I am thinking about changing my fridge out to a residential unit but I would need to be able to run it from my inverter for up to 8 hours at a time. (I have 4 new Trojan T105 batteries) I have read where the residential refrigerators do not work on Modified Sine Wave. In my manual it says my inverter (Xantrex Freedom 458) is a Filtered Modified Sine Wave. What is the difference between Modified Sine Wave and Filtered Modified Sine Wave? Does anyone have any experience running the residential fridge on this inverter? I do not want to change out the inverter to a Pure Sine Wave.

Some of the HIGH DOLLAR HIGH END Modified Sine Wave units will work... I wouldn't do it myself but mayby you should try out something with a motor like maybe a 20-inch portable fan. If the motor speeds up normal and DOES NOT START GETTING HOT OR MAKING LOUD HUMMING NOISE then you should be OK I guess...We have found anything with motors-transformers-solid stat electronics really need the PURE SINVE type Power Inverters. These duplicate the SINWAVE much like is being produced from the shore power and generator connections...Again I would not do that here as I have always purchased PURE SINE WAVE Power Inverters which works well with all things RV Camping...I did have a HIGH END 2000WATT House UPS Setup that had internal Batteries to swith to when loss of power. It was a MSW type Power Inverter circuit and looked good with an oscilloscope hooked up to the unit and worked with everything I had conencted to it. This was a high dollar item however...I kinda put the Xantrex Freedom 458 in the high end catagory just because of the cost of the unit... What you are reading about on-line is these cheap built and low cost chinese items that you find in the auto parts stores and Walmart-Lowes... Hopefully some one on here that has the Xantrex unit will dime in here... but a local test using a 20-inch portable electric fan might give you an good feeling as well... You can tell right away if it is not liking your Modified Sine Wave. It will HUM real loud and try to run at a normal high speed when you plug it. If you leave it plugged in very doing this thene you will soon see the so called 'BLUE SMOKE' coming out of the motor for a few seconnds then it is toast... Your fridge uses an electric motor so it will do the same thing if it doesnt like your MSW Power Inverter. Just my two cents from experience..Roy Ken

RoyB wrote:Some of the HIGH DOLLAR HIGH END Modified Sine Wave units will work... I wouldn't do it myself but mayby you should try out something with a motor like maybe a 20-inch portable fan. If the motor speeds up normal and DOES NOT START GETTING HOT OR MAKING LOUD HUMMING NOISE then you should be OK I guess...We have found anything with motors-transformers-solid stat electronics really need the PURE SINVE type Power Inverters. These duplicate the SINWAVE much like is being produced from the shore power and generator connections...Again I would not do that here as I have always purchased PURE SINE WAVE Power Inverters which works well with all things RV Camping...I did have a HIGH END 2000WATT House UPS Setup that had internal Batteries to swith to when loss of power. It was a MSW type Power Inverter circuit and looked good with an oscilloscope hooked up to the unit and worked with everything I had conencted to it. This was a high dollar item however...I kinda put the Xantrex Freedom 458 in the high end catagory just because of the cost of the unit... What you are reading about on-line is these cheap built and low cost chinese items that you find in the auto parts stores and Walmart-Lowes... Hopefully some one on here that has the Xantrex unit will dime in here... but a local test using a 20-inch portable electric fan might give you an good feeling as well... You can tell right away if it is not liking your Modified Sine Wave. It will HUM real loud and try to run at a normal high speed when you plug it. If you leave it plugged in very doing this thene you will soon see the so called 'BLUE SMOKE' coming out of the motor for a few seconnds then it is toast... Your fridge uses an electric motor so it will do the same thing if it doesnt like your MSW Power Inverter. Just my two cents from experience..Roy KenThat is my fear. I do not want to spend $1200 on a fridge and the time and trouble to install it then toast it the first time I run it on the inverter.

Hi,This might help you decide:Hi all,This protocol was suggested by mexicowanderer whom I have the greatest respect for:TEST: Shore power versus alternative power. Put glass of water in microwave and start, if voltage drops to 109 vac or less at same outlet as microwave is plugged into, end of test. Energy source is inadequate.Stage 2 Same glass of water, start at room temperature with oven thermometer. Set timer for one minute high. Remove glass measure temperature on shore powerStage 3 Do the same with alternative power source and compare temperature difference to test above.If there is a large temperature difference, then your microwave is going to unlove you trying to suffer through inadequate voltage or waveform.

You might consider adding an inverter dedicated to the refrigerator.

Pure Sine Wave vs Modified Sine Wave for fridge

35 Replies

time2roll
Nomad
Jul 05, 2016
JnJnKatiebug wrote:
I bought a plug in volt meter this weekend and plugged into one of the outlets that is powered by the inverter. It only shows 95 volts. Looks like I have a problem with my inverter anyway. Show power ranged from 115 to 120.
Need a True RMS meter to read MSW.
And as I said earlier motors and microwaves are looking for this peak voltage that does not exist with MSW.
Yes check it again with an appliance running.
MrWizard
Moderator
Jul 05, 2016
Try reading the voltage with something plugged in and using power
Your TV a small fan ?

Often the no load idle voltage will read low
SoundGuy
Explorer
Jul 05, 2016
JnJnKatiebug wrote:
I bought a plug in volt meter this weekend and plugged into one of the outlets that is powered by the inverter. It only shows 95 volts. Looks like I have a problem with my inverter anyway. Show power ranged from 115 to 120.

Of course ... any meter designed to read a pure sine wave signal will incorrectly display voltage from a modified sine wave inverer which you indicated in your original post is what you have. :R
JnJnKatiebug
Explorer
Jul 05, 2016
I bought a plug in volt meter this weekend and plugged into one of the outlets that is powered by the inverter. It only shows 95 volts. Looks like I have a problem with my inverter anyway. Show power ranged from 115 to 120.
dclark1946
Explorer
Jul 04, 2016
wa8yxm wrote:
Modified sine wave: Long list of things that do not play nice with it. Can generate major Radio Frequency interference affecting nearby Radios, Televisions, Sat Receivers and audio ampolifers

Filtered modified sine wave: Same list of things that do not play nice.. Filtering greatly reduces the radio frequency interference in some cases to the point where it drops below the "noise floor" and is thus undetectable (good thing).

True Sine Wave.. Very very short list of things that do not play nice (Entier list: Anything needing more power than it can produce) Very little if any Radio Frequency Interference.. Very clean power. often better than commercial power.

Batteries: 2 pair of Trojan T-105 or equal is minimum for a 2KW inverter

You have 220 Amp Hours times about 10 for Watt hours there, or 2,200 watt hours

Fridge is about 100-300 watts depending on model. that's 10 hours max if your wiring is perfect and you are lucky.

This is reduced by other loads (Explosive gas detector for example) and increased by Fridge's "Down time" (when nothing is running)

Page 3: Many have run Compressor type (residential) fridges on MSW and no problem... However the manufacturers say "Do not"... Me.. I prefer the absorption fridge cause I can run it on very little 12 VDC plus a tank of Propane if I have to.. and sometimes.. i ahve to.

Has anyone looked at the filtered MSW inverter output waveform on an oscilloscope? Depending on the cutoff frequency and the number of poles of the low pass (or bandpass)filter it could be a pretty decent waveform meaning the 2nd and higher order harmonics are attenuated significantly. If however the filtering is only removing much higher (past the 5th harmonic) frequency components such as switching noise then it will probably not act much different than other MSW inverters.
bmet2000
Explorer
Jul 03, 2016
MrWizard wrote:
Yes that's it

Thanks, I'll make sure Amazon knows you directed me there...
MrWizard
Moderator
Jul 03, 2016
Yes that's it
bmet2000
Explorer
Jul 03, 2016
Which Tripp Lite 1250 is it? Amazon has a PV1250FC for $243. Is that the one?
time2roll
Nomad
Jul 02, 2016
MrWizard wrote:
i can tell you this
my 80w florescent kitchen fixture behaves better on my tripp-lite 1250 than my it does on my go power 300 PSW

how ever my electric mattress pad will not turn on with the PV1250 and runs soley off my go power 300
I read start power is about 5x on fluorescent so they are looking for about 400 watts and that GP is not huge on surge performance.
brulaz
Explorer
Jul 02, 2016
MrWizard wrote:

...
i can tell you this
my 80w florescent kitchen fixture behaves better on my tripp-lite 1250 than my it does on my go power 300 PSW

how ever my electric mattress pad will not turn on with the PV1250 and runs soley off my go power 300

Was looking at some PSW inverter Ebay China specials.

Some have tables showing that for some reason nominally low wattage fluorescent lights require large amounts of wattage ... maybe just to get started?

Example Ebay inverter with table