Gavita 6/750 Heat Issues

[Mad Lab]

I'm a little concerned I just bought 12 of the 750 de, for a room the measures 15×30×9. I was hoping to cool this with one 5 ton, what's the amount of btu your coming up with to cool each fixtur? Are you running a burner or on the bottle?

the 5 ton Excel Air AC unit with fabric ducting does 15 1000w gavita DE's just fine.

also have cool damper systems to use in 2 flower rooms.


not the biggest fan of idealair. never had much success with running the number of DE's that i should be able to so i switch to Excel.

 

[Tropical Sun]

Ideal air just sucks! Their de humidifiers are like heaters, anything from Lowes is better than them. Thats the problem, a watt is a watt DE dont run hotter.

 

[Rolldaddy]

If your ac is cooling properly the air coming out of the ac should be roughly 15 degrees cooler than the air temp in the room where it is pulling air in from

 

[tussenvanons]

I'm a little concerned I just bought 12 of the 750 de, for a room the measures 15×30×9. I was hoping to cool this with one 5 ton, what's the amount of btu your coming up with to cool each fixtur? Are you running a burner or on the bottle?

I'd go by the btu calculator Ideal air has as a rough guideline. It said I needed 4 tons to cool my lights, ballasts and dehumidifier. (I'm running bottled co2 btw) What do you know I threw in another ton of a/c in the form of a window unit and I can now push my lights to 750w no problem in the mid 70s and even up to 862 the temp only gets in the high 70s.

So if 4 tons can cover 9 lights it 5 should be able to cover 12. (also putting the info in the calculator your right over the 5 ton limit with 12 lights in your space by around 1200 btus, nvm co2 and dehumidifier.

 

[tussenvanons]

the 5 ton Excel Air AC unit with fabric ducting does 15 1000w gavita DE's just fine.

also have cool damper systems to use in 2 flower rooms.


not the biggest fan of idealair. never had much success with running the number of DE's that i should be able to so i switch to Excel.

My friend is running a room with similar wattage (only 8 DE fixtures and the rest hangers) and he has to keep his lights dimmed to 50% because the 5 tons excel isnt enough.

I think both companies aren't concerned with producing the highest quality merchandise because they know the crowd its going too and it's less likely to be brought up as a bad product.

 

[tussenvanons]

If your ac is cooling properly the air coming out of the ac should be roughly 15 degrees cooler than the air temp in the room where it is pulling air in from

I checked my air handler with a IR temp gun and it's around 17-20 degrees cooler than the room temp air.

 

[queequeg152]

you must also consider heat gain and heat loss figures based on myriad of variables such as exterior wall areas, wall assembly r values... air leakage, sun exposures... it goes on and on.

ideally what you need to do to predict the heat gain accuately, is to perform a Manual J calculation. Its a semi PITA to do properly, but worth while when sizing AC systems... because over sized systems tend to be more inefficient than a smaller properly sized system...

humidity control is generally the best benifit of a properly sized ac, what with the smaller system running longer, and thus dehumidifying for a greater amount of time.

an accurate manual J is probably not worth the hassle... but perhaps you gentlman should perform some rudimentary J calculations prior to buying such expensive equipment.

 

[tussenvanons]

Yes we all know you have to account for variables such as the ones you mentioned. Questions, issues, and general advice are all posted here so that people can figure out problems and get help from someone who may have encountered said problem and has the answer or a solution that worked for them. Usually when you specify upon the solution it helps.

So instead of being a pompous ass and telling people not to spend a fair amount of capital on equipment before doing calculations how about you either A) be a useful dick and elaborate more about "rudimentary J" calculations, you know such as how to do them or where to go to get the framework for such calculations, so others looking at the form can find their answer further down the line instead of coming here to go someplace else, you know be helpful. Or B) be more understanding and think of more than one narrow minded possibility of someone going out and spending thousands on a piece of equipment just for the heck of like hey there was a great deal on this piece of equipment so i can save a couple thousand might just have to dump a couple hundred bucks in after or a buddy has something that he's no longer using.

Try to not be such a dick...i can imagine that's very hard for you tho so I wish you the best of luck

 

[queequeg152]

Yes we all know you have to account for variables such as the ones you mentioned. Questions, issues, and general advice are all posted here so that people can figure out problems and get help from someone who may have encountered said problem and has the answer or a solution that worked for them. Usually when you specify upon the solution it helps.

So instead of being a pompous ass and telling people not to spend a fair amount of capital on equipment before doing calculations how about you either A) be a useful dick and elaborate more about "rudimentary J" calculations, you know such as how to do them or where to go to get the framework for such calculations, so others looking at the form can find their answer further down the line instead of coming here to go someplace else, you know be helpful. Or B) be more understanding and think of more than one narrow minded possibility of someone going out and spending thousands on a piece of equipment just for the heck of like hey there was a great deal on this piece of equipment so i can save a couple thousand might just have to dump a couple hundred bucks in after or a buddy has something that he's no longer using.

Try to not be such a dick...i can imagine that's very hard for you tho so I wish you the best of luck

the irony in the last few sentences of your post is absolutely delicious.

you infer i mean offense when none in intended. instead of practicing what you preach, you jump up my figurative asshole.
perhaps the pot need not call the inferred kettle black.

regarding me not being helpful, let me ask you the following:

hypothetically speaking. if i were to tel you that you should change the oil on your car to extend its useful life.
is this not helpful?

Would you prefer that i tell you exactly how to change the oil on your car?
do you agree that a typed message is a far less powerfull medium through which to convey information than say, a youtube video, or a picture ?

whould you not reasonably ... google " oil change" to find more information on this hitherto unknown procedure?

it not unreasonable to expect myself to spend a great deal of time explaining a procedure that is, in all likelihood impossible to explain over a message board?
especially considering that interest in said procedure is not immediatly evident?

is is not logical to allow folks to read about the manual J, at least to some small extent first? where after any questions could surely be fielded...

 

[tussenvanons]

you must also consider heat gain and heat loss figures based on myriad of variables such as exterior wall areas, wall assembly r values... air leakage, sun exposures... it goes on and on.

ideally what you need to do to predict the heat gain accuately, is to perform a Manual J calculation. Its a semi PITA to do properly, but worth while when sizing AC systems... because over sized systems tend to be more inefficient than a smaller properly sized system...

humidity control is generally the best benifit of a properly sized ac, what with the smaller system running longer, and thus dehumidifying for a greater amount of time.

an accurate manual J is probably not worth the hassle... but perhaps you gentlman should perform some rudimentary J calculations prior to buying such expensive equipment.

If you think the last sentence in this post is not talking down to people then idk what to tell you. If you didn't mean to then sorry for jumping to conclusions and calling the sky blue.

Anyway to preform the calculations you need to know the heat your combating in the room and this would require to buy some of that equipment firsthand and do tests yourself (as the manufacturer of the lighting and cooling equipment don't agree on cooling requirement's capabilities)...and the point is to make it easier for the next guy. We're talking about a subject that's been kept underground and in very limited circles and expanding it to the internet growing an information database more and more day by day. The whole idea is to contribute something so people can look and find their answer quickly instead of weeding through a vast amount of information.

Just be as helpful as possible...

 

[queequeg152]

regarding the heat output of an HPS light fixture, id suggest looking towards industrial sources, and use it as a high bench mark.

magnetic high bay 400-1000watt light fixtures have been around for half a century. There will be data available, with respect to its head load inside a conditioned space. when i have time( test week), ill look in my Manual J load calc book to see if there are any tables that cover this.

regarding the manual J itself. Its literally just a very complicated spread sheet. you input values such as your location, design temp, deign humidity, environmental conditions etc.

you then input the parameters of your walls... exterior walls, or partion walls(garage walls, attic knee walls etc) are the only walls that appreciably add to the heat load.

you need to input the wall area, window and door area, slab or floor area, and ceiling areas. wall window/door etc. R values are based on its construction, how much insulation, how much drywall, how much sheating and siding... and its exposure.
part shade, full sun, or full shade etc.

if you dont know whats inside your walls, ceiling, floor, then you should find out in the least invasive way possible.

when you do all this you can generate a crude projected heat gain. add to this gain, your high estimations of the HPS lights based on the above mentioned numbers.

alot of the reference information you need to put together this information is available online, but most of it is inside the manual J book.

this book is like 100 bucks new. but i bought mine for like 60 bucks on amazon. id suggest doing the same.

the book should also contain a CD. this CD has some videos that explain the procedure in better detail.

in addition to the above, id reccomend reading about the J calc on what ever HVAC forums you can find. the minuta are endless, and far too numerous for me to get into.

 

[queequeg152]

ok ill do you a solid here.

i found the table, as well as the approximation formula.

qel = 3.41WFulFsa (1)

where
qel = heat gain, Btu/h
W = total light wattage, W
Ful = lighting use factor
Fsa = lighting special allowance factor
3.41 = conversion factor

so now we go to table 2 and find our light variables for 1000 watt HPS.

(1) 1000 W lamp HID 1000 1 1000 1100 1.10

so... 3.41*1000 fixture wattage* 1 usage factor* 1.1 allowance factor.

equals a heat gain of 3751 BTU/hour.



1 usage factor means the light is on full blast all the time.

the allowance factor is for lights that vent heat into a non conditioned space.

high bays are totally enclosed by the conditioned space. they do not vent.

hence this factor is 1100/1000 = 1.1

 

[queequeg152]

oh yea. 1 watt = 3.41 btu per hour.

basically ashrae concludes that watts to the light fixture = watts of heat generated.

upon reflection this does not sound reasonable to me.

this equation is from the 2005 ashrae fundamentals... im inclined to see what revisions were made in the subsequent versions.

 

[queequeg152]

so the 2013 version( version i do not have, nor can i even begin to afford) makes a number of revisions mostly with respect to electronic ballasts and high power factor ballsts...

if i had to guess id say that these fancy ballasts are closer to 1 than they are to 1.1... if you can give some numbers however i can revise that calculation, or you yourselves could.

just divide the actual consumption by 1000w and use that as the new allowance factor.

upon further reflection the watt to watt heat DOES make sense to me now.

 

[Reel Tight]

Well I can confirm that a 5ton is plenty of cooling for 12 750de. Now I'm having some problems with a couple of them firing up. Anyone using the el1 to control their lights?

 

[queequeg152]

my calculations based on the above equation suggests you have roughly double the cooling capacity that you require.

admitidly did this calculation rather quickly... but 12 lights at 750 watts, should yield around 32k btuh.

a 5 ton ac can remove 64kbtuh ideally.

 

[olekingkole]

Before building that dog house, I would measure the temps coming out of the air handler to see if they vary with the outside temperature.

 

[Rondon]

I realize this is in older thread but its similar to my setup if not exact. I too have 8 x Gavita 6/750's. In an "almost" 7 foot basement from concrete floor to bottom of floor joist. A Mitsubishi Mr. Slim 3 ton works fine for me. But I did a few "tricks". Me Gavita fixtures fit perfectly in betwixt the floor joices up top. Using exact eye bolts so they dont pop through my floor...receesed in between the 10" joices Iam gaining almost another foot. Anyways...then (its been fully operational for almost 3 years now) I used that R whatever silver mylar backed insulating foam board from Lowes in 4x8 sheets for walls and ceilings. I cut out exactly for each Gavita reflector only thereby eliminating ballast heat which isnt much but its clearance I was after. Real deal expensive ass silver foil duct tape covers all gaps and over all cap nails to 2x4 framing insuring a sealed room. Bottled spray foam for that extra touch. A santa fe dehuey similar to a Quest 110 for RH control and bottled Co2 for gas. I go through bottles (I have a double tank injector...when one is empty I just switch over) but it saves me heat and humidity concerns with burners. I run a low clearance (drain tables will not cut it) run to waste coco system with irrigation drip manifolds and plumbed together pot saucers and using Growpro Nx Level 15" plant riser platforms to keep roots away from salty spent waste solution. Solution runs out the saucers into the tubing and tubing runs outside the room across basement to sump well. 4 35 gallon trash can reservoirs are outside the room as well. Aany rate...the system works just fine for a 3 ton Mr Slim mini split and santa fe dehuey. Canopy temps rock solid at 78 to 82 degrees in the hottest months (right now). I too have a "dog house" over the condenser outside. I also shut co2 down in the dead of winter as well as the mini split and 4 automatic louvers with blowers, ducting and a thermostat to take advantage of January through March 20 or colder freezing winter temps. The loss in yield during the non co2 winter months is offset by the shutting down of the split. I thought it silly to try and run a split when its 20 or colder outside and Iam taking advantage of that. With a production cut run like Dream or Sour Amnesia (a very underrated strain from Hortilab) I can pull down 25 to 30 zips per lamp depending on 600 or 750 watt setting. Knocking down crops like Mike Tyson.