Central Air: 2 x 3 Tons or 6 Tons?

[queequeg152]

over sizing is inefficient. an over sized system will cycle too often, dehumidify poorly, and filter poorly owing to short duty cycles. what do you think all that costs you?

the golden rule for sizing any hvac system is the manual j(for small systems) or similar approximations based on ASHRAE documentation.

 

[Snype]

i cant visualize your dice analogy honestly. draw somethng out in paint or auto cad or a slip of paper if you really want my opinion/ advice here.

the manual j basically calculates the amount of heat that is driving inward into your cold conditioned space. regardless of wether or not this space is directly adjacent to the exterior walls, you WILL gain heat...

what is the climate like ouside this space? is this a semi enclosed warehouse type environment? if so great, that means you have no direct solar heat gain, but you still gain from the ambient air temperatures surrounding what ever r value structure you are building. you also gain or loose heat from the slab your room is built on. your ducts( if they are exterior) also gain heat from this unconditioned area.

id still highly reccomend a proper manual J for any work involving such expensive equipment... a properly sized unit will pay for the cost of the j calculation 10 fold over just a few years operation.

also, something that i had not mentioned earlier... growing plants indoors obiviously produces tremendous amounts of water vapor...this translates to latent heat. latent heat adds to your total heat gain values , so be cognizant of this fact, and also be aware that you may not be able to remove all of this latent heat with just the air conditioner. evaporator coils are not 100% efficient at removing water vapor... only part of the water vapor is removed as it passes through. what happens is, you will have to over cool the space in order to control the humidity adequately... this is where separate non split dehumidifiers come into play.

this dehumidifier will generate heat, and add to your total heat gain.
J calcs are just lovely right?

regarding that york affinity unit.. this is a VERY expensive condensing unit you have selected here. This is a 2 stage unit, with 2 compressers... one small and one large. these units are for affluent homes with high quality construction and insulation.

2 stage units absolutly must be sized correctly for you to see any efficiency gain what so ever.

you size a 2 stage too large, and it runs on low the whole time, negating the need for the second stage. size them too small, and the 1st stage almost never runs alone, and negates the advantage of having both stages.

2 stage units are also inherantly more complicated and prone to failures. you have 2 compresses here, and all the wiring, instrumentation, brazing and instrumentation that goes along with it.

for something like you are proposing, it is entirely ill suited. york makes some good cheapish units if its a brand that you favor... i believe their 15-16 seer units are highly thought of and something like 5 grand for a split 4 ton? i dont recall exactly.
alternativly you could save a grand or so on each unit, and just go with the cheap as dirt, goodman 13-14 seer units... they will work just fine here. their reputation for durability and longevity, PROVIDED THEY ARE INSTALLED WELL, is comparable to that of the big brands. they just cost more in electricity to run over the long term, around 5ish years.

generally speaking though, they get a bad rap from all the low bidder work that is done with them. low bidder hacks generally speaking, do terrible quality work. low bidders, as you might guess bid the cheapest possible systems... and these cheap units then fail sooner as a result of the poor quality work.


you ask wether or not a particular unit will work in 20 below. i cannot answer this with any practical experiance, as i have never worked on this york unit you mention, nor am i a professional installer. im just a lowely pleb engineering student that just knows more about hvac than most, and more about ducting and supply/distribution systems than probably 99% of hvac installers.

that being said, your ac will work fine, COOLING at 20 below... provided you can actually get the area warm enough to require cooling in such brutal temperatures. if you are asking if it will work as a heat pump at these temperatures, the answer is a most definate no.

heat pumps work very very poorly in such low temperatures. most heat pump function their best around 40-50ish farenheight, hence why they are so popular in hot humid climates. in the rare events where we have temps below those mentioned above, we have emergency electrical heat strips installed into the air handlers. these are basically giant 60 amp hair dryers. these heaters absolutely sodomize your electrical bill, so generally they only come on when indoor temps plummet beyond what is reasonably bearable... poor folks will sometimes just fire up an electric blanket rather than use the heat strip.

with ALL of the above being said, why would you even try cooling with equipment when the outside temps are so favorable? you might consider installing an economizer unit... this will sense outdoor temp and humidity and blend, or wholly divert outside air into the air distribution system.

i know what you are saying though, Oh noes, what about the co2? well fuck it, what do you think costs more, electricity or burnt propane or natural gas? simply over size or stage what ever equipment you use to generate co2. its absolutly insane to use an ac system in that circumstance lol.

at -20 your condensing units should collecting snow, awaiting summer time.

Wow! You bring up some really good points and great information! I didn't realize that the Yorks have 2 compressors and the size of the duct is really going to matter.

I would go with the Goodman but I need as much savings in electric possible due to the fact that I'll be close to running almost the Max Load for the panel (accounting for 80% rule). So now that I know I'm going to run 2 x 3 Ton York's, I have to figure out this duct work.

So you don't know what the number 5 on a dice looks like? You know like the dice at the casino when you are playing Craps and you throw those cube dice? If you look at the number 4, there are 4 dots on that dice. Those will represent the lights. The other dot on the number 5 will represent a vent. So for each 4 lights in the room, there will be 1 vent which would make 4 vents in the 16 lighter.

So each 3 ton AC will have 2 vents in the room. Do you have any idea what size vents that I would use so that both compressors work?

As far as dehumidification, I'm going with Santa Fe dehumidifiers.

Again I thank you for your knowledge. You seem to really know your stuff and want to talk so I'm going to pick your brain in case you disappear when I really need you. Then I'll have everything in this thread to look at.

 

[billyboat]

over sizing is inefficient. an over sized system will cycle too often, dehumidify poorly, and filter poorly owing to short duty cycles. what do you think all that costs you?

the golden rule for sizing any hvac system is the manual j(for small systems) or similar approximations based on ASHRAE documentation.

Disagree...as manuals don't work for grow room design...two 4 or even a 4 and a 3 ton units with the thermostats set about 5 degrees apart will work very well for the room. I've always used the 6k btu per fixture as that accounts for all the wild cards....Dehuys running full blast end of flower, end of flower and its super hot outside....This isn't over sizing by a bad amount

In my 20 light rooms I also have no ducting for each of the 5 ton ac's and it cools very evenly in there.

 

[Snype]

Here are the specs for the York 3 ton CZH03611(C):
https://www.theacoutlet.com/docs/CZH.pdf

Unit Supply Voltage: 208-230V, 60Hz
Normal Voltage Range: 187 to 252
Minimum Circuit Ampacity: 23.6
Max. Overcurrent Device Amps: 40
Min. Overcurrent Device Amps: 25
Compressor Type: 2-Stage Scroll
Compressor Amps
Rated Load: 16.7
Locked Rotor: 82
Fan Motor Amps - Rated Load: 2.8
Fan Diameter Inches: 24
Fan Motor
Rated HP: 1/3
Nominal RPM: 685
Nominal CFM: 3200
Coil
Face Area Sq. Ft: 23.6
Rows Deep: 2
Fins / Inch: 16
Liquid Line Set OD (Field Installed): 3/8
Vapor Line Set OD (Field Installed): 3/4
Unit Charge (Lbs. - Oz.): 14 - 10
Charge Per Foot, Oz: 0.62
Operating Weight Lbs: 305

 

[queequeg152]

i dont think you understand what the manual j actually is.

the 'manual' in the name referrs to the reference material that you buy from ACCA. inside this manual you find tables and equations and procedural and work flow information that instruct you how to fill out the spread sheet properly. if you were just handed the J calculation spread sheet... it would make zero sense what ever. you refer to the manual J book to fill everything out.

the actual manual J calculation is just a set of agreed upon parameters and estimataion equations based on established ASHRAE documents.
you can do the manual J calculation completely within BIM software, or within stand alone hvac software, or inside an excell spread sheet, or on a paper spread sheet( the origional way).


that pdf is meaningless to us. its simply a collection of equipment specifications.
give it to your installer. he will need it to select the equipment, as well as to make calculations, if any are done at all.

these tables give you values like sensible cooling... total cooling and various capacities of vairous pieces of equipment. without knowing exactly what is going into your building, this document is usless in this discussion.

when you are making calculations... you can put in the design outdoor temps, design indoor temps, and find your projected total cooling and sensible cooling for each stage. to find the projected CFM of a particular air handler, you need to calculate the TESP, and compare it against the air handler documentation, find the cfm it will produce at such and such static pressure, then go back to your coil and condenser data sheet and collect your tc and sc.

some of the fancier air handlers will read from a pitot static system, and ramp up to reach a specific cfm, but most are simpler 3 speed ECM blowers that simply run up to a specific RPM and hold.

this is very important information for your hvac tech because a 5 ton system will almost NEVER be removing 64kbtu. generally speaking, the hotter it gets, the less efficient these units become. also, generally speaking, the lower the volume of air passing the coil, the less effieicnt the unit becomes. in the worst case scenarios... 100+ degrees out, your 64kbtuh 5 ton condensing unit might only remove like 55kbtuh.

again though, i HIGHLY reccomend you avoide a 2 stage system... unless you extensively calculate the heat gain and losses... they make 0 sense financially speaking if they are not sized properly as i said above.

 

[stoney917]

Im not saying oversize but more like correct size with some play... not maxing a unit out n having to turn lights off.... 1/2 ton per 1k light...

 

[queequeg152]

i know what you are saying, but its a rule of thumb. rules of thumb are not what i would call a golden rule.

a half ton per 1kw light might means you have an excess capacity upwards of 2000btuh per light.

someone in a basement, with a conditioned space above will have almost 0 heat gain from their surroundings.. hence that half ton approximation becomes oversizing.

rules of thumb are the reason why brand new 1200sqft houses here in texas are being fitted with 4 and even 5 ton air conditioners.... people take their particular rule of thumb thats based on shitbox 1970's tract homes, and apply it to tighter better insulated newer homes.... resulting in terribly oversize units with poor IAQ control.

yea that 5 ton will keep folks happy in the summer time, but they could of had a 2-3 ton doing the same job, more efficiently, filtering longer, dehumidifying better, with smaller quieter equipment.

 

[Snype]

i know what you are saying, but its a rule of thumb. rules of thumb are not what i would call a golden rule.

a half ton per 1kw light might means you have an excess capacity upwards of 2000btuh per light.

someone in a basement, with a conditioned space above will have almost 0 heat gain from their surroundings.. hence that half ton approximation becomes oversizing.

rules of thumb are the reason why brand new 1200sqft houses here in texas are being fitted with 4 and even 5 ton air conditioners.... people take their particular rule of thumb thats based on shitbox 1970's tract homes, and apply it to tighter better insulated newer homes.... resulting in terribly oversize units with poor IAQ control.

yea that 5 ton will keep folks happy in the summer time, but they could of had a 2-3 ton doing the same job, more efficiently, filtering longer, dehumidifying better, with smaller quieter equipment.

Everything you are saying is making a lot of sense to me. You have my full attention. Would you happen to know about the duct size from what the variables I stated in post #22?

 

[queequeg152]

Wow! You bring up some really good points and great information! I didn't realize that the Yorks have 2 compressors and the size of the duct is really going to matter.

I would go with the Goodman but I need as much savings in electric possible due to the fact that I'll be close to running almost the Max Load for the panel (accounting for 80% rule). So now that I know I'm going to run 2 x 3 Ton York's, I have to figure out this duct work.

So you don't know what the number 5 on a dice looks like? You know like the dice at the casino when you are playing Craps and you throw those cube dice? If you look at the number 4, there are 4 dots on that dice. Those will represent the lights. The other dot on the number 5 will represent a vent. So for each 4 lights in the room, there will be 1 vent which would make 4 vents in the 16 lighter.

So each 3 ton AC will have 2 vents in the room. Do you have any idea what size vents that I would use so that both compressors work?

As far as dehumidification, I'm going with Santa Fe dehumidifiers.

Again I thank you for your knowledge. You seem to really know your stuff and want to talk so I'm going to pick your brain in case you disappear when I really need you. Then I'll have everything in this thread to look at.

my last post of the night. this is becomeing too distracting for me, and ive studying to do. HVAC and refrigeration tech is one of those strange areas where i became ultra obsessive and fixated on.


i see what you are saying now regarding the lightings and position of the supply register.

let me first say that ive no first hand experiance in heating and cooling grow rooms. and also ive no idea what other means of air circulation will be in use in this room. conventional wisdom in the placement of registers has registers close to, and blowing onto sources of heat gain, such as windows and exterior walls.

if we extend that concept into the grow room, it stands to reason that it is reasonable to orient and position the registers such that they hit each light, or atleast get directed in their general direction like in your design.


however let me say this. 3 ton units typically run around 1100-1300ish cfm. thats 650 cfm roughly per register.
in order to achieve the throws you need to effectivly cover a room this size with only 4 registers, you are probably going to need something like 700-800 feet per minute at the throat of the register.

this velocity is somewhat inefficient.
pressure losses accumulate as a function of velocity pressure aka ram air pressure( think momentum of moving air).
velocity pressure varies with the SQUARE of velocity... meaning at 500 fps you might get a pressure drop of say .1 inches but at 1000fps you get far more than double that, say .4 inches.

this higher velocity system will result in a marginally higher pressure loss, which will inturn result in marginal increases in power consumption with most blowers. you will however save money on duct construction.

now... if the only downside was marginally higher losses in the duct system it would be a non issue. these losses account for very little interms of overall energy efficiency, with respect to the system as a whole at least ... but unfortunately a supply layout like this could suffer from poor distribution.

too few registers throwing air not far enough will result in stratification of warm and cooler air. this stratification can cause issues with percieved comfort levels and shit like return air intakes...

in a situation like this, where you have huge fluxes of heat inside the conditioned space coming not only from the fixtures themselves, but from the IR light baking into the surfaces of what ever the lighting is pointed at....

IMO you would want to have the supply somewhat closer to the gorund, much closer if you have higher ceilings... several feet above these fixtures im thinking is ideal. Your return air should be on a high side wall or ceiling.

i would argue that high velocity drum louvers would work better, however im not sure if they would throw far enough to reach the middle of this room. and it makes no sense to combine the two diffuser types.
you said it was like 25 feet wide?
drum louver diffusers would work perfect if this room were thinner and longer...

i HIGHLY reccomend you consult the hart and cooley duct diffuser specifications and find a ceiling type round, or 4 way diffuser.

you will want a balancing damper in each of these supply branches.

your supply trunk should be simple.

something like 16x16 cross sectional area feeding the first branch duct(branch duct should be around 10x10 or 11x11 or 11x10 etc), then necking down to 10x10 or 11x11, then terminating with a long radius elbow or vaned elbow into the terminal register.

you will balance these registers with that anemometer i mentioned earlier.

these are crude estimations, with no basis in maths or any real calculations... id still highly suggest you getting a proper j calculation done, if to no other reason than that they are cheap at least when compared to the cost of HVAC equipment and labor.

 

[Snype]

my last post of the night. this is becomeing too distracting for me, and ive studying to do.

IC will do that to you.

I think I got every bit of information that I could ever need! I'm going to print this out and show it to my HVAC guy. If he doesn't know what you are talking about, then I'll know he's not the guy. Good people who do great work are hard to find these days. Thanks again for all your information and help. I didn't expect to get any of these types of details. This information is going to help a lot of members out. Good luck on your studying.

 

[queequeg152]

here are the hart and cooley catalogues...

look through these, and figure out what registers work best for you.... find something that can throw the whole distance to all of the lights... AND is in the configuration that you want, ceilings 4 way direction... then find what velocity that you need to accomplish this ,then size your duct, and duct velocity accordingly.

http://www.hartandcooley.com/assets/files/1/hartandcooley_grd_commercialcatalog_0914_ed10.pdf

http://www.hartandcooley.com/assets/files/1/hartandcooley_grd_commercialcatalog_0914_ed10.pdf

generally speaking commercial registers are better quality... but also cost a shit load.
drum louver type side wall registers mentioned above are examples of very neat, well engineered commercial quality registers. These registers cost a shit load though. probably 10x what you would pay for a shitty stamped steel home depot type register.

 

[Snype]

Glad I started the thread. I was trying to figure this out before in other threads. I finally have some information to work with. Just happened to be the right place and time. Thanks again!

So many things I don't think the HVAC guy would have thought of. 4 way deflection with those vents. Sounds great!

The only thing I'm confused about is:

however let me say this. 3 ton units typically run around 1100-1300ish cfm. thats 650 cfm roughly per register.

It says on the Spec Sheet that it's 3200 CFM. But don't bother answering it now. Anytime you are free.

 

[queequeg152]

no thats the condensing units fan not the air handler.

 

[Snype]

no thats the condensing units fan not the air handler.

Ok but I see the spec sheet for all the models and if you add them both up it's still around 1,800 - 2,100 CFM on page 4 and 5. Maybe this AC is better than you thought. One register is around 800 and the other one is around 1200 which is 2,000 CFM. So I guess it pushes more air than you thought.

https://www.theacoutlet.com/docs/CZH.pdf

 

[Snype]

York® Affinity™ Residential Communicating Control
http://www.york.com/residential/pro...finity-residential-communicating-control.aspx

 

[r2k]

You can purchase your own copy of Manual J online for $154 at this link: http://www.acca.org/technical-manual/manual-j/ (click on the "Buy from ACCA" link). Then again, google has it for $99.20 with the link to google on that same page. You can also rent it from Amazon for $65, again with a link on that page. Supposedly, you can find a free online calculator here: http://www.loadcalc.net/ but I haven't tried it.



I would vote for two units of 3 tons each (or whatever). If one fails, you still have the other as backup and won't be totally stuck with no AC.

Depending on what you do, you might want to think about splitting the room in two and run 8 lights at a time. That will cut your AC needs down to 3 tons instead of 6 tons. This would reduce the electric service requirements you have and all kinds of other considerations. This won't do much if you want to run the entire room and all 16 lights at the same time during veg, but I suspect you won't want to do that. If you get it down to 3 tons capacity, you could buy two or three split systems. Home Depot has a 1 ton split system for $1200 + tax.

I have a 3 ton A/C unit on my house and the outside unit is quite large, probably 3 ft square and 4 foot tall. I can't imagine what a 6 ton looks like, but I think it will be really big. The indoor air handler is also something to respect. I sometimes have to do repairs on it and the blower motor in there is scary. I definitely take all precautions to avoid contact with moving parts. That thing will slice and chop rocks when it gets up to speed.

-r2k

 

[berad4guvna]

Hey Snype

Hey Snype

The room is 25 feet by 33 feet. I finally found an HVAC guy but I'm used to people not being as anal as me and getting shabby work. These are the same questions that I'm going to ask him but I trust you guys more. I want to be able to know what I'm talking about when I talk to him so I want to here some opinions.

I'm wondering if it would be better to have 2 x 3 Tons or 1 x 6 Tons?

Also, I'm looking for a top of the line commercial model. Any suggestions?

Hey, Synpe it's been a min. I enjoyed your threads over at a place not worth mentioning. "especially your food pics lol!"

I saw your post last night and did some digging for ya...

Not sure if you have ever seen jackmayoffer's Aptus grow. He rocks 80 Kw HPS/Gavitas. This may help its a direct quouted from Jack "With a fully sealed and fully insulated room we run 2 x 5 tons or 1 x 10 ton units for every 20 to 25 lights the 40 k room has 2- 5 ton splits and 1- 10 ton package unit for a total of 20 tons of ac."

He mentions the benefit of AC overkill. The AC run bes cycled via relays as mentioned. It cuts down on your system load. He also recommends over kill because if one unit fails/goes out, your not fucked. Besides who wants an HVAC guy around when your rocking a 16 lamper.

^This guys climate, and room was the best Ive seen. Clean setup. I'll post a few pics.


This image show a bit of his duct work.

Also You spoke about controlling heat spikes. I wasn't sure if you new about this Gavita controller. "It makes you basically the light God in your room." Hope this helps.

Lighting control at your fingertips



Using a Gavita Master controller to control your e-series fixtures offers you maximum control, ease of use, plug and play installation and safety. Just connect the controller cables to the fixtures with the included T-splitter (see diagram), set the dials on the fixtures to EXT (External control), plug the controller and the fixtures directly into mains and you are set to go.
The controller can switch all the interconnected fixtures on and off with its internal timer, adjust them to your required output level (in percentage or exact output power) and even simulate sunrise and sunset to gradually adjust the climate in your grow room when your lights go on or off. This electronic controller replaces expensive lighting timers and contactors while preventing ballast current in-rush when switching on your lights.
Two very important features are the autodim function and emergency shut-down. When the temperature in your grow room rises beyond the control level of your climate control your crop can be damaged beyond recovery. The temperature probe senses this and will automatically dim the lights to not overshoot your safe temperature, and maintain it. The display and warning LED indicate when this happens, and also indicate if this has happened while you were away so you can correct the problem. If for any reason your climate control completely fails and the temperature rises to unacceptable levels the system will perform an emergency shutdown of all connected equipment. The alarm contact of the controller can be connected to your alarm system for instant notification.
You can connect all your e-series fixtures to one controller, even divided in 2 separate rooms with their own temperature sensor for auto-dim at high temperature and emergency shutdown at extreme temperature. For auxiliary equipment you can connect up to two accessory Gavita ECM contactor modules, one to switch equipment when lights are on (for example a humidifier, CO2 equipment or air conditioning) and one for during lights off (for example a room heater).

Features & Benefits

• No need for a switchboard
• No high inrushes (ballast is always stand-by)
• Easy and safe installation (low voltage device)
• Protected against shortcuts
• Double temperature safety feature (autodim/auto shutdown)
• External alarm connection (txt/e-mail/alarm)
• For 80 ballasts, or 2x40 in two 12/12 rooms
• For DigiStar and Pro-lines e-series, incl. LEP
• Sunrise/sunset built in (0-30 mins)
• Show output in % or Watts
• Celsius or Fahrenheit and 24 hr/AM/PM
• Calibrate temperature sensor

Specifications

• 24 hour timer (on/off): Yes
• Set output level: 50-115%
• Select ballast type: 400/600/750/1000W
• Show output as W or %: Yes
• Auto-dim at set temp: Yes
• Auto shutdown at set temp: Yes
• Sunrise / sunset period: Yes
• Outputs: 2 (main/aux)
• Number of ballasts per output: 40
• Total number of ballasts: 80 (either in one room or 2x40 in 12/12)
• Temperature sensors: 2 (for two rooms 12/12)
• Alarm contacts NO/NC: Yes
• External Contactor Modules (ECM): 2 optional
• Warrenty: 3 years
• Article Number: 60.56.00.23.10 (EU) | 60.56.00.24.11 (UK) | 60.56.00.12.20 (US) | 60.56.00.24.60 (AU)
• EAN code: 8718403051742 (EU) | 8718403051766 (UK) | 8718403051780 (US) | 8718403051803 (AU)
• 

 

[berad4guvna]

Missing Jack my offer pics.

Missing Jack my offer pics.

I Don't know why the pictures will not post? Damm

 

[berad4guvna]

Hopefully below you can see the pic's sorry for three posts. lol

 

[queequeg152]

Ok but I see the spec sheet for all the models and if you add them both up it's still around 1,800 - 2,100 CFM on page 4 and 5. Maybe this AC is better than you thought. One register is around 800 and the other one is around 1200 which is 2,000 CFM. So I guess it pushes more air than you thought.

https://www.theacoutlet.com/docs/CZH.pdf

im not sure where you are looking to find those numbers, but look at page 5.

find your 3 ton unit... the czh03611. move over to the right, select your air handler model, then move over to the right again, find your coil... then you find your stage 1 and 2 cfm values.

these are stages, so the cfm is NOT cumulative... its first running at 860 for example, then 1300 in stage 2.

a 3 ton unit with a 5 ton air handler would be a terrible thing as it would dehumidify very poorly.

nm nm. i re read your post. you dont add the stage cfm values like i said above.