MEP-803s and UPS loads

[gatorbob]

Does anyone have good experiences with the MEP-803s and UPS loads? I have 4 of them. I'm hoping someone will tell me they're going to beep periodically and don't worry about it.

A couple of times during testing the MEP with my house loads, my standby APC UPS (consumer grade) will beep indicating the AC power isn't "clean". I don't have any way to tell if that's voltage drop, voltage spike, or frequency change out of spec.

I am pretty sure it happened when my heat pump compressor was starting. I have a soft start kit and am certain I had plenty of capacity. The load before it started was 2kW. Before any of this happened, my CT monitoring system in my garage said my voltage was above 240V and frequency above 60Hz.

I haven't been able to reproduce the problem while watching my CT system or clamp on meters. I am honestly a bit nervous testing with my house as a test load and my DIY load bank testing never showed any problems above 100%.

Does anyone know of a way I can monitor my voltage and frequency remotely or something that will log it?

 

[kloppk]

Some UPS's have a sensitivity setting on them. If yours have it you may want to set them to be less sensitive.

Since UPS's are designed to instantly kick in they will beep when a load kicks on like your heat pump and the line voltage to the UPS dips for a fraction of a second.

They are going to beep occasionally, shouldn't be an issue as long as their batteries can support their load for a second or two.

 

[Suprman]

You need to get an oscilloscope and take a look at the power going to the ups. They can be very sensitive. It could be a slight under voltage issue. Or you are not getting a good sine wave for some reason.

 

[DieselAddict]

I see the same thing. If the AC or well pump kicks on you can see the LED lights flicker and the computer UPS beeps. I don't worry about it.

 

[gatorbob]

You need to get an oscilloscope and take a look at the power going to the ups. They can be very sensitive. It could be a slight under voltage issue. Or you are not getting a good sine wave for some reason.

Thanks. I never thought I might not have a good sine wave. I've only ever used pure sine wave inverter generators in the past and haven't given it a second thought.

 

[gatorbob]

I see the same thing. If the AC or well pump kicks on you can see the LED lights flicker and the computer UPS beeps. I don't worry about it.

Ok, I am not going to worry too much about it. If I can ever get a used oscilloscope at a good price, I'd probably grab one more out of curiosity.

 

[Daybreak]

Howdy,

The best rule of thumb would to adjust the generator running speed (hertz) and voltage regulation to be close to perfect at the point of use.

Using a known good meter, measure your hertz and voltage where the UPS is plugged in. Make adjustments for a good 60Hz and 120v here.

That will be your best baseline to start from.

 

[rhurey]

Large load starting, likely a quick under voltage while the govenor catches up. Wouldn't worry.

Most of my UPS's had no issue with the 803a. The SMC1500 was finicky until I set it's sensitivity to medium instead of high. Waveform was pretty good, but between being near the low voltage line already, and the slight lag in response...

 

[Demoh]

These generators tend to generate a lot cleaner power than 3600rpm gens as they are brushless and have a proper voltage regulator. Not perfect but clean enough for a lot of consumer UPSs. Ive had some not like them, Ive had some not have an issue.

I personally dont own any standby or line-interactive UPSs anymore except 1 (3000VA while I repair it's replacement of a 6000VA). All of my UPSs have been transitioned to true double conversion UPSs where it literally doesnt matter what power you feed it, it will take it. (because they rectify the AC to DC, boost it, then run it through an inverter.) Some ive seen go to 'bypass not available' because it knows the power isnt clean but it still is running as intended.

Basically for the home I would say just deal with the occasional beeps where the UPS flips onto battery and back off a few seconds later for these smaller generators. And if you end up in the market for a UPS, grab a used double conversion UPS off ebay for the same price as a new line-interactive. Those deals exist but we are also talking about 1000va minimum.

Unrelated but: We had a facility I took an emergency call on (nursing home) where power went out. When it came back on missing a leg and the neutral reference was wrong (transformer shorted and L-N on 1 leg was twice what it should have been on a wye system). While the UPS was screaming that something was wrong (it didnt have a neutral) so it had 2 of the 3 phases. It went ahead and used that power to keep from discharging the batteries but at 1/3 of it's capacity due to only 1 of the 3 banks of rectifiers getting power. That would be an extreme case of what is possible.

 

[NATCAD]

These generators tend to generate a lot cleaner power than 3600rpm gens as they are brushless and have a proper voltage regulator. Not perfect but clean enough for a lot of consumer UPSs. Ive had some not like them, Ive had some not have an issue.

I personally dont own any standby or line-interactive UPSs anymore except 1 (3000VA while I repair it's replacement of a 6000VA). All of my UPSs have been transitioned to true double conversion UPSs where it literally doesnt matter what power you feed it, it will take it. (because they rectify the AC to DC, boost it, then run it through an inverter.) Some ive seen go to 'bypass not available' because it knows the power isnt clean but it still is running as intended.

Basically for the home I would say just deal with the occasional beeps where the UPS flips onto battery and back off a few seconds later for these smaller generators. And if you end up in the market for a UPS, grab a used double conversion UPS off ebay for the same price as a new line-interactive. Those deals exist but we are also talking about 1000va minimum.

Unrelated but: We had a facility I took an emergency call on (nursing home) where power went out. When it came back on missing a leg and the neutral reference was wrong (transformer shorted and L-N on 1 leg was twice what it should have been on a wye system). While the UPS was screaming that something was wrong (it didnt have a neutral) so it had 2 of the 3 phases. It went ahead and used that power to keep from discharging the batteries but at 1/3 of it's capacity due to only 1 of the 3 banks of rectifiers getting power. That would be an extreme case of what is possible.

I am looking for a single phase 240v 4-6 kva double conversion true online with bad or no batteries I can put back in operation (run whole house on it) can you recommend any makes or models you see online ?


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[Demoh]

In the 6 - 10 kva range Ive used Toshiba they seem to be decent (they take 21 7ah batteries). Also had some OneAC sinergy II units around that size. I really like the Liebert GXT3 units, but the GXT2 units would suffice even though they are older.

5kva and below the suspects are mainly tripplite. Sometimes Eaton/Powerware but we deal with few of those between 3 and 10kw. Most of our Powerwares are 20-25kva

For the standby / line-interactive type my company normally just installs lowest bidder which is normally APC. I think those are garbage. Whenever I quote a job its never APC because APC 5kw and below is like a cracker jack box UPS to me. If you dont use APC, Genesis, or Yuasa batteries expect the unit to scream at you for bad batteries. Of course I might have 200 in production right now and they work and are affordable.

For failures I have a liebert which is stuck in REPO (unknown condition when acquiring, dont know if fixable or just config), had a OneAC fail on the DC bus / boost area and ended up inadvertently turning it into a firework display (when salvaging it I am very impressed with the construction of it, but its older and may not be as efficient as newer models), have had lots of smaller 1.5-3kva powerware failures (like 80% after 6-9 years on a fleet of maybe 60). Basically stay away from Powerware and APC and you should be fine.

As for the house. You must make sure the UPS outputs split phase. 240 3 or 4 wire input, but the output must be 4 wire. Having the neutral normally drives the cost up but unless you are like me and have 240v everywhere (almost all switching power supplies work from 100-240v) you are going to need the neutral. What I ended up doing was pulling 80 amps off my main panel, to my UPS bypass switch / ups connection box, then feeding a sub panel from there. The UPS connects to the bypass switch both input and output. All of my 120v circuits are moved over to the sub panel as well as my 240v computer circuits. (boxes next to each other with nipples, the ups bypass panel is below both panels). Basically my heavy loads that shouldnt be on UPS are on my main panel and UPS loads on my dual fed sub panel.

For the curious, gen feeds main panel so it trickles downstream from there. Also to be up to code the UPS must be hardwired. No cords / plugs. After looking into it there may be some loopholes but any UPS for this application should be hardwired anyways because 6kva is 50A and that would be the absolute smallest I would go for a house. (just going off what ive seen on nameplates and memory)

Sorry (not sorry) for being long winded, lets just say Im passionate about double conversion UPSs and whenever I am designing a server room I love the UPS and generator side of the design. Most of my designs are in buildings with much bigger generators so the power is pretty clean so double conversion isnt really required. Depends on how cheap the client is though. (75% of all 3kva - 6kva UPSs we install are used/refurb and 100% of all 6kva - 30kva are used).... I signed on to wind down for the night. So much for that

 

[NATCAD]

I’ve sent you a pm
Thanks for all the info


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[gatorbob]

Does this sine wave look right? This is with no load.

 

[DieselAddict]

Yep. Looks typical for a 12 wire alternator in single phase configuration.

If if you put it in 3 phase mode and look again the peak should be rounded a little more.

BUT there is nothing wrong with the overall shape of the waveform. Everything in the house should be quite happy with it.

 

[Demoh]

Yep. Looks typical for a 12 wire alternator in single phase configuration.

If if you put it in 3 phase mode and look again the peak should be rounded a little more.

BUT there is nothing wrong with the overall shape of the waveform. Everything in the house should be quite happy with it.

I was wondering why the peaks were a bit pointed. Care to explain the fundamentals behind that? I mean I understand its double delta and its the sum or difference and some geometry. Or maybe just what I could search for so I could look it up and read for hours when I should be sleeping.

 

[DieselAddict]

To oversimplify it its due to a 3 phase winding setup being connected in series. You are looking at the sum of all the vectors of the three phase coils in the series circuit. There is some cancellation of energy which shows up as a slightly less than perfect sine wave.

To get into the weeds of it might be a bit more than the masses here are interested in. If you remember vector derivatives in calculus this will feel familiar.

 

[USAMilRet]

Man I hated calculus. All portions of all three courses. Of course after that there was even more math......well, it's mostly theory with calc 3 and beyond. Differential equations.......what a headache that was.

 

[Demoh]

I regretted not going past half a year of calc 1. I was the kid who took took 2 maths in a year just so I could take calc 1 my final year in highschool. Had some life events which caused me to drop it though.

I might self teach myself in the future but I barely have time to grab lunch, let alone anything else.

So basically what you are saying is that double delta single phase is better than zig zag for wiring up a 12 wire? 1 leg has some lost energy (the 120degree and 240 degree legs in series) where the straight leg wouldnt have the same effect which means the L1 waveform and L2 waveform are different? Well at least thats how I conceptualize it. I have been pondering this for a few years but havent gotten the scope out or done the research yet.

 

[DieselAddict]

You're on the right track but here is the kicker, a double delta is not better than zigzag in these generators because a double delta allows for a series parallel operation of the coils and what that does is any phase imbalance is converted to circulating current in the coil's. This leads to heat generation and energy that is not usable outside the generator head. This means you have to derate the generators output more than what happens with zigzag. At least with a zigzag configuration the energy is not actually wasted as circulating current since everything is in series. It only manifest itself as a slight deformation of the waveform.

Since the waveform is slightly deformed and steeper it will create a little higher average current in inductive loads. We're talking a couple percent. Nothing to worry about.

Compared to a big box store generators these things make really nice power. We are really being nit picky and the discussion is more theoretical than impactful in actual conditions.

 

[gatorbob]

Yep. Looks typical for a 12 wire alternator in single phase configuration.

If if you put it in 3 phase mode and look again the peak should be rounded a little more.

BUT there is nothing wrong with the overall shape of the waveform. Everything in the house should be quite happy with it.

Thanks. I was just ruling out what Suprman mentioned (he said check that the sine wave is good). I'll check it in 3 phase mode just to see the difference. My friend with the scope also has one of those little Honda inverter generators and I'll try to check that out as well for comparison.