Generator Damage Electronics?

[Ken]

Retired from a power co. and during outages due to tornado or ice storms was always surprised at what customers thought was a large enough generators. They would add up the wattage and buy this size of generatyor to then load to twice its rating and wonder why the breaker kept tripping. A dairy man asked me to check his PTO 25K s/b gen. It used to do the job. Then he added larger milking stalls larger milk tank. more chillers. then a well larger pump.so had several 5 h.p. motors close to 150 amps of total load.
Convinced him to purchase a 60 KW gen and this last ice storm he lost power and had no problems with load. also had shut off all not needed power to stay with in limits.We forget how dependent we are on power until it is gone.
ken

 

[Travelover]

Thanks for the good comments.

On the subject of a UPS, it would seem that if used with a generator, it would not really provide any protection. My logic is that if it senses line voltage (now supplied by the generator) it would just bypass this power to the load.

I guess you could plug something like a furnace directly into the UPS and unplug the UPS from the generator, but it would take a really big UPS to run the furnace for any time and you'd need to keep recharging the UPS battery when the furnace cycled off.

 

[aczlan]

On the subject of a UPS, it would seem that if used with a generator, it would not really provide any protection. My logic is that if it senses line voltage (now supplied by the generator) it would just bypass this power to the load.

a decent UPS is also a power conditioner, it will "clean up" the power that comes into it, the highs get cut off and it uses the battery to bring the lows up to the proper voltage, IIRC, it wont fix improper hertz (ie: 50 hz instead of 60)

Aaron Z

 

[RonMar]

All the UPS's I now work with are switching type. The input is fed right thru to the output(with a little going to charge the battery) untill an over voltage or under voltage condition is sensed. That condition is usually one that exceeds +/- 10 percent of the normal 120VAC. If the voltage drops below about 108VAC, the unit switches to the battery powered inverter and disconnects the input power from the load. This is typical, but some come set with higher tollerances, or can be switched to higher tollerances if desired.

If not overloaded the inverter output should provide 120VAC. This switching occurs very fast(usually less than 1/2 cycle of 60HZ). The UPS continues to monitor the input power and when it returns to within specification, it re-connects the input power to the load and resumes charging the battery. I have 3 ups's in my home. One for the entertainment center, one for the computer and one for the pellet stove. They are great for short power failures and for momentary generator overload conditions. I only have 3KW available from my generator, but my largest load is also only a 2/3HP well pump that dosn't run very often. I will occasionally overload it though, and the UPS's protect the expensive equipment while this is happening. The Beeping UPS is also good for bringing my attention to an overload condition that I might otherwise be unaware of while on generator power.

If you are taking power drops down to 95VAC, your generator is too small to deal with your surge loads. This is especially true if they last long enough to see on a kill-a-watt meter. Your generator is probably fine for most of your normal emergency loads. My house on backup power typically pulls less than 2KW. That big pull from your furnace startup, or a combination of loads is pulling the voltage down too low. Get a bigger generator, reduce the load to within the capabilities of your existing generator, or put the critical items on UPS's. I have done the latter 2 of these to live comfortably within my 3KW limit.

To the gentelman who lost a computer power supply when the UPS exhausted it's battery, I would say you have a bad UPS. The UPS should have shut itself down when the inverter was no longer able to maintain rated output, just like it disconnected from line power when it was not receiving correct voltage from that source. Another issue could also be caused by a cheap UPS. A cheap UPS is probably not going to give a real good sine wave output. Switching power supplies such as those found in computers do not like square wave or modified sinewave outputs.

 

[heehaw]

"If you have to do with out then why in the world have a gen in the first place"
strictly for lights, frig and freezer: have gas wall heaters to stay toasty warm.
one thing i do plug into the generator thats electronic, the microwave: but then i have such a cheap one, i wouldn't fuss if it failed because of the generator: also use the washing machine, which has no electronic devices, electric skillet and toaster..not all at the same time of course: i only use a 3500watt generator:
also about losing a computer ps that was on a ups: most ups's come with software that can be loaded on your computer, so the computer will shut down properly as the ups battery goes down.
heehaw

 

[whistlepig]

All the UPS's I now work with are switching type. The input is fed right thru to the output(with a little going to charge the battery) untill an over voltage or under voltage condition is sensed. That condition is usually one that exceeds +/- 10 percent of the normal 120VAC. If the voltage drops below about 108VAC, the unit switches to the battery powered inverter and disconnects the input power from the load. This is typical, but some come set with higher tollerances, or can be switched to higher tollerances if desired.

If not overloaded the inverter output should provide 120VAC. This switching occurs very fast(usually less than 1/2 cycle of 60HZ). The UPS continues to monitor the input power and when it returns to within specification, it re-connects the input power to the load and resumes charging the battery. I have 3 ups's in my home. One for the entertainment center, one for the computer and one for the pellet stove. They are great for short power failures and for momentary generator overload conditions. I only have 3KW available from my generator, but my largest load is also only a 2/3HP well pump that dosn't run very often. I will occasionally overload it though, and the UPS's protect the expensive equipment while this is happening. The Beeping UPS is also good for bringing my attention to an overload condition that I might otherwise be unaware of while on generator power.

If you are taking power drops down to 95VAC, your generator is too small to deal with your surge loads. This is especially true if they last long enough to see on a kill-a-watt meter. Your generator is probably fine for most of your normal emergency loads. My house on backup power typically pulls less than 2KW. That big pull from your furnace startup, or a combination of loads is pulling the voltage down too low. Get a bigger generator, reduce the load to within the capabilities of your existing generator, or put the critical items on UPS's. I have done the latter 2 of these to live comfortably within my 3KW limit.

To the gentelman who lost a computer power supply when the UPS exhausted it's battery, I would say you have a bad UPS. The UPS should have shut itself down when the inverter was no longer able to maintain rated output, just like it disconnected from line power when it was not receiving correct voltage from that source. Another issue could also be caused by a cheap UPS. A cheap UPS is probably not going to give a real good sine wave output. Switching power supplies such as those found in computers do not like square wave or modified sinewave outputs.

You have gotten my curiosity up on the UPS. I know nothing about them. I This sounds like something I could connect to the pellet stove so my wife could keep the house warm until I got home from work to hook up the generator. I think the pellet stove draws about 200 watts. How would I know a good UPS from a bad one?

 

[Dargo]

Oh, while we are mentioning UPS and such I thought I'd mention what worked and what didn't work when I got a huge power surge. My two main computer systems on APC UPS systems survived with no issues at all. The computers, monitors and printers plugged into the APC UPS units received zero damage. If you have a Belkin surge protector you are just fooling yourself. Everything I had behind Belkin surge protectors got destroyed. They didn't protect at all. If you believe Belkin will pay on their "guarantee", just try calling them on it. They don't pay. It's almost like their guarantee is void if you had a power spike, which leaves me wondering why they call their items "surge protectors". While calling repair places each and every last one said that the APC brand of UPS are the only ones they see as working every time.

I wish I'd known this before I had the huge power surge! With my APC units I have the software that allows me to select the sensitivity and voltage ranges that are allowed to pass through. They also keep logs showing me how often and why they kicked in. I am always surprised at how often they kick in due to "electrical noise" even when I have no known power problems. That usually happens several times a week. I know APC units are expensive, but after I get past this terrible experience I am going to buy several more. If you have a big screen TV you better consider one. State Farm, like most insurance companies, now will only pay a maximum of $1000 for any TV that gets destroyed. Try to replace a high quality 52" 1080p 120hz LCD or plasma set for a thousand dollars. In general, you're gonna come up a couple grand short. Take that a couple of times and it makes the cost of the APC units not sound so bad.

 

[whistlepig]

Dargo,
That's good information on the surge protectors. I agree with you. Spending a few dollars more for the APC surge protectors would be worth it.

 

[BobRip]

Not to disparage others comments, but I have been running my computer (laptop), TV, radios, telephone, modem, and etc. off of my 5kw generator for many hours (100 or so) with no failures. Maybe I was lucky. Of course the laptop has it's own battery, so maybe that protects from the drop outs. I noticed that the Northern 5Kw generator had a graph with it and bragged about the good sine wave it put out. I wonder if it is better than some. I did see a major dimming of lights and shrinking of TV picture when I start my 1.25 HP well. I won't do that again without turning off stuff. But no damage occurred. The well takes a long time to come up to speed, so it drops the voltage from many seconds. What I am saying, it that the damage is not guaranteed. Of course with a high dollar furnace you want to be careful. I am thinking that the electronics on your furnace may reduce the surges that it generates on start up. This is called a soft (for slow) start. Talk to your furnace manufacturer. They might know something and can make recommendations.

 

[George2615]

Not to disparage others comments, but I have been running my computer (laptop), TV, radios, telephone, modem, and etc. off of my 5kw generator for many hours (100 or so) with no failures. Maybe I was lucky. Of course the laptop has it's own battery, so maybe that protects from the drop outs. I noticed that the Northern 5Kw generator had a graph with it and bragged about the good sine wave it put out. I wonder if it is better than some. I did see a major dimming of lights and shrinking of TV picture when I start my 1.25 HP well. I won't do that again without turning off stuff. But no damage occurred. The well takes a long time to come up to speed, so it drops the voltage from many seconds. What I am saying, it that the damage is not guaranteed. Of course with a high dollar furnace you want to be careful. I am thinking that the electronics on your furnace may reduce the surges that it generates on start up. This is called a soft (for slow) start. Talk to your furnace manufacturer. They might know something and can make recommendations.

Bob,
Its not the items you mention that cause problems running on a generator since they don't draw a lot of current. What causes problems is when a high current device such as a 220V well pump, freezer compressor, refrigerator compressor, or A/C unit come on they create a large current draw on a generator. A compressor from fridge/freezer/AC can initially pull over 20A on start up. Add that to the load the generator is already supplying and it causes an overload for a 4K unit. If the generator is not large enough to handle that load the output voltage drops below where it should be which is what you saw as major dimming of lights and TV picture shrinkage. Had your freezer or fridge started as the same time you would have probably tripped the 20A breaker on your Generator.