Wanted: High Voltage DPDT Contactor / Relay

The problem is not the operating voltage of the lamp tube. A MH tube typically operates at ~140V, and an HPS tube typically at ~90V or so.

The problem occurs when the lamp starts - the igniter applies a high-voltage pulse (~1KV for MH, ~3KV for HPS) to the lamp, and this is most likely contributing to frying your contacts.

The other part of the problem occurs immediately after the arc is struck on startup. When the arc strikes, the impedance of the lamp drops to a very low value, and then slowly climbs as the lamp warms up. This means that on startup you get an initial current surge through the relay that is greater than the normal operating current.

One can only wonder why it is easier to dream up this unorthodox method of controlling the lamps, when there are more orthodox solutions already in common use.

I do not advise doing this. Ignoring the large inductive inrush currents and voltage spikes, the (electronic) ballast itself is not designed to have its output switched in this way and may fail.

Why do you want to switch the lights like this (are you trying to save money instead of buying a second ballast), what is the application?

Well this is the setup people r using to save money on buying another ballast. I plan on doing this setup for a garden. Where there will be 2 rows of 2-3 lights which will be operating in a zig zag/checker board lighting style every 2 hours. Well what are the other ways to have the lights zig zag/flip every 2 hours? this is i guess the most cost effective way and common way people have been doing it. i've seen upto 20 ballast controlling 40 lights in a setup similar to what i want to run. This is the only setup that ive seen that accomplishes this. they setup goes by the name of flip flop light controller. I open to suggestions even if it means possibly buying another ballast. On how to pull this off safely as possible. thank you

this is it. put im a diy. i know i can make my own.

http://www.progressive-growth.com/proddetail.php?prod=43015

the setup im looking for is like example 3.

http://www.horticontrol.com/howitworks.html

It would be surprising if the lamp or ballast manufacturers would support the use of their products in a system like this. Live changeover switching of lamps would be particularly hard on ballasts whether electronic, inductor or transformer type. The changeover contactor would need to be rated for several times the run current of the lamp to have a hope of surviving.

If you were to kill the power to the ballast before switching over, the voltage and current rating of your changeover contactor could a lot less, perhaps 2-3 times run current.

Still seems like a pretty dodgy trick though. Better by far to buy extra ballasts.

Beyond the world of 30 amp coil type power relays you enter into (magnetic) DPDT IEC Contactor , that is, when you go above 30 Amps.

http://www.grainger.com/Grainger/items/3DA90

you also will need an overload relay,..good idea to use one.

http://www.grainger.com/Grainger/items/3DE26?BaseItem=3DA90

these may not be the exact ones you need..ok? i just pulled up a couple for example sake.

Grangers tech pros.(well if you had an account) will walk you through it..they are very helpful..i mean the phone tech people not the counter people..they will not know!. hope that helps.. do more homework.. and always over wire and over amp everything so your lights can drink all the juice the posibly can.. they last longer that way..

( I'm an electrician..sometime for growers, and have designed many systems.)

I see no cost benefit to leaving your ballasts on while you do the light switching!

as others have mentioned.. bad for ballasts of all kinds.

look ,if your bulb need a surge/pulse charge to ignite, but you do not allow your ballast to build up and send the charge properly,a bit different with electronic ballasts granted, then you lights will not get the designed charge to start up correctly, and these bulbs are tempermental.. it does not take much before you have done a small amount of damage to the bulb'sefficiency and your lumens have dropped.

those expensive ballast switchers use this technology..(but they wont tell you..they don;t want you to make your own for cheaper.

cheers,

I don't see the point of this excecise. What are you saving, the cost of one ballast? For that you have to buy, build and install a controller and logic circuit to do this switching, all the while risking the very life of the single ballast you are now even MORE reliant upon and adding so many extra parts that your MTBF will drop through the floor. Even if you assign no value to your time and energy, this offers no tangible benefit IMHO. Just buy another ballast and be done.