Suddenly, Not Enough Airflow


  #1  
Old 08-08-15, 11:41 AM
T
Member
Thread Starter
Join Date: Feb 2008
Location: Many Places US
Posts: 330
Received 1 Upvote on 1 Post
Suddenly, Not Enough Airflow

My family and I are in a casual, temporary rental. The landlord is a thousand miles away and we're only here for a couple of months, while we look for a house. Though I've tried, the person who owns the condo isn't picking up the phone to authorize me to call someone to repair.

It's now late in the day. Saturday is almost done and rather than incur the expenses myself -- the company whose number is on the machine is going to voicemail anyway -- I'm thinking about exploring DIY (after a drive) because it's way too hot.

The outside unit is working. The inside unit is making a good hum, but the airflow in and out (via the ducts and the return) is minimal.

The inside unit (heat pump) is a Rheem and the outside is Goodman. There's a digital thermostat that appears to be working fine.

Any suggestions of where to start?

ETA: A couple of weeks ago, also on a weekend, we had the same thing happen. I turned the unit off at the thermostat, went to bed and tried the next morning. When I tried 6 hours later, everything worked and it didn't have another problem until last night. We've tried turning it off for two hours and that changed the hum from obviously broken to maybe it's fixed, but it was not. Now it's five degrees warmer in the house than it was last night.

Thanks
 
  #2  
Old 08-08-15, 11:58 AM
Bob14525's Avatar
Member
Join Date: Jun 2013
Location: USA
Posts: 1,646
Received 81 Upvotes on 71 Posts
In all likelihood, the evaporator coil is frozen up, restricting the airflow. There are normally two possible reasons for the evaporator coil to freeze up: low airflow due to a clogged air filter or very dirty evaporator coil, or the system is low on refrigerant.

Since you had this problem before, and the airflow returned to normal after turning the unit off overnight (ice melted off of evaporator coil), the problem is likely due to low refrigerant. If you turn the A/C off but set the fan to ON (rather than Auto), the warm air blowing over the evaporator coil will melt the ice sooner. Until the system gets repaired (likely adding more refrigerant after trying to find and repair the leak), the only thing I can suggest is to run the A/C for short intervals to prevent it from freezing up (after letting it thaw).
 
  #3  
Old 08-08-15, 01:10 PM
T
Member
Thread Starter
Join Date: Feb 2008
Location: Many Places US
Posts: 330
Received 1 Upvote on 1 Post
Thanks. The last time it broke, two weeks ago, I rushed out and bought a filter to go inside the return. The previous one was quite clogged, but this one is new and it looks fine.

I'm trying the fan thing you suggested. Last night, we turned it off for two hours and today I've tried turning off for a little more than an hour after turning it off and back on again a few times.

The "sounds like it's broken" hum doesn't sound like the "it might be working" hum, which is what I'm getting with the fan and what I've had since a couple of reboots last night. The "sounds like it's broken" is a more consistent hum and you sort of feel the vibration in the slab, ten feet away. The "might be working" hum sounds like a fan in an air exchange. I wish I could describe them better, but that's what I've got.

A couple of weeks ago, I could feel the vibration and heard the weird sound, which is what alerted me to the problem. The next day after being off for at least six hours, it sounded normal and everything worked fine. Because it started working, I didn't call anyone.

This time, I felt the vibration and the fact that it was warm around the same time. My daughter had turned the thermostat down a couple of times because she had been hot, so I guess it had been building for a while. After rebooting, the fan sounds normal (like it does now without the A/C), but there's not a lot of air coming out of the vents and though the return is sucking, it doesn't have a lot of force.

Thanks

BTW: Every air conditioner I've ever had had one filter, but this is the first system I've noticed with a filter over the return. There's not another filter somewhere that I'm missing?

Edited to Ask: Right now I have it set to fan only. The airflow is still nowhere near where it was when the A/C worked. Am I offbase thinking that if the fan-only melts the frozen evap coil, the airflow would increase and that would tell me to try the A/C?
 
  #4  
Old 08-08-15, 01:28 PM
S
Member
Join Date: Feb 2014
Location: USA
Posts: 1,771
Received 0 Upvotes on 0 Posts
Try pulling the cover off the blower section of the furnace. Press the door safety switch and see what kind of airflow you are getting.
 
  #5  
Old 08-08-15, 01:31 PM
T
Member
Thread Starter
Join Date: Feb 2008
Location: Many Places US
Posts: 330
Received 1 Upvote on 1 Post
Update: After posting my "edited to ask", I went to feel a vent. What it's doing now, set to fan-only, is cycling on and off. It's no longer a steady "might be working" hum with hardly any airflow to now every minute or so, the fan turns on with full force for about a second or two, then everything shuts down until the next round. In between, there is no "might be working" sound or restricted airflow.
 
  #6  
Old 08-08-15, 01:38 PM
Bob14525's Avatar
Member
Join Date: Jun 2013
Location: USA
Posts: 1,646
Received 81 Upvotes on 71 Posts
As the ice melts from the evaporator coil, the airflow should start to increase until it gets to "normal" airflow. All this assumes that the "blower" is running normally. As skaggsje suggested, check to see if the blower seems to be running normally. If the blower motor isn't starting, it's possible that you have a bad motor capacitor.
 
  #7  
Old 08-08-15, 01:43 PM
Bob14525's Avatar
Member
Join Date: Jun 2013
Location: USA
Posts: 1,646
Received 81 Upvotes on 71 Posts
If the blower is turning on/off by itself, you likely have an airflow problem. With the power turned off (and door switch NOT bypassed), try to reach in and feel the blower motor. If the motor is very hot, the thermal cutout may be engaging, thus accounting for the on/off behavior (when motor turns off, it cools down until thermal switch turns motor back on). It's still possible that the capacitor for the blower motor is bad, causing the motor to overheat.
 
  #8  
Old 08-08-15, 01:53 PM
T
Member
Thread Starter
Join Date: Feb 2008
Location: Many Places US
Posts: 330
Received 1 Upvote on 1 Post
Since my last update, like fourteen minutes ago, the cycles are getting longer. They're now maybe up to four seconds long and they're happening more often.

The only heat pump I've ever had was like thirty years ago and there was a metal door in the hallway that just popped-off. The air handler here is in a closet and there's a bunch of stuff stored around it. I've found what looks like the panel to come off, but because I'm in the process of moving, my nut drivers are in a storage unit down the road.

We finally got ahold of the owner and she's calling the fellow she knows, but she's already said something about it being Saturday night and it might be too late for him to come. I'll go get my nutdriver and get psyched because unless I'm going to wait until Monday, if it's an easy fix, it could be done by me. The thermostat says it's 82 degrees and because this is hot and humid Florida, I'm reluctant to open a window while there's still a chance.

Of course I've already gone to the orange box and they don't stock air conditioner capacitors; it's an online order product. If need be, I'll have to look for a hardware store.
 
  #9  
Old 08-08-15, 02:01 PM
Bob14525's Avatar
Member
Join Date: Jun 2013
Location: USA
Posts: 1,646
Received 81 Upvotes on 71 Posts
If you have a Grainger's near you, they carry motor capacitors. If you replace the capacitor, be sure to get the same mfd value. The voltage rating can be the same or higher.
 
  #10  
Old 08-08-15, 03:13 PM
T
Member
Thread Starter
Join Date: Feb 2008
Location: Many Places US
Posts: 330
Received 1 Upvote on 1 Post
Before I headed over to the storage unit, I called the two hardware chains and found that both of their local stores are out of capacitors and wouldn't have one until next week. The "Helpful Hardware Man" suggested a pump supply store, but they're closed for the day. His other suggestion was to drive down the strip and flag down a repair truck. Apparently back when he was in the A/C business, he sold capacitors out of the truck all the time.

While all of this was going on, the fan switched from intermittent to running continuously with full force, so I set a timer for fifteen minutes and just for kicks, I asked the kids to listen to see if it went back off. Of course they didn't really pay attention and neither did I, but it seems like it may have run continuously, so I switched it back to A/C.

Maybe it's my imagination, but the air doesn't seem to be as cold. The fan is still running full force and the temperature has gone down by three degrees. As suggested, I'll probably swich back and forth from fan to A/C for a while, but I called the landlord and told her that thanks to the internet and a very helpful forum that's my go-to for advice, it's no longer an emergency. She says she's called and texted the person she knows, but I told her that now, it can probably wait until next week.

Thanks to @Bob14525 and @skaggsje for the help.

When I couldn't get ahold of the landlord, it was a rough afternoon.

Thanks!
 

Last edited by TryAgain; 08-08-15 at 03:29 PM.
  #11  
Old 08-09-15, 11:07 AM
T
Member
Thread Starter
Join Date: Feb 2008
Location: Many Places US
Posts: 330
Received 1 Upvote on 1 Post
Thanks again for all the help. Though it continued to work with no problems, I did run the fan for like 45 mins in the middle of the night and it has worked well since.

The last time this happened, I turned it off for like six hours, then it worked for two weeks.

The landlord's guy -- he's the one whose sticker is on the unit -- is supposed to call me early next week. Other than the commonality of the cure and the fact that they happened on Friday nights, plus there's that whole "stuck-fan/sounds-broken/slab-vibrating hum" thing, the only other similarity between the two events is that both times, my fifteen year old had been the first to feel warm and had incrementally turned it down to 70, while I didn't realize there's a problem until the temperature has gotten up to 78.

I've asked her to not do that anymore. She can keep flipping it between 73 and 75, but if she's feeling the need to go below 73 and the temperature hasn't been responding, she should say something to me.

With all of this info, so that I can talk to the repairperson, does anybody have any ideas? The reason I didn't contact anyone two weeks ago was because the system had been working since, so there wasn't anything to repair. Now, it's sort of like the same thing, except it's happened twice.

Again, thanks.
 
  #12  
Old 08-09-15, 04:15 PM
Bob14525's Avatar
Member
Join Date: Jun 2013
Location: USA
Posts: 1,646
Received 81 Upvotes on 71 Posts
Glad to hear that we were able to help get you going again. As to what to tell the A/C tech when he comes this week, you can tell him that the evaporator coil is freezing up. What is unclear is why it's freezing up. As I mentioned earlier, the two normal causes of evaporator freezing is either insufficient airflow through the evaporator, or low refrigerant charge. Since it appears that your air handler fan (blower) may have problems (intermittently turning off), I'm not sure if that's the cause, or if the system is low on refrigerant. I would have the tech check the blower motor & capacitor, making sure the capacitor is within its capacitance spec. If the capacitor is OK, I would ask him to check the current draw. If the blower motor & capacitor check out okay, then I would ask him to check the refrigerant level (subcooling & supercooling).
 
 

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