Rooftop A/C For 3,000 Sq Ft Shop - HVAC - Page 4 - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 04-29-2011, 07:10 PM   #46
Member
 
JJboy's Avatar
 
Join Date: Oct 2010
Location: Austin - Texas
Posts: 1,402
Rewards Points: 500
Default

Rooftop A/C for 3,000 sq ft shop


Quote:
Originally Posted by John D in CT View Post
"Your questions are impossible to answer without knowing the load".

I respectfully disagree.

If you are so right about this why you're asking?


Is there anyone who is willing to share some thoughts on some general principles and strategies involved in striking a balance between maximized cooling capacity and acceptable cycle times?

Why your concern over these subjects? If you do not want to pay someone to do the load calc. Ask whoever is going to do the load calc
.

Thanks.

Get the load calc, buy the a/c system, pay a pro to install and go drink a beer

Advertisement

__________________

**Always kill the power ** Hot air rises, but heat will always move from higher to lower temperatures. ** Real man shoot in manual. ** If it ain't grounded, it ain't dead.
JJboy is offline   Reply With Quote
Old 04-29-2011, 07:17 PM   #47
Hvac Pro
 
Join Date: Nov 2008
Location: Winnipeg, Canada
Posts: 10,084
Rewards Points: 806
Default

Rooftop A/C for 3,000 sq ft shop


I agree.
Attached Images
 
__________________
"Cut it twice and it is still too short".

Last edited by yuri; 04-29-2011 at 07:21 PM.
yuri is offline   Reply With Quote
Old 04-29-2011, 07:23 PM   #48
Member
 
Join Date: Nov 2010
Posts: 37
Rewards Points: 25
Default

Rooftop A/C for 3,000 sq ft shop


"If you are so right about this why you're asking?"

Because it makes no sense to me that there aren't general principles involved in balancing cooling capacity and cycle times that are independent of load; but then, I've already said that.


"Why your concern over these subjects?"

I've already gone into that at length as well. And do you really care why I care?


"Ask whoever is going to do the load calc".

I choose to ask here, if that's OK with you.


Would anyone be so kind as to share some general thoughts on what I see as an inherent trade-off between having maximum cooling capacity for the hottest days of the year, while maintaining acceptable cycle times during the majority of the cooling season?

Thanks.


John D in CT is offline   Reply With Quote
Old 04-29-2011, 07:35 PM   #49
Member
 
JJboy's Avatar
 
Join Date: Oct 2010
Location: Austin - Texas
Posts: 1,402
Rewards Points: 500
Default

Rooftop A/C for 3,000 sq ft shop


Quote:
Originally Posted by John D in CT View Post
"If you are so right about this why you're asking?"

Because it makes no sense to me that there aren't general principles involved in balancing cooling capacity and cycle times that are independent of load; but then, I've already said that.

Why doesn't it make sense to you? What makes you think that?

"Why your concern over these subjects?"

I've already gone into that at length as well. And do you really care why I care?


"Ask whoever is going to do the load calc".

I choose to ask here, if that's OK with you.


Would anyone be so kind as to share some general thoughts on what I see as an inherent trade-off between having maximum cooling capacity for the hottest days of the year, while maintaining acceptable cycle times during the majority of the cooling season?

Thanks.



You need to ask this in the HVAC PRO forum.
__________________

**Always kill the power ** Hot air rises, but heat will always move from higher to lower temperatures. ** Real man shoot in manual. ** If it ain't grounded, it ain't dead.
JJboy is offline   Reply With Quote
Old 04-29-2011, 07:53 PM   #50
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,458
Rewards Points: 4,562
Default

Rooftop A/C for 3,000 sq ft shop


Quote:
Originally Posted by JJboy View Post
You need to ask this in the HVAC PRO forum.
He's not an HVAC pro.
beenthere is online now   Reply With Quote
Old 04-29-2011, 09:41 PM   #51
Member
 
Join Date: Sep 2010
Posts: 135
Rewards Points: 75
Default

Rooftop A/C for 3,000 sq ft shop


I have a 2000 sq industrial condo in hamden, ct. It has two insulated overhead doors. The walls are insulated and there is a drop ceiling with 2 inch pads covering the entire unit. The building is metal construction.

The cooling is 5 tons and does a great job.
I would think 3 tons will work for each 1000 sq foot space.
Artco is offline   Reply With Quote
Old 04-29-2011, 10:04 PM   #52
Member
 
Join Date: Nov 2010
Posts: 37
Rewards Points: 25
Default

Rooftop A/C for 3,000 sq ft shop


Thanks for that Artco.

Before anyone has a heart attack, I'd like to reiterate that I'm going to have my load requirements calculated by a professional. I keep seeing that "Manual J" is a well-respected method, so I'll look into having that done.

Did you have your system professionally sized? As others have pointed out I'm not an HVAC professional, but 5 tons sounds a little high. Do you find that it cycles on and off a lot when it's not very hot out?

***

To whom it may concern:

Let me try to present my big question another way:

If you did a load calc and it was exactly midway between two sizes, would you go up, or down, and why.

If you went down, would the system then be unable to achieve the "design" indoor temperature on the hottest day(s) of the year? If it couldn't (and I don't see how it could), would this seem like a worthwhile compromise to you in order to maintain system efficiency for the majority of the cooling season?

If you went up, would you be sacrificing some energy efficiency and dehumidifying capacity in order to achieve sufficient cooling on the hottest day(s) of the year?
John D in CT is offline   Reply With Quote
Old 04-29-2011, 10:21 PM   #53
Member
 
Join Date: Sep 2010
Posts: 135
Rewards Points: 75
Default

Rooftop A/C for 3,000 sq ft shop


We are in the air conditioning business and the 5 ton unit was there when we bought the building.
Again this is a metal building with a 2 inch thick drop ceiling covering the entire building. It has two 10 ft by 15 foot overhead doors the height from the cement floor to the ceiling pads is 18 feet and above the pads another 4 feet to the roof deck.
When we use the cooling it cools the space good. On really hot days 95+ it runs longer.
Calc loads on industrial buildings is more difficult that a residence especially if you are opening and closing the overhead doors etc...
We air conditioned another unit in our same complex and installed a three ton for 1000 sq ft. And it worked fine.

What kind of heat are you using at thsi time?
Artco is offline   Reply With Quote
Old 04-29-2011, 10:33 PM   #54
Member
 
Join Date: Nov 2010
Posts: 37
Rewards Points: 25
Default

Rooftop A/C for 3,000 sq ft shop


I started out with two 125,000 BTU gas unit heaters that did fine, and now have a 200,000 BTU Energylogic waste oil furnace that also does fine (by itself). It keeps the 3,000 sq. ft. as warm as I want it on the coldest days.

Since you're in the business, might you be interested in doing a load calc for me if you're out this way? (I'm in Canton). If so, feel free to send me a private message with contact info. And are you familiar with Manual J, or do you use another method?

Last edited by John D in CT; 04-29-2011 at 10:37 PM.
John D in CT is offline   Reply With Quote
Old 04-29-2011, 10:55 PM   #55
Member
 
Join Date: Sep 2010
Posts: 135
Rewards Points: 75
Default

Rooftop A/C for 3,000 sq ft shop


We don't do any new installations. We are a commercial HVAC service company. I would guess that 7.5 tons would cool the 3000 sq feet space yo have.
You should if you haven't done so already gasket (seal) the overhead doors.
Do you have a duct system or is there just duct outlets coming off the top of the furnaces?
Remember cool air drops so you are not really cooling too much above 12 to 15 feet off the floor.
In my building the gas furnace/air handler/ "A" coil is located on a 12 foot mezzanine located in the back of the building with horizontal ducts running out about 20 feet with 6 foot down drops and supply registers. This puts the supply registes about 15 feet off the floor.
The return grille is located at floor level so it draws the cooler air back to the unit.

Where you have the duct work is important for cooling and heating this type of building.

We have paddle fans (two) variable speed and use them in the winter to help pump some of the heat from the ceiling down. These are usless in the summer.
Artco is offline   Reply With Quote
Old 04-29-2011, 10:57 PM   #56
Member
 
Join Date: Sep 2010
Posts: 135
Rewards Points: 75
Default

Rooftop A/C for 3,000 sq ft shop


What do you do in your building?
Are cooling temperatures really critical?
Is humidity control really critical?
Artco is offline   Reply With Quote
Old 04-29-2011, 11:12 PM   #57
Member
 
Join Date: Nov 2010
Posts: 37
Rewards Points: 25
Default

Rooftop A/C for 3,000 sq ft shop


The heaters are all suspended about 10' off the floor. None of them involve any ductwork at the moment, just your basic blow-out-that-heat unit heaters. The waste oil furnace is in the middle of the 3 units and does a surprisingly good job of keeping the whole place fairly uniformly warm. I can only imagine what it would do with some ducting. I do have four paddle fans that help keep the heat down where it belongs, and circulating somewhat.

I do a wide variety of things here; woodworking, metal fabricating/welding, light machine work, some automotive stuff.

No, cooling temperatures really are not at all critical, considering I've been suffering through more seasons than I care to think about with no AC at all.

Humidity control is slightly more important with the woodworking; also, we tend to suffer from "wet slab syndrome" on really muggy days.

Advertisement

John D in CT is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
damp concrete floor in shop Richo Building & Construction 18 04-11-2011 04:56 PM
Installing a furnace in my shop pdwoods55 HVAC 3 11-16-2010 06:03 PM
Wiring Shop Scrubbie Electrical 6 03-09-2010 07:23 PM
Wiring shop need advice stqevo Electrical 14 09-03-2009 01:18 PM
Sizing wire/breaker to new shop. Roy Rowlett Electrical 8 04-22-2009 01:29 PM




Top of Page | View New Posts