# Fridge not working with Mod-Sine



## greg273 (Aug 5, 2003)

Well not sure if this question belongs in Shop Talk, or here, but here it goes...

I'm a little dissapointed today, finally after YEARS of talk, and months of action, my new 1KW solar array and MPPT controller is functional... so the first thing i did was plug in a GE compact fridge... thinking finally i have enough electricity for this to work,well it worked fine for awhile, but eventually the motor didnt sound right, it stopped cooling, and the power draw went from 100 watts to 400!!. I have a 'kill-a-watt' meter hooked up to it. This occured both with and without the meter hooked up in-line.
The inverter is a Xantrex DR2424. 
Now I am guessing the inverters mod-sine output is the problem, this is the second fridge that has done this same thing! (I paid $40 for the first one, used, and found the other one with a 'Free- It works' sign on it. One is Danby, the other GE).
Strange thing is, i have a smaller, 1.1.cuft Absocold fridge that runs no problem on the inverter. 
How does a fridge with a 1.1 Amp motor draw 400watts?? That is apparently a very bad sign... 
I have one more fridge in storage, an older Danby with a 6amp motor, but i fear that may be a little much for my solar budget...only other option, besides a DC fridge, is a pure sine wave inverter. Both extrememly expensive options at this point....


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## Harry Chickpea (Dec 19, 2008)

IIRC, a kill-a-watt won't give accurate readings on mod-sine, but that isn't the issue. _Could be_ a toasted run or start capacitor. Any standard fridge uses a lot of electricity, and especially so in inverter situations. If your inverter has an overhead and efficiency that uses 20% of the rated capacity, that is 200 watts on top of the actual usage by the refrigerator. In general, you want an inverter to be off or in standby mode as much as possible. Modern refrigerators use small compressors that require lots of run time.

This is a long shot, but since the motor on at least one of your units is already fried, you might try opening up the compressor can, and seeing if there is any way you can remove the old motor and install a 24 volt DC motor to power the compressor. If the seals are OK, the freon shouldn't leak out.


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## damoc (Jul 14, 2007)

do you have battery storage or are you trying to run directly from panels?


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## Jim-mi (May 15, 2002)

The good ole DR's have powered a whole lot of things for lots of folks.
But there is a list of items that refuse mod/sine . . . perhaps you've found one more item for that list.
If you can stand to run it again watching the current flow when it funks out reach in (with the unit un plugged) and feel how hot the compressor is.........????
Mod/sine will make most motors run hot. . . . .
If it is very hot then go to plan B . . . . . .

Can you run it on grid power to see if it *runs* . .??
If it doesn't then go to plan C


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## wy_white_wolf (Oct 14, 2004)

They do make smaller sine wave inverters and you could get one to power only the frig. If it pulls 100watts than a 300-500watt invertor should work for it. I've seen 300watt sinewave for about $150.


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## greg273 (Aug 5, 2003)

Jim-mi said:


> The good ole DR's have powered a whole lot of things for lots of folks.
> But there is a list of items that refuse mod/sine . . . perhaps you've found one more item for that list.
> If you can stand to run it again watching the current flow when it funks out reach in (with the unit un plugged) and feel how hot the compressor is.........????
> Mod/sine will make most motors run hot. . . . .
> ...


 Thanks, and yeah, I'm gonna haul them over to a friends house with 'normal' (hehe) electricity and see what happens. 
I've been happy with the DR inverter, its performed well so far, I've even ran cordless DeWalt and Makita chargers on it, with no problems at all. I've had a few cheap box fans that made inordinate amounts of noise when running, but thats about the only issue i've noticed.


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## greg273 (Aug 5, 2003)

wy_white_wolf said:


> They do make smaller sine wave inverters and you could get one to power only the frig. If it pulls 100watts than a 300-500watt invertor should work for it. I've seen 300watt sinewave for about $150.


 Yes, that is definitely an option. Certainly less expensive than upgrading the main inverter, and more affordable than a DC fridge. May be a good near term solution...


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## Harry Chickpea (Dec 19, 2008)

Actually, inrush from the motor startup will overwhelm small inverters. BTDT.


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## mightybooboo (Feb 10, 2004)

Im surprised to hear that,my heart mod sine runs refer fine,bud has a dr and it runs his house fine.

Something sounds amiss with the inverter.Or as suggested you just have a knack for finding things that dont like mod sine.

Very odd for sure.

Heart 458 runs everything I own fine unless it has a digital clock on it.


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## WisJim (Jan 14, 2004)

This isn't exactly on subject, but those little dorm sized refrigerators usually use almost as much power as a full sized (14 to 20 cu ft) new refrigerator. Where I used to work a lot of folks had them in their offices, and I checked a number with my Kill-a-watt and other watt-hour meters, and found that they typically used half or more of the power that a "regular" late model kitchen refrigerator uses.
My SW4024 (sine wave inverter) has run our refrigerator and one or two freezers for many years with no problems.


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## mightybooboo (Feb 10, 2004)

Jim,funny you should mention that,I was just looking up energy star ratings today and noticed that very thing,those dorm style refers are real energy hogs for the size.


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## greg273 (Aug 5, 2003)

Harry Chickpea said:


> IIRC, a kill-a-watt won't give accurate readings on mod-sine, but that isn't the issue. _Could be_ a toasted run or start capacitor. Any standard fridge uses a lot of electricity, and especially so in inverter situations. If your inverter has an overhead and efficiency that uses 20% of the rated capacity, that is 200 watts on top of the actual usage by the refrigerator. In general, you want an inverter to be off or in standby mode as much as possible. Modern refrigerators use small compressors that require lots of run time.
> 
> This is a long shot, but since the motor on at least one of your units is already fried, you might try opening up the compressor can, and seeing if there is any way you can remove the old motor and install a 24 volt DC motor to power the compressor. If the seals are OK, the freon shouldn't leak out.



I wish i knew more about fridge technology. But the Kill-A-Watt, while it may not give accurate readings on mod-square wave, did register the same numbers with grid-supplied electricity as it did on the inverter. 80-110 watts running, and 455 in 'fault mode', for lack of a better term. I did test one of the refers on grid power, and it did the same thing. Its almost like the motor is off balance, or stuck somehow, I can hear and feel it acting strange. I'm no fridge repairman, so this is a mystery to me. It seems to happen when the fridge is cycled too fast. It was running fine during the test, and when I turned the fridge down, it shut off as normal. But checking a theory, I turned it up again...thats when it went a little crazy. Now I'm not sure if the mod-sine inverter fried something internally....OR if somehow the inverters load-sense function was doing something funny, which I replicated by turning it off and on too quickly....


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## adamtheha (Mar 14, 2007)

I would never run a house on Mod-Sinewave. You may save $1000 up front, but all of your electronic items will have a shortened lifespan, costing you more down the road. The inverter is NOT the place to save money. I bought the Outback 2425, and the little panel to control it, and I couldn't be happier, but I almost went with the mod-sine Xantrex before I thought better of it. Now, I have complete control over every aspect of my operation, including charging voltage, EQ settings, charge rate etc. Because of the extra money, I wasn't able to get the size of wind turbine that I wanted, but I don't regret it one bit. I'll just save that purchase for later.
Don't do it. Buy the best inverter and batteries, and fewer panels. Charge with a generator if you have to. That's the heart of your system right there!


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## Harry Chickpea (Dec 19, 2008)

greg273 said:


> I wish i knew more about fridge technology. But the Kill-A-Watt, while it may not give accurate readings on mod-square wave, did register the same numbers with grid-supplied electricity as it did on the inverter. 80-110 watts running, and 455 in 'fault mode', for lack of a better term. I did test one of the refers on grid power, and it did the same thing. Its almost like the motor is off balance, or stuck somehow, I can hear and feel it acting strange. I'm no fridge repairman, so this is a mystery to me. It seems to happen when the fridge is cycled too fast. It was running fine during the test, and when I turned the fridge down, it shut off as normal. But checking a theory, I turned it up again...thats when it went a little crazy. Now I'm not sure if the mod-sine inverter fried something internally....OR if somehow the inverters load-sense function was doing something funny, which I replicated by turning it off and on too quickly....


Short cycling a compressor is almost never good for it. The compressor has run up to speed and pushed the gas into the high pressure line, and then shut off. It expects the high pressure line to be back at low pressure by the time it is needed again. If it isn't, the combination of the startup and high pressure can stall the motor.


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## Jim-mi (May 15, 2002)

Sorry Greg but another bit of "doom" . . . . . .
From what your posting . . .I would turn that unit into a boat anchor for fear of it catching fire............

Your 'bargin' is now a hazard.


Very good post Adam...........


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## greg273 (Aug 5, 2003)

mightybooboo said:


> Im surprised to hear that,my heart mod sine runs refer fine,bud has a dr and it runs his house fine.
> 
> Something sounds amiss with the inverter.Or as suggested you just have a knack for finding things that dont like mod sine.
> 
> ...


 I dont think the problem is in the inverter, as the older, very small Absocold fridge works fine. Its been in use for a few weeks now with no problems. Perhaps there is something in these somewhat newer fridges that dont tolerate mod-sine? The GE and Danby fridges were built in 2000 and 2001 respectively. The Absocold was manufactured in 1997 I believe.


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## greg273 (Aug 5, 2003)

Harry Chickpea said:


> Short cycling a compressor is almost never good for it. The compressor has run up to speed and pushed the gas into the high pressure line, and then shut off. It expects the high pressure line to be back at low pressure by the time it is needed again. If it isn't, the combination of the startup and high pressure can stall the motor.


 That sounds like what is happening. I've been looking this up, and came across the term 'locked rotor amps'. Could that be the 455 watt power draw I was seeing? (on a 1Amp motor?? That sounds like a real bad situation) Thanks for the help!


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## Harry Chickpea (Dec 19, 2008)

Yeah, that is very likely. Capacitors don't play well with mod sine either, so it could be entering into the problem as well.


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## Jim-mi (May 15, 2002)

Locked rotor amps = BIG time heat = fire

not worth taking a chance............


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## greg273 (Aug 5, 2003)

Jim-mi said:


> Locked rotor amps = BIG time heat = fire
> 
> not worth taking a chance............


 I dont have much invested in these two dorm fridges... $40 in one, and the other was a freebie. Which is obviously much less than I have invested in my house, so I agree, a fire would not be a good thing. But I would definitely like to know what has caused this problem though.
So I believe the course of action is to acquire a small pure-sine inverter, Samlex makes a few that should satisfy the running and surge loads imposed by a medium sized 'normal' fridge.
Such as this one...looks like a good price, also...

http://www.ecodirect.com/ProductDetails.asp?ProductCode=Samlex-PST-60S-24A&site=google_base


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## Jim-mi (May 15, 2002)

. . ."Normal sized fridge" . . . .. . . .

Unless you look hard to find/order a *manual defrost* . ."normal" fridge you will get a fridge with a "defrost cycle" which could be 500 watts . . .not good to be running a 600 watt inverter on. 
Also that mentioned inverter quite likely will not have the balls to handle the start up surge of that "normal fridge".


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## mightybooboo (Feb 10, 2004)

Yikes! Our bud Tango here went thru 2 Samlex's if i recall,very lousy product in her experience.


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## mightybooboo (Feb 10, 2004)

Also look at the energy star ratings for 120 volt fridges.Gives you real food for thought on sizes and power usage.

The whole list is online under 'energy star'


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## Jim-mi (May 15, 2002)

That DR2424 will power a "normal" fridge OK.
The motors will be warmer than usual but other wise it will work.
The DR series have a very large surge capacity.

Yes I've heard that those Samlex's *smoke* very easy . . . . .what do ya expect for that kind of price..

Just looked it up . . . .that 600 Sam only surges to 1000 W


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