UPS on light circuits

uksparks · Jan 27, 2016

Hi,

I have not thought this through yet so don't give me stick yet.

I was just thinking of putting emergency lighting around the house as saw some really slick little LED things which are very discrete, anyway, it made me think, well why not just stick a UPS supply next to the consumer unit to feed a or many light circuits??

Like I say, I have not thought this through yet, but was thinking of using something like a 11 pole relay so you can switch live, neutral and earth.

So you would have a relay which is normally open and the mains grid supply would hold it closed, when the grid dropped out, it would switch to the UPS supply.

The grid would go from the consumer unit, via the RCBO, through the relay and out to the lights, the UPS supply, would be powered from one of the light circuits, the load side of the UPS which would be the offline supply for the lights so to speak, this would then go back into the enclosure via a 30mA RCD.then onto the relay to the light circuits.

Now the only thing would be, at present, lets take three light circuits for example, they are all standalone separate circuits with RCBO's, if i connected them to relays, maybe through in an MCB inline with each for good measure, im just thinking, they will all end up common back one on RCD unless i put at RCD or RCBO on each light circuit and didnt feed the UPS from one of the light circuits, but an MCB on its own.

I guess i would link out all the A1 - A2 terminals to pull each contactor on, so they are all piggy backed off each other so they all switch together.

Can anyone see any issues with this? The other thing i was thinking was what about if the grid was still on and the lights tripped say? would it be a problem running the lights off a UPS whilst the rest of the house is on the grid?

I appreciate UPS supplies are more designed for computers and the like, but I also don't see the problem in doing this.

The other thing i was thinking, would you switch the earth as well? or not? Not sure where the earth would come from if i did switch it to the UPS? Presumably its common with the Neutral?

What do you think? I know it sounds crazy.

shanky887614 · Jan 28, 2016

marc8 said:
like the link #4,
I know the guy is using at he says for power cuts ECT, but on a dual rate elec meter eco 7 or 10, charging up during the cheap rate & then discharging during the expensive time does look good don't know what the losses would be if any. but hell of a project

could use solar panels on your roof to charge the batteries and a charger to top it up the last bit at night

uksparks · Jan 28, 2016

right ok, here goes, well as you hopefully know, I fitted a Hager Invicta 3 board in my house... See photo below for circuits to show what I mean.

What I am going to do is put everything on L1 that I would like to have UPS power, so basically if i put all the light circuits on L1 and maybe the alarm too, then the incomer at the bottom, remove the link to L1, so the Grid only feeds on to L2 and L3, that means there will be nothing on L1 ok.

So, what I then propose is to have an MCB on L2 in the board feed a wall mount UPS supply of say 3000VA and the load side of the UPS connect to L1 in the bottom of the main switch.

So basically all the light circuits are still independent of each other in terms of earth faults etc, but L1 is ok fed via the same supply, but all the circuits will be via the UPS, so in the event of power failure all L1 circuits will remain running.

No need for contactors or relays etc, this is much better and simpler, and if i was to switch off the main switch, everything will be dead. I see this to be the easiest, safest and most compliant option as the circuits will all be running via the UPS as if they were plugged in the back of it essentially.

as for the earth and neutral and earth, this is where I am not 100% sure, I can take the line from the load side of the UPS and connect it to L1, the earth, I suppose just connect it back on to the earth bar, and the neutral, I can't see it doing any harm putting it back on to the neutral bar?

I don't know though, does that sound ok with the neutral?

Reason for doing this is... Ok we hardly every get a power cut, but I want to be the one house in the street that has all its lights inside and out on like a beacon when the rest of the estate is in darkness!

Its not going to cost a great deal of money for a UPS as thats all I need as have everything else.

[ElectriciansForums.net] UPS on light circuits

I would just need to move a couple of circuits around so that only lights were on L1.

davesparks · Jan 28, 2016

I'd want to know a bit more info on the output of the ups before common Bing up the neutral!

uksparks · Jan 28, 2016

thats my problem, I don't know what it would do or how it would be have etc... Ill be honest, I have no idea.

On one hand im thinking, well the neutral is the same neutral I would think....(i think) and its just the line thats cut and fed maybe?

The other hand says I have no idea?

Im guessing here...

davesparks · Jan 28, 2016

uksparks said:
thats my problem, I don't know what it would do or how it would be have etc... Ill be honest, I have no idea.

On one hand im thinking, well the neutral is the same neutral I would think....(i think) and its just the line thats cut and fed maybe?

The other hand says I have no idea?

Im guessing here...

Guessing is no good, you need hard facts! Get researching or get a ups and test it.

Worst cases could be a constant circulating current through the ups or significant constant nuisance tripping of the rcbo's

shanky887614 · Jan 28, 2016

it would be better if you routed all the circuits through another board otherwise it wont comply.

it will be no differnet than linking a genny to the grids neutrel and earth

davesparks · Jan 28, 2016

shanky887614 said:
it will be no differnet than linking a genny to the grids neutrel and earth

How so?

shanky887614 · Jan 28, 2016

davesparks said:
How so?

or are you thinking of putting a tpn changeover switch with the ups only on one phase?

uksparks · Jan 28, 2016

shanky887614 said:
it would be better if you routed all the circuits through another board otherwise it wont comply.

it will be no differnet than linking a genny to the grids neutrel and earth

How would it not comply? Surely if it is labelled accordingly it would be ok?

I was just thinking, I wouldn't need to link the neutral to the supply neutral, I could just disconnect the neutrals from the main neutral bar and put them into to their own isolated neutral bar that only goes via the UPS.

The earth I would still connect to the main bar though.

davesparks · Jan 28, 2016

shanky887614 said:
or are you thinking of putting a tpn changeover switch with the ups only on one phase?

I'm not thinking of doing anything with it.
I want to know how this would be the same as joining a generator N and E to the public supply.

davesparks · Jan 28, 2016

uksparks said:
How would it not comply? Surely if it is labelled accordingly it would be ok?

I was just thinking, I wouldn't need to link the neutral to the supply neutral, I could just disconnect the neutrals from the main neutral bar and put them into to their own isolated neutral bar that only goes via the UPS.

The earth I would still connect to the main bar though.

The plan is getting better, but covering it in labels won't achieve anything.

uksparks · Jan 28, 2016

Maybe I should just put an expansion board on the bottom with the light circuits in with the supply to it from the UPS, that way it's all separate.

do you think that would be better?

i know you say it wouldn't comply the other way, can you point me in the direction of a reg to look at as I'm not sure I can find one as I feel it seems possibly wrong but don't think it is.

i can't see that having in the same board would be a problem but would probably be better in a separate enclosure I suppose.

spark 68 · Jan 28, 2016

uksparks said:
How would it not comply? Surely if it is labelled accordingly it would be ok?

I was just thinking, I wouldn't need to link the neutral to the supply neutral, I could just disconnect the neutrals from the main neutral bar and put them into to their own isolated neutral bar that only goes via the UPS.

The earth I would still connect to the main bar though.

This is a more sensible Idea, but ideally Shankys separate board idea is the way I would do it with the UPS primary supplied from a way in your existing board , with totally separate N and E bars for the UPS supplied circuits

Depending on the UPS they run in at least two different modes, some of the better ones have three modes.

Mode 1 is just in bypass while everything is healthy, Line + Neutral (*leaving the E for the moment)
Mode 2 in UPS mode, when the primary supply has failed, depending on how the UPS is configured, this output can be totally isolated from the incoming supply (both L + N), now to the E, * depending on the type of UPS if it is of the totally isolated type it can switch the out going CPC onto one side of the now fully floating side (ie. the designated out going N) making a pseudo TNC-S (CNE link) system on the output side only, this is to maintain the protective measure of ADS.
As you can see during power failure if you joined the incoming N (main side N) to the out going N (and like wise incoming and out going CPCs) you would be creating a N-E short on the outgoing side of your now dead main DB, and also still be partially connected to the grid which is against regulations when using a backup supply.

Mode 3, some computer type UPS have a so called "brown out" mode or "power clean up mode", this mode is less clear cut, and not all makers will divulge fully how they implement this mode being a "propriety" technology aka selling point, types with this facilities are less suitable for what you have in mind.

Dcf · Jan 28, 2016

I sorted out a bit of a shambles left by some mob with ups supplies for commercial led strips.
i think it was about 300va load each
schneider made the ups which were large and considerably heavy
there were 2 Spurs one for the supply and one for the output if I remember correctly.
the units themselves were about 600mmx300mm
they seem to work similar to an inverter drive with AC in rectified to a DC bus line and then turned into a nice smooth AC out the other end
the led strips were fed through a dmx board with relays and the like but I've no idea how it was programmed .
i think your idea should work but you will be surprised of the size and cost of a decent ups

uksparks · Jan 28, 2016

Spark 68, thank you for this, very informative.

May e putting an expansion board on with the RCBOs for the circuits fed from the ups with its own neutral and earth would be best. That way i know it's separate and will be ok.

The other way is easier but equally this way sounds better and more sensible.

Ill have a look into the UPS supplies and find a suitable one, I don't need a massively powerful one as it's only for lights which are all LED and like now for example only using 36w on one circuit and about 15w on another...

I wonder if I could put a manual change over switch in it too so that I can override the UPS should it go faulty.