View Full Version : Bulb lifespan problem

12-03-2005, 09:46 PM
Recently have gotten a few callbacks to replace some mr-16 lamps and a couple bipin lamps. These lamps were in from 3-5 months. Voltage is between 10.8-12, hub method, so I am wondering if anything else could be causing premature lamp burnout.

12-05-2005, 01:08 PM
not sure, but if I were you, I would consider using LEDs instead. Never need to be replaced (maybe every 10 to 20 years)

12-06-2005, 06:59 AM
could be voltage spikes in the main line..
the transformer is merely a 10:1 stepdown, so if there is a spike in the incoming line voltage, it will be carried out through the lines.

12-06-2005, 09:14 AM
On the MR16 bulbs maybe someone touched the bulb with a bare hand? The halogens don't like that and can cause a hot spot...causing lower life spans.

BTW...I hardly believe the life expectancy claims of those bulb manufacturers...you shouldn't expect to get the hours they claim on every bulb.

Az Gardener
12-06-2005, 09:39 AM
When a light burns out in a hub system all the other lights in the hub spike which shortens the life if the bulbs. (I don't like hubs) Then you have a domino effect, lite burns out-spike another burns out-another spike. I believe the fewer lights on the hub the bigger the spike too, so as you lose lights you loose the next light faster. Betcha that wasn't in the literature. The way they rate a bulbs lifespan is; get 100 bulbs lite them up if 50% of them last 1,000 hours they have a 1,000 hour life span. Sucks for you if you get the underachievers. Try to lower the voltage, drop down a tap from 13 to 12 or whatever.

12-06-2005, 12:08 PM
I agree about the hub system...I have never trusted it..never installed one either. Those hubs have caused fires in extreme circumstances.....dry pine needles and well lights....using a highvoltage tap and only one unburned bulb left...creates a ton of heat....be careful with the hub system.

12-06-2005, 01:10 PM
Thanks Guys, for the input, Touching mr-16 with glass cover shouldn't create a problem correct. I'm hoping its just bad lamps here and there as I recheck voltages and see no problems. May switch to the 10,000 hr. lamps available.

12-06-2005, 05:07 PM
my bad...some of the halogens are unsealed..mr16 are sealed...and yes, touching them is fine....

Frog Lights, LLC
12-07-2005, 01:33 PM
Some bulbs are not of very good quality and will have a short life. Other reasons are higher voltage, water and dampness from sprinklers and rain. I have noticed if the bulb is not well seated in the holder it will generate heat and fail sooner. Please check the number of hours it is on during the evening, some customers will leave it on all night.

12-14-2005, 04:47 PM
When I first install a job I use only 10,000 hour Ushio MR16 lamps. I used to use the cheap lamps from my distributor and I was changing lamps all the time. NEVER use Satco lamps!!! I balance the voltage to the lamps between 10.8 volts and 11.5. I have had very few problems since I changed to Ushio.

12-14-2005, 05:38 PM
can you get ushio on the web anywhere don't know if I have seen them at any distributors.

Thanks for the input

12-14-2005, 05:55 PM
I'm not sure. Try either www.longhorninc.com or www.terradek.com I believe they can help you out.

01-14-2006, 04:22 PM
Regarding the comment that the hub method is responsible for increased lamp burnout, here's some info you might find useful. I did calculations to find out how lamp voltages will vary with a lamp burnout comparing the hub method to the t-method.

Set-up: With a 75' wire run (to the t-junction or to the hub), of #12/2 wire connecting (5) 35W fixtures. In hub method, fixtures are all 25' from hub requiring use of 15V tap. In T-method, fixtures have 35' wire between each one, requiring use of 16V tap.

Initial voltages: all five hub fixtures at 10.8 volts; t-method fixtures are at (end to end) 10.7v, 11.1v, 11.6v, 11.1v, and 10.7 volts.

If one lamp burns out in the hub method, all other fixtures end up at 11.4v (no problem).

With the t-method, if the center fixture burns out, the remaining fixtures are at 11.5v, 11.7v, 11.8v and 11.4v (no problem).

With the t-method, if one of the end fixtures (in this case, the right end) burns out, the remaining fixtures are at 11.4v, 11.6v, 12.2v and 12.1v (the fixtures over 12 volts are at risk of burn-out).

This illustrates how the hub method effectively equalizes the voltage when lamps blow out.

This problem of voltage increase after burnouts is worsened on long runs using higher voltage taps - a strong case for using 10/2 instead of 12/2 and for positioning additional transformers to make wire runs shorter.

One last note, many contractors put yearly (or every 18 months) complete lamp replacement into their maintenance contracts.

01-14-2006, 04:34 PM
I'm glad that you mentioned using 10/2 wire instead of 12/2. I would never put 175 watts on 12/2 wire. One other thing, any time you use voltage taps above 15 volts, you are no longer in compliance with UL1838.

01-18-2006, 06:00 PM
John Deere Landscapes carries Ushio Bulbs. And I have to reccomend that if you do use a hub system, check your amperage with a clip on amp meter. I have seen 15+ volt taps melt!

01-23-2006, 02:53 PM
Any voltage tap can melt (even 12V). There are only two reasons that I know of.

1. Tap screws are not tightened down on the wire strands. This causes arcing between strands, burning the tap.

2. Some transformers can not carry the full transformer load on a single voltage tap. A popular 1,120W brand only allows 600W on a single tap.

A properly designed transformer will trip a breaker or blow a fuse if the amperage on a single secondary tap exceeds ratings.