What relay to use for DIY light controller??

[Cam]

Hi, I believe this is my first post here. I've been growing for about 5 years now though so I'm not exactly a n00b anymore.

I am also a semester away from a degree in computer engineering so I have some electrical experience.

I have plans to build a 10 ballast 20 light flip flop relay in the near future. Before I start that though I'd like to redo my distribution box to include a timer and a relay.

I plan on using this timer:
http://www.acehardware.com/product/index.jsp?productId=3797829&CAWELAID=404468204

But I am having a hard time finding a breaker to fit my setup.

It will need to be controlled by 120 volts and be capable of supporting 40 amps at 240 volts. I have heard that overkill is generally a good idea when dealing with relays so I will want a much stronger relay. Maybe a 100 amp one?? I will have 8 gauge running to the new box at 240v.

Are other people designing their light controllers the same way roughly? Any tips from someone whose done this before?


Thanks guys!

 

[growshopfrank]

figure 45 amps for 10kw @240v so say 60a 2 pole definite purpose contactor with a 120v coil and you might want to go to 6ga wire. Myself I wouldn't use a hardwired timer because if it fails it would be more of a bitch to replace.

 

[Cam]

Only doing 6 1k's then 4 600's. Its a short run from my main line. Like 6 feetish. 8ga is good.

Really though, I know pretty much what I need. I just can't find where to get it. I'm looking at:
http://www.alliedelec.com/search/productdetail.aspx?SKU=4280106

Even with that one I'm not sure it can handle the wattage....meh....

But there is no way I want to pay 140 for it. Should I expect to pay that much?

 

[toastfighter2]

Ok, I will be the first to admit that I have very little experience building flip flops, but the Pontiac diy link(ICMAGS Offical diy) in my sig should send you in the right direction(lot's of good info in there). What I do know about is that some ballast have a tendency to mess with digital timers(the same thing happens with some flouros too (but I see "they say" it is cfl compatible). Personally, I would not run the risk, and I would go with a heavy duty manual timer. I know it is harder to sync up a couple of them, but if it is just triggering a bank of lights, it really won't be that huge of a deal.

 

[Cam]

Thanks. I've read those flip flop DIY links already. I understand pretty much exactly what I need. I already have a good flip flop relay found. I'm not trying to build that just yet tho.

I still think I'll go with the dig timer. Its only 30 dollars and looks pretty cool. I could always add a trigger cord in like 10 min if the dig timer fails.

The only relay I have found that is designed for exactly what I want to do is 170 dollars...the question is, is there a cheaper way?


This is probably the minimum I would need:
http://www.alliedelec.com/search/productdetail.aspx?SKU=4280110#tab=Specs

 

[growshopfrank]

Thanks. I've read those flip flop DIY links already. I understand pretty much exactly what I need. I already have a good flip flop relay found. I'm not trying to build that just yet tho.

I still think I'll go with the dig timer. Its only 30 dollars and looks pretty cool. I could always add a trigger cord in like 10 min if the dig timer fails.

The only relay I have found that is designed for exactly what I want to do is 170 dollars...the question is, is there a cheaper way?


This is probably the minimum I would need:
http://www.alliedelec.com/search/productdetail.aspx?SKU=4280110#tab=Specs

Here is a 3 pole relay that would do the trick if you look around you will likely find it for less
http://cgi.ebay.com/NEW-Definite-Pu...850?pt=LH_DefaultDomain_0&hash=item5adb30df5a

 

[Marshall]

there seems to be some debate on the type of contactors used. It seems like HID ballasts have a high inrush of current and they may not be able to handle it. Not sure if it is a safety issue or just a longevity issue.

Thats the jist of what I have read.

I have used several DP contactors w/o issue. 30A were like $20 with trade discount (family member). otherwise 20-30$

Instead of one large 40A circuit, maybe split it

 

[Cam]

The Amp rating is a little misleading. As far as I can tell the relay needs to be able to ALSO support the wattage at whatever voltage you are putting through the relay.


The one thing I'm not sure about though is how that rating is defined. A 240 volt line in USA is basically two 120 volt lines 180 degrees out of phase. I would be putting two 120 volt lines through a 2 pole relay.... so do I look at the 240 volt HP rating or the 120 volt hp rating? I just don't have enough experience with relays. ugh....

 

[Cam]

Through a bunch of emails and a picture in mspaint drawn I ended up finding this... Its a little confusing though. It depends on what load your switching. So since my relay is between my main breaker box and another distribution box I am actually switching the 240v so I can get away with the 40amp breaker.

Cameron,
Thanks for the explanation.
Sorry I thought you had a motor. At 8400 watts and 240 volts that is 35 amps or at 8400 watts and 120 volts it’s 70 amps.
If your ballasts are actually 120 volts then use the 70 amp figure or if they are rated at 240 volts use the 35 amp figure.

The Allied 428-0110 you mentioned is a full load 75 amp 2 pole contactor with a 120 volt coil (8400 watts at 120 volts)
The Allied 428-0096 is a full load 40 amp 2 pole contactor with a 120 volt coil (8400 watts at 240 volts)
Choose the contactor based on your ballast voltage rating.

Since your load is not a motor you do not need to be concerned with the HP rating on the contactors. Since motors are very inductive and can have 6-8 times their rated current for a short period of time that’s when you need to match the HP rating to the motor nameplate information.

I hope you find this useful. If this works for you, you can either order them online at www.alliedelec.com , or simply call our branch office at 800-433-5700. They’ll be glad to help.



Mr. [I Changed his name] | Allied Electronics
Technical Product Specialist
Ft. Worth, TX

 

[Marshall]

I think you over complicated it. Just match the contactor in amp rating.

You can find contactors at any local electrical supply house

 

[David762]

Actually, it is possible to get a single phase 240VAC

Actually, it is possible to get a single phase 240VAC

The Amp rating is a little misleading. As far as I can tell the relay needs to be able to ALSO support the wattage at whatever voltage you are putting through the relay.


The one thing I'm not sure about though is how that rating is defined. A 240 volt line in USA is basically two 120 volt lines 180 degrees out of phase. I would be putting two 120 volt lines through a 2 pole relay.... so do I look at the 240 volt HP rating or the 120 volt hp rating? I just don't have enough experience with relays. ugh....

Actually, it is possible to get single phase 240VAC power to a residence or commercial building -- it just isn't typical. (Most commercial machinery, like welders, air compressors, and metal & wood working equipment normally use 240VAC single phase.) I have no idea what the entire process might cost these days -- building permits, licensed electrician, installation fees & coordination with the local power company, and a separate power meter. It also requires a separate breaker box and circuit wiring. It can be done and, given a large enough project, might expect a ROI of 5 years. (This is in the USA, BTW.)

Those 2 120VAC single phase lines that you would run through the 2 pole relay would, I presume, be the "hot" wires. Remember that nearly all 240VAC 2-phase is only 3 wire -- 2 "hot" wires and 1 "return" wire -- there is no ground wire. In the USA, most 240VAC 2-phase electric dryers use a dedicated grounding wire from the dryer chassis to a cold water pipe (or dedicated grounding rod), if the installation is properly done.

 

[Cam]

Well first off, I'm being so cautions because I don't want to start a fire by getting an incorrectly sized relay and having it melt. I want to fully understand how to size a relay myself.

And David. Your right. This is a generic part. Like almost all electronics parts transistors, resistors, capacitors, regulators, or pretty much any chip, it has certain design limitations. Voltage and current define this...some parts need to be able to briefly handle an inrush of current beyond their rating. This (in relays at least) is what PART of what the HP rating is for. HP is just the same as wattage. 1HP = 745 Watts. I haven't had much experience with HP rating's or using them so I made the assumption it was just an overall rating of how much power a relay can handle.

So then..if the HP rating had worked the way I thought, it would actually make a difference how they did there voltage rating. If 5HP @ 240 volts on a 2 pole connector meant two 120 volt lines I would be able to use a smaller relay than if that meant I had to use two 240 volt lines. I found the rating at 120 volts was typically less than half at 240. Like 2 instead of 2.5.

Anyway, it doesn't matter. My assumption about what the HP rating meant was wrong. I can ignore it..

Marshall, you are right too. For our purposes we only need to match the amp rating. An easy way of explaining it is if your using a 40 amp breaker at 240 volts you need a 40 amp relay. If your using an 80 amp breaker and 120 volts you'd want an 80 amp relay. I still think it could be confusing for some. But basically if you used a double pole 80 amp relay each pole could handle 80 amps.

I did probably over complicate it. I do that a lot. I like to really understand things though. And now that I understand all the ratings and types of relays I could size one for any application I may have in the future rather than ask and risk the chance of someone else making a mistake.

Yeah, I use 3 wire with ground since my ballasts are all 120volt.