Sizing a service for marijuana grow building

[Stevenj100]

I can not find any help in the code to help apply any demand factors to any of the equipment. Except for 220.60 noncoicidental loads.

When sizing my service is it really just add up all the loads and add up all the continuous loads at 125%?

This makes sense for the lighting loads but seems excessive for the hvac equipment.

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[kwired]

Not familiar with such operations, but seems they put in a lot of hi wattage HID lamps that do run pretty continuously. You won't necessarily have coincidental heating loads but likely do have coincidental cooling loads when the lighting is in use whether it just be exhaust fans, or actually is refrigerant type systems.

 

[electrofelon]

There is some information on the topic in this thread:

http://forums.mikeholt.com/showthread.php?t=186128

There isnt much to it really: mostly lights at 125% and the MCA of HVAC (if there are multiple HVAC units, adding up the MCA's wil give you a higher number than necessary, but probably not much of an increase in the scheme of things).

 

[Stevenj100]

These are existing rooms. One room has 16 light and 3 minisplit AC units. The AC units have a MCA of 19.5 amps. So by the math the AC systems need 75 amps. But they generally draw about 6 amps while running. My real world testing is so out of line with the math. I figured I must be doing something wrong.

And these room have been running off of 2 , 200amp services. And now my math says I have to tell the owner not they really need 2, 400 amps services. Again I was questioning my math because it doesn't line up with what is occurring in the field.

So I figured my calculations must be wrong. But it sound like I am doing the math correctly

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[ramsy]

Its "High Time" for a code proposal for this new article.

I propose "Article 548 Marijuana Grow Buildings" just after "Agricultural Buildings"

Or, should it be Article 527 "Pot Growers" just after "Carnivals, & Circuses.."

 

[ActionDave]

These are existing rooms. One room has 16 light and 3 minisplit AC units. The AC units have a MCA of 19.5 amps. So by the math the AC systems need 75 amps. But they generally draw about 6 amps while running. My real world testing is so out of line with the math. I figured I must be doing something wrong.

And these room have been running off of 2 , 200amp services. And now my math says I have to tell the owner not they really need 2, 400 amps services. Again I was questioning my math because it doesn't line up with what is occurring in the field.

So I figured my calculations must be wrong. But it sound like I am doing the math correctly

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First of all, the NEC load calcs are massively conservative. Ever look at the the size of those tiny POCO wires, being fed by a 15kva transformer, hooked up to the fat wires coming off you 200A service?

Second of all, for A/C units the 125% is already figured into the MCA.

 

[Stevenj100]

First of all, the NEC load calcs are massively conservative. Ever look at the the size of those tiny POCO wires, being fed by a 15kva transformer, hooked up to the fat wires coming off you 200A service?

Second of all, for A/C units the 125% is already figured into the MCA.

Can you point me to a reference for the 125% is already included?

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[Open Neutral]

Its "High Time" for a code proposal for this new article.

I propose "Article 548 Marijuana Grow Buildings" just after "Agricultural Buildings"

Or, should it be Article 527 "Pot Growers" just after "Carnivals, & Circuses.."

I think you meant Article 420.

 

[Dennis Alwon]

Can you point me to a reference for the 125% is already included?

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Look at the definition of continuous and then look at 210.19

(a) Where a branch circuit supplies continuous loads or
any combination of continuous and noncontinuous loads, the
minimum branch-circuit conductor size shall have an allowable
ampacity not less than the noncontinuous load plus
125 percent of the continuous load.

 

[JFletcher]

I think you meant Article 420.

:lol:

re: the mini splits, do they have electric heat? Sounds like they do if the MCA is 19.5A. If heat is needed, personally I would look into recycling the waste heat from all those lights vs running electric heat. Probably not an issue*.

Are these 2 200A services 240V 1ph? 16 1kW HPS ballasts draw ~17,500W; 71A @ 240V. Even if the ACs were on heat mode continuously, along with all lights, you're still only around 130A on one panel. How many rooms do they have?

*eta: I see you're in Maine. I suppose heating would be used in the winter months.

 

[kwired]

Can you point me to a reference for the 125% is already included?

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If you take the compressor RLA x 1.25 then add all other loads in the unit - you will come up with nameplate MCA or very close to it pretty much every time. In the absence of having a MCA for whatever reason this is what you are supposed to do (this required somewhere in art 440).

Reality is many compressors don't draw RLA, especially when brand new and the system is clean and everything in good condition.

Amount of heat being moved results in changes in refrigerant pressures which results in changes in compressor loading. Plugged condenser coil - less heat is given up at the point it was intended to be given up - which is recirculated through the system - more work for the compressor.

 

[Open Neutral]

Given the power costs, I'd a thunk there was a line of LED emitters out there designed to promote plant growth.... and save $$$.

 

[augie47]

Given the power costs, I'd a thunk there was a line of LED emitters out there designed to promote plant growth.... and save $$$.

perhaps the profit margin is such that they don't give much thought to overhead or perhaps they "juts don't care" due to the environment

 

[petersonra]

the calcs are what they are.

often they seem to come out a lot more than anyone ever sees in real life, but that is what they are.

I don't see that you have a lot of choice if you want a permit. do the calcs and see what comes up.

 

[310 BLAZE IT]

Split your panels to continuous and noncontuous loads. Also you could run your lights on for 2 hours and 59 minutes and then off for an hour and trick the plants into growing faster and also consider your lights a noncontuous load!

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[JFletcher]

Split your panels to continuous and non-continuous loads. Also you could run your lights on for 2 hours and 59 minutes and then off for an hour and trick the plants into growing faster and also consider your lights a non-continuous load!

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Yeah and when that happens widespread the NEC will make all lighting loads continuous no matter how long they actually operate.

Staggering grow and bloom cycles over 24 hours gets you almost half again as many lights you can realistically operate on a service.

 

[Coppersmith]

Given the power costs, I'd a thunk there was a line of LED emitters out there designed to promote plant growth.... and save $$$.

You would probably have the best growth if you use pot lights.

 

[jumper]

You would probably have the best growth if you use pot lights.

View attachment 18344

 

[kwired]

Given the power costs, I'd a thunk there was a line of LED emitters out there designed to promote plant growth.... and save $$$.

I did a little looking around and seems the amount of photons delivered to the plants (any kind of grow operation not just marijuana) is critical to how fast the plant develops. Sounds like there is some LED technology out there that targets the grow industry, might be kind of pricey for initial investment though.

Then mix that in with the recent legalization of marijuana in some places and others thinking about legalizing - you have a setup for increased demand - which will result in a rise in construction of growing facilities wanting to make quick profits while demand is high and supply is low.

I'd guess other growing industries are more seriously looking into LED's as a way to improve overall economics of their operation as they maybe aren't as enticed by high profit margins as the marijuana growing industry may be seeing. Those building the marijuana grow houses today are probably looking for quick profits and someday if enough supply is developed and prices start to go down - they sell the operation and it isn't their problem anymore to try to make it more efficient at that time.

 

[Coppersmith]

View attachment 18344

Admit it. You laughed.