Stearn Mini Festoon Lights

[Badger]

Does anybody know the power rating of the secondary side of the transformer for the miniature festoon lights as shown in the photo, they are from stearn on product number 785, need to put the cables to the tree lights and wopndered what size aroured is need to supply 12 sets of these light off one transformer lacted at the base of the tree, with the armoured being 12v ac going to the lights in the tree.

cheers badger

 

[Badger]

anybody ????

 

[Andy™]

anybody ????

quickly checked their site and couldnt find them.

do you know what watt the lamps are and how many there is?

 

[Badger]

theres a 100 on each strand but ot sure of the wattage

 

[Badger]

wondered if anyone had installed them before.

 

[SPECIAL LOCATION]

wondered if anyone had installed them before.

Were all waiting for you to do yours so we don't mess ours up!!! ]

 

[Badger]

no come on lads/lassies help me out if you can, need to know what size supply i need

 

[Andy™]

without knowing the watts of the lamps it almost impossible to give an answer.

assuming 0.5W each, thats 600W. or 50A at 12V

or is 3W each, thats 3.6KW, or 300A at 12V. gonna need a very large cable i think....

 

[ian932]

Might be a daft answer but can't you measure the resistnce of the bank of bulbs then use ohms law to get current once you got that you just mutiply the voltage by current and thats your watts.

 

[Badger]

i could do tbh i hadent thought if doing that :_|

 

[Andy™]

i would have suggested that, but i thought you didnt yet have the lights!

 

[SPECIAL LOCATION]

Might be a daft answer but can't you measure the resistnce of the bank of bulbs then use ohms law to get current once you got that you just mutiply the voltage by current and thats your watts.

not sure that would work correctly...?

e.g. it wont work with 230v GLS bulbs, the resistance changes as it warms up when working with power through it...

I have read anything between 40ohm to 200ohm on 100w/60w/40wbulbs,

which would theoretically give a range of 5.75a to 1.15a for an individual bulb!

or 1300+w & 260+w !!!!

never tried measuring a 12v ac bulb??????

but I got a hunch it wont work..

curiosity killed the cat!!!!

you just got me getting me meter out and reading a 12v 20w Halogen jobbie!

0.8ohm which in theory is 15a which is 180watt!!!!

 

[SPECIAL LOCATION]

If you have a spare 12v transformer with a fairly chunky output..

you could actually power the set up & read the current drawn actually under load.

then calc backward IxV for your power?

 

[Evans Electric]

If you can't read the resistance, what chance is there of ever working out anything ever again. At 12v you could have a drastic volt drop problem in your armoured to the tree, methinks. Resistance is the only way I can think of.

Deke

 

[Andy™]

At 12v you could have a drastic volt drop problem in your armoured to the tree, methinks.

the transformer is at the tree

 

[Badger]

Yes 240v 1.5mm armoured supplied from 6a RCBO to tree, then on concrete base installed yesterday waiting for it to go off will be a transformer then run up tree about 4mtrs to lights

 

[Evans Electric]

If there are 100 lamps on each strand and the smallest I can find are M9 capsule lamps at 12v X 5 watts = 500 watts = 41.6 amps !!! On the secondary side of course, primary about 2 amps.

Blimey they're some fairy lights. !!

Deke

 

[Andy™]

maybe stick to 230v lights next time!

 

[Badger]

yes tell that to the pub

 

[Andy™]

yes tell that to the pub

give me their number then!

and how big is this tree? 1200 lights seems a bit much....