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Hot Patching

Discussion in 'Question of the Day' started by Mayhem, Jan 31, 2006.

  1. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    In the a recent topic ship and I refer to a practice known as "hot patching" and we both (strongly) advise against it.

    Coming from Australia – I hadn’t hear the term before reading here some time ago. This prompts me to ask the following questions:

    1. What does the term "hot patching" refer to;

    2. Why it is unsafe (or, do you think it is safe?) and;

    3. What precautions and steps should be taken to achieve the same end result safely?
     
  2. soundman

    soundman Well-Known Member

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    1. unplugging a fixture or any part of the chain from the dimmer to the fixture while the dimmer is on.

    2. Arcing can occur and will cause carbon build up over time, also an exposed arc is no ones friend.

    3. User training.
     
  3. ship

    ship Senior Team Emeritus Premium Member

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    Wouldn't that than be hot un-patching?
     
  4. jonhirsh

    jonhirsh Active Member

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    I dont know about you but i generaly dont want to see a light go out on deck and then a random light come on in the middle of a scene. Usualy hot patching is dont when the dimmer for the chanel is off. and is coordeinated so that you do not see the switching on stage.

    Hot patching is an accepted way to gain more dimmers for a show its not unsafe. its is also acctepted practice to hot swap gels from fixtures during a show. if they are in the gird and accsessible during the show.

    the only way hot patching could be dangerous to the look of your show is if you dont label properly. so its simple label, label , label.

    JH
     
  5. soundman

    soundman Well-Known Member

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    pluging the fixture back in with the dimmer on. Sorry should have added that.
     
  6. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Well we are getting close to an answer on part one of the question (is it limited to dimmers?).

    Anyone care to discuss parts 2 and 3?
     
  7. AVGuyAndy

    AVGuyAndy Active Member

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    Assuming you mean hard-patching things while the dimmer is on, I do it all the time. But, we have an "old-school" system, 16 dimmers and about 130 circuits. I only do it because it's a long way back to the booth when I'm doing things by myself.

    It's dangerous because you can shock yourself, since conductors are exposed which plugging/unplugging things. I always make sure my hand is towards the back of the connector. And I tell people around me "Don't do that" :)
     
  8. koncept

    koncept Active Member

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    I am not sure what it means to "hot/hard patch" yet. Judging by what has been said I do it on a regular basis. I have never until now heard it is dangerous.
     
  9. propmonkey

    propmonkey Well-Known Member

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    what exactly is hot patching? is it plugging a fixture directly into an "always on" circuit and not a dimmer? or is it jsut plugging a fixture into an "on" dimmer?
     
  10. jonhirsh

    jonhirsh Active Member

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    All hot patching is is when you repatch the dimmers during the show to gain more dimmable circuts.

    JH
     
  11. fosstech

    fosstech Active Member

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    I've heard the term used in both instances...both plugging an instrument into a hot circuit, and switching circuits to dimmers.

    Our old system that is now thankfully gone had 15 dimmers and 66 circuits. All patching was done with these sliders on the wall that would assign each circuit to a dimmer or non-dim (each circuit had its own slider). For load testing we would patch the group of circuits into non-dim 5, which was the 60A non-dim relay that had an ammeter in line. Normally we would just patch them hot right into the non-dim since the meter was at the patch board and not up at the console where the non-dim switch was. Normally this isn't a good idea since the contacts in the sliders could arc and promote carbon buildup which could ultimately result in high resistance, but we did it anyway since we knew we were getting it replaced soon.

    Hot patching (plugging or patching an instrument into a hot circuit) is generally not a good idea for more than one reason. Lamps don't like to be patched like that, the resistance of the filament is different at room temperature than it is at 3000 degrees. Ship can elaborate on the actual figures, because I don't know them. This results in a current surge at the instant the lamp gets that full 120V, which can lead to the breakage of the filament. Ever notice how most of the time when the light bulbs in your house go out, they go out the instant you turn on the switch? This is exactly why. You might have gotten more hours out of that light bulb if it were on a dimmer. The second reason is what I was talking about in the previous paragraph. Hot patching, either with patch cables, sliders, or just plugs on the instruments isn't a good idea because of the arcing that leads to deterioration of contacts.
     
  12. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    OK – now we are getting there and yes, hot patching refers plugging something into a live or ‘hot’ circuit. It doesn’t matter if the power is coming from a dimmer or out of a wall receptacle.

    Now think of the actual process of joining a plug to a receptacle, it is something that we do on a daily basis and most of you would actually have to stand back and think because it is something that most do as second nature.

    Once you have thought about it you will be able to expand further on the dangers.

    Still waiting on someone to tell me what you should do if you want to test a fixture (for example). How would you go about doing it?

    Good work thus far – keep it up.
     
  13. AVGuyAndy

    AVGuyAndy Active Member

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  14. koncept

    koncept Active Member

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    dont we do that every day when ever we plug anything into a standard home outlet such as a light, hair dryer, ect??

    dangers
    - water -if wet location
    - fingers can come in contact with the prongs of the plug

    after readin what has been posted i am going to assume that we should be using a dimmer swtched outlet that way a) the power is off, b) it can be slowly increased so as not to give the lamp full power off the bat.
     
  15. tenor_singer

    tenor_singer Active Member

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    I had a drama student come visit after her junior year of college. She had interned at a playhouse for Pittsburgh and mentioned how they used "hot patching" as part of their lighting design. I thought... wow... this is a possible way to increase my dimmer space.

    I never really got into that practice with high school. Primarily I was concerned about students getting hurt (ie- falling off of the grid as they rushed through a hot patch, getting burned as they rushed through a hot patch...). I find that high schoolers... in their zeal to be good at what they do and to make you proud of them... are prone to speed errors, so I try not to increase their chances of injury by doing something that may cause them to rush around haphazardly.
     
  16. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    koncept - with a hair dryer or a desk lamp, circular saw, drill etc, they have a switch. A PAR can, leko, Fresnel etc does not. Now consider what that means to the circuit created when plugging a switched item into a receptacle versus plugging a non-switched item in.
     
  17. ship

    ship Senior Team Emeritus Premium Member

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    Wouldn't that be re-patching?
     
  18. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Surely we don’t need to give any more hints do we?
     
  19. Diarmuid

    Diarmuid Active Member

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    I don't think this is what you were hinting at, but if the channels were all seperated by different phase power supplys, and you tried to patch between, them, I believe things could go badly wrong, because over here (in the UK) our phases our seperated by something like 419 Volts.

    Also, with a non switched Item, it will start as soon as it makes any form of contact with both live nad neutral connections, so, it may easily give u a large electric shock.

    Also, to test a fixture, I normally just run a continuity test with my multimeter.
     
  20. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Hot patching is plugging an item into a power point that is live. For example, if you were to plug a 1K PAR 64 lamp into a live power socket so that the lamp lit up as soon as the pins on the plug came into contact with the blades is the socket, what bad things could happen?

    Voltage between phases on a 240V three phase system is 415V.
     

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