Thoughts needed - Battery back-up

[rmaynard]

Iv been thinking about a way to keep the lights on during a power cut and have come up with the following idea, it will be mainly used in domestic properties, iv included an automatic change-over, im picking up a ups today and am going to trial it at home, just wondering if anyone has any thoughts or ideas before i go ahead????

 

[Lucien Nunes]

The UPS contains its own transfer relay - why are you duplicating this with an external contactor? That's the whole point of a UPS!

Importantly, you must provide the correct level of isolation between the output of the UPS and the DNO supply using the correct contactor type etc. otherwise it poses a serious hazard to DNO workers in the event of a fault. Wiring some random contactor with an NC contact up to do this probably won't meet the requirements, so if for some reason you need external switching I would suggest buying a turnkey solution that has been type approved for the purpose. But I don't see what purpose it serves.

 

[rmaynard]

The internal relay only handles switching between ac and battery, the reasons I included a nc no contactor was to allow for automatic switching and to isolate the ups from the ccu in the event of a power cut, it has nothing to do with dno as this setup won't affect any isolation

 

[Clive P]

Hi,

I'm with Lucien on this one. A UPS is a UPS and does what it's designed to do. Why the need for a seperate contactor? In the event of a Mains failure the Battery backup would be used for your lighting via the UPS, that's what you are trying to achieve isn't it? Also it gives the correct segregation from the DNO and UPS supplies.

Regards.

 

[Guest111]

Agreed with the above,when wiring an UPS you feed your power in and your load comes out so no need for a separate contactor,you will not need this as when the ups lose it's feed and goes to battery mode there is nothing coming back down the feed cable so no danger of feeding back onto the network.If you have an UPS then just try it on the bench and you'll see what we mean.Wiring wise you power the UPS from your CU then remove L N and E for lighting circuit from CU and feed from UPS via a suitable device to give isolation and overload protection E.G a 1 way CU,just remember to isolate at this point when working on the circuit.