175W mercury vapor

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nizak

Senior Member
Will a MV bulb "cycle" on and off ? Customer called saying it will stay on for an hour or so, turn off, then re light. My guess is either lamp or ballast, which would be the most likely? BTW owner says lamp is about 5-6 years old. Thanks.
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Dennis,
I don't think that ballasts of that type have thermal protectors. At least I have never seen one that did.
I know that with HPS and MH types of lamps that the cycling of the lamp is a sign of lamp failure. Not sure about MV, but I think it is the same.
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
Couldn't it be as simple as looking at the hour life of the lamp or even the ballast?
5-6 years seems quite a lot of years...

As I've read here most people will go in and replace everything in the encloser!


It's not so much a service to repair "call", as it is a replacement service call... :)

What do I know, I don't do that line of work...
 
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ceb58

ceb58

Senior Member
Location
Raeford, NC
nizak said:
Will a MV bulb "cycle" on and off ? Customer called saying it will stay on for an hour or so, turn off, then re light. My guess is either lamp or ballast, which would be the most likely? BTW owner says lamp is about 5-6 years old. Thanks.
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Usually they will cycle more often than an hour or so but this is the customers description and we all know how that goes;). I would do a complete rebuild and be done with it. You may also find it cheaper to replace the complete fixture than rebuild.
 
kwired

kwired

Electron manager
Location
NE Nebraska
I have never seen a MV lamp cycle on and off at end of life - they usually put out less light as they get more hours on them. I have seen some that still light up but put out less light than a 100 incandescant when they have some age to them.

MH lamps lose some light output as they age but it drops somewhat rapidly at first and then levels off at a certain level until the lamp reaches end of life and usually it just will not illuminate anymore.

HPS lamps draw more current as the hours accumulate on them. They start cycling on and off when they get close to end of life because the amount of current required to continue to operate is more than the ballast will deliver so the arc is extinguished. After a short cool down period the arc restrikes and the cycle starts over. The cycle gets shorter as time goes on because it starts requiring even more current to maintain the arc.

Other things to look for is if this is a photo cell controlled luminaire make sure the photocell is not malfunctioning or that it is not receiving artificial light causing it to turn the controlled circuit off.
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
I live down the street from what I know (is from what the newspaper said) was the most expensive intersection of I-85. I beleive there's HPS not MV but everything was wired in 1/2 PVC and it looks like one circuit(fine I'll give you two circuits)! How can 8 per side and a spared circuit raceway to the other side handle all that voltage?

This is an underpass!

When I go thru routinely two lights maybe three on side are lite, on the other side one will re-light since I'm there? I watched as the they installed it and pondered it all... Did they install it right? Well who am I to say, is it right, I'll say no!
 
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kwired

kwired

Electron manager
Location
NE Nebraska
cadpoint said:
I live down the street from what I know (is from what the newspaper said) was the most expensive intersection of I-85. I beleive there's HPS not MV but everything was wired in 1/2 PVC and it looks like one circuit(fine I'll give you two circuits)! How can 8 per side and a spared circuit raceway to the other side handle all that voltage?

This is an underpass!

When I go thru routinely two lights maybe three on side are lite, on the other side one will re-light since I'm there? I watched as the they installed it and pondered it all... Did they install it right? Well who am I to say, is it right, I'll say no!
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Voltage? the higher the voltage the smaller the conductors need to be to handle the same load. I'm sure you knew this though.

If you had 8 - 1000 watt loads you could easily power them with multiwire circuits @ 277 volts in a 1/2 raceway, or put them all on one 480 volt circuit.
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
don_resqcapt19 said:
Dennis,
I don't think that ballasts of that type have thermal protectors. At least I have never seen one that did.
I know that with HPS and MH types of lamps that the cycling of the lamp is a sign of lamp failure. Not sure about MV, but I think it is the same.
Click to expand...

I have seen this a few times and have always replace the ballast. If it were the lamp I would have guessed that it would start to light and then shut off but not stay lit for an hour. I have learned something new if this is the case.

So I guess I will try changing the bulb next time and see what happens.
 
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nizak

Senior Member
The "hourly" time frame is coming from a homeowner, I guess i can take that for what it's worth.I will need a lift or bucket truck to get to the fixture to replace, changing the lamp can be accomplished with a 28' ext ladder and spotter on the ground. I will try the lamp first and see if that solves the problem. Really should not even get involved, elderly couple(parents friends)who will most likely go into corronary arrest if I have to tell them it's a $300 bill for lift, fixture and labor to replace it. Thanks.
 
C

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
Dusk-dawns aren't worth the cost of troubleshooting. Go up there and change the twist-on photocell and throw a lamp in it. If that doesn't fix it, just replace the whole fixture. Half the time the photocell socket is loose and twisting around when you try and remove the old photocell anyhow, so I always take a new fixture with me just in case.
 
kwired

kwired

Electron manager
Location
NE Nebraska
nizak said:
The "hourly" time frame is coming from a homeowner, I guess i can take that for what it's worth.I will need a lift or bucket truck to get to the fixture to replace, changing the lamp can be accomplished with a 28' ext ladder and spotter on the ground. I will try the lamp first and see if that solves the problem. Really should not even get involved, elderly couple(parents friends)who will most likely go into corronary arrest if I have to tell them it's a $300 bill for lift, fixture and labor to replace it. Thanks.
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You need safety belt like linemen use or fall arrest harness and a positioning strap and you can change the fixture from the ladder. I have probably done hundreds of them that way and all by myself. Tie equipment to a rope and hoist it up when you need it. A helper on the ground does help from needing multiple trips up and down the ladder. This allows you use the positioning strap to hold you in place freeing up both hands to work with. Or you could use pole climbing spikes that linemen use. I don't recommend that without some formal training on how to use them. It is not as simple as it looks.
 
480sparky

480sparky

Senior Member
Location
Iowegia
nizak said:
The "hourly" time frame is coming from a homeowner, I guess i can take that for what it's worth.I will need a lift or bucket truck to get to the fixture to replace, changing the lamp can be accomplished with a 28' ext ladder and spotter on the ground. I will try the lamp first and see if that solves the problem. Really should not even get involved, elderly couple(parents friends)who will most likely go into corronary arrest if I have to tell them it's a $300 bill for lift, fixture and labor to replace it. Thanks.
Click to expand...


Changing out a fixture 30' up on a pole isn't the same amount of labor & tools to change out a lamp in the light over the bathroom sink.
 
ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
kwired said:
You need safety belt like linemen use or fall arrest harness and a positioning strap and you can change the fixture from the ladder. I have probably done hundreds of them that way and all by myself. Tie equipment to a rope and hoist it up when you need it. A helper on the ground does help from needing multiple trips up and down the ladder. This allows you use the positioning strap to hold you in place freeing up both hands to work with. Or you could use pole climbing spikes that linemen use. I don't recommend that without some formal training on how to use them. It is not as simple as it looks.
Click to expand...

A lineman school in NE recentlyhad a trainee die from a fall while learning this pole climbing skill. We have done it from a ladder for years but more & more I start looking for a bucket truck.
 
kwired

kwired

Electron manager
Location
NE Nebraska
ptonsparky said:
A lineman school in NE recentlyhad a trainee die from a fall while learning this pole climbing skill. We have done it from a ladder for years but more & more I start looking for a bucket truck.
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I was talking to one of the local POCO managers today - he said this trainee was one of their interns last summer. From what he understood the guy apparently froze up (nervous attack or something like that) and eventually fell. You would think they would be over that kind of thing if in their second year. I know this POCO makes their summer interns do a lot of pole climbing so it should not have been that new to him. Everyone does a fair amount of climbing but the interns do even more of it.

Of course I don't care as much for climbing around on high elevation equipment anymore, but I'm not 19-25 years old and weigh at least 50-75 pounds more than I did then.
 
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