400/800W Inverter can't run fan?

[GrayWhale]

It runs, but it's making a buzzing noise that continuous, like when the fan is just powering on and needs to get over that power hump initially; to then run smoothly.  This is a big fan, but it's only 45w (verified by Kill-A-Watt).  First it did the same with a weak inverter (80w/160w) so I thought going up to 400/800w would work, but it's doing the same thing.

Battery is new.

Underpowering an appliance would burn out the motor, right?

http://www.harborfreight.com/400-watt-continuous-800-watt-peak-power-inverter-66814.html

 

[SternWake]

HF inverters are known to have a very sloppy modified sine wave, and many electric motors simply despise anythng but a cleaner sine wave.

many things buzz on MSW inverters.

I use a PWM router speed control on some 20 inch box fans. the 30 year old box fan slows nicely without noise on the controller, the newer fan, perhaps 15 years old, makes a horrible racket and its motor gets noticeably hot.

So it is not the wattage of your inverter, it is the steps in the modified sine wave that do not agree with your fan's motor.

The quality of the stepped wave varies greatly among MSW inverters with HF right at the bottom of the dung heap.
PSW inverters are a much better call on anything with an electric motor

 

[GrayWhale]

So this is bad news to keep running the fan on this cheapo inverter right?

 

[DannyB1954]

Starting current is always higher with any motor. Sometimes it is not the inverter, but the wires feeding the inverter. At 800 watt that is 66.7 amps. Even at 400 watts, that it is 33.3 amps. These inverters often come with thin wires for cigar lighter outlets. I would increase the wire size to the inverter before anything else.

 

[BradKW]

While it's possible that the fan motor was damaged on the smaller inverter, it is much more likely that that HF 400 watt inverter for $25 is barely worth the packaging it came in. If that.

Danny's advice about wire size is good, but I'd hesitate to put any effort into making that thing work. Just for comparison purposes, here's a 400 watt inverter for $500.

Certainly not saying you need to buy it to run a fan, but sticker shocks like that are what first woke me up to the wide and varied world of inverters. Not having any experience with them, I too was confused...but then I learned that I was buying a Yugo and expecting it to perform like a NASCAR...

 

[GrayWhale]

While it's possible that the fan motor was damaged on the smaller inverter, it is much more likely that that HF 400 watt inverter for $25 is barely worth the packaging it came in. If that.
 

I don't think that the motor is damaged. I stopped using it after about 2 minutes on these 2 inverters. After that, used it only with shore power and the fan's ok. Now I need to figure out what kind of inverter to get.  Not just for the fan, but should I dare run a dorm size freezer for a couple of hours a day off of a battery?

 

[GrayWhale]

Is it normal to get a pretty big spark when connecting the alligator clips from the inverter (off w/nothing plugged to it), to the battery?

 

[SternWake]

Is it normal to get a pretty big spark when connecting the alligator clips from the inverter (off w/nothing plugged to it), to the battery?

In my experience, yes.

The start up surge of some dorm fridges can require upto a 1200 watt inverter. It seems to vary widely from the reports.

I am not sure how much faster a buzzing motor would wear out from a cheap square wave inverter.  My 120vAC box fan which does not like the router speed controller I use, has dealt with it OK in the several hours It might have accumulated buzzing. 

A 12v fan could be an option.

I view inverters as a necessary evil, I have 2, 400psw and 800msw,  but I seek to avoid having to use them in favor of 12vDC.

https://www.amazon.com/Wagan-EL2601-Elite-400W-Inverter/dp/B007Y4BL1C

That's my 400 watt PSW inverter.  Very small, quiet or silent under small loads( less than 100 watts) .
 I've seen it hold 440 watts for 5 minutes.  0.25 amp parasitic draw, turned on powering nothing.

My 800 watt MSW inverter is a very old Coleman whose fan is always loud & annoying and has been replaced once already.  It draws 0.68 amps turned on, powering nothing.

 

[BradKW]

Now I need to figure out what kind of inverter to get.  Not just for the fan, but should I dare run a dorm size freezer for a couple of hours a day off of a battery?

You should take a read through this for some ideas:  DIY-How-to-make-your-own-12V-Fridge

 

[GrayWhale]

Damn, that's a lot at 0.68 amps for just the inverter. I may have to rethink this.

My dorm freezer, I filled the bottom half, full of plastic containers of water to make thick ice blocks. Then I run it about 60-90 minutes each session, 1-3 times a day. 1-2 times more when it's really hot as it can get to 115 deg. inside the van. This keeps the ice frozen enough to prevent the food from spoiling. I chose a freezer instead of refrigerator because they both use the same amount of watts, while the freezer cranks up the cold way more. Biggest drawback is that soft vegetables get frosted, but carrots and such, are ok. This is kind of like using the cooler and buying ice every few days. It doesn't beat a high efficiency 12v refrigerator, but it only cost $120.

 

[SternWake]

Damn, that's a lot at 0.68 amps for just the inverter. I may have to rethink this.

That 0.68 amps over an hour, is generally more than my vitrifrigo c51is uses 75% of the time over an hour time span.

The standby parasitic draw of any given inverter turned on, powering nothing, can also vary widely.

Have you tried the chest freezer on the inverter?  If it works, does its motor sound different on MSW inverter than on grid power?

 

[GrayWhale]

Have you tried the chest freezer on the inverter?  If it works, does its motor sound different on MSW inverter than on grid power?

No I haven't. Kind of scared. The inverter is only 400/800w peak. You said it may need 1500w startup. What do you think? Should I try it? Can something real bad happen?

 

[SternWake]

 What do you think? Should I try it? Can something real bad happen?

I guess the freezer could release the magic blue smoke of the compressor controller, worst case scenario.

  How likely is that?  I do not know.  If it were almost any brand MSW inverter but for harbor freight.........

The fan buzzing is not a good sign.

 

[GrayWhale]

Ok, tried the dorm freezer on the 400/800w inverter and it just sets off the alarm w/o turning on the compressor, indicating not enough power.

Also, this dorm freezer set up is pretty good. I only need to run it 3 times a day at 1 hour each time (more in the summer though) to keep the plastic containers of ice frozen enough to keep everything cold inside, like a cooler w/o needing to buy ice every 3 days. And it runs well using my Harbor Freight $70 generator.

 

[SternWake]

Thanks for the report.

While there are a few reports of some 300 watt inverters running dorm fridges, most say 1000 to 1200 watt ones are required to cover the start up surge which can easily be 10X the running rating.