240v - 12v downlighter transformerkeeps blowing.

vinpug · Jan 31, 2012

Hi,

I have replaced this twice and they have both blown within a few minutes of fitting. There are 3 lights on the circuit each with their own transformer and a dimmer switch. This installation has been up for 10 years with no problems till now, the other 2 lights are fine. 2 transformers blowing one after the other seems a bit of a coincidence and I was wondering if anyone has any ideas? Thanks.

Marvo · Jan 31, 2012

Are the transformers electronic or inductive wire-wound?

Might sound obvious but have you checked the fuse in the transformer, especially on the secondary side?

ruston · Jan 31, 2012

Is the rating of the new transformer the same as the original one. And have you done anything that may have increased the heat build up on that tx?

vinpug · Feb 1, 2012

Marvo said:
Are the transformers electronic or inductive wire-wound?

Might sound obvious but have you checked the fuse in the transformer, especially on the secondary side?

Hi Marvo, Thanks for replying so quickly. It is inductive. there is no fuse as it is a sealed unit.

vinpug · Feb 1, 2012

Hi Ruston,
I didn't expect a reply so soon, thanks for that. The original tx was a JCC model JCLVEL60 primary 240v - 60va, secondary 11.6v max - 4.9a and the replacement is a Halolite model HA-560TA Primary 240v - 0.26a, secondary 11.4v - 5a, both dimmable.

Marvo · Feb 1, 2012

When the transformers 'blew' was it the primary or secondary side that failed?

If the transformers are wire-wound and they're only feeding a single lamp each then there's really no reason I can see that would cause failure apart from a short on the wiring between the Tx and the lamp itself. It could just be coincidence but to play it safe if you fit another transformer maybe add an in-line fuse on the secondary side. Also maybe fit a new ceramic lamp and lamp holder just for good measure.

Just as an after thought I googled the halolite transformer and I see they're only available on e-bay. I'm not sure that this is a good thing, I couldn't find any comments on them from independent sources. Maybe try a recognizable brand name transformer from a local wholesaler unless another member on here who's from the UK has something good to say about them.

ruston · Feb 1, 2012

I agree with Marvo, check the wiring to the lamp holder as well as the holder.

What was the circumstances of the original failure, and did the lamp fail at the same time.
The reason I asked about heat build up is that some transformers have a one shot thermal cut out if they overheat.Eg insulation stopping airflow, or the TX to close to the lamp.
although the TX you got is dimmable it may not be compatible with the dimmer you have.

Use a good quality lamp (Sylvania/Osram) and transformer from a reputable Wholesaler.
12 volt holders take a lot of stick and may of damaged the elv wiring too.