Need Help Starting a Fridge that Doesn't Like to Start

williaty · May 2014

I've got a modern (bought this year) fridge (runs off 120VAC) that starts fine on the grid but won't start reliably off grid. With my generator (Yamaha EF2400iSHC), it'll start about 1/3 to 1/2 of the times it attempts to do so. Once started, it runs perfectly and only draws about 100W. The other times, it'll sort of click, whirr for a few seconds, hum a bit, and then give up. If I power it via my inverter (Victron Phoenix Multiplus Compact 24/2000), it won't ever start, it just clicks, whirs, and hums. Even though steady state power consumption is quite reasonable, I have a feeling the inrush current on this motor must be insane and that's why it's finnicky about starting. The HC portion of EF2400iSHC means that it has a "hard start kit" included in the generator in order to start difficult to deal with RV air conditioners, which I suspect is why it can start the fridge. I assume this primarily takes the form of a lot of capacitance on the output to provide short current spikes.

Is there any way to add something similar to the "hard start kit" directly to the 120VAC circuit that feeds the fridge so that the solar system can run the fridge via the Victron inverter?

mike95490 · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Since you are dealing with AC, a capacitor won't do a lot, since it stores DC. But what may help, is a Motor Run capacitor, which combined with the windings of a motor, shifts the AC phase of the inductive loading around - sometimes going through a box of different sized Run capacitors, you can find one that helps the starting. Another avenue is to locate someone with a Peak Hold AC amp meter and see what the fridge pulls from the grid. You may find the easiest is a larger inverter.

waynefromnscanada · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Many modern high efficiency fridges already have a "run" capacitor, often in the range or more or less 7 MFD. If yours does, try adding (only while starting the compressor) a motor Start capacitor of roughly 70 MFD to the already existing Run capacitor. You may well find the compressor will start right up. But as soon as it's running you MUST take the START cap out of the circuit. If this works, then you can use a timed relay to control the Start capacitor so it's only connected while the motor is not running and when it's starting. Once the motor is up and running, the timed relay must disconnect the Start capacitor, otherwise the motor will overheat and soon be damaged. A 1 to 3 second timed connection should work very well.
You could well be amazed at the difference this Start Capacitor will make. I've done this many times with really great results. Some compressors like a bigger start capacitor, close to 100 MFD, while other more modern ones like something coser to 60 Mfd much better. You may have to try several values to see which works best.

williaty · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Thanks for the info guys. I'll continue to check for updates but if I don't reply to the thread super-quick, it's because my supposed on-grid house just became off-grid for at least 4 days and we're finding out that some of the problems with the backup electric we thought we'd solved are, in fact, not solved. I can't wait for the power to come back on Monday so I can shower!

Figures that I'd start thinking about this fridge in the woods issue and then my "city" location would break down.

bill von novak · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

williaty wrote: »

Is there any way to add something similar to the "hard start kit" directly to the 120VAC circuit that feeds the fridge so that the solar system can run the fridge via the Victron inverter?

Not to the AC side, but what about the DC side? If the inverter can handle the load but the battery bank is sagging that can cause your problem.

williaty · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

bill von novak wrote: »

Not to the AC side, but what about the DC side? If the inverter can handle the load but the battery bank is sagging that can cause your problem.

The Victron monitor logs once a second. There's no DC side fluctuation at all in the logs but obviously a second is a VERY long time when talking about inrush.

Blackcherry04 · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

The first two questions I have would be, Is the Generator in the ECO mode or what ever Yamaha calls it ?? Is the Inverter in the UPS or Idle standby mode ?? Either of those will cause issues on a refrigerator. I have some success using a Supco hard to start kicker E class kit. With one on a 5000 btu A/C it'll start on a Honda from the idle mode.

Both of your sources ( gen & Inv ) should have more that enough power too run a Refrigerator. Some Refrigerators once they have not started and popped the overload will have a hard time getting back in cycle, turn it off for 15-20 minutes and let it the compressor cool.

http://www.supco.com/eclass.htm

Cariboocoot · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Notes on motors and capacitors:

The capacitors used for AC motors are not the same as would be found in a DC circuit.
Most often there will be a start capacitor if there is any at all, but not a run capacitor.
Adding a run capacitor will not aid starting.
You need to know what you're dealing with in the motor in order to figure out what power is necessary to start and run it. Otherwise you're guessing and that can be expensive and even dangerous.
The surge ratings on inverters are often for ridiculously short times that are of no practical value, so don't rely on them.
Any added capacitor needs to be at the motor or exclusively on its wiring so that it doesn't "help start" other loads (which will reduce its effectiveness).

jonr · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

When starting, motors have a poor power factor which adds to the excessive startup current problem. This can be fixed with a capacitor - but even with a power factor of 1.0, there could still be too much load (current draw) to start. At that point, a little bit of resistance might help. Or it might prevent the motor from starting.

I'm not aware of a simple, low cost device to measure these things and tell you what the problem is. Ie, something like a kill-a-watt, but focused on instantaneous values during start-up.

jonr · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Has anyone tried using a cheap 500W grid-tie inverter connected to a battery as a "generator assist" to get a motor started? As soon as the motor is running, the inverter could be turned off. I would guess that it would sync with the clean sinewave coming from an inverter generator.

Cariboocoot · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

jonr wrote: »

Has anyone tried using a cheap 500W grid-tie inverter connected to a battery as a "generator assist" to get a motor started? As soon as the motor is running, the inverter could be turned off. I would guess that it would sync with the clean sinewave coming from an inverter generator.

That is a recipe for a disaster.
First of all GTI's are not meant to be powered by batteries; they will try to pass current and a battery is almost unlimited inn current.
Second GTI's require time (like five minutes) to qualify Voltage & frequency and sync.
Third generators are not designed to be back-fed current; the GTI could easily blow out the gen's circuits.

Yes I read the part about shutting it off. Let's see you do that in 1/120 of a second.

The only way you can do something like this is with an inverter that features gen support, and in that case you probably have enough inverter capacity to start the 'frige anyway.

South Africa · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Another thought. I solved my standard cheap mass market fridge start-up current, which is a wee bit more than 1000w by getting a 2nd hand 3kva online UPS which, when the fridge starts, supply's the extra current draw required from its internal small batteries for those few seconds whilst the 1600w inverter, which is already powering a lot of other stuff, does not even know there was a spike in the load requirement.

Was cheaper than getting a bigger inverter / jenny or having to 'make a plan'.

But it must be a online, not inline or off-line UPS, online.

williaty · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

So, having nothing better to do over the weekend than play around with this problem, I did find something interesting that might help you guys help me.

Case #1: Generator>Fridge=starts
Case #2: Batteries>Inverter/Charger>Fridge=No-start
Case #3: Generator>Inverter/Charger>Fridge=start (Phoenix Multi has a "boost" feature where it can sum the battery power and "shore" power on tough loads)
Case #4: Generator>DC Power Supply>Batteries>Inverter/Charger>Fridge=start (I actually charge using a DC power supply rather than the Phoenix Multi in order to get the charging profile I want)

Case #4 is the one that interests me. The DC power supply is a 30A-30V that runs off of 120VAC. I have it set to the absorb voltage of the battery bank (29.4VDC). So the power comes out of the generator, into the DC power supply and is converted to DC, and is then attached to the battery bank in parallel to the wiring for the Inverter/Charger. In this configuration, you don't see the current displays on the battery monitor or the DC power supply move farther than the 100W running load for the fridge. However, when the fridge starts, the generator goes "HOLY CRAP! VROOOOM!" before settling right back down. So obviously for a time domain too short for any of the meters to display, the inverter is pulling the batteries down so far that the current load on the DC power supply spikes to the point it freaks out the generator.

Is there any way to tell if a bigger battery bank would solve this? I've got 4 50Ah AGMs on it right now to produce a 24V/100Ah bank.

Cariboocoot · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

williaty wrote: »

So, having nothing better to do over the weekend than play around with this problem, I did find something interesting that might help you guys help me.

Case #1: Generator>Fridge=starts
Case #2: Batteries>Inverter/Charger>Fridge=No-start
Case #3: Generator>Inverter/Charger>Fridge=start (Phoenix Multi has a "boost" feature where it can sum the battery power and "shore" power on tough loads)
Case #4: Generator>DC Power Supply>Batteries>Inverter/Charger>Fridge=start (I actually charge using a DC power supply rather than the Phoenix Multi in order to get the charging profile I want)

Case #4 is the one that interests me. The DC power supply is a 30A-30V that runs off of 120VAC. I have it set to the absorb voltage of the battery bank (29.4VDC). So the power comes out of the generator, into the DC power supply and is converted to DC, and is then attached to the battery bank in parallel to the wiring for the Inverter/Charger. In this configuration, you don't see the current displays on the battery monitor or the DC power supply move farther than the 100W running load for the fridge. However, when the fridge starts, the generator goes "HOLY CRAP! VROOOOM!" before settling right back down. So obviously for a time domain too short for any of the meters to display, the inverter is pulling the batteries down so far that the current load on the DC power supply spikes to the point it freaks out the generator.

Is there any way to tell if a bigger battery bank would solve this? I've got 4 50Ah AGMs on it right now to produce a 24V/100Ah bank.

What you've shown here (and kudos for an accurate systematic analysis) is that the problem is Voltage sag on the DC side of the inverter when the surge demand is high. The addition of the DC supply to the batteries is making up for the sag.

You have four 50 Amp hour 12 Volt batteries? That would be 100 Amp hours @ 24 Volts. That should also handle a momentary demand of 240 Watts. If you are trying to supply 1kW plus on 24 Volts that's 50 Amps which would instantly flatten that battery bank. You should have about 4 or 5 times as much battery.

williaty · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Weirdly, this system had a totally different purpose before we moved and it used to run a 3/4hp water pump. In that duty, it did just fine even though the pump drew about 600W continuously when running and god knows how much when starting. Same batteries, same inverter, same everything. Yet it won't run this tiny fridge motor!

Also, in testing, I've put a sustained load of 2kW on the system for a few minutes, which it supported, though with considerably shortened run-time

BB. · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Try using a "cheap" extension cord to your refrigerator... If you have a 50 foot or longer 14 or 16 AWG--So much the better. The additional AC resistance from the extension cord may shave the top off of the starting peak.

Also check very closely on the DC side of the system. Make sure you do not have excessive voltage drops in wiring/connections/dirty or loose connections/etc...

-Bill

Cariboocoot · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

I think the main problem is we don't know exactly how much of a start surge there is. It's possible for a 'frige to draw more than a water pump on start-up even though the pump may draw more running.

Another thing to check is the gauge and length of the battery cables as significant Voltage sag can occur there too.

westbranch · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

A DC clamp meter would help here to measure the DC amps being pulled...

jonr · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Cariboocoot wrote: »

Third generators are not designed to be back-fed current; the GTI could easily blow out the gen's circuits..

But many inverter generators are designed to be paralleled with a matched source of AC power and people have synced inverter generators (like a Honda EU2000) with off grid sine-wave inverters without problems. But shutting down the generator, starting the inverter, then starting the generator is less convenient. Maybe not if the grid-tie inverter needs 5 min to sync.

> First of all GTI's are not meant to be powered by batteries;

But some seem to work fine that way - see numerous Youtube videos. Not surprising, since people can also connect too many parallel panels to a GTI and so it needs be designed to self limit itself. Hmm, the same videos show the GTI kicking in immediately (not after 5 min).

Cariboocoot · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Well you can believe me or you can believe Youtube.
If you're going to believe Youtube warn the neighbourhood and alert the fire department before you try it.

bill von novak · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

jonr wrote: »

Has anyone tried using a cheap 500W grid-tie inverter connected to a battery as a "generator assist" to get a motor started?

Yikes. At least three things wrong there:
-GT inverters don't like batteries as a source (different V/I curve)
-Cheap GT inverters don't like feeding generators (they often skimp on islanding protection; not a good thing when used with a generator!)
-Impossible to sync turn-on with the surge and turn-off with the end of the surge

bill von novak · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

williaty wrote: »

Case #4: Generator>DC Power Supply>Batteries>Inverter/Charger>Fridge=start (I actually charge using a DC power supply rather than the Phoenix Multi in order to get the charging profile I want)

Ha, thought it might be DC sag. This is one of the few cases where bulk capacitance may help.

Is there any way to tell if a bigger battery bank would solve this? I've got 4 50Ah AGMs on it right now to produce a 24V/100Ah bank.

Very likely. Both a larger and a newer battery bank will tend to have less ESR, which means more power available for inrush.

waynefromnscanada · May 2014

Re: Need Help Starting a Fridge that Doesn't Like to Start

Cariboocoot wrote: »

Well you can believe me or you can believe Youtube.

I much prefer the youtube videos that show how to build machines that produce all the electricity we will ever need by running specially modified electric motors with lots of special magnets that self power the motor and produce all kinds of extra power. I also like the videos that show how to use cow urine to produce "Natural" cures for any disease that ails us. I just have to teach the cow to stand still long enough to collect the raw material. Of course in both cases the government doesn't want us to know about any of this.
Now if you'll excuse me, the guys in white coats are here to take me away - - they say I'll like where we're going - - -

Need Help Starting a Fridge that Doesn't Like to Start

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