600w Inverter won't run 1.2a chest freeze?
YostFMX
Solar Expert Posts: 94 ✭✭✭
I tested my converted chest freezer today on my prowatt sw600 (1200 surge) It wouldnt start? It runs at 1.2a, the start up on the freezer is 7.2 amps, 864 watts (so the tech from the company that makes it said). I have 4 RV 115ah batteries, and 2' of 4AWG wire to the inverter. Whats wrong? Why wont it start? Is the wire gauge not big enough? Or do I have to buy the sw1000 or sw2000 (watt) inverter?
Comments
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Re: 600w Inverter won't run 1.2a chest freeze?
Is it a sinewave inverter or a modified squarewave inveter ?
Standard fridge/freezers usually wont start on less than 1500 w MSW inverters in most cases.
Sometimes if good sine wave inverter 600 w may start it but it will be marginal.. 800w is really minimum. and 1000 w is ok -
Re: 600w Inverter won't run 1.2a chest freeze?
Its a true sinewave xantrax 600w. I would think the thats what the 1200w surge is for, right? If I was to get the 1000w inverter I don't know if it would be chancing if would even work off that or I would have to get the 2000w to be sure? -
Re: 600w Inverter won't run 1.2a chest freeze?
What is the Power factor of the freezer? While it may draw ~700 watt starting, with poor PF it might draw nearly twice that again. You may also be going to low voltage shut down, if you have such a big draw the batteries might not be able to deliver that current fast enough, causing the inverter to shut down.
Tony -
Re: 600w Inverter won't run 1.2a chest freeze?
the $64000 question is, is the inverter still working? -
Re: 600w Inverter won't run 1.2a chest freeze?
it wont hurt the inverter not being able to start the freezer.
1000 W tsw should start the freezer PROVIDING it can get sufficient from the battery/ies. AND also distance from inverter to battery/ies. #4 ok if 2ft max if more than that #2 and from what you say you have met those requirements. Check with multimeter to see what the voltage is at the inverter terminals when it tries to start. if it below 11.5 it may be a battery or cable connection problem also. -
Re: 600w Inverter won't run 1.2a chest freeze?
I assume it has a "solid state" varistor type start control in series with the start winding, nearly all now do compared to the older mechanical relay types. If you are good around electrical, you can add a 150 MFD Start Capacitor in series with the varistor. You MAY have to play with the 150 MFD value a bit to get the perfect match, but this will HUGELY reduce the start surge of the compressor and also in some cases allow it to restart even under full back pressure that hasn't been given a chance to bleed down. I've done this with both my freezers and my converter fridge, as well as other older fridges and freezers. All with fantastic results.
Some of the older freezers worked best with 200 MFD, but my newer upright converter freezer works best with 140 MFD. If you have lots of surge capacity you won't see much difference, but if things are cut close, finding the value that matches best definitely does make a difference. AND, it helps if you're friends with someone who owns or operates a motor repair shop, they'll let you try several values till you find the best. Also be aware that the value marked on the capacitor can be way off. I've run into that and had it verified with a capacitor value tester. With the added Cap Start, your freezer should definitely start no problems on your 600 watt PS inverter.
In fact, with additional and rather complicated external circuitry, I run all three of mine on a single dedicated Morningstar SureSine 300. One at a time of course, and the additional circuitry also takes care of that. The "fridge" has priority, followed by the freezer in the basement, then if neither one of these are running, finally the freezer in the outside shop - - if indeed it needs to run. Been working fine this way for years. -
Re: 600w Inverter won't run 1.2a chest freeze?
Yes the inverter still works just fine. But I think it was shutting off do to low voltage. I'm going to try the volt metter, then try hooking up the battery from my RV to the bank of 4 to see if it helps. I'll try some stuff and post how it goes...
@ waynefromnscanada, Man that is way over my head, would love to try it if I knew how! -
Re: 600w Inverter won't run 1.2a chest freeze?
Very cool waynefromnscanada. It's great to hear what people are able to do with these very small systems. -
Re: 600w Inverter won't run 1.2a chest freeze?
Wayne, that is way cool! I've been thinking about it for a couple of hours.... before I beg you to share your circuitry secrets, please give me a clue...waynefromnscanada wrote: »with additional and rather complicated external circuitry, I run all three of mine on a single dedicated Morningstar SureSine 300. One at a time of course, and the additional circuitry also takes care of that. The "fridge" has priority, followed by the freezer in the basement, then if neither one of these are running, finally the freezer in the outside shop - - if indeed it needs to run. Been working fine this way for years.
If the basement freezer is running and the fridge wants to cycle on, will the fridge cut off the freezer, or will the freezer be allowed to finish its cycle before the fridge gets its turn?
--vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i -
Re: 600w Inverter won't run 1.2a chest freeze?
Hooked a volt meter to the 12v side of the inverter, tried to start the freezer, the volt meter was at 13.7v the whole time. The error read out on my inverter was "Overload" not low voltage (the inverter will run from 15.5v - 10.5v). So do I have to buy a new higher watt inverter now? -
Re: 600w Inverter won't run 1.2a chest freeze?If the basement freezer is running and the fridge wants to cycle on, will the fridge cut off the freezer, or will the freezer be allowed to finish its cycle before the fridge gets its turn?
--vtMaps
Haha No, the Fridge ALWAYS has priority. When it goes to start, the first thing happens is a relay switches power from the freezer and passes it to the "fridge" which only runs about 5 minutes out of every 65 minutes, then when the "fridge" shuts off, the relay reconnects the freezer. Freezers can wait.
To get the compressors started on the PureSine 300, I have a small autotransformer, 115 volt with a 15 volt tap. When a compressor goes to start, a relay connects the autotransformer in such a way that only 100 volts is supplied, but as a result, more amps are available to get things up to speed. As soon as the starter kicks out, the autotransformer is removed from the circuit and the compressor connected directly to the inverter. From then on, it's business as usual. Keep in mind though that all the compressors have been changed to capacitor start. Took a lot of trial and error to find what worked best, and the varistor start controllers on the compressors were exchanged for timed relays. Timed too long and the excess load would kick out the inverter. Timed too short, and the starter would kick out before the motor got up to speed. A very fine line, but has worked for several years with no problems. -
Re: 600w Inverter won't run 1.2a chest freeze?
Probably--somewhere around 1,200 to 1,500 watts minimum. You might need to ask the retailer which inverters have better overload/surge capabilities (NAWS knows their products pretty well).
Regarding Watts for VA (volt*amps)... Depending on how and what they measure for AC surge, they can get different answers. For example that 7.2 amps... Unless you have a meter that can measure the very first few cycles (50/60 Hz) and record the actual starting surge, you may be only measuring the peak current over a once second period.
Also, a manufacturer can measure Watts or Volts*Amps (a "vector" quantity that has both magnitude and direction). For example, they may measure 864 watts at 120 VAC. So an assumption may be:- Power = Volts * Amps
- Amps = Power/Volts = 864 watts / 120 volts = 7.2 amps
But, with AC, the voltage and current sine waves are not always "in phase"... In fact, starting motors may have a power factor of 0.6 or less:- Cos-1 (0.6) = 53 phase lag of current
And the "real" equation for AC Power is:- Power = Volts * Amps * Cos(phase angle) = Volts * Amps * Power Factor
- Amps = Power / (volts * PF) = 864 watts / (120 Volts * 0.6) = 12 amps starting current
- VA = Volts*Amps = 120 Volts * 12 Amps = 1,440 VA
For inverters and smaller gensets, they usually assume maximum Watts equals VA rating... So, in my above "made up case", a 1,500 watt inverter (really 1,500 VA rated inverter) is needed to start that motor.
I assume you measured the Current with a standard Amp Meter and not some sort of Power Meter--So--in your case, you are probably measuring the "true" 7.2 amps and do not need to do the 1/PF calculation.
In some cases, Inverters get "confused" by heavily inductive loads (PF ~0.6 or lower) or the first few very high surge current sine wave cycles (it is not unusual to see 45 amps for the first couple cycles on a good sized 120 VAC plug in load). Either may be causing your inverter to "latch off" until the unit is reset or the power draw drops to near zero.
Wayne's use of a 120-200 MFD capacitor (I assume this is motor start capacitor and is in the motor start circuitry) is probably limiting the peak current to something more reasonable for the inverter to support in those first few cycles.
Sorry for the not quite on topic to your post--But this Watts<>VA is important for small power systems (solar, generators, etc.). There are a lot of "energy efficient" but lousy PF devices out there (120 VAC CFL and LED lamps, many computer/electronic power supplies, etc.) that can "overload" an inverter but yet still be well below the inverter's wattage limit.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: 600w Inverter won't run 1.2a chest freeze?
So all in all short of rewiring my freezer I'm going to need to buy a 2000 watt (15A) inverter, right?
(I'm not so up on the electrical tech, so I only understand it half way) -
Re: 600w Inverter won't run 1.2a chest freeze?
1,500 to 2,000 watts--Again, you might talk with NAWS about specific brands/models.
Next, if you are getting a larger inverter, what about the battery bank (12/24/48 volts, AH size)? And what about charging (solar, AC power)? Genset?
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: 600w Inverter won't run 1.2a chest freeze?
It is likely the starting is more then 7.2 amps peak on 120v, but you did not specifically state your battery type/size and wiring size/to inverter. With the inverter efficiency dropping on surge (like 50-60% vs. 80% for full rated load) you may be looking at 110 to 140 amps on a 12v battery during startup. This is about the same as starting a car engine, depending on engine size.
It is also very important to let the fridge/freezer equalize its refridgerent pressure before attempting to startup. Most refrig/freezer will pop their own safety overload protection if 120v supply flickers on/off/on. The starting current against a built up compressor head pressure is very large. -
Re: 600w Inverter won't run 1.2a chest freeze?
If I had all the money in the world I would go bigger with everything, but I don't. My three 215w PVs and four 12v RV batteries are going to have to do. I just need a my fridge to work, that its, everything else works like a champ! Looks like a new xantrex prowatt sw2000 inverter for me (after xantrex e-mails me back). -
Re: 600w Inverter won't run 1.2a chest freeze?It is also very important to let the fridge/freezer equalize its refridgerent pressure before attempting to startup.
How do I do this?
And maybe I'll add my RV battery and try to move the inverter 3' from the batteries and use #0 wire, see if it starts... -
Re: 600w Inverter won't run 1.2a chest freeze?How do I do this?
Let it sit, not running, for at least 10 minutes before trying to restart the compressor if it was just running.
If it's been off for a while, the pressures will have leveled out and all will be OK. -
Re: 600w Inverter won't run 1.2a chest freeze?
Thanks Wayne!
So doesn't linking the four 12v 115ah batteries make one big 12v 460ah battery? So thats enough right? -
Re: 600w Inverter won't run 1.2a chest freeze?
One of the problems in the RV folks have with limited amps coming out of a pedestal is starting AC units and one solution is the use of a hard start capacitor, good call Wayne. Supco makes a kit for this purpose and a good source of information is their booklet http://www.supco.com/images/pdfs/AC%20Hardstarts%20Booklet.pdf -
Re: 600w Inverter won't run 1.2a chest freeze?
This seems like its worth a try, the kits are $10 - $30. What do you guys think? Will it really help my problem?
Heres my freezer> what kit would I get for it? -
Re: 600w Inverter won't run 1.2a chest freeze?
I have the prowatt 2k in my motorhome. It does not have any issue running the refrigerator and a norcold chest freezer.
Do a test on what the freezer draws over a 24 hr period. My norcold runs a LOT. It will consume about 3Kw in 24 hrs. Not very battery friendly. I only use it when I really have to. -
Re: 600w Inverter won't run 1.2a chest freeze?
Had a look at the "Hard Start" devices in the link and found them to be Capacitor Start kits that do pretty much what happens with my freezers. Only difference is these are, or at least seem to be designed for AC units which don't have a dedicated start winding like most fridges/ freezers do, although most modern freezers/fridges use the start winding as a combo start/capacitor run winding. The problem I see on the link is that there doesn't appear to be one listed that would work with your fridge - - they're mostly wrong voltage/wrong cap values for what you need. BTW if you did find one that is close enough to work, it would connect to the same two wires going to the silver colored little cylinder showing just above and slightly left of the compressor, That item will be the Run capacitor that your freezer uses. The properly sized Hard Start kit, if you can find one, would wire across (in parallel with) that Run Capacitor. You should aim for a hard start unit with a capacitor value of roughly 150 MFD, but you'd likely have to measure the AC voltage across that existing Run Capacitor when the compressor is actually running, and let the Hard Start supplier know what that voltage is. From that, they should be able to recommend a unit that will work - - if they have one.
Good luck. I'm confident that if you can find the right sized Hard Start kit, it will work. That said, I don't believe it's going to be easy to find the right one, and indeed may not be available in the size/values you will need. -
Re: 600w Inverter won't run 1.2a chest freeze?
Ok, I checked the voltage with it running and it was going from 155.6v to 157.4, mostly around 156.5. So do that mean its a 150 cap? And if i can get one of those hard starter kits, I leave that cap in there and just link off it, right? (I don't want to fry this thing) -
Re: 600w Inverter won't run 1.2a chest freeze?
"155.6v to 157.4, mostly around 156.5 (volts)."
am i missing something here as the output voltage of an sw600 should not be this high?
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Re: 600w Inverter won't run 1.2a chest freeze?
Its what wayne said to check, the run capacitor voltage in the freezer. I plugged the freezer into my honda eu2000 and ran it, checked the capacitor while running and it was 156.6. This is all I know... -
Re: 600w Inverter won't run 1.2a chest freeze?
Supco E Class SPP7E
Operating Voltage
90V – 277V
Equipment Range
1/12 hp to 10 hp*
Recommended Range
1 hp to 4 hp
Capacitor
130 – 156 µF
Would this be the right model to use? Is Capacitor uF the same as voltage? The people I called were no help... -
Re: 600w Inverter won't run 1.2a chest freeze?
uF is the current storage rating of the capacitor...
One equation is (note that "W" here is work or Joules or Watt*Seconds--Not for Watts as is usually the case here):- Work = (1/2)CV2
C is sort of like the Amp*Hour rating of a battery bank (and here "Work" is in Watt*Hours--not really a standard engineering/physics unit--used for power billing purposes for residential and commercial uses--as well as designing off grid power systems):- Work = Amp*Hours*Voltage
The operating voltage is simply the safe maximum voltage (RMS) that can be applied to the capacitor without damaging the internal insulation between the metal foil/plates.
The uF (micro Farad) value of standard capacitors is a fairly wide range (-20/+80% is standard for many caps). So the value/model you have is good for a start.
If you still have problems, try to get a capacitor 1/2 the uF.
By the way, typically motor folks use MFD as the unit--Not really correct as "m" is milli or 1/1,000 in standard units--"u" or "micro" is 1/1,000,000 instead--In this case they use upper case "M" as "Micro" or 1/1,000,000). So, MFD = uF for our discussions here.
Wayne--by the way, are you using Motor Start capacitors (only in the starting circuit path) or a Motor Run capacitor (always in the motor power circuit)?
Generally, Motor RUN Capacitors are smaller values (<70 uF) and rated for AC power to be applied 100% of the time.
Motor START Capacitors are larger values (>70 uF and only rated to have voltage applied while the motor is starting. Some more details:Two basic types are used in electric motor:
1) Run capacitors are rated in a range of 3-70 microfarad (mfd). Run capacitors are also rated by voltage classification. The voltage classifications are 370V and 440V. Capacitors with ratings above 70 microfarad (mfd) are starting capacitors. Run capacitors are designed for continuous duty, and are energized the entire time the motor is running. Single phase electric motors need a capacitor to energize a second phase winding. This is why sizing is so critical. If the wrong run capacitor is installed, the motor will not have an even magnetic field. This will cause the rotor to hesitate at those spots that are uneven. This hesitation will cause the motor to become noisy, increase energy consumption, cause performance to drop, and cause the motor to overheat.
2) Starting capacitors are housed in a black plastic case and have a mfd range as opposed to a specific mfd rating on run capacitors. Start capacitors (ratings of 70 microfared or higher) have three voltage classifications: 125V, 250V, and 330V. Examples would be a 35 mfd at 370V run capacitor and an 88-108 mfd at 250V start capacitor. Start capacitors increase motor starting torque and allow a motor to be cycled on and off rapidly. Start capacitors are designed for momentary use. Start capacitors stay energized long enough to rapidly bring the motor to 3/4 of full speed and are then taken out of the circuit.
Potential relays are also as important. Potential relays are used to electronically connect and disconnect to starting capacitors from the motor circuit. Each relay has a specific voltage rating to place the start capacitor in series with the start winding and a specific voltage to take it out of the circuit. Each rating is based on the electromagnetic field generated by the rotation of the motor. The motor manufacturer studies the effect of placing in and taking out the capacitor to increase starting torque with as little winding flex as possible. Potential relays have four ratings; (1) continuous coil voltage, (2) minimum pick-up voltage, (3) maximum pick-up voltage, and (4) drop out voltage. A potential relay is difficult to check and should always be replaced when a start capacitor is replaced. The exact size designed for that particular motor must be reinstalled. The potential relay must also be replaced if contacts are found to be open.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: 600w Inverter won't run 1.2a chest freeze?Supco E Class SPP7E
Operating Voltage
90V – 277V
Equipment Range
1/12 hp to 10 hp*
Recommended Range
1 hp to 4 hp
Capacitor
130 – 156 µF
Would this be the right model to use? Is Capacitor uF the same as voltage? The people I called were no help...
It would probably be a good one to TRY, and I would STRONGLY recommend only trying it while you are monitoring power consumption with a Kill-A-Watt, so you will see if the Hard Start relay is taking the Start Capacitor out of the circuit once the compressor comes up to speed. Compare running watts without the Hard Start, with running watts after installing Hard Start. There should be no difference other than that caused by changing pressures the compressor is dealing with from time to time. Otherwise, if the Start Cap stays in the circuit after the comp is up and running, there will be way too much current in the start winding of your compressor and will shortly burn out that winding.
It's a rather tricky thing to ensure it's going to work right for your freezer.
BTW, the reason for finding the AC voltage across the Run Cap is for the supplier of the Hard Start to determine which relay to give you. That voltage will be quite low until the motor comes up to speed, at which time it raises dramatically, usually above the line supply voltage. It's this higher voltage that's used to activate the Hard Start relay that cuts the Start Cap out of the circuit.
Oh, and NO, that voltage does NOT indicate the MFD of the capacitor that should be used. It would however indicate the MIN voltage rating of the capacitor.
And BB, I'm using a START Capacitor, as it is only in circuit while the compressor is being started. It is however, when in action, connected by relay, across the existing (if any) Run Capacitor that was supplied with the freezer. The two capacitors are in parallel until the compressor is up to speed, then the Start Cap is disconnected and only the Run Cap remains in circuit.
Additional info: My older freezer has no run capacitor. The other has I think (memory) roughly 14 MFD run cap, and the "fridge" I believe has a 12 MFD run cap. In all cases, where the compressor was designed for and came with a run cap, that capacitor stays in circuit at all times. Only the Start Cap is connected and disconnected as required for starting. (I'm not trying to beat a dead horse here, just trying to be perfectly clear, as best I can) -
Re: 600w Inverter won't run 1.2a chest freeze?
Thank you for all the info!
The distributors I've called are no help at all! The give me the short answer, "yes we have them" no help with tech, they seem to think its a one side fits all thing. The one they carry will work for me, sad...
Not sure what to do?... Bigger inverter, or mess with trying to get a hard start capacitor? $350 inverter, or only $10, maybe fry my fridge, burn down my new house, and or fry me... haha
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