Sizing Furnace - HVAC - Page 3 - 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 09-08-2009, 07:17 PM   #31
Hvac Pro
 
Join Date: Nov 2008
Location: Winnipeg, Canada
Posts: 10,137
Rewards Points: 912
Default

sizing furnace


Now you got it. The newer homes are a LOT better/tighter. My walls have R20 instead of his R14. My vapor barrier is all glued at every joint in the walls,ceiling. I have close to 1400 sq.ft and easily heat my home with a standard G51 70 which put out 66,000 BTU's but there is a huge difference in house construction in the last 30 yrs. He has a good house but you can only improve so much and then you still need an adequate furnace whith a few extra BTU's. And yes, blown out pilots were a problem, not many left now.

Advertisement


Last edited by yuri; 09-08-2009 at 07:20 PM.
yuri is offline   Reply With Quote
Old 09-08-2009, 07:25 PM   #32
Member
 
hvaclover's Avatar
 
Join Date: Oct 2008
Location: Suburbs of Detroit Mi
Posts: 3,704
Rewards Points: 2,000
Default

sizing furnace


Quote:
Originally Posted by beenthere View Post
Higher winds require higher infiltration rates to be used.

Thats what many miss. They use average, or tight construction ratings.
When the home is actually loose. While a .7 may be ok for many homes.
In high wind areas, a 1, or 1.25 may be more appropriate. And makes a BIG jump in the BTU requirement.

And that is one of the equations that seem to differ enough from load calc to load calc to make a diff in furnace size and comfort.

i have read enough stuff on load calcs that make me want to just put them aside. I have been told at HVAC TALK that it's all in how you use it or that it is like learning to use any new tool, you have to learn how it works.

In this age of high tech electronics you'd think you could buy load programs that all give the same answer every time. That is not true.

If I have to take time to learn a system that doesn't agree with other programs even though they are derived from Man J, what advantage is that.

Look, I am not bragging but I have compared my short form to bids that had three or four manJ calcs all from diff vendors. None of them agreed.
Most were ball park with one another but with the accuracy computers bring they should do better than Ball park. My shortform was in the middle of the ballpark.

I'll stick to it since it is what I know.
__________________
Just slow, not stupid.
hvaclover is offline   Reply With Quote
Old 09-08-2009, 08:05 PM   #33
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,571
Rewards Points: 4,780
Default

sizing furnace


I've seen the same load calc program done by 2 different people come up with a difference BTU.

Its like any other tool. It must be learned. And it does take time.
The more you use one. The closer you can get to the true BTU needed, weather for heating or cooling.
beenthere is offline   Reply With Quote
Old 09-08-2009, 08:07 PM   #34
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,571
Rewards Points: 4,780
Default

sizing furnace


Quote:
Originally Posted by yuri View Post
Now you got it. The newer homes are a LOT better/tighter.
LOL...

Sad thing is.
Houses built in Canada 30 years ago, were often built better, then homes down here in the states are today.
beenthere is offline   Reply With Quote
Old 09-08-2009, 08:19 PM   #35
Hvac Pro
 
Join Date: Nov 2008
Location: Winnipeg, Canada
Posts: 10,137
Rewards Points: 912
Default

sizing furnace


You should visit Europe. There are buildings in Vienna and Switzerland I visited that go back to the 1100's. All stone but they sure last. If they last 150 yrs here we will be lucky. Too cold for termites.
yuri is offline   Reply With Quote
Old 09-08-2009, 08:22 PM   #36
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,571
Rewards Points: 4,780
Default

sizing furnace


Everything is too expensive in Europe.
Even to visit.
beenthere is offline   Reply With Quote
Old 09-08-2009, 08:26 PM   #37
Hvac Pro
 
Join Date: Nov 2008
Location: Winnipeg, Canada
Posts: 10,137
Rewards Points: 912
Default

sizing furnace


Not if you have relatives and friends there. European custom is that the host pays for everything ie: meals etc. I couldn't even give them $$ for anything w/o insulting them. If they visit here then I pay. Hope they stay home. LOL
yuri is offline   Reply With Quote
Old 09-08-2009, 08:36 PM   #38
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,571
Rewards Points: 4,780
Default

sizing furnace


Quote:
Originally Posted by yuri View Post
Not if you have relatives and friends there. European custom is that the host pays for everything ie: meals etc. I couldn't even give them $$ for anything w/o insulting them. If they visit here then I pay. Hope they stay home. LOL
ROFL
beenthere is offline   Reply With Quote
Old 09-08-2009, 09:29 PM   #39
Member
 
hvaclover's Avatar
 
Join Date: Oct 2008
Location: Suburbs of Detroit Mi
Posts: 3,704
Rewards Points: 2,000
Default

sizing furnace


Quote:
Originally Posted by yuri View Post
Not if you have relatives and friends there. European custom is that the host pays for everything ie: meals etc. I couldn't even give them $$ for anything w/o insulting them. If they visit here then I pay. Hope they stay home. LOL
Oye!

Don't remind me! My brother in law kept me drunk on Johnny Walker Red so I couldn't complain.I couldn't even buy a coke. He's married but had a girl friend who sang at a club we were at. I got pictures of me breaking plates and Greek dancing. They didn't tell me you had to pay for the plates.

Woke up the next after noon and looked in the mirrior...I had a black eye!

My brother in law clapped me on the shoulder and said, "You should see the other guy. You left him bleeding in the gutter."

I went back to bed and covered my head with the pillow. Haven't been back since.
__________________
Just slow, not stupid.
hvaclover is offline   Reply With Quote
Old 09-08-2009, 11:14 PM   #40
Newbie
 
Join Date: Sep 2009
Posts: 5
Rewards Points: 10
Default

sizing furnace


You guys are all great. Thanks for all your replies. I enjoyed reading your comments and the funny stuff that people throw in away from the topic e.g., beer, Europe, etc. There are merits to everybody's opinions. I am leaning towards 100K BTU input and 80K BTU output. This is one size lower than what I have right now which is 120Kinput and 96 output. This 80K output that I am thinking of putting is what 3 of my Edmontonian friends who are in refrigeration trade, have told me. The load calculation has its own merits but my house is old and the insulation is old as well and for this kind of weather (extreme cold and wind chill ), a little over calculation is to be expected. They say that we have two seasons here in Edmonton and the same is true for Winnipeg, winter and July. It's so cold out here, it's not funny. Thanks again everyone. I am glad I put this question out here. It definitely made up my mind.
mindoreno is offline   Reply With Quote
Old 09-08-2009, 11:23 PM   #41
Member
 
hvaclover's Avatar
 
Join Date: Oct 2008
Location: Suburbs of Detroit Mi
Posts: 3,704
Rewards Points: 2,000
Default

sizing furnace


Get a two stage furnace with two stage stat.
__________________
Just slow, not stupid.
hvaclover is offline   Reply With Quote
Old 09-20-2009, 02:26 AM   #42
Member
 
GetYourShineBox's Avatar
 
Join Date: Sep 2009
Location: Waterford, MI
Posts: 72
Rewards Points: 75
Default

sizing furnace


my a.c. teacher gave us a great way to check your btu. you multiply the width of the house by the length then multiply the sum by the height of your interior. so for example. 25Wx40L=1000x8H=8000. then you would use a multiplier to determine your btu/hr. this multipliers are determined by your homes construction and insulation. if you lived in a older home with thinner walls that is not as tight you would use 10. a home that has 3.5 inch walls with tighter insulation and better windows you would use 6, and if you have a home with 6.75 inch walls, with the tight insulation and the best windows you use 4.5 so to make this make sense....

25x40=1000x8=8000x10=80000 btu/br
25x40=1000x8=8000x6=48000
25x40=1000x8=8000x4.5=36000

its easy and it works.
GetYourShineBox is offline   Reply With Quote
Old 09-20-2009, 05:34 AM   #43
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,571
Rewards Points: 4,780
Default

sizing furnace


Quote:
Originally Posted by GetYourShineBox View Post
my a.c. teacher gave us a great way to check your btu. you multiply the width of the house by the length then multiply the sum by the height of your interior. so for example. 25Wx40L=1000x8H=8000. then you would use a multiplier to determine your btu/hr. this multipliers are determined by your homes construction and insulation. if you lived in a older home with thinner walls that is not as tight you would use 10. a home that has 3.5 inch walls with tighter insulation and better windows you would use 6, and if you have a home with 6.75 inch walls, with the tight insulation and the best windows you use 4.5 so to make this make sense....

25x40=1000x8=8000x10=80000 btu/br
25x40=1000x8=8000x6=48000
25x40=1000x8=8000x4.5=36000

its easy and it works.
And its a bunch of garbage.

Learn how to do a proper load calc. Your teacher doesn't know how to do them. Or he would teach you the proper way.

Might as well just sell 120,000 BTU furnaces for any size house as use that method.

Using/teaching those kinds of methods are what makes this industry an industry in which more then half don't know what they are doing.
beenthere is offline   Reply With Quote
Old 09-20-2009, 08:05 AM   #44
Member
 
hvaclover's Avatar
 
Join Date: Oct 2008
Location: Suburbs of Detroit Mi
Posts: 3,704
Rewards Points: 2,000
Default

sizing furnace


Been you are being WAY too hard on the youngster (assuming age here).

Loadcalcs in long form are very difficult because of all the math and voc schools will usually go short form to get the student familiar with the concepts until they can get in the field and start using software.

GetYourShineBox, I use a short form calc myself, but I know my area and how the homes are construction methods used. So I can tweak my numbers as experience dictates. Beenthere is right about doing a proper load calc but I differ with him because the software available will give a different result from each different brand.

That being said I say if you are using a short form that puts you in the ball park with everybody else's software calc then I would stick with using it.

But it's like anything else, you have to refine your technique and know where to tweak you own calculations to meet the needs of the market you you will be working.
__________________
Just slow, not stupid.
hvaclover is offline   Reply With Quote
Old 09-20-2009, 08:51 AM   #45
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,571
Rewards Points: 4,780
Default

sizing furnace


Not when he is using such a guess method. With no real logic behind it.

In some areas, a 1000 sq ft house with 8' foot high ceiling might need 80BTUs per sq ft.
If the area has temps below -30F and a lot of wind, and the house has walls with R values of less then 2.

Advertisement

beenthere 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
Sizing a furnace - can't find one small enough Jim W HVAC 30 05-13-2009 09:38 PM
Problems with new furnace..Overheating, having to reset. Furnace too big? Tommy2 HVAC 41 12-01-2008 02:55 PM
New Cased Coil - Install to Furnace - PICTURES!! hartkem HVAC 39 11-18-2008 02:45 AM
Furnace Sizing Swolef HVAC 2 09-18-2008 12:07 PM
Question Re: New Furnace and Duct Sizing DSimo HVAC 3 06-17-2008 08:24 AM




Top of Page | View New Posts