# Bulb lifespan problem

Discussion in 'Landscape Lighting' started by lightsaber, Dec 3, 2005.

1. ### lightsaberLawnSite Memberfrom upstate nyMessages: 16

can you get ushio on the web anywhere don't know if I have seen them at any distributors.

Thanks for the input

3. ### steveparrottSponsorfrom Tampa, FLMessages: 1,255

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.

4. ### NightScenesLawnSite Silver MemberMale, from Kingsland, TexasMessages: 2,209

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.

5. ### ShepDogLawnSite Memberfrom MarylandMessages: 18

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!

6. ### steveparrottSponsorfrom Tampa, FLMessages: 1,255

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.