Diesel generators & UPS

[wudisc]

We've got a small office where both LAN & WAN access are crucial to stay productive. We need a solution that will provide us power through the 150 minute blackout window - our UPS's only get us through about +/- 20 minutes.

TDP for crucial infrastructure is less than 1000W (modem, headless PC running PFsense, PC acting as server, switch, wireless router, VOIP base station).

I've read a few articles that advise against powering computers directly from a generator - is this still true (most of the sources are old, like 5+ years)?

If still true, can I use a 1100VA UPS as an intermediary? And if not, what alternatives are available?

 

[xumwun]

As long as you don't get some cheap rubbish generator it should be fine.

 

[CriticalConsumer]

Do not connect a PC or other sensitive IT equipment to a generator. Rather connect a UPS to the generator (to assist in charging the battery). Then connect your equipment to the UPS. The UPS has surge and filter circuits to take care of spikes generated by the generator so that it does not impact your clean power to the IT equipment.

The UPS you should use is around 1200VA resulting in around 1kW of power. The kicker will be the deep cycle battery size and price associated. A typical high end 100Ah battery will be in the region of R6k for a deep cycle long life. You will also have to ensure that this is wired into the existing infrastructure or you will end up using many multi-plugs.

 

[Sinbad]

Make sure your generator has AVR (automatic voltage regulation), and yes, run it through the UPS. So UPS cleans both your municipal and generator power, and provides bridging time for when you switch over.

 

[xumwun]

Only if it's an online UPS.

 

[CriticalConsumer]

Only if it's an online UPS.

Yip it should be an online UPS.

 

[wudisc]

Thanks all - you'll have to excuse my ignorance, I'm not too familiar with all the terms.

We have a 650VA UPS from APC which supposedly has AVR, from what I've seen this won't power our equipment through the intermission of blackout to generator.

We're thinking of getting one of these:
http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=BX1100CI

This has AVR (not sure if this the same as 'online'?).

Any brand of generator you guys would recommend? Budget is tight of course (like Eskom after bonuses - sorry, I had to get at least one punch in).

 

[ponder]

We have a 650VA UPS from APC which supposedly has AVR, from what I've seen this won't power our equipment through the intermission of blackout to generator.

You will need a 10 000VA ups to carry a 1000W load for 150min.

 

[Sinbad]

You will need a 10 000VA ups to carry a 1000W load for 150min.

VA rating does not relate to run time. It is power not capacity.
You just need big ass batteries, not necessarily a high power inverter.

 

[Sinbad]

Only if it's an online UPS.

Line interactive is good enough Imho

 

[CriticalConsumer]

Look at the runtime graph for the product you linked to:



I don't think that this will meet your load requirements for the time you want to run this unit...

I have solution which I use but it's not cheap based on the battery capacity and size. Come with a kick a$$ inverter module capable of handling the load you are referring to and the runtime.

 

[bruce_the_loon]

What UPS setup do you have at the moment? If the UPS kit can run your computers for 20 minutes, then you should be able to get away with just adding a generator of appropriate size and get it plumbed into your main DB via a manual changeover switch. You might have to restructure the wiring for it to work properly. I assume you have one or more UPS with the computers plugged directly into them?

If you get a generator that can provide all your power requirements, including air-con, fridges, lights etc, then you can changeover between the main breaker and the DB itself. If you only want to power the computer hardware, then you need to get all the UPS's connected to a dedicated section of the DB and install the changeover switch to power only that section of the DB.

The proper solution though is to have a single UPS fed from the changeover switch and feeding a dedicated DB that all the computer plugs are wired into. That requires significant rewiring if you don't have such a setup already.