back up generator

grousedogtom

Looking to buy a second hand diesel generator to power house when esb fails something about 8/9 kva,is there anything in particular i should look for as voltage regulator etc etc.

Stoner

you could search the forum here, I don't really know much about small units, but i do remember some good posts here before, someone recommending a Honda all in one unit, have a search back.

Mike2006

I purchased a 3kW petrol generator from Aldi for €200 and it is a super job.
Plenty to keep my lights, fridge freezer and tv and a few small bits going if/when the power fails.
Put in a 100A rated changeover switch.

For the amount of time that it will fail I didn't see the payback in an expensive diesel unit.

btw, if you have an oil boiler, it probably will not like the generator power so it won't work.

Mike.

Tim.Bunce

Mike2006 wrote: »

btw, if you have an oil boiler, it probably will not like the generator power so it won't work.

Ah, that's useful to know. Thanks.

Why is that? Is the power too noisy?

I have a small UPS at home. Would that clean up the supply enough to keep the oil boiler happy?

I saw a comment elsewhere that a "regular, cheap UPS most likely won't accept cheap generator as power source". Mine is an APC SU700 700VA. Too cheap?

Tim.

Randyleprechaun

I'd go for a Honda powered 3.5kVA generator, will provide enough power for the vital stuff.

Put in a good changeover switch and put a small indicator light in parallel with the ESB mains so that you'll know when the mains is back. You could have a switch on the indicator light so that it's not always on when ESB is healthy.

That's how I've done my own.

Alternative generators would be the ALDI or B&Q ones of 2.5 to 3.5kVA. Good value to be got there

PrismES

I would be careful about running any sensitive electronic devices from a generator supply, any variation in the frequency of the supply can fry power supplies in minutes.
Was recently involved in upgrading a supply to the laboratory of a hospital. The hospital hired in a 50kva genset as there where some machines which must be kept operational, the generator proceeded to fry one of the machines valued at €250k.

Tim.Bunce

Ouch!

I understand the need to use something like a UPS to smooth out the supply for electronic gear. My question at the moment is whether my specific UPS would be happy enough with the supply from the generator. I'll do a tech support request with APC and see what they say.

Tim.Bunce

It turns out the question is answered in the APC support pages:

ISSUE #1: The Back-UPS product stays on battery power while attached to a generator:

This is generally due to the generator being undersized. To prevent voltage distortion and complications with a UPS, the generator must be selected so that it will supply the peak current required by the computer load, not only the average current. It has been determined experimentally that this typically requires that the generator have a rating at least 3 to 5 times the rating of the entire load to be connected to the generator. However, due to wide differences in output impedance for generators, it is not possible to specify an oversizing factor that guarantees compatibility with all systems.

SOLUTION: The only solution would be to use a properly sized generator.

ISSUE #2: The Back-UPS product keep transfering on line to on battery power:

Using non-linear loads with a smaller generator will result in the output waveform of the generator to be very distorted. This distortion will most likely result in the Back-UPS product frequently transferring back and forth from On-Line to On-Battery.

SOLUTION: APC reccomends that Back-UPS units be desensitized thru their respective software to allow the unit to be more tolerant of voltage distortion and, therefore, make less transfers to battery. All current Back-UPS UPS products support this functionality. Legacy model Back-UPS products (such as the BK series) may not support this functionality.

In most cases, to desensitize the UPS you will need to install the Powerchute software that is included with the UPS. Once the Powerchute software is installed, you can lower the sensitivity from the default setting of High, to either Medium or Low.

M cebee

an 'inverter' generator will do the same thing as sticking a ups in front of sensitive equipment

they're prob a bit more expensive though