Size of inverter to start a refrigerator?

[Roger Moss]

I want to get an inverter to run my refrigerator. It is a normal size
(850*600*600mm), "A" efficiency refrigerator. The running power is pretty
small - 70W I think - but I'm not sure how much current is needed to start
up the induction motor in it.

Will a 250W inverter get it started, or do I need something bigger?

Thanks

Roger

 

[John Smith]

Once you get it started off an inverter check the servo motor for the defrost
timer. They are power picky and it may not run at all.

 

[Vaughn Simon]

Will a 250W inverter get it started, or do I need something bigger?

I would be very surprised if it would start on that little inverter.
Refrigerators can easily take up to 10X their run power for starting. You did
not mention what type of inverter, many refrigerators do not seem to like square
wave power (or MSW). My 'fridge (about 200 watts run power) will not start on
my little 600-watt Honda "lunch box" genny, and it will not start reliably on my
1000-watt inverter, but does run very well on my 2000-watt Honda inverter genny.

Vaughn

 

[JoeSP]

Once you get it started off an inverter check the servo motor for the
defrost
timer. They are power picky and it may not run at all.

This and many other similar postings points to the necessity for a
demand-surge capacitor bank. A very common problem with alternate power is
the need for a much higher load for a brief period of time for things like
starting motors.

I'm not aware of any such devices on the market, but I'm sure a good
engineer could enlighten us.

 

[Dave Nay]

This and many other similar postings points to the necessity for a
demand-surge capacitor bank. A very common problem with alternate power is
the need for a much higher load for a brief period of time for things like
starting motors.

The problem there is that capacitors are a DC device, and actually will
filter AC. For a capacitor bank to be of any use, it needs to be on the
DC side of an inverter, and therefore still limited by the capacity of
the inverter.

 

[JoeSP]

The problem there is that capacitors are a DC device, and actually will
filter AC. For a capacitor bank to be of any use, it needs to be on the
DC side of an inverter, and therefore still limited by the capacity of the
inverter.

And therein lies the engineering challenge.

 

[surfnturf]

Joh, thanks for the kick starter tip. May want this some time in the future
for some larger drives in my future full sized application.

Agree that fridge should start with small inverter for the OP. Just need to
use decently sized wiring and securely connect inverter to battery. Then the
battery is the "capacitor" and most inverters will handle the temporary
surge. Of course, better inverters will handle more for longer.

surfnturf

 

[Eric Sears]

Dunno about super high efficiency refrigerators, but after Wilma I ran
my 1680 watt-hr per day refrigerator for a couple of weeks off my
Trace 2000W MSW inverter, with daily doses of generator power to
recharge the batteries. I also run a small "dorm" type refrigerator
in my van using the same inverter. The clicking doesn't destroy
anything, but what does become noticable is the noise when the battery
power can't supply the startup power, and the compressor and overload
circuitry fight. Other than that, both refrigerators ran quite
happily.

Thanks for your comments Harry.
I wonder if you could further comment on these questions:

Does the Trace send a pulse about every second - which clicks a relay
in the fridge on/off? (I'm not talking about the normal clicking
associated with turning the motor on/off at the usual intervals)

Does the inverter shut down or go into "standby" mode at intervals
when the motor is not running?

What make is the fridge?

Does it seem to have electronics which run all the time (things such
as timers, fan etc).

Generally the small "dorm" type fridges are no problem because they
are just a compressor with a thermostat.

Any further comments appreciated.

(PS - the "super-effficient" fridge I have just remembered is a Gram)

Eric Sears.