# of lights on a 400 amp breaker (for the whole grow)

[SirStynkalot]

Hi guys,

I have a dilemma:

I'm building in a big grow. We just recently had to look for a new lease and the building in question only has 400 amps of power. I believe what we have to work with exactly is two 200 amp 120v boxes, though it may be a bigger line that they just broke down. I'll know better once we take possession of the property and have an electrician look at it, but I have to have some rough estimates before that stage to get through licensing.

Can anyone ballpark guesstimate what will fit on that? We're going bare bulb and cooling with AC, not fans. We'll be using 15+ SEER AC units assuming they make those models for 120v.

We have to have some outside air coming in to stay up with OSHA codes for air quality in a work environment, but it's not going to be our main source of cooling.

I should also note that any estimates should probably be undershot a little. We don't have to worry about 2012 electric codes because grow lights can be exempted from the overall efficiency equations for the building, but the place is still about 30 years old and we don't want to burn it down. Running at about 75-80% of the building's max capacity is at our landlord's request.

I believe this puts us somewhere in the 30-40kw range for available plant lighting. Does that sound about right?

Also, please do not ask about or comment on the project unrelated to electricity. My contract won't allow me to respond. Thanks.

 

[packerfan79]

At 120 l volts a 1k light pulls about 10 amps slightly less with digital ballast. of 240 is availAble u would be better off half the amps for each light 5 amps per 1k.and they run cooler thus they save on cooling cost and equipment last longer. With 400 amps available I would cap at 300. I would say 20 1k is a safe spot using 120 v, that would leave 100 amps for cooling and accessories. At 240 v, you could double those if every thing was 240B.C. Either way that's going to be a massive power bill. Hope you got deeplly pockets.hope you lgot a top notch electrician and a schemAtic to help with any potential hick uls

 

[SirStynkalot]

Thanks man. That sounds about right.

Cost and contractor quality aren't really issues for the moment. Right now we're more trying to calculate how much we need to produce to hit the margins we want and I don't think 20k is going to cut it. We need about double that, preferably triple.

Probably should have also mentioned we'll be using digital ballasts and have flower rooms set on flip flops to negate surges. Hoping to pull a bit more juice outta the lines if I can stabilize the draw.

 

[packerfan79]

With flips u should be able to run 40 lights. Not in veg though.if u can run 240 it has a lot of advantages. I only run 4 lights and I use 240.Man I hope you don't like sleep cause that's going to be a shit ton of of work

 

[rives]

Aside from the landlord's wishes, the NEC limits your draw to 80% of the breaker rating for continuous loads, which are defined as being over 3 hours in duration. Loads of shorter duration can bump up to the full breaker rating. Running your ballasts on 240v is obviously the first step to optimize the light count, but getting a handle on your other power needs is also going to be very important. Air handling/filtration is going to fall into the continuous category, and with that many lights, it's very likely a/c and dehumidification will too.

Contrary to popular opinion, having the lights on a flip are not going to eliminate surges on startup. It may seem instantaneous to you, in the electronic world, contactors take a very long time to switch over. Also, the lamps are starting cold and have completely different characteristics than when warm. As long as you have a reasonable amount of headroom left on the circuit, as required, the short duration of the spike will not affect the circuit protection.

Many electronic ballasts are not adaptable to hot switching, where the ballast is never turned off. A better way to limit any surges would be to switch the lighting sequentially over a period of time rather that everything at once.

 

[DHF]

Aside from the landlord's wishes, the NEC limits your draw to 80% of the breaker rating for continuous loads, which are defined as being over 3 hours in duration. Loads of shorter duration can bump up to the full breaker rating. Running your ballasts on 240v is obviously the first step to optimize the light count, but getting a handle on your other power needs is also going to be very important. Air handling/filtration is going to fall into the continuous category, and with that many lights, it's very likely a/c and dehumidification will too.

Contrary to popular opinion, having the lights on a flip are not going to eliminate surges on startup. It may seem instantaneous to you, in the electronic world, contactors take a very long time to switch over. Also, the lamps are starting cold and have completely different characteristics than when warm. As long as you have a reasonable amount of headroom left on the circuit, as required, the short duration of the spike will not affect the circuit protection.

Many electronic ballasts are not adaptable to hot switching, where the ballast is never turned off. A better way to limit any surges would be to switch the lighting sequentially over a period of time rather that everything at once.

As stated in PM Bro.....Consult an electrician and PRAY yas find someone with Rive`s knowledge and experience......

Good luck....DHF.........

 

[rives]

Thanks for the kind words, Fred. It means a lot.

 

[dansbuds]

I'm an ex sparky myself .... but Rives knowledge well surpasses mine by a LONG SHOT !!! He is THE MAN when it comes to electrical knowledge here at ICmag !!

My hats off to ya brutha

 

[Jhhnn]

Too many variables to really judge from here, but there may be better industrial voltages on the pole outside. Depending on the Code, the circumstances & the local utility, you may want a separate drop & meter just for the lights & HVAC, leave the rest of it alone if you can.

Having 480/277 or 208/120 would be ideal.

 

[SirStynkalot]

Wow, thanks guys! Rives especially! That was much better information than I was expecting and with a much better turnaround time. I'll take the advice to heart.

A bit of disclosure wouldn't hurt - our long term site manager is a journeyman carpenter with a LOT of experience in residential work. We're plugged in pretty tight with a lot of local builders and contractors. Once we sign the lease we have an electrician to consult on exact limits but I needed some baseline my boss can quote me on to strike down bad leases with first.

Thanks again!

 

[hvac guy]

Is the 400A service single or three phase?