Furnace Not Blowing Hard - HVAC - Page 2 - 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 08-09-2010, 08:28 AM   #16
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Furnace Not Blowing Hard


Quote:
Originally Posted by diyordie View Post
I just moved into a new house and the motor for the blower seems to be running slow. It is a belt drive blower and the belt seems to be in good shape. Would an electric motor run slow if it's ready to fail or would a faulty run capacitor cause this?

Thanks for any help.
Why do you feel it is running slow? Furnace motors don't have to blow the curtains around in the living room when they run. Slower moving air across the heat exchanger will absorb more heat and this warm air will rise on its own when it enters the room. Make sure it is broke before you try and fix it...

Advertisement

a7ecorsair is offline   Reply With Quote
Old 08-09-2010, 08:49 AM   #17
Newbie
 
Join Date: Aug 2010
Posts: 15
Rewards Points: 10
Default

Furnace Not Blowing Hard


@a7ecorsair: I don't expect the curtains to blow around but the air coming out of the vents could barely move a feather. I'm not have a heating problem, it's a cooling issue. The AC runs for 2 days straight and the temp doesn't get under 80F (AC system about 2yrs old). The air coming out of the vents is cold. The vents themselves are very cold to the touch but the air isn't moving into the rooms with any kind of force. I haven't tried to fix anything yet. That's why I'm here trying to avoid throwing parts at it and get some help from people who know a lot more about this stuff than me.

@rjniles: I guess I assumed that the motor would already be wired properly but I'll take a look to see if it isn't wired for the higher speed setting.

Does anyone know if a motor will begin run slow if it is failing?

Thanks for all the good suggestions.
diyordie is offline   Reply With Quote
Old 08-09-2010, 09:16 AM   #18
A "Handy Husband"
 
rjniles's Avatar
 
Join Date: Feb 2007
Location: South Carolina Low Country
Posts: 4,228
Rewards Points: 2,366
Default

Furnace Not Blowing Hard


You say the AC is 2 years old but obviously the furnace is much older than that. I assume it is an add-on unit with the coiling coil cut into the furnace plenum. With floor mounted duct registers a slow fan sped will move the heated air properly in the winter as hot air naturally rises. In the cooling mode the cold air wants to sink so you need to push it up from the floor with a higher fan speed. When they put in the AC they should have changed the blower speed or installed a new one if it did not have adjustable taps.

I had a system like this years ago and I added a switch on the fan motor wiring to use a slow fan speed in the winter and a higher fan speed during the cooling season. I used a standard 3 way (SPDT) wall switch.
__________________
Location:
Coastal South Carolina

Last edited by rjniles; 08-09-2010 at 10:06 AM.
rjniles is online now   Reply With Quote
Old 08-09-2010, 09:55 AM   #19
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Furnace Not Blowing Hard


Yes, cold air is harder to blow than warm air. Do you have a thermostat that has both AC and Heat? If not, how do you change over from heat to cool?
In a properly installed system, there should be a relay that switches the motor between a low speed for heat and a higher speed for cool. Since this is an add-on, a switch like suggested may be an easy way to handle this.
a7ecorsair is offline   Reply With Quote
Old 08-09-2010, 10:33 AM   #20
Newbie
 
Join Date: Aug 2010
Posts: 15
Rewards Points: 10
Default

Furnace Not Blowing Hard


@rjniles: Great suggestion. Yeah, it's definately an add-on. That makes a lot of sense. I think I'd prefer to have an HVAC specialist to verify that this thing is set to run at higher speeds for cooling.

@a7ecorsair: The thermostat is a newer electronic programmable model. It has a Heat/Cool switch. I'm guessing that ideally this switch should dictate the blower speed.

I haven't tried to turn the blower on the heat setting but I think I'll give it a try to see if it actually runs slower (if that's even possible).

Thanks guys. This is why I love these forums.
diyordie is offline   Reply With Quote
Old 08-09-2010, 03:33 PM   #21
" Euro " electrician
 
frenchelectrican's Avatar
 
Join Date: Apr 2006
Location: WI & France { in France for now }
Posts: 5,369
Rewards Points: 2,000
Default

Furnace Not Blowing Hard


looks like you may have older single speed motor there and as few other members here did suggest few good idea as well one good way is get multi speed motor so with the heat mode it will run at the oringal speed while when in cooling mode you need to bump up the speed.

However there is very neat gotcha is when you increase the speed some case you may have to bump up from 1/3 HP to 1/2 HP motor so it will handle better at higher speed.

Merci,
Marc
frenchelectrican is offline   Reply With Quote
Old 08-09-2010, 06:05 PM   #22
Hvac Pro
 
Join Date: Nov 2008
Location: Winnipeg, Canada
Posts: 10,061
Rewards Points: 760
Default

Furnace Not Blowing Hard


A belt drive blower is NOT a high speed blower like a direct drive type. The different sized motor and blower pulleys are the reason. We sometimes increase the speed by putting a 3 3/4" or 4" pulley on a 1/2 hp motor on the fan but it does get loud and wheel croak your bearings soon. You should get ball/roller bearings for that fan and ideally a new furnace.
__________________
"Cut it twice and it is still too short".
yuri is online now   Reply With Quote
Old 08-10-2010, 07:43 AM   #23
Newbie
 
Join Date: Aug 2010
Posts: 15
Rewards Points: 10
Default

Furnace Not Blowing Hard


I watched the blower run in heat and cool modes last night and it appears to be running at the same speed. Looks like I need to call in a pro to see 1.) if the motor is bad or 2.) the thing needs re-wired to run at dual speed.

Thanks for all the help. I'll check back in and let you know how it goes.

From what I've read here and on other forums most furnaces are set up to run at low speed for heating (because hot air will rise on its own) and higher speed for cooling. Last night I watched the blower run in both heat and cool modes and there was no change in speed. Either my furnace blower was never set up for this when the new AC was installed, or the motor is failing and won't get up to the high speed. Any thoughts?
diyordie is offline   Reply With Quote
Old 08-10-2010, 08:04 AM   #24
Member
 
Join Date: Jul 2010
Posts: 1,827
Rewards Points: 1,168
Default

Furnace Not Blowing Hard


On a separate, but related path, also check the crawl space or basement for any openings in the ducts, and make sure that any basement louvers are closed; you can only push so much air out of so many openings, and it is going to take the path of least resistance.
DexterII is offline   Reply With Quote
Old 08-10-2010, 08:29 AM   #25
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,424
Rewards Points: 4,494
Default

Furnace Not Blowing Hard


Belt drive blowers are only 1 speed.


You were reading about multispeed direct drive blower motors.
beenthere is online now   Reply With Quote
Old 08-10-2010, 09:17 AM   #26
fabrk8r
 
fabrk8r's Avatar
 
Join Date: Feb 2010
Location: Iowa
Posts: 849
Rewards Points: 500
Default

Furnace Not Blowing Hard


Are you sure the motor's direction of rotation is correct?

It may have been worked on before you bought the home and has been rotating the wrong direction the whole time you've lived there. A squirrel cage blower wheel will move air in the proper direction even if rotating backwards, but the volume of air moved will be about 1/2 what it would be if the rotation is correct.
__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright
fabrk8r is offline   Reply With Quote
Old 08-10-2010, 09:48 AM   #27
Newbie
 
Join Date: Aug 2010
Posts: 15
Rewards Points: 10
Default

Furnace Not Blowing Hard


@beenthere: well that certainly dashed my hopes. I thought I had found the problem. Thanks for keeping me from heading in the wrong direction.

@fabrk8r: is there any way to tell if it's going the wrong the direction other than re-wiring and seeing if you get better airflow the other way? Looking at the pictures I posted earlier in this posting the squirrel cage is going clockwise.
diyordie is offline   Reply With Quote
Old 08-10-2010, 09:51 AM   #28
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,424
Rewards Points: 4,494
Default

Furnace Not Blowing Hard


By the pictures. Looking into the blower from the perspective of pic 2. The blower wheel should be spinning counter clockwise.
beenthere is online now   Reply With Quote
Old 08-10-2010, 10:04 AM   #29
fabrk8r
 
fabrk8r's Avatar
 
Join Date: Feb 2010
Location: Iowa
Posts: 849
Rewards Points: 500
Default

Furnace Not Blowing Hard


Do a thorough check for a label or stamp indicating direction of rotation.

If there is no indicator, then I would try reversing the rotation to CCW. Most blower that are designed to only move air are of the "forward curved blade" type. It appears in your pictures that the rotation may be backwards.

If you are comfortable working with electric motors it's easy to reverse the rotation. Just make sure you shut the power off before attempting this.

You beat me beenthere!
__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright
fabrk8r is offline   Reply With Quote
Old 08-10-2010, 10:43 AM   #30
Newbie
 
Join Date: Aug 2010
Posts: 15
Rewards Points: 10
Default

Furnace Not Blowing Hard


Well, I was just informed that a belt drive blower is generally set up to be single speed only so now I'm at a loss.

Advertisement

diyordie 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
Electric furnace blowing breaker burnt03 HVAC 27 01-04-2011 09:50 PM
dayton furnace blowing cool air luckysc47 HVAC 2 12-05-2009 01:04 PM
Help! Furnace blowing cold air. Thanks. crosely HVAC 0 11-30-2009 11:17 AM
"Freedon 90" Furnace Blowing out Cold Air LAFAYETTEGIRL Introductions 0 11-27-2009 09:05 AM
Olsen BFL 120 Furnace DaleB HVAC 12 12-19-2008 11:42 PM




Top of Page | View New Posts