Blower Fan Bad - HVAC - Page 2 - DIY Chatroom Home Improvement Forum

 DIY Chatroom Home Improvement Forum > HVAC Blower Fan Bad
 Register Blogs Articles Rewards Search Today's Posts Mark Forums Read

06-05-2009, 08:47 PM   #16
Member

Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000

Quote:
 Originally Posted by beenthere So tell me. Why the same house can lose 23,075 BTUs on a 25HDD day, or can lose 16,400 BTUs on a 25 HDD day.
Insolation? Wind? Rain? Snow?

(23+16)/2 = 19.5, 19.5 -16 = 3.5, so it's 3.5/19.5 = ~18%, so it's a +/- 18% variation. Not bad for doing economics numbers.
And the best you can do with Manual J is +/-5%? I've seen this accuracy limit somewhere. . .?

The other thing is a statistical effect. You make the measurement above once and you +/- 18% accuracy. If you make it 100 times over several months you get to be within +/- ~2% of the true value.

Last edited by Yoyizit; 06-05-2009 at 08:53 PM.

06-05-2009, 08:58 PM   #17

Join Date: Oct 2008
Location: Somewhere
Posts: 34,599
Rewards Points: 8,184

Quote:
 Originally Posted by Yoyizit Insolation? Wind? Rain? Snow? (23+16)/2 = 19.5, 19.5 -16 = 3.5, so it's a 3.5/19.5 = ~18%, so it's a +/- 18% variation. Not bad for doing economics numbers. And the best you can do with Manual J is +/-5%? I've seen this accuracy limit somewhere. . .? The other thing is a statistical effect. You make the measurement above once and you +/- 18% accuracy. If you make it 100 times over several months you get to be within +/- ~2% of the true value.
Yes, you can keep fudging it till you get it close.

Out of 4 guesses, you got 3 things. Your still missing atleast ONE big one.

06-06-2009, 09:53 AM   #18
Member

Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000

Quote:
 Originally Posted by beenthere Your still missing atleast ONE big one.
Yeah, a girl said that to me, once.

Absorption of the exterior surface? Ground temp. variation?

Fudging puts me in good company
http://en.wikipedia.org/wiki/Fudging

Last edited by Yoyizit; 06-06-2009 at 10:02 AM.

06-06-2009, 10:31 AM   #19

Join Date: Oct 2008
Location: Somewhere
Posts: 34,599
Rewards Points: 8,184

Quote:
 Originally Posted by Yoyizit Yeah, a girl said that to me, once. Absorption of the exterior surface? Ground temp. variation? Fudging puts me in good company http://en.wikipedia.org/wiki/Fudging
Doesn't put you in good company.

If you don't know all the things that can throw off the HDD calculation.
Then how can you come up with anything but a false result.

HDDs doesn't need to be known, to set up a dual fuel system.
Or to determine if a dual fuel system is appropriate for an area.

An area with 10,500HDDs may not be a good place for a dual fuel system. While another place with 12,000HDDS may be an ideal pace for a dual fuel system.

Its just an abused number.

06-06-2009, 11:40 AM   #20
Member

Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000

Quote:
 Originally Posted by beenthere HDDs doesn't need to be known, to set up a dual fuel system. No, only to determine if it's economical. Or to determine if a dual fuel system is appropriate for an area. An area with 10,500HDDs may not be a good place for a dual fuel system. While another place with 12,000HDDS may be an ideal pace for a dual fuel system. Its just an abused number.

Here's what I've got to go on.

"A dual-fuel heat pump is an electric heat pump and a gas furnace all in one. In the Tennessee Valley, where temperatures are typically above freezing and we enjoy some of the lowest electric rates in the U.S., a heat pump is the most efficient way to heat your home. In those few instances when the temperature drops below freezing, a gas furnace provides heat more economically. By combining the two, you can have the benefits of both systems.
How it works
When the temperature is above 35 degrees or so, the dual-fuel heat pump uses electricity to heat your home as necessary. This type of heat circulates evenly throughout your home, and isn't too dry. When it gets really cold outside (around 35 degrees or lower), the heat pump automatically switches to supplemental gas heat for better efficiency."

And, HDD For Knoxville, Tenn.

6/1/08
13
7/1/08
7
8/1/08
7
9/1/08
26
10/1/08
264
11/1/08
586
12/1/08
712
1/1/09
880
2/1/09
627
3/1/09
447
4/1/09
272
5/1/09
77

With HDD totaling 3800 and change.

 06-06-2009, 01:42 PM #21 An old Tradesmen   Join Date: Oct 2008 Location: Somewhere Posts: 34,599 Rewards Points: 8,184 See, in reality. The HDDs tell you nothing. You don't know the heat output of the heat pump. You don't know how much heat the house needs under what conditions. A load calc. And the extended data specs for the heat pump will tell you when the heat pump can't handle the load anymore.
 06-06-2009, 03:18 PM #22 Member   Join Date: Jul 2008 Location: NW of D.C. Posts: 5,990 Rewards Points: 2,000 I give up.
06-06-2009, 03:25 PM   #23

Join Date: Oct 2008
Location: Somewhere
Posts: 34,599
Rewards Points: 8,184

Quote:
 Originally Posted by Yoyizit I give up.
Finally.

 06-06-2009, 03:29 PM #24 Hvac Pro     Join Date: Nov 2008 Location: Winnipeg, Canada Posts: 16,129 Rewards Points: 396 We are in the wrong business Beenthere. You, me Clover et al should startup HVAC consulating.com. LOL. for \$\$ of course. Last edited by yuri; 06-06-2009 at 03:31 PM.
06-06-2009, 03:42 PM   #25
Member

Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000

Quote:
 Originally Posted by beenthere Finally.
But I might pop up elsewhere if I get more data; kind of like a weed.

06-06-2009, 03:42 PM   #26

Join Date: Oct 2008
Location: Somewhere
Posts: 34,599
Rewards Points: 8,184

Quote:
 Originally Posted by brohar Secondly, is oil the right way to go? I dont have access to gas but what about a heat-pump (i live in cincinnati)? - How much more would a heat pump system cost? Could i get a tax credit also? - Should i just fix my existing blower? Anyone know if there is a match for my make and model? Thanks

Your area has enough hours above 40°F to make a dual fuel very practical.

Or even a heat pump with electric aux back up.

You have a low enough summer design temp, that a heat pump sized to the cooling load, will probably not be able to handle the heating load at temps much below 40°F outdoor temp.
Depending on how high of an efficiency heat pump you would get.

So 40°F is a good switch over temp for a dual fuel system, and will eliminate going into a defrost cycle, and blowing cold air out of the registers.
It takes too long for an oil furnace to heat up for it to be able to counter the cold air from defrost.
Unless your going for max efficiency. Then you would leave the thermostat decide when to switch over to the oil furnace, by indoor temp drop.

06-06-2009, 03:44 PM   #27

Join Date: Oct 2008
Location: Somewhere
Posts: 34,599
Rewards Points: 8,184

Quote:
 Originally Posted by yuri We are in the wrong business Beenthere. You, me Clover et al should startup HVAC consulating.com. LOL. for \$\$ of course.
LOL...

Hmmmm.

06-06-2009, 03:45 PM   #28

Join Date: Oct 2008
Location: Somewhere
Posts: 34,599
Rewards Points: 8,184

Quote:
 Originally Posted by Yoyizit But I might pop up elsewhere if I get more data; kind of like a weed.

My lawn mower makes short work of weeds.

 06-08-2009, 08:23 PM #29 Newbie   Join Date: Jun 2009 Posts: 6 Rewards Points: 10 Ok the OP is back and this thread just blew up while I was away. Soooo im still pulling my hair out over this decision. My Electric rates are currently around .08-.09. My Oil tank is probably the original so sticking with oil makes me nervous considering the cost of replacing a leaking oil tank if that was to happen. Additionally, resale value is affected negatively with oil heat. On the other hand the Heat-pump with electric backup, sounds like a whole new beast to get used to. Im also, nervous about huge electric bills in the cold months. Granted with my 30 year old furnace i was using about 600 gallons of oil a year. So for my little house with good insulation what is best choice? Are Heat pumps noiser than a normal AC unit? In cold weather does the Heat pump and electric run at the same time? THe unit i was looking at has a 10 year parts and labor warranty, is there some fine print i should worry about there?
06-08-2009, 08:40 PM   #30

Join Date: Oct 2008
Location: Somewhere
Posts: 34,599
Rewards Points: 8,184

At 600 gallons of oil. If, your oil cost \$2.30 a gallon, and your furnace was 80% efficient, then your oil bill would have been \$1,381.00

A heat pump, should be able to lower that bill to about \$1,000.00

A dual fuel might get you down to \$800.00

Those numbers are without lnowing your areas heating hours or conditions.

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post jh44ny HVAC 12 07-31-2011 06:41 PM aczer HVAC 12 02-13-2011 06:57 AM John_NH HVAC 15 11-21-2010 12:49 PM simonb HVAC 1 01-17-2009 10:56 AM GhostBuster HVAC 15 11-30-2008 09:08 PM

Top of Page | View New Posts