Do you think my SureSine inverter will handle this fridge?

jmiller968 · May 2020

I'm putting a fridge in my cabin. It is a 13.9 cubic foot frigidaire ffht1425vw. Energy star placard states 332 kwh. I did a bit more digging and found: Voltage Rating – 120V/60 Hz/15 Amps • Max Connected Load (kW Rating) @ 120 Volts = .36kW • Max Amps @ 120 Volts = 3.0 Amps.
So the sure sine is a 300 watt inverter that can surge to 600 for 15 minutes. Assuming minimal other loads (an LED light or two), do you think that this inverter is enough? If not, what inverter would you recommend?

706jim · May 2020

Somebody on this board was running a fridge off of a 300 watt Samlex inverter. You would have to search to find the post. Normally, users go with a larger inverter than 300 watts to provide for the starting surge of the compressor. Inverter style fridges have less of a starting surge from what I've read here.

BB. · May 2020

It looks like this is a frost free/self defrosting refrigerators... The heating element may take a fair amount of power to run (larger refrigerators can take 500-600 Watts for the defrost heater). Perhaps this smaller one takes less.

-Bill

softdown · May 2020

Might work - might not. The compressor surge is unknown. Back in the 90's the biggest units had such large surges that a 1500 watt inverter fell short. Though I suspect the fellows electrician may have "monkeyed stuff up" due to not knowing solar particulars.

706jim · May 2020

BTW surge is not needed for 15 minutes. More like 5 seconds for my fridge. And can I say once again just how much I love my old transformer couple MSW inverter? Been running great since 1994!

softdown · May 2020

jmiller - those are favorable offgrid energy usage stats. Have useful price and source information? Thanks.

jmiller968 · May 2020

Thanks for the input guys. I bought the fridge at Home Depot on sale last week for 480.

jmiller968 · May 2020

I really like the suresine inverter. If the fridge pulls too many watts to work on it, is it possible to stack this inverter? Could I buy another one and parallel them to double the wattage?

softdown · May 2020

Good question - looking forward to answers for that one.

BB. · May 2020

As far as I know, unless the inverter explicitly supports stacking/paralleling, it does not.

At the bottom of the page, are the specifications... But from what I can see, NO it does not support parallel/stacking outputs:

https://www.solar-electric.com/morningstar-si-300-115v-ul-inverter.html

-Bill

BB. · May 2020

And for completeness, it is possible to run some refrigerators and converted chest freezers from a MS-300 Watt AC inverter, our retired poster Wayne has some posts on how to do that:

https://forum.solar-electric.com/discussion/14862/my-latest-freezer-converted-to-fridge-showing-very-good-results/p1

-Bill

softdown · May 2020

My converted upright ~18 ft commercial freezer needs comparatively very little energy to stay at ~45F. About .3kW/day. I have considered making a thread about how important the thickness of the insulation is. Fridges have 1". Freezers have 2".

Keep in mind it is in the garage at ~60F which certainly helps. The controller also allows an ~3F temp range so cycling is reduced. When cooling it uses about 150 watts - which varies some.

I would consider betting the freezer part of our fridges use most of the energy. Defrost heating cycle being much of that reason. My Samsung produces no frost on the food but it certainly likes to stay on for prolonged periods between 4am and 7am. At a rated 550kWh/year - it is no energy miser for an 18 ft model. Made in 2008 btw. Nice unit though - I like the outside digital readouts and ability to "fast freeze" and "fast chill".

mike95490 · May 2020

jmiller968 said:

I really like the suresine inverter. If the fridge pulls too many watts to work on it, is it possible to stack this inverter? Could I buy another one and parallel them to double the wattage?

Years ago, morningstar engineers told me NO, not stackable. I too, was hoping.

petertearai · May 2020

Or try looking for an inverter fridge .

jmiller968 · June 2020

Leaving an update for future fridge searchers out there. I got the fridge installed, with a kill-a-watt to monitor usage. As soon as I plugged it in, the inverter failed. Unfortunate, but I had another 2000w pure sinewave just in case. Swapped inverters and tried again...success! The watts jumped to 750 on startup, which explains why the suresine didn’t work. I continued to check power usage. First day was 1600w, but that was of course starting from scratch with a warm fridge and freezer. The next day was in the 900w range. We then left for a week and just returned tonight. We used a total of 4800w over 7.5 days, which comes out to 640w per day. Very impressive #s, and much better than I was expecting. Of course the door stayed closed the entire time, but it was very warm last week, and most importantly, the beer was cold when I got here. All for a measly 26w per hour!

BB. · June 2020

Yep... Generally suggest a 1,200 to 1,500 Watt AC inverter minimum for "typical" Energy Star Fridge.

Also... Just to be clear. Watts is a Rate--Like Miles per Hour. And Watt*Hours is an amount (like total miles driven).

So, your 1,600 Watts the first day was actually 1,600 Watt*Hours in first day (total amount of energy used).

And dropped to an average of 640 Watt*Hours per day--Which is not bad at all for a standard fridge.

The 26 Watt "average load" is usually something like a 100 Watt load, running ~1/4 the time, for an average of 26 Watt*Hours of energy per hour (i.e., 100 Watts for ~15 minutes out of 1 hour).

A typical residential fridge runs around 100-120 Watts average load, and >~600 Watts (really VA, but another time) starting (less than 1 or 2 seconds).

Also, if frost free--You could be running a 500-600 Watt defrost heater every 12 to 24 hours or so (just long enough to melt the ice on the inverter "evaporator" (the "cooling coils").

-Bill

petertearai · June 2020

My lg inverter 450 l fridge uses .3 kw per day while not in residence . The inverter uses more energy than the fridge .

softdown · June 2020

petertearai said:

My lg inverter 450 l fridge uses .3 kw per day while not in residence . The inverter uses more energy than the fridge .

That unit keeps getting brought up - mostly by you I think? Yet they seem to have quit making it as I recall?

One way to get really low energy figures is to buy a fridge only unit. It is the defrost on the freezer that seems to use an unseemly amount of energy.

It is interesting to see Costco only stocking monster size fridge/freezers and fewer and fewer very serious bargains. They seem to be losing their way - perhaps like Sears did so many years ago?

petertearai · June 2020

I have looked it up and it looks to be discontinued. I will have to stop talking about it.

Do you think my SureSine inverter will handle this fridge?

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