Lennox 14 Seer/3.5 Ton Central AC Not Blowing Very Hard


  #1  
Old 08-22-11, 09:18 AM
A
Member
Thread Starter
Join Date: Aug 2011
Location: USA
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
Lennox 14 Seer/3.5 Ton Central AC Not Blowing Very Hard

Our Lennox AC Central Air unit that we had installed in 2005 seems to be operating, but not blowing hard enough. The air coming from the vents is cool, but the velocity is low.

I changed the filter at the furnace which is where the blower is. I typically change it every 90 days. It was dirty but not black.

We had our wood floors redone recently and I am concerned that the amount of dust that comes from that job may have gotten into the system and caused some damage.

Does anyone have any other ideas/reasons or troubleshooting I should do to determine the root cause of this issue?
 
  #2  
Old 08-22-11, 09:26 AM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 19,281
Received 8 Upvotes on 8 Posts
Has it changed since it was installed or has it always done this? Does airflow increase noticeably when the fan is running w/o the filter in place? A filter doesn't have to LOOK dirty to be blocked up enough to decrease airflow. Depending on the filters you use...you may need to reduce the interval during heavy A/C usage. 90 days seems like a pretty long time to me.

When was the evaporator coil (the finned coil that cools the air...after the air handler) last cleaned?
 
  #3  
Old 08-22-11, 09:42 AM
A
Member
Thread Starter
Join Date: Aug 2011
Location: USA
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
I use a Merv 12 Filter that suggests changing it every 3 months and in the Pacific NW, the air does not get that dirty and we do not have pets so it seems like a reasonable interval.

I did not test the air flow without the filter, but after changing it to a brand new one, the air flow did not change.

I suspect it has been a while since the evaporator coil has been cleaned. Is the "evaporator coil" on the unit outside the house with the fan blade on top of it? Are the fins on the sides of that unit? If so, what is the best way to clean them.

Thanks for your help.
 
  #4  
Old 08-22-11, 10:03 AM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 19,281
Received 8 Upvotes on 8 Posts
No...the evap coil is inside near where the fan that blows air around the house is. Normally there is a panel that can be removed to access it. The seams may be taped up...but there should be a way to get to it. It's a good thing to at least look at it every year or so...though mine back in VA only got cleaned twice in my 15 yrs there...but I changed filters every 30 days. If work such as your floors was done...possible some dust got by the filter.

The unit outside contains the compressor, fan, and condenser coil. That is what gives up the heat removed from the inside to the outside air. Those coils should also be cleaned at least yearly. A search for "how to clean your condenser/evaporator coils" would probably be more helpful than my description.

btw...Welcome to the Forums! Your name looked familiar and I thought you had been here a while.
 
  #5  
Old 08-22-11, 10:37 AM
A
Member
Thread Starter
Join Date: Aug 2011
Location: USA
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks for the welcome. Helpful place.

OK, so I need to shut the system off. There is a power throw arm near the outdoor compressor. That should do it. Go look inside for the evap coil and clean it. Is a shop vac and stiff non metal brush the best way? Then head out to the condenser, remove the panel and clean it in the same way.

If this does not work, I may just need to call a tech, but I wanted to eliminate as many potential issues on my own first to see if I could solve it.
 
  #6  
Old 08-22-11, 10:58 AM
G
Member
Join Date: Oct 2008
Location: USA
Posts: 2,606
Received 28 Upvotes on 27 Posts
Originally Posted by akinisky
OK, so I need to shut the system off. There is a power throw arm near the outdoor compressor. That should do it.
No, that switch will not cut off power to the indoor unit. Look for a power switch near the air handler (or furnace?). Better yet, shut off the two breakers in the main panel supplying the outdoor and the indoor unit. The breaker for the outdoor unit will be a 2-pole, 240-V breaker. The breaker for the indoor unit may be single-pole or two-pole.
 
  #7  
Old 08-22-11, 11:13 AM
A
Member
Thread Starter
Join Date: Aug 2011
Location: USA
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
You are correct. There is a toggle switch (looks like a horizontal light switch) on the outside of the furnace that must shut it off but the breakers would be a better and more certain way to do it. Thanks for the clarification. I hope cleaning these things does the trick.
 
  #8  
Old 08-23-11, 09:09 AM
A
Member
Thread Starter
Join Date: Aug 2011
Location: USA
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
I had another look at it last night and removed the cover on the unit in the garage to look for the "evap coils". I did not see anything that resembled coils. I did notice down below a valve with copper tubing coming out of it that had iced up and was dripping a little. This could be a symptom of the problem. Attached is the video.

http://www.youtube.com/watch?v=BggDGRCgsEc I am at a loss so I have schedule a tech from Brennan Heating and AC to come out today and have a look. I hope that he can show me what I should be doing/cleaning/changing on an annual basis so avoid this problem in the future.
 
  #9  
Old 08-23-11, 09:36 AM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 19,281
Received 8 Upvotes on 8 Posts
I can't say for certain what the frost would be from....but your coils are what that pipe connects to inside the unit. Prob accesible by removing the screws that appear in the vid.

Prob a good idea to have the tech out.
 
  #10  
Old 08-23-11, 10:37 AM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 5,491
Upvotes: 0
Received 4 Upvotes on 4 Posts
Looks like low refrigerant or low air flow or bad TXV ...... time to call a pro.
 
  #11  
Old 08-23-11, 10:41 AM
A
Member
Thread Starter
Join Date: Aug 2011
Location: USA
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
TXV? Can you tell me what that is? Low air flow could mean the blower unit. Why would refrigerant run low?
 
  #12  
Old 08-23-11, 10:51 AM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 5,491
Upvotes: 0
Received 4 Upvotes on 4 Posts
TXV = thermal expansion valve (the valve you showed in the video that was icing up). Refrigerant systems are sealed systems. The only way refrigerant is missing is if there is a leak somewhere. Only a epa certified tech can check your refrigerant charge in the a/c. Low air flow could be closed registers, bad capacitor, weak blower motor,a number of things....
 
  #13  
Old 08-23-11, 11:16 AM
A
Member
Thread Starter
Join Date: Aug 2011
Location: USA
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
Ok, thanks. If I have closed a couple of the registers downstairs in the laundry and office for example with the expectation that it will increase the airflow to the other ones upstairs is that sound logic?
 
  #14  
Old 08-23-11, 11:24 AM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 5,491
Upvotes: 0
Received 4 Upvotes on 4 Posts
The system is designed for all registers to be open.... some can be throttled down, but should not ne closed all the way. Most likely the problem is refrigerant related.
 
  #15  
Old 08-25-11, 03:23 PM
A
Member
Thread Starter
Join Date: Aug 2011
Location: USA
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
Final Outcome - Tech spend 2hrs replacing the TXV valvle and patching up the evaporator coils. Blowing hard and blowing cool again. $540 repair. Thanks for your input everyone.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: