Surge is killing me!

[lkruper]

I was reading the manual for my current portable generator, the Generac ix 2000. Got it from Costco to replace my Smarter Tools which started acting up. Perhaps I added to much oil at the first oil change... good thing Costco has a good return policy!

But I digress... it said that I should use a factor of 3X for surge for refrigerators. I am seeing this online as well.

I had it in my head, for some reason, that surge was more like 2X. I am also assuming that surge happens each and every time the fridge cycles, not just when it is initially turned on.

Does this change with a particular refrigerator? My energy efficient 14.5 fridge takes 6 amps when first cooling and then it cycles. But 3X uses up ALL the capacity of the my inverter generator which is 2000/2200! And to make matters worse, I have another small fridge as well. I have a kill-o-watt meter, but it does not measure surge. Is there a way to measure this? Also, what are the chances that if I have two refrigerators on at the same time, they both surge at exactly the same time? Should I worry about that?

Since my generator is only for emergency usage, I suppose I could run just one fridge or maybe only at night when other loads are off. Maybe I need to take this genny back and get a bigger one?

[Mike90250]

Motor starting surge is generally 4-10x running power. That's why an battery inverter has a hard time. Inverter generators have a harder time, as there is no battery storage to draw upon, just the power in the alternator. So a 2Kw inverter gen should be able to start a fridge, and a good 1Kw battery inverter with good batteries and cables can do the same job.

For 2 fridges, you may want 2 small generators, one for each fridge, or a single, larger generator.

Small generators have small rotating mass for starting surge demanding loads, and sometimes cannot do it.

[lkruper]

Motor starting surge is generally 4-10x running power. That's why an battery inverter has a hard time. Inverter generators have a harder time, as there is no battery storage to draw upon, just the power in the alternator. So a 2Kw inverter gen should be able to start a fridge, and a good 1Kw battery inverter with good batteries and cables can do the same job.

For 2 fridges, you may want 2 small generators, one for each fridge, or a single, larger generator.

Small generators have small rotating mass for starting surge demanding loads, and sometimes cannot do it.

Thanks Mike, but I am having a hard time with the math. My generator will take up to 2200 surge at 120v. So that is 18.33 amps. My fridge documentation and my kill-o-watt was measuring 6 amps when I first started it up. With this calculation 3x maxes out the generator and 4x is higher. How can it handle 10x running power?

[Mike90250]

the kil-a-watt meter is not a peak reading meter, and can only by chance, record the half-second starting surge. The surge is very often, quite large and that is where the surge capacity rating of inverters comes in. The surge is too short to trip a breaker, but is enough to often fault a small inverter generator, which has NO surge capacity, the rotating mass is too small to respond to heavy loads, where battery inverters have a large battery that can supply a brief spike in power.

So you have to try it and see how it works with your generator and fridge. Every combo will be different, and not all will succeed.

[lkruper]

the kil-a-watt meter is not a peak reading meter, and can only by chance, record the half-second starting surge. The surge is very often, quite large and that is where the surge capacity rating of inverters comes in. The surge is too short to trip a breaker, but is enough to often fault a small inverter generator, which has NO surge capacity, the rotating mass is too small to respond to heavy loads, where battery inverters have a large battery that can supply a brief spike in power.

So you have to try it and see how it works with your generator and fridge. Every combo will be different, and not all will succeed.

I will test. I did test with everything connected but did not have a prolonged test or inspect the fridges. Do you think a small UPS for the fridge would give it the surge it needs and how would I size it?

[Mike90250]

A
UPS is an inverter, and a inverter needs to be about 1KW and good battery feed to start a fridge.

BUT some UPS are mod square wave, you need PURE Sine Wave for a fridge (or any motor). And it should have at least 2Kw surge capacity

[lkruper]

A
UPS is an inverter, and a inverter needs to be about 1KW and good battery feed to start a fridge.

BUT some UPS are mod square wave, you need PURE Sine Wave for a fridge (or any motor). And it should have at least 2Kw surge capacity

I am thinking that since the next phase of my backup strategy was to have some battery backup it makes sense to add:

Samlex 30 amp Smart Charger SEC1230A - $208
SSW-1000-12A 1000W Pure Sine Wave - $291
2 T105 - $280
---------------------------------------------------------------
TOTAL "UPS" $779

50% DOD on the battery should conservatively run all my loads for 5 hours and longer if I conserve.

Am I correct in the assumption that if the inverter is connected to my transfer switch and the generator is powering the charger, that when the battery is full, the power comes from the charger and the batteries don't kick in until the generator runs out of gas or is turned off?

### Found out that Samlex has a special mode for charging batteries under load.

[Mike90250]

A UPS has a small transfer switch/relay built in. To use a inverter in your house, you will need to either move the appliance cord to the inverter power outlet, or use a transfer switch (manual or automatic) to switch some loads in your main electrical panel.

[inetdog]

Yet another factor in inverter (as in inverter generator) behavior is how it reacts to overload.

A simple spinning generator with auto throttle and active voltage regulation will react to excessive current draw by letting the voltage drop below the regulated voltage until the current draw from the motor is within its capability. This "reduced voltage starting" is actually deliberately used for large motors where the starting surge might affect other utility customers. As long as the motor is able to spin up far enough to reduce the current drain, this is actually a winning outcome. If the motor does not spin up and so continues to draw high current, either the generator breaker or the generator thermal protection will kick in.

With an inverter fed by DC from a generator, the reduced voltage reaction is possible. But the current limit is pretty much a hard limit to protect the semiconductors which can overheat very fast. In that case the inverter may shut down before the motor is up to speed.
An even worse outcome happens if instead of just dropping the voltage the inverter reacts by immediately shutting down. That is a guaranteed losing situation for motor starting.

Unfortunately most if not all manufacturers do not give you the information you need to decide in advance how the inverter will behave.
That makes starting a refrigerator or other compressor type load a crap shoot unless the inverter generator is significantly oversized.

[lkruper]

A UPS has a small transfer switch/relay built in. To use a inverter in your house, you will need to either move the appliance cord to the inverter power outlet, or use a transfer switch (manual or automatic) to switch some loads in your main electrical panel.

I do have a manual transfer switch installed as of last week that allows me to select 110v circuits to be selectively powered by a generator. If my new inverter generator will power my fridge, then I am in no hurry to do anything. If it cannot start the compressor then I have to decide whether or not I will replace the generator with a larger one, decide not to power the refrigerator at all during an outage or add battery backup. Another option (since I have two fridges, one in the kitchen and one in the basement) is to replace the small 3.2 cu ft fridge in the kitchen with one of those highly efficient models that does not have a surge.

[lkruper]

Yet another factor in inverter (as in inverter generator) behavior is how it reacts to overload.

A simple spinning generator with auto throttle and active voltage regulation will react to excessive current draw by letting the voltage drop below the regulated voltage until the current draw from the motor is within its capability. This "reduced voltage starting" is actually deliberately used for large motors where the starting surge might affect other utility customers. As long as the motor is able to spin up far enough to reduce the current drain, this is actually a winning outcome. If the motor does not spin up and so continues to draw high current, either the generator breaker or the generator thermal protection will kick in.

With an inverter fed by DC from a generator, the reduced voltage reaction is possible. But the current limit is pretty much a hard limit to protect the semiconductors which can overheat very fast. In that case the inverter may shut down before the motor is up to speed.
An even worse outcome happens if instead of just dropping the voltage the inverter reacts by immediately shutting down. That is a guaranteed losing situation for motor starting.

Unfortunately most if not all manufacturers do not give you the information you need to decide in advance how the inverter will behave.
That makes starting a refrigerator or other compressor type load a crap shoot unless the inverter generator is significantly oversized.

Now I understand the insecurity of wanting something but not wanted to risk the expense just in case it does not work. I am being drawn to Harbor Freight to purchase everything I need for $99.99 .... I think I need an intervention

[Mike90250]

Now I understand the insecurity of wanting something but not wanted to risk the expense just in case it does not work. I am being drawn to Harbor Freight to purchase everything I need for $99.99 .... I think I need an intervention

Harbor Freight, the place to buy things that look like they should work.

[lkruper]

Harbor Freight, the place to buy things that look like they should work.

I am somewhat torn regarding what to get for battery backup if I go that route. It does not have the requirement of continuous usage, and I know that is not an excuse to skimp on quality, but for a system that might not get much use I can't see the expense of Magnum or Outback. I am also considering Sam's club or Costco Golf cart batteries. If there is a natural disaster (worst case scenario) and if we are stranded for weeks my gasoline will be depleted long before I can ruin the batteries.

[SunEagle]

I am somewhat torn regarding what to get for battery backup if I go that route. It does not have the requirement of continuous usage, and I know that is not an excuse to skimp on quality, but for a system that might not get much use I can't see the expense of Magnum or Outback. I am also considering Sam's club or Costco Golf cart batteries. If there is a natural disaster (worst case scenario) and if we are stranded for weeks my gasoline will be depleted long before I can ruin the batteries.

I have a couple of Interstate 6v 232Ah batteries for my RV. While they are not rated RE deep cycle they do a pretty good job for about $130 each.

If you don't plan on using those batteries daily it is better to get a less expensive set and just keep an eye on their SOC. They should still produce a good output a couple years down the road if you run into a long grid outage. But don't expect them to last very long after they go into daily use for a few weeks.

[lkruper]

I have a couple of Interstate 6v 232Ah batteries for my RV. While they are not rated RE deep cycle they do a pretty good job for about $130 each.

If you don't plan on using those batteries daily it is better to get a less expensive set and just keep an eye on their SOC. They should still produce a good output a couple years down the road if you run into a long grid outage. But don't expect them to last very long after they go into daily use for a few weeks.

Thanks for the tip. I just looked at Sam's club (don't have a membership) online and Energizer GC2 for $84.52 and GC8 for $99.72. I read some old posts somewhere that said they were made by Johnson Controls at that time. Do you or anyone else have information on these?