Generator with Symmetra

[Anonymous user]

Hi,

I just had a Generac CorePower 7kW generator installed to power a Symmetra RM 6kVA UPS. The UPS will not accept the power from the generator, you can hear it click on and off like it's trying to accept the power but it never comes off battery. I talked to a couple people at APC and one said he has seen several problems with the Symmetra line and generators. He suggested getting a better generator with cleaner output or a different UPS that has input sensitivity settings, the Symmetra does not. The second tech made no mention of any issue with the Symmetra but thought that the 250v that the generator is outputting was too high, when on the building mains it's using 208. He had me change the output voltage to the step-down transformer on the UPS from 208 to 240 when on the generator but that didn't help.

I only have 4kVA worth of power modules in the UPS and only use half that. I've even tried taking all the load off the UPS and reducing to 1 power module, so 2kVA, and it still won't turn on.

What would likely be my problem? Every suggestion involves buying all sorts of hardware (new UPS, new genny, transformers) and just hoping it'll eventually work. I don't want to waste the time and money.

Thanks,
Todd

[Anonymous user]

Excellent news! The replacement Tripp-Lite unit did the trick! I don't know what it was about the Symmetra, must have been too sensitive. If you know of anyone in the Durham, NC area that needs a Symmetra (and doesn't have a generator!) send them my way.

Thanks for all the help!

Todd

[Anonymous user]

Here's some more info. I got out a freq meter and was going to take some more measurements. First I plugged the meter into a regular 110 outlet that's on the same main panel as my APC Symmetra. The readings were all over the map, in the 100's and 110's. I then threw the breaker to my UPS and the readings went rock steady to 60. This is all while not on the generator, just normal building power. Can this be right? It seems the UPS is causing some insane interference to the entire building, I don't know how anything could be functioning if these readings are accurate. I have other much smaller APC UPSs (for a couple desktops) plugged into outlets on the same main panel and those don't seem to cause any interference.

Todd

[Anonymous user]

I flipped the breaker that powers the Symmetra, that's the only thing connected to the breaker. This is in a subpanel from the main panel for the building. The subpanel was added to move circuits to that we wanted to protect with the generator. I then tested with the frequency meter on random 110 outlets throughout the office that are connected to the main panel (the one the subpanel is fed from). When the UPS was connected to the mains I would see different frequency readings from each outlet. One would vary between 100-110 Hz, another 65-75, another 80-90. As soon as I flipped the breaker off/open for the Symmetra all the outlets I tested dropped to a steady 60 Hz.

So all this testing has nothing to do with the generator, but seems to be identifying a possible problem with the UPS. I called APC and they say this is definitely not normal and they would have the electricians that moved the UPS circuit off the main panel and into the new subpanel check the wiring. What could possibly be wrong with the wiring to cause this? The Symmetra reports no errors and the other devices in our office seem to be fine. The Symmetra also reports 60Hz in and out when on the mains. But it seems to me it's causing all sorts of back-talk interference, which I would imagine could easily mess with the generator regulator enough to not allow the UPS to come online when on the generator.

Todd

[Anonymous user]

OK here's some more info. I wired in a 110 outlet into the generator panel so I could test a smaller 110 UPS I have and the resistive load idea (I read that adding load helps stabilize the generator output). When on the generator with both the big Symmetra trying to get back online and the smaller Back-UPS 1500, neither would go. The very second I flipped the breaker to the Symmetra the smaller UPS came online. This test combined with the odd frequency readings tell me there is something wrong with the Symmetra and it's causing interference. Thoughts? I didn't even have to mess with the sensitivity settings on the small UPS.

Since I had the 110 outlet hooked up I removed the smaller UPS and plugged in a running toaster-r-oven to act as the resistive load. The Symmetra still wouldn't come off battery. I then added a small microwave (and started it) and that didn't help, either.

Does anyone disagree with my conclusion that my problem is the Symmetra UPS? What could be wrong with it that it would function fine but seemingly have this odd frequency problem?

Thanks,
Todd

[Anonymous user]

Meter is a Cornwell ES-C585 that the mechanics in our garage use. Couldn't find a whole lot of info on the web about it, but appears to be a $150-$200 unit. Unfortunately, I don't have another meter to test with. Even if the meter isn't entirely accurate, it still tells me there's some type of distortion going on when the UPS is on the mains.

Todd

[Anonymous user]

Well it looks like all the frequency problems may have been a wild goose chase. I got a hold of a Fluke True-RMS meter and it shows no major distortion like my other meter did. But the fact my original meter showed some kind of difference between when the Symmetra UPS was connected and wasn't tells me there was something going on, maybe not as extreme as I thought. And the fact I couldn't get the smaller UPS to come online with the Symmetra on the generator tells me it was creating some form of interference. At this point I'm at a loss of what to do. I think my only economical solution is going to be to try a different UPS, clearly some models are compatible with this generator.

I'm also still a little confused on the online (double conversion) UPS type versus the standard line interactive. Some things I read says the online type has the best chance of working with a generator. But then I also read that this type of UPS does inherently create some noise on the lines and can interfere with a generator. Seems to me a line interactive type would be the better route. Clearly the online one I have doesn't work. So what do you recommend to try for a UPS?

This Tripp Lite unit looks pretty good:
http://www.tripplite.com/en/products...xtModelID=3824

This is a comparable APC unit:
http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SMT3000RM2U&total_watt s=2000&tab=features

The Tripp Lite has a greater capacity, especially when hard wired. But the APC specifically states it has some input tolerance adjustments. Granted, I didn't need those with my other smaller units that worked, but it would be nice to have some options in case it doesn't work out of the box. The Tripp Lite may, just doesn't say so specifically.

What do you think?

Thanks!
Todd

[Anonymous user]

Do you think I'm wrong to be looking at regular line-interactive units as opposed to the generally recommended online/double conversion type? I'm hesitent to get another online unit given my experience with the Symmetra on the generator. The only ones I've been able to get going have been the basic line-interactive type, granted they were much smaller units.

Decisions! Decisions!

Thanks,
Todd

[Anonymous user · Accepted solution]

Well I had to bite the bullet and do something so I just ordered this guy:

[http://www.tripplite.com/en/products/model.cfm?txtModelID=4210|http://www.tripplite.com/en/products/model.cfm?txtModelID=4210]

I called Tripp Lite first and they said they've spec'd many of these units for generator applications without issue. I was just too hesitant to buy a line interactive unit since it doesn't provide the same line filtering the online units do, I really don't want to run my equipment direct from the generator.

I'll report back in a few days when I know if it works or not!

Todd