Forums | Home Repair | Home Improvement | Painting | Interior Decorating | Remodeling | Landscaping


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

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

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-01-2009, 08:11 PM   #1
Member
 
Join Date: Mar 2009
Location: South Caroling
Posts: 59
Share |
Default

Tons


How do you figure what ton unit (heat pump) to use. Is it based off the heated square footage of the home.
Toolmaster is offline   Reply With Quote
Old 06-01-2009, 08:20 PM   #2
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 23,450
Default

Tons


Use HVAC CALC. Its advertised on this site.
beenthere is online now   Reply With Quote
Old 06-01-2009, 08:27 PM   #3
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Default

Tons


Here's another source,
http://www.vonwentzel.net/HVAC/HVAC-...ors/index.html
and most libraries have books on this subject, either to loan or as reference books.
The calculations are very tedious.

Last edited by Yoyizit; 06-01-2009 at 08:29 PM.
Yoyizit is offline   Reply With Quote
Old 06-02-2009, 07:21 AM   #4
Member
 
Join Date: Sep 2008
Location: Upstate New York
Posts: 368
Default

Tons


As a ball park estimate you can use the rule-of-thumb of sq ft per ton, but for a home run get a copy of Manual J from your local library, or as been has suggested buy HVAC-CALC. Once you see what variables Manual J considers you will understand why sq ft per ton is inadequate.
dac122 is offline   Reply With Quote
Old 06-02-2009, 10:58 AM   #5
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Default

Tons


For heating of single family homes, some heat loss values are

.....x......x.x..x.....x.x
0.....|.....|.....|.....|....|
..............................10

where the units are
BTU/sq. ft./HDD

The 1.7 on the left is probably the best that anyone can do. My leaky old house comes in at 8.0. If additional, future data that I collect follows the same pattern you can be reasonably assured that most houses fall between 1.7 and 9 BTU/sq. ft./HDD, with newer houses being tighter.

If anyone has similar data for single family homes for cooling (heat gain) normalized to house sq. footage and cooling degree days I'd like to see it. When I had the 1985 Manual J in my hands I should have used the house in their example.
The cooling datapoints will probably be scattered more than above because the COP varies with outside temp, but oil/gas appliances have a more or less constant efficiency.

There should be some (loose) connection between the heating and cooling load since they're both related to insulation value.

Last edited by Yoyizit; 06-02-2009 at 11:15 AM.
Yoyizit is offline   Reply With Quote
Old 06-02-2009, 05:25 PM   #6
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 23,450
Default

Tons


Quote:
Originally Posted by Yoyizit View Post
There should be some (loose) connection between the heating and cooling load since they're both related to insulation value.
Nope.

Heating is calculated with no solar gain(middle of the night).

Cooling calculated with solar gain(hotest part of the day).

So no real correlation.
beenthere is online now   Reply With Quote
Old 06-02-2009, 05:48 PM   #7
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Default

Tons


Quote:
Originally Posted by beenthere View Post
Nope.

Heating is calculated with no solar gain(middle of the night).

Cooling calculated with solar gain(hotest part of the day).

So no real correlation.
Bit by bit I learn the hands-on of HVAC.
So some of the scatter in my data is due to solar heating and the Manual J calc. is pessimistic since it assumes no insolation?
Yoyizit is offline   Reply With Quote
Old 06-02-2009, 06:03 PM   #8
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 23,450
Default

Tons


Manual J doesn't assume no insultation. It has HTM for multiple insulation values.

The new ver 8 also takes into consideration radiant barriers.
beenthere is online now   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
How many tons Trane XR12 pcampbell HVAC 2 06-09-2008 04:53 PM
Finishing the basement- tons of insulation questions QueenL Building & Construction 2 04-01-2008 01:25 PM
only 3 Tons for 3700 Sf Ft? 1K2GO HVAC 7 11-23-2007 06:13 PM
Very Newbie with tons of questions Aerovette Building & Construction 37 06-13-2007 10:04 PM
figuring what tons are needed pbuzz3323 HVAC 2 07-31-2006 06:40 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.