Fluorescent lights and relays

[Ken77]

Hi all,

I've just been to test a number of faults and have found a number of classrooms have relays on fluorescent lights? Can anyone think of a logical reason why someone would have installed them like this?

Thanks in advance.

 

[Deleted member 72666]

So that they can be switched by timers and or photo cells perhaps.
How many lights to each cct, relay/contactor?

 

[Pete999]

What he said^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 

[Ken77]

Depending upon the classroom there are between 4 - 8 twin 5ft tubes per relay.

I can see any evidence of a timer, (not to ay one does not exist).

 

[Deleted member 72666]

Depending upon the classroom there are between 4 - 8 twin 5ft tubes per relay.

I can see any evidence of a timer, (not to ay one does not exist).

Are there any occupancy sensors?

 

[Ken77]

None that I can see.

 

[Jonspark]

isn't there anyone available to ask how there controlled?

 

[Ken77]

Currently controlled via a 1 gang switch - which is why I can't see the point of the relay.

 

[davesparks]

Are they all on the same circuit ?

 

[Jonspark]

its normally like that if the design current is too high for the switch, so this way the switch only carries the load of the relay

 

[Ken77]

I haven't yet determined if all the classrooms are on the same circuit, but there is a relay in each classroom. What where you thinking?

 

[Jonspark]

the load is distributed through the relay instead of the switch. how many channels on the relays are in use?

 

[Ken77]

1 channel

 

[Jonspark]

will the switch take the load?

relays could have been used for future expansion.

 

[Deleted member 9648]

Could be linked to an alarm system to switch on the lights if there is an alarm. ie the security alarm.

 

[Marvo]

Is the relay coil LV or ELV?

 

[Jonspark]

you can't be looking at more than a few amps per circuit and if their controlled by a suitably rated switch can't see the point in relays really

 

[Jonspark]

Could be linked to an alarm system to switch on the lights if there is an alarm.

is there another circuit that energisers the coil

 

[Ken77]

Nor can I. I was trying to understand why this may a have been done as I am not familiar with use of Relays. Thanks for all the help.

 

[Jonspark]

trace out what energisers the coil/whats connected to A1/A2

 

[Ken77]

I'll give that a try. Thanks again

 

[GEOFF S]

Well as a rule of thumb, you will only get 10 x 58W on a 16amp contactor.

Cheers

 

[Clive P]

Hi,

I've fitted them before, where this an external light sensor that switches lights off if the ambient light is good; but you can bypass this by switching the lights off/on at the switch. This was done as an energy saving measure, it's not always necessary to have lights on all the time.

Regards.

 

[davesparks]

Well as a rule of thumb, you will only get 10 x 58W on a 16amp contactor.

Cheers

Surely that will depend on the contactor?

 

[R G]

I worked on a few schools about 3 years ago , where we fitted Pirs through the carbon trust scheme and had to put relays in if there where 6 or more twin florrys in use , also installed relays several years ago to protect the contacts of the switch when switched of due to the back EMF ....

As already said , trace the switch feeds to the relays to where they go to..

 

[Deleted member 72666]

It could be that there's a gang of master/key switches near the entrance so the caretaker can make sure none of the lighting is accidently left on.

 

[GEOFF S]

Surely that will depend on the contactor?

To a degree, i doubt they would be vastly different.

Cheers

 

[Charlie_]

Specific lighting contactors are good for their ratings..
i.e. A 20 amp lighting contactor is rated to 20 amps for resistive, magnetic and tungsten

 

[davesparks]

To a degree, i doubt they would be vastly different.

Cheers

They can be vastly different, the switching duty will make a big difference, one which can handle heavy inductive loads will cope with a lot more fluorescents than one only rated for resistive/light inductive loads.

 

[GEOFF S]

They can be vastly different, the switching duty will make a big difference, one which can handle heavy inductive loads will cope with a lot more fluorescents than one only rated for resistive/light inductive loads.

Well the schneider 16amp contactor states 10 x 58w fluorescent, do you have an example?

cheers

 

[GEOFF S]

Abb do a contactor A26 45amp (high rating than the schneider) with a 25amp CB, and that can handle 35 X 65W. I was referencing a 16 amp, do you have one in mind Dave?

Cheers

 

[Marvo]

Check out the IEC utilisation code on the device. It will usually rate the switch contacts AC-1 linear load to AC-4 motor load, the ratings will be between AC-1 and AC-23. http://support.automationdirect.com/docs/iec_contactors.pdf