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Old 02-19-2013, 10:50 PM   #46
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Will the size of my ducts have to be changed?


I fine tuned this load calculation program today and found a few mistakes I made. But I was really surprised when the total results today ended up recommending only 1 ton when the 1st one I did recommended 1.5 ton.

How I figured out how this happened was when I was inputting living
room numbers the selection for ceiling type in living rooms gave 4 choices: 1.) under ventilated attic 2.) under unheated room 3.) roof on exposed beams/rafters 4.) roof-ceiling combinations.

My living room ceiling is under the 2nd story. There are two bedrooms above the living room ceiling.So there is no choice to make with the program so I assume I just dont put anything regarding the living room ceiling.

I realized when I got the 1.5 ton recommendation on my 1st calculation that it was because I put the living room ceiling information into the program. I had inputted one of those 4 choices when in fact I should not have put anything. When I leave the ceiling type out of the calculations the program recommends 1 ton.

The total on the sheet of 1600 plus sq feet is the right square footage for my house. I just want to make sure my load calculations are right before I walk into to meet HVAC guy and he thinks I am crazy. I entered all exterior walls,window sizes,patio door,ceiling sq ft where it is applicable,doors,etc,... I dont look at these sheets with the results everyday but once a person goes over this program a couple of times its not that hard. The recommendations are also based on outdoor temperatures which are listed on the front of this sheet. Any thoughts?
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Old 02-20-2013, 04:37 AM   #47
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Will the size of my ducts have to be changed?


Since they don't make a 1 ton, you'll still get a 1.5 ton. id you enter a value for additional heat gain for kitchen appliances.
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Old 02-20-2013, 09:24 AM   #48
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Will the size of my ducts have to be changed?


Your at 13,800 with no heat load consideration as BT said, I would do the 1.5, even if they had a 1.0.





Quote:
Originally Posted by Pawl View Post
I fine tuned this load calculation program today and found a few mistakes I made. But I was really surprised when the total results today ended up recommending only 1 ton when the 1st one I did recommended 1.5 ton.

How I figured out how this happened was when I was inputting living
room numbers the selection for ceiling type in living rooms gave 4 choices: 1.) under ventilated attic 2.) under unheated room 3.) roof on exposed beams/rafters 4.) roof-ceiling combinations.

My living room ceiling is under the 2nd story. There are two bedrooms above the living room ceiling.So there is no choice to make with the program so I assume I just dont put anything regarding the living room ceiling.

I realized when I got the 1.5 ton recommendation on my 1st calculation that it was because I put the living room ceiling information into the program. I had inputted one of those 4 choices when in fact I should not have put anything. When I leave the ceiling type out of the calculations the program recommends 1 ton.

The total on the sheet of 1600 plus sq feet is the right square footage for my house. I just want to make sure my load calculations are right before I walk into to meet HVAC guy and he thinks I am crazy. I entered all exterior walls,window sizes,patio door,ceiling sq ft where it is applicable,doors,etc,... I dont look at these sheets with the results everyday but once a person goes over this program a couple of times its not that hard. The recommendations are also based on outdoor temperatures which are listed on the front of this sheet. Any thoughts?
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Old 02-20-2013, 11:20 AM   #49
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Will the size of my ducts have to be changed?


1.) I included 1200 btuh's for the kitchen appliances and another 1000 btuh's as suggested by this program for the computer in the family room.

2.) Is it also safe to say that under Design Conditions the outdoor temperature given by the program for summer temperatures is correct? I assume those numbers are the most update average over a lot of years.

3.) Is a 1.5 ton unit large enough to cool my house during a heat wave where we are up the high 90s and even higher. I understand heat waves are not an everyday normal temperature I am just asking how a 1.5 ton unit will handle a heat wave. Southern Calif in notorious for high temps.

4.) How does a 1.5 ton unit handle keeping my house warm during the winter. Is a 1.5 ton recommended size for a unit from a load calculation a measurement for air conditioning only or is it for both heating and air conditioning? My current 1975 heating unit is rated @ 100,000 btuh and 80,000 btuh (bonnet capacity).
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Old 02-20-2013, 02:38 PM   #50
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Will the size of my ducts have to be changed?


I need help with this:

When I first filled out the Manual J Calculations online program I inputted under "Design Conditions" the name of my city (Cypress,Ca) it automatically showed for my city a Summer temperature of 80 and a Winter temperature of 43, Summer grains of moisture @ 84,and a daily temperature range was Medium.

When I look at neighboring cities on these tables I see Summer temperatures of 88/89 so I felt something was not right. So I brought up the Manual J Load Calculations chart which shows a California Micro Climate table on page 32 that lists my city of Cypress. For Cypress this table shows a Summer Temperature of 89 and a Winter temperature of 38.

Now when I manually input this Summer Temperature of 89 and Winter Temperature of 38 it now shows I need a 2 ton unit.

1.) Does this sound right to everybody?

2.) If that in fact is right does the "Summer grains of moisture 84" change and does the "Daily temperature range of Medium" change?

Click here for Manual J load calculations chart: http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf
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Old 02-20-2013, 02:52 PM   #51
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Will the size of my ducts have to be changed?


Quote:
Originally Posted by Pawl View Post
Now when I manually input this Summer Temperature of 89 and Winter Temperature of 38...

Does this sound right to everybody?
You're the one who lives there. You tell us if it sounds right.

Thirty five years ago lived up the coast a bit in Newport (and Costa Mesa)
I don't recall it being that cold (or warm).
http://en.wikipedia.org/wiki/Newport...fornia#Climate

Last edited by TarheelTerp; 02-20-2013 at 02:57 PM.
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Old 02-20-2013, 03:22 PM   #52
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Will the size of my ducts have to be changed?


Will a 1.5 work, dont know sounds like my scenario with the 3 ton. It worked mostly, but would run a very long time on the hot days and just be ok. If that bothers you, then I suggest you go to 2 tons and make sure you can be comfortable on the extreme days.

REMEMBER i am speaking to you as a homeowner to another homeowner, I am not an expert.


Quote:
Originally Posted by Pawl View Post
I need help with this:

When I first filled out the Manual J Calculations online program I inputted under "Design Conditions" the name of my city (Cypress,Ca) it automatically showed for my city a Summer temperature of 80 and a Winter temperature of 43, Summer grains of moisture @ 84,and a daily temperature range was Medium.

When I look at neighboring cities on these tables I see Summer temperatures of 88/89 so I felt something was not right. So I brought up the Manual J Load Calculations chart which shows a California Micro Climate table on page 32 that lists my city of Cypress. For Cypress this table shows a Summer Temperature of 89 and a Winter temperature of 38.

Now when I manually input this Summer Temperature of 89 and Winter Temperature of 38 it now shows I need a 2 ton unit.

1.) Does this sound right to everybody?

2.) If that in fact is right does the "Summer grains of moisture 84" change and does the "Daily temperature range of Medium" change?

Click here for Manual J load calculations chart: http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf
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Old 02-20-2013, 05:17 PM   #53
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Will the size of my ducts have to be changed?


An almost 10 degree increase in outdoor summer design temp would easily increase size by 1/2 ton. What was the new sensible load it gave you for cooling.
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Old 02-20-2013, 05:48 PM   #54
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Will the size of my ducts have to be changed?


I am assuming that the information the Acca Manual J Load calculations program is putting out is accurate but I am a 1st time user of this program and following a lot of recommendations to do a load calculation on my home first. I have not had anyone tell me to be careful about any misinformation coming from this program so I assume it is up to date but that is all I can be certain of until I do some more research.

I am going to try and find out some more sources of information to come to a conclusion on the temperatures in my area. With that said I am going to have to do some more homework on how they are coming up with their numbers.

1.) Are the summer and winter outdoor temperatures an average of the last 5 years,10,20 or even the last 30?

2.) What specific months are considered winter months and what months are summer as far as the calculations are concerned?

I looked up Newport Beach and Costa Mesa under the California Micro Climate table shown on the Acca Manual J Load calculations program.

(Summer/Winter temperatures/Elevation) for N.Beach were S76/W41/E10' --- Costa Mesa were S77/W38/E75' --- both of these cities are right by the ocean.

These next 4 cities including mine are all next to each other. We are approximately 14 miles from the ocean. Summer/Winter temperatures/elevation for Cypress are S89/W38/E75' ----Cerritos are S89/W40/E34' --- Stanton S88/W38/E45' --- Buena Park S89/W38/E75'
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Old 02-20-2013, 06:08 PM   #55
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Will the size of my ducts have to be changed?


The summer design temp is the 97 1/2% temp. meaning only 2.5% of the time in a normal summer will the temp get above the design temp.

Not sure how many years the design temp is calculated from.
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Old 02-20-2013, 07:13 PM   #56
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Will the size of my ducts have to be changed?


Quote:
Originally Posted by beenthere View Post
An almost 10 degree increase in outdoor summer design temp would easily increase size by 1/2 ton. What was the new sensible load it gave you for cooling.
updated calculation which is 9 degrees higher on the summer temperature than the original calculation of 80 degrees and its saying or recommending a 2 ton unit. If you scroll up the original calculation is at the top of this page
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Last edited by Pawl; 02-20-2013 at 07:32 PM.
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Old 02-20-2013, 07:43 PM   #57
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Will the size of my ducts have to be changed?


A 2 ton will just barely meet your sensible cooling load. A 2.5 ton with the blower set to 350 CFM per ton will meet it with a little to spare. And provide better heat in the winter.
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Old 02-20-2013, 08:21 PM   #58
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Will the size of my ducts have to be changed?


Quote:
Originally Posted by beenthere View Post
A 2 ton will just barely meet your sensible cooling load. A 2.5 ton with the blower set to 350 CFM per ton will meet it with a little to spare. And provide better heat in the winter.
I am trying to understand how the CFM works. 1.) Are you saying at 350 CFM per ton a 2.5 ton unit will produce 875 CFM?

2.) If 875 CFM is true then will the new duct system will be designed to deliver that amount to all the rooms in my house and the HVAC people will balance the system distribute to this amount?

3.) What specific months are considered winter months and what months are summer as far as the calculations are concerned?

4.) And provide better heat in the winter <<<< did you mean a 2.5 ton versus a 2 ton will provide better heat?
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Old 02-21-2013, 02:10 AM   #59
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Will the size of my ducts have to be changed?


From what I have read it sounds like for Design Conditions concerning Outdoor averages regarding Summer and Winter temperatures they are actually tracked over the entire year.
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Old 02-21-2013, 04:35 AM   #60
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The temps are tracked over many full years. How many is what I'm not sure of anymore.

The duct system should be designed for the full 400 CFM per ton(1000CFM for a 2.5), and then the blower set to only move 350 CFM per ton(875CFM). The installers should balance it out to each rooms needs then. With any excess air being equally allotted to each room.

Which months are in what category varies slightly by area. Here Sept is neither winter or summer, since or the most part neither heat or cooling is needed. Look up the heating and cooling degree days for your area, And you be able to see what months are in which category.

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