated power?

In my use case there are only 5 loads and I’ve measured them all (sustained, peak, and startup surge)…

By the wattage listed on the device? Not so fast. Those numbers rarely if EVER list surge amounts. They are supposed to but in real life settings from my experience... nope.

So IF you get lucky and never drive it past 50% of its load then the HF should do fine.

That is comforting to hear.

But you can see this going south fast just playing with small 500watt and 1000 watt inverters and watching them shutdown when you plug in something that shows it shouldn't be using but 1/2 of what the inverter can handle. Surge or start up loads if you will is an ugly hidden problem and has been the death of many a nice HF inverter.

Appreciate the caution. And in my case, I’ll take it to mean that I should be exceedingly cautious before adding additional loads to my off-grid CL panel (do cautious, conservative, and accurate worst-case power budgeting).

Putting 120VAC sockets into the CL panel is obviously something to stay away from if powering from an HF inverter…

 

[fafrd]

I have not attempted to shutdown all other loads and start only the disposal. The other loads would be minimal, only a TV and a few LED bulbs. Doubt over 200W total.

My 65” TV consumes 350W…

But I get your point - under 500W of other loads means 2000W available to startup the 1/2HP disposal.

If we take the 11X locked rotor current of the compressor from that video (highest I’ve ever heard of), that 1/2HP = 372W of running current would translate to 4092W of startup surge.

So the 200% surge rating your 2500W HF inverter claims to deliver is either overstated or cannot be sustained for the amount of time needed to get your disposal running.

Reliable does state that inverter size for running inductive loads should be at least 10X sustained consumption, so 3720W in the case of your 1/2HP disposal…

So maybe you need to upgrade your 2500W HF inverter for a 4000W model .

Sizing HF inverters at 10X maximum inductive load + average load does not sound like a bad rule of thumb…

 

[k490]

No, those are extreme loads. If building a true off-grid system where all home loads are being powered by a single inverter with no access to grid power, LF is almost certainly the better choice than HF.

If only powering a modest CL panel with known loads of modest consumption, different use-case entirely.

On my case, I’m only trying to take my fridges/freezers off-grid. As long as I have an HF inverter with sufficient surge capacity to start each fridge/freezer while all others are running, I should be fine.

The compressor had an 11X locked rotor current, which is the highest I’ve ever heard of.

Average load for all 5 of my fridges and freezers is 400W and the largest one has locked rotor power of less than 11 x 200W = 2200W.

So a 2600W HF inverter should probably handle my CLs just fine.

I’ve got a 3000W WZRELB inverter currently and am toying with the idea of getting a 5+5kW split-phase model.

But part of the rationale of getting a higher-powered split phase inverter was to have the freedom to move other frequent loads such as the toaster oven and coffee maker off-grid, and that was a good video for bringing the importance of power-budgeting home.

5kW per leg gets chewed up awfully quickly at 1800W per bite…

I want to try and offload my 4-ton heat pump. When that thing starts up makes my panel buzz pulling so much current. I will install a soft start to fix that. It does pull 20 solid amps on each leg after startup. I was looking at this split phase bundle two EG4 off grid inverters 13k watts of power. With a soft start installed should be enough to run my AC 2400 watts of power per leg.