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Inverter size for running fridge?
#11
Thank you everyone!  

Good point about allowing for theoretical versus usable capacity.  I built in a 20% reduction (i.e when I say a 2kwh pack, it is theoretically  2.4kh) in my calculations to give me a buffer but, I hadn't thought about not wanting to completely discharge the pack, although, I guess that would depend on what's in my fridge at the time Wink

How can I determine if my fridge has this new inverter+compressor mode?  I looked through all the documents available online and didn't see anything about it but, it is entirely feasible I didn't recognize it if it was spelled out.

So if I have a regular compressor, I am seeing suggestions between 3x to 7x.  I'm guessing that each person has a different point of view based on their experience.

What number should I use to multiplying by 3-7?.  For ex. the fridge specs say max load is 864w, does this mean I need to do 7x 864w?  This would mean I need an inverter with surge capacity of of 6000w.  Or could that number be taking a number of other systems into account, and is the peak number recorded so far (560w) more reasonable?  

If I plug and unplug my fridge into my energy monitor a number of times, let's go with 10, would this help me to more precisely pinpoint what I need?.  For example, if I unplugged my fridge and opened the fridge and freezer doors for a couple of minutes, then plug it back in, let it get the temp in both compartments back up to normal, then rinsed and repeated 10 times.  Would this cause the compressor to kick on 10 times, and I can simply take the highest spike recorded as a reasonable baseline? 

I guess that would also mean I need all my fuses and wiring to be able to handle 50A.    Lol, I just bought 40amp relays.  
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#12
Is there actual examples posted such as the LRA raiting etc.?
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#13
(06-22-2020, 04:54 PM)Dax Wrote: Thank you everyone!  

How can I determine if my fridge has this new inverter+compressor mode?  I looked through all the documents available online and didn't see anything about it but, it is entirely feasible I didn't recognize it if it was spelled out.

So if I have a regular compressor, I am seeing suggestions between 3x to 7x.  I'm guessing that each person has a different point of view based on their experience.

What number should I use to multiplying by 3-7?.  For ex. the fridge specs say max load is 864w, does this mean I need to do 7x 864w?  This would mean I need an inverter with surge capacity of of 6000w.  Or could that number be taking a number of other systems into account, and is the peak number recorded so far (560w) more reasonable?  


I guess that would also mean I need all my fuses and wiring to be able to handle 50A.    Lol, I just bought 40amp relays.  

How about posting your fridge model? Maybe we can find something you don't. Otherwise, if you have a clamp meter with a inrush current capability you can take a look at that. If all else fails, put a table lamp on the same socket as the fridge. If the fridge goes 'hummmm.. ' and your light bulb dims, then most likely a hard start full on compressor!

If it's hard start, you will be looking at a 2.5-3kw inverter, or figure a way to put a soft starter on the fridge. So either spend some money on a bigger inverter or some money on a soft starter.

Also no on the fuse. The fuse/breaker needs to be rated to the inverter or cabling (whichever is less). Any inrush current will not trip a breaker as it typically has a time delay. For a fuse, you can get a time delay fuse as well, which is used in situations like this.

I also found out not to buy LG refrigerators... seems like they use a new technology called a linear compressor...
https://www.digitaltrends.com/home/lg-re...n-lawsuit/
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#14
3rd chart down. The chart does not show the true AC current draw but gives a closer picture...
https://www.wired.com/2011/11/power-and-...ic-motors/

2nd chart down shows the actual a bit closer....
https://forum.solar-electric.com/discuss...ating-mean

out of the max wattage for your fridge exclude the 6 lights as they are just effectively resistors for this process.. unless they are filament lights (not LED) and you open the fridge within a fe milliseconds of the compressor starting.

The noise of the fridge when the compressor starts for an inverter model is unmistakable. If you don't know if your fridge is inverter or hard start then I'd be close to say don't even touch an inverter to power from a battery.
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#15
So my model is a Whirlpool WRS588FIHZ00.  Bubba used a term I wasn't familiar with LRA, so after I looked that up I went and looked on the compressor and it has LRA 3.3A and RHA 3.3A.  So, does that answer what I need for an inverter?  As long as it can handle the max indicated for the fridge over all of 7.2A, that covers the compressor.  Which means, that a 1000w inverter should cover me, correct?  Any thoughts on why the compressor LRA is so low?  Is this one of those inverter fridges?
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#16
(06-22-2020, 08:20 PM)Dax Wrote: So my model is a Whirlpool WRS588FIHZ00.  Bubba used a term I wasn't familiar with LRA, so after I looked that up I went and looked on the compressor and it has LRA 3.3A and RHA 3.3A.  So, does that answer what I need for an inverter?  As long as it can handle the max indicated for the fridge over all of 7.2A, that covers the compressor.  Which means, that a 1000w inverter should cover me, correct?  Any thoughts on why the compressor LRA is so low?  Is this one of those inverter fridges?

I believe a typical 1000W inverter which has surge 2000W would have no problem starting the fridge.  I couldn't find anything out about your compressor.  Perhaps there is a soft start or protection built in?

The Energy Star rating seems good for your model.
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#17
I'm 95% sure this model fridge DOES have an inverter, see here:
https://www.searspartsdirect.com/model/1...ator-parts

That's good, means an inverter doesn't need so much surge capability to start it. 2-3 times running current should be fine.
Running off solar, DIY & electronics fan :-)
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#18
Go into google and enter "W10710090 filetype:pdf" (inverter replacement part no)
Click on the "VARIABLE CAPACITY COMPRESSOR EELECTRONIC" pdf link (embraco inverter - not exact part match)
Within page 5 is the 3.3A figure what you are seeing (3 phase output at 3.3A) ?
The compressor LRA may be showing the 3-phase amps at the motor voltage and not necessarily the supply input Amps.
Page 18 through 21 show the rough control running mode

Then search : W10695094 filetype:pdf (the W10695094 may need to be in quotes)
(compressor replacement part no)
select link : service sheet switch diagram - ApplianceBlog
Page 1
This shows the actual compressor no detail and wiring diagram for a different fridge (supply 115V to 127V) with the winding resistances between 4.4Ohms and 5.1Ohms for run and 5.7Ohms and 6.25Ohms for start.
With the upper V of 12V and lower start winding Ohms of 5.7 Ohms then worst cast start Amps on the compressor is 22A peak (rms).

The part number indicates the fridge compressor is bump start (2 phase) while the inverter board part no is not clear enough to detail the spec fully.

The wiring diagram shows a 3-phase compressor but it's not the right model number to match your fridge ?

Separate user manual document indicates the supply with : "15- or 20-amp fused" (user manual page 8)
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#19
I have a twin door ice making fridge with hard start. It uses 60Ah over 10 hours overnight. I have a 1600watt multiplus inverter and it starts no prob. Doesn’t upset anything else also running off inverter. Hope that gives you some info.
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#20
(06-23-2020, 07:04 AM)completelycharged Wrote: Go into google and enter "W10710090  filetype:pdf" (inverter replacement part no)
Click on the "VARIABLE CAPACITY COMPRESSOR EELECTRONIC" pdf link (embraco inverter - not exact part match)
Within page 5 is the 3.3A figure what you are seeing (3 phase output at 3.3A) ?
The compressor LRA may be showing the 3-phase amps at the motor voltage and not necessarily the supply input Amps.
Page 18 through 21 show the rough control running mode

Then search : W10695094 filetype:pdf  (the W10695094 may need to be in quotes)
(compressor replacement part no)
select link : service sheet switch diagram - ApplianceBlog
Page 1
This shows the actual compressor no detail and wiring diagram for a different fridge (supply 115V to 127V) with the winding resistances between 4.4Ohms and 5.1Ohms for run and 5.7Ohms and 6.25Ohms for start.
With the upper V of 12V and lower start winding Ohms of 5.7 Ohms then worst cast start Amps on the compressor is 22A peak (rms).

The part number indicates the fridge compressor is bump start (2 phase) while the inverter board part no is not clear enough to detail the spec fully.

The wiring diagram shows a 3-phase compressor but it's not the right model number to match your fridge ?

Separate user manual document indicates the supply with : "15- or 20-amp fused" (user manual page 8)
I don't think this fridge is 3 phase.  A typical fridge in North America is single phase.
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