# 208 to 120 via relay?



## jtcleek1122 (Apr 30, 2010)

I'm trying to decipher a wiring technique a client has used for a 1,000 watt HPS ballast. The ballast is 208v and it is wired to a KRPA-11AG-120 8-pin relay on one side. The other side has two 120v plugs wired from the relay. When both 120v cords are plugged in the light turns on. There doesn't seem to be a ground involved.

I do not understand why someone would have done this. Please explain.


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## Dennis Alwon (May 9, 2009)

Well it does seem a bit flaky doesn't it. I would assume that the plugs have to be plug in to circuits of different phases. 

A creative but hack solution to the problem.


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## Electric Al (Mar 13, 2010)

I can't figure out why this was done, but be very careful,you could unplug one cord, assume it is not live,and still have a 120 volt live!! if I understand what you are saying!!!


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## jtcleek1122 (Apr 30, 2010)

When I observed the operation both plugs were plugged into the same socket. The gentleman who did the wiring is very creative and had done a lot of different hack jobs.

I'm more or less trying to figure out how and why this relay was used. I'd ask him but he has since passed away. To my understanding a relay is just a switch but obviously he has used this as a step-down transformer?

The ballast is getting pretty old, and I plan on replacing it with a 120v ballast for simplicity and safety. At this point, I am exploring this out of curiosity.


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## Electric_Light (Apr 6, 2010)

208Y120v provides 120v between neutral and anyone of the phase. It's grounded at the service entry. 
The relay you mentioned is a 120v coil, DPDT (normally on and normally off and normally on contact is just unused). 

With this, you can feed the common of two poles to each leg of 120v outlets on different phases. connect the normally off contacts to luminaires using two of the wires using an orange extension cord only rated for 125v.

The two halves of a duplex outlet can be separated by breaking off the little tab, so its possible that the top and bottom halves are wired to different phases. 

Bond one end of the relay coil to one of the phases, then attach the other end to one of the conductors in CAT5, thermostat, phone, security system wire or whatever that's already in the wall, then have the switch just short it to the ground. Even CAT5 is adequate to carry the 2.5W or so needed to operate the two pole relay and only one conductor is needed, since ground is used for return path.

The ultimate hack job.

Blue wires = thermostat wire.

Anything downstream of relay remains de-energized, because it's a two pole relay. The squiggly thing on the bottom is relay. 

A=an outlet
B= another outlet


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## jtcleek1122 (Apr 30, 2010)

Electric_light - that was very informative. Thank you. You obviously understand this hack job. Is their an advantage to leaving this wiring system? I could just re-do the wiring with a new 208v ballast if this has some sort of advantage over a simple 120v ballast design.

Using the picture attached which pins are wired to what. I'm gonna take a stab and say pins 3 & 6 are wired to the light. Pins 1 & 8 would be the hot from the 120v line and leaving pins 2 & 7 for the common of each line. Pins 4 & 5 would be left unused.

Also, are you saying the only possible way for this to work is each 120v line plugged into an outlet of a different phase.


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## Electric_Light (Apr 6, 2010)

What exactly is the application of this lighting or should I even ask...?



jtcleek1122 said:


> Electric_light - that was very informative. Thank you. You obviously understand this hack job. Is their an advantage to leaving this wiring system? I could just re-do the wiring with a new 208v ballast if this has some sort of advantage over a simple 120v ballast design.
> 
> Also, are you saying the only possible way for this to work is each 120v line plugged into an outlet of a different phase.


If you do line-lo-line on same pole or phase, you'll get 0v. 

The only way you can get anything other than 120v from 120v outlets is by taking power from two receps on different poles/phases. It would be 240v pole to pole from a single phase transformer, 208v phase to phase from power from three phase transformer.
Are you sure ballast is running on 208v? 



> Using the picture attached which pins are wired to what. I'm gonna take a stab and say pins 3 & 6 are wired to the light. Pins 1 & 8 would be the hot from the 120v line and leaving pins 2 & 7 for the common of each line. Pins 4 & 5 would be left unused.


For on/off function on two connections, you only need DPST, so yes, two connections remain unused, whatever they're on that particular relay.


Do you have switch wired in the manner I described? 

This hack job isn't safe, especially if the thermostat wire hack is being used. The only reason to use 208v is if the current power carrying wiring isn't able to handle 10A or so based on voltage drop for distance at 120v. 

It would be almost safer to just get a RF controlled 120v appliance remote switch and go away without the hack. 

Using 208v would reduce current so you can reuse the existing wiring, but you'll have to make sure the two phases are on a common trip breaker, use dual pole switch along the way etc.


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## jtcleek1122 (Apr 30, 2010)

Positive the ballast is 208v. It is clearly marked on the side as a 208v 1,000watt metallic HPS ballast. 

From what your saying I can only think of two theories why he would have wired them in this manner:
a) he already had 208v ballasts and couldn't get obtain 120v versions
or
b) it made more electrical sense to have two outlets, both on different phases, powering these two ballasts. I forgot to mention this setup included two 1,000watt ballasts. Both wired exactly the same way.

And there is no thermostat wire or any ground for that manner. I'm telling you the relay on one side has two wires ruining out, one going to the ignitor, the other the the core&coil. On the opposite side of the relay there are two hots and two commons. I can see the green wire cut just inside the cord on both connections.

It doesn't seem logical to me that he wouldn't have been able to obtain wire able to handle the 10A on 120v.


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## Electric_Light (Apr 6, 2010)

jtcleek1122 said:


> Positive the ballast is 208v. It is clearly marked on the side as a 208v 1,000watt metallic HPS ballast.
> 
> From what your saying I can only think of two theories why he would have wired them in this manner:
> a) he already had 208v ballasts and couldn't get obtain 120v versions
> ...



1000W lamp, 80% efficiency, 90% PF =1400VA ea
2800VA for both 
Since you must not load circuit beyond 80% for continous use, you'll need 3500VA, which is just short of being satisfied by 20A 208v circuit, but with him being a hack, loading to 80 to 100% was probably allowed. 

Best corrective actions depend on your setup, such as difficulty of changing wiring, length of run, practicality of installing a proper 20A feeder instead of using outlets, etc. 

What is this structure? A warehouse? a barn?


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## Electric Al (Mar 13, 2010)

Why are we discussing this? The ONLY right way is to scrap it, then do it right and SAFE !!! Anyone Agree??


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## jtcleek1122 (Apr 30, 2010)

Structure is a wielding / wood working shop. That is what has me so confused. When it was built all the wiring was done and these ballasts were purposefully wired like this. He could have easily ran 240v outlets to power the ballasts. This is why I was seeking the help from others. Just wondering if there is some sort of benefit to doing it the way he had as opposed to wiring 240v outlets and having 240v ballasts or 120v outlets and 120v ballasts. 

At this point he must have done it simply because he already had 1,000watt ballasts in 208v configuration. Being cheap and a intuitive he must have devised this hack to save money.

Electric_Light - Would that be your best guess? or has this more info shed light to this messy and dangerous wiring configuration.


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## frenchelectrican (Mar 15, 2007)

Electric Al said:


> Why are we discussing this? The ONLY right way is to scrap it, then do it right and SAFE !!! Anyone Agree??


 Oui I agree with this part.



jtcleek1122 said:


> Structure is a wielding / wood working shop. That is what has me so confused. When it was built all the wiring was done and these ballasts were purposefully wired like this. He could have easily ran 240v outlets to power the ballasts. This is why I was seeking the help from others. Just wondering if there is some sort of benefit to doing it the way he had as opposed to wiring 240v outlets and having 240v ballasts or 120v outlets and 120v ballasts.
> 
> At this point he must have done it simply because he already had 1,000watt ballasts in 208v configuration. Being cheap and a intuitive he must have devised this hack to save money.
> 
> Electric_Light - Would that be your best guess? or has this more info shed light to this messy and dangerous wiring configuration.


I will keep it simple I know many peoples do buy used large HID luminaires and 90% of the time they never double check the luminaire voltage setting and if they want 240 volt or 208 volt luminaire in the shop it far much easier and safer to just run new circuit instead of someone make hookydooky gimzo set up.

Merci,Marc


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## user4818 (Jan 15, 2009)

jtcleek1122 said:


> Structure is a wielding / wood working shop.


Sure, we believe you. :no:

What you mean to say is a grow room, right?


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## jtcleek1122 (Apr 30, 2010)

LOL. It does look like a stoner situation. Wired the grow room to 120v when he was baked and then realized the ballast was 208v haha. 

This is a huge shop. Their are already 240v outlets for wielding equipment as well as large saws and the likes. My questions has been answered so I appreciate it. Let's not turn this into a debate of what application the bulbs are actually used for.


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## Electric_Light (Apr 6, 2010)

Actual application does matter, because it's running the wires that is the most time consuming and costly. 

It's easy to rewire a grow set that is in the confine of one room with exposed wires. It's quite another to have to run hundreds of feet of wire through conduit, wall, etc. 

Then...
Why does this building have both 208 and 240?

Where's the option for borrowing 7200v power from the PoCo's overhead lines and bringing it inside with 26AWG wires suspended by fishing lines from cross beams and stepping down to 240v using a pole pig borrowed from the power company's maintenance yard?


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## jtcleek1122 (Apr 30, 2010)

I never said the building has both 208 and 240. The ballasts are 208 but the hack job has them running off of the 120. That is what I was trying to explain to you so maybe someone with more knowledge could tell me WHY!

To rewire this building would not be easy. When it was built, the wiring was ran all in the walls. I guess I could run conduit and but like you said, that would be a pain in my ass for a building this size.

I already intend on replacing the ballasts with 120v to get rid of the hack. I will likely just purchase smaller 400 watt ballasts to make the amp load lower. From the beginning I said I was wondering out of curiosity. I thought there might have been a reason for this weird and unsafe set up. Apparently it was to save a few bucks on new ballasts


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## Electric_Light (Apr 6, 2010)

jtcleek1122 said:


> I never said the building has both 208 and 240. The ballasts are 208 but the hack job has them running off of the 120. That is what I was trying to explain to you so maybe someone with more knowledge could tell me WHY!


You said there are 240v outlets.


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## jtcleek1122 (Apr 30, 2010)

Yes. 240v outlets are in two sections of the shop for equipment. These outlets are about knee high on the walls. There are plenty of 120v outlets throughout the shop. Overhead the wiring is 120v for the lighting. Make sense?


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## Electric_Light (Apr 6, 2010)

jtcleek1122 said:


> Yes. 240v outlets are in two sections of the shop for equipment. These outlets are about knee high on the walls. There are plenty of 120v outlets throughout the shop. Overhead the wiring is 120v for the lighting. Make sense?


If you have 240v outlets, and you have 208v, that means you have both 208v and 240v by logic. 

1.) you have 240v and 208v ballast is forced to operate at 240v
2.) you have 208 and the "240v" outlets are really 240v
3.) you have two services, one derived from two phases of 208Y120v system and one from a single phase 120/240 or 240v delta 3 phase. 

I'm getting more and more confused. At this point, I suggest you hire an electrician to do it for you.


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