Need advice on commercial generator for animal hospital


Apr 29, 2005
So my animal hospital customer notified me that they want to install a commercial generator to power the entire facility.
The facility is what I would consider large. Two floors and maybe 50 employees in the building. Large OR, labs, etc.

The contractor contacted me and said they need suitable UPS units for the servers to protect them from dirty power.
The dirty power meaning surges and voltage/frequency varying out of normal AC specs.

Such UPS units need to be "dual conversion" with the low end being about $640/unit.

I told the contractor that protecting IT infrastructure only starts with the servers.

What about routers, switches, workstations, VOIP phones, diagnostic equipment (X-Ray and digital biological diag equipment)?

He said he didn't know about any of that, he just recommends high end UPS units for the servers.
To me that's a very incomplete answer and a dangerous attitude.

I asked him about a better generator or separate whole facility power conditioning equipment and got no answers.

Any of you guys have experience with this stuff?

I don't know the KW rating he spec'ed out.

To me it makes more sense to install power conditioning right with the generator and not do a hodge-podge of dozens of
expensive UPS units. For you guys with experience, does that make sense?

Any recommendations on a commercial generator (say 50KW 3-phase) that provides clean power suitable for electronics?

I will ask my son he's an electrician on some big projects and may have some recommendations. I'm assuming it will be natural gas powered and not diesel right?
If that building has significant HVAC, I don't think 50kW is going to cut it. I've hit overcurrent limits on my 35kW whole house generator (multiple heatpumps running plus laundry and the oven).

But either way, a generator needs time to start up, especially a larger one; if most of the stuff is ok to turn off for a few seconds to half a minute, it may be much less costly to put UPSes on the critical equipment and let everything else turn off and on.

As long as the generator has enough capacity and the loads aren't crazy awful, I'd expect a new large generator to have pretty clean power. You get nasty power out of portable small engine generators because the regulation is poor and there's not much inertia, but something that's got more or less a car engine in it will have inertia to help with transient loads and a modern generator is going to have good regulation because it's not that expensive compared to the overall cost and better regulation makes a better product.

I'm happy with my Cummings, but there's a handful of companies in the business. The quality of installation and maintenance is probably more important than which equipment.
The way I would handle this is to put the decision to the people overseeing/responsible for each machine or machine type. Xray and other business line equipment stakeholders should talk to the electrical contractor individually. Might need to talk to the OEM of the machines about power requirements.

For the IT equipment. Most phones are POE and get their connectivity as well as power from the switch. The switch should be on a UPS same as servers. Desktops should be on a UPS but I don't put laptops on them. Double conversion online UPS units are expensive and I would always have servers and core switches on them. If there are switches outside of the server room or datacenter then that's a grey area for me. If the generator is sized correctly and delivers clean power then an AVR UPS for those remote closets and offices may be fine. I believe it's the THD or total harmonic distortion of the generator output combined with the sensitively of the UPS being used that will determine if it will "like" the power provided. I'm an IT guy and not an electrician.

I can tell you what works and what doesn't in my very specific experience in this area. I have three generators for IT equipment ranging in size from 17-20 KW. One diesel and two natural gas. A $100 Cyberpower 685 AVR UPS doesn't have any issue with the power generated by them. There are six double conversion CyberPower UPS units that have no issue as well. At home I have a 11 KW portable Westinghouse generator. The same $100 Cyberpower AVR unit and a $300 APC Backups Pro AVR will not charge off the power regardless of load or sensitivity setting. They will cycle on and off every few dozen seconds and eventually be depleted, shutting off.
Thanks for the good comments and advice guys.

I told them that HVAC was a concern as well.

Don't know if the gen in question is NG or diesel, but I suspect it's NG. The guy provided me zero info on it.

>> They will cycle on and off every few dozen seconds and eventually be depleted, shutting off.

That's exactly how the generator vendor brought this up to me. He said the existing UPS units would be constantly switching
between generator power and battery power and it would trash the batteries quickly.

I told him and the customer that if it's doing this to normal UPS units, then the generator power is not suitable to run any electronics.

As of right now, one of the docs at the hospital said the project is scrapped. He said it's getting too expensive and too complicated.

I asked the vendor to look at better generator models that have cleaner power and he said the original one he specified is the only
one that they install. I also asked him about separate power conditioning (whole facility) and he wasn't interested in that.

I asked about liability from the vendor to replace any damaged equipment. No answer on that either.

To me, this attitude from the vendor is unacceptable. The customer is upset that he said nothing about protecting all of
their equipment other than servers. They have all kinds of expensive equipment, X-Ray being only one of them.
They have sensitive diagnostic lab equipment, a system to track and dispense narcotics, etc.

I feel bad that the whole thing looks to be cancelled now, but they came to me for advice and I gave it to them.
I couldn't sign-off on this project the way it was presented.

We have a Generac 100kw unit that runs on natural gas, the server racks have APC server rack UPS, all computer workstations have APC UPS.