A question for you HVAC techs

[Bateluer]

So, last night, I woke up around 2300, with my undershirt soaked in sweat. Checking the thermostat revealed that it was over 86F. Since I could hear the AC unit running, I checked the vents for airflow. Nothing.

Slipping some shoes on, I walked outside and checked the unit. Hot air exhausting from the top, supposedly a good sign? One of the pipes appeared to have ice built up on it. It was difficult to see in the dark, but it felt like ice. I went back inside, grabbed a flashlight and went back out. There was a small amount of ice built up around the pipe, which fell off and melted when I brushed it off the pipe.

Going back inside, cooler air was flowing from the vents again.

I kicked my fan up to a higher setting and went back to bed. Around 0200, I woke up again when my alarm went off for work. From 2300 to 0200, it had only dropped from 86-ish to 82-ish. I know the AC unit is about 11 years old, rated 11 SEER, but it shouldn't take that long to drop the temperature a measly 4 degrees in 3 hours. There doesn't seem to be much in the way of airflow coming from the vents either.

I replaced the AC filter when I moved in, roughly 10 days ago. Looking at it now, it looks pretty dirty again. Not super dirty, but there's definitely a carpet of light gray dust over it. I know these were rated at 3 months, but judging by my old HEPA filter unit, 1 month is probably more accurate in Phoenix. Still, it shouldn't need to be replaced after 10 days?

I do plan on getting a replacement AC unit next year with the FTHB credit, but it needs to function adequately for the next year.

I'd go through my home warranty to have this looked at, but they and I disagree on whether or not AC counts as an emergency. They stated they could sent their contractor out to look at it sometime between 1000 and 1600, any day between today and Thursday. Apparently, they think it's okay to go 4 days with no AC and 105+ temps. My pets would be dead in a day. So I called another service and scheduled a service Tuesday after 1330. Anything in particular I should inquire?

They also offer programmable Honeywell thermostat installations. I was going to do this myself, but since the jackass who wired the thing originally didn't use color coded wires or label the terminals, it'd be a royal pain.

Read, don't be lazy.
No cliffs.

 

[mchammer187]

try turning off the AC for like 5 hours and run fan only


my AC unit does this and I think it has something to do with the compressor freezing or something freezing I'm not an HVAC expert or anything

run fan only till you get solid air flow coming out your vents

you should have some air flow within 2 hours and it should gradually get better the longer you have it on fan only if this is the problem

 

[Nik]

I had something like this happen at my house with frost/snow/ice buildup around the return. The furnace fan went out and had to be replaced. I am a hardcore hvac nub, but it sounds very similar to what happened last summer at my place.

 

[BUTCH1]

Sounds like a low freon charge condition, if it's a slow leak it can be recharged and used but a larger/faster leak will have to be repaired.

 

[Billb2]

You did the right thing, calling in a tech, but too late.
Everyone calls when it isn't working, but you need to have AC checked yearly, they require maintenance, and if you can't do it someone has to.

The tech will check compresssor high and low side pressures and superheat and check if the coils are dirty. From that he'll be able to tell you what the problen is and what it costs to fix it.

I'd bet it's a dirty condenser coil.

 

[Red Squirrel]

I don't think ice on the pipe would affect air flow, that pipe is for the refrigerant (R-410A I think is what they use now as freon is bad for the ozone) and that pipe coils up in the furnace vent where the blower is so the air passes through it as it absorbs the heat and the air becomes cold.

I'm guessing something is blocking the air way in your ducting and due to lack of air the AC pipes aren't absorbing enough hot air and just freezing up.

I'm just guessing here though, I'm not a hvac expert.

 

[FlashG]

Time for a new unit. Get yours serviced for now and start looking. I was getting nickle and dimed to death @ $400 a pop. Wait until the season is over and you will get a better price. I wound up replacing my Trane with another Trane of similar size and a new digital thermostat. Stick to the basics the add-ons aren't worth it.

 

[Bateluer]

Originally posted by: FlashG
Time for a new unit. Get yours serviced for now and start looking. I was getting nickle and dimed to death @ $400 a pop. Wait until the season is over and you will get a better price. I wound up replacing my Trane with another Trane of similar size and a new digital thermostat. Stick to the basics the add-ons aren't worth it.

I intend to replace it. Its 11 years old, no warranty left and grossly inefficient by today's standards.

I just don't have the cash on hand to replace it now, need to wait until the Home Buyer's Tax Credit next year, then it'll get replaced.

Until then, I want it to function decently.

 

[Turin39789]

Originally posted by: Bateluer

Originally posted by: FlashG
Time for a new unit. Get yours serviced for now and start looking. I was getting nickle and dimed to death @ $400 a pop. Wait until the season is over and you will get a better price. I wound up replacing my Trane with another Trane of similar size and a new digital thermostat. Stick to the basics the add-ons aren't worth it.

I intend to replace it. Its 11 years old, no warranty left and grossly inefficient by today's standards.

I just don't have the cash on hand to replace it now, need to wait until the Home Buyer's Tax Credit next year, then it'll get replaced.

Until then, I want it to function decently.

File an Admended 2008 return showing the house purchase and get the 8k faster

 

[Bill Brasky]

Originally posted by: BUTCH1
Sounds like a low freon charge condition, if it's a slow leak it can be recharged and used but a larger/faster leak will have to be repaired.

I had EXACTLY the same symptoms as the OP, and this was the problem. I'm still completely clueless on how low coolant can cause frosting... anyone care to explain?

 

[Modelworks]

Low refrigerant means it leaked out somehow. Refrigerant last as long as there are no leaks.

If I remember correctly the heat pump is suppose to go into a defrost cycle anytime there is icing on the coils. I had a unit that used to scare the crap out of me if I was standing near it when it switched to defrost, It would let out a large hiss and steam would come off the unit, then it would let out another hiss and go back to working.


from the web

I get lots and lots of inquiries about air conditioners and heat pumps icing up the indoor coils and the large line to the unit in the Air Conditioning or Cooling mode.

This is usually caused by a lack of refrigerant in the system due to a chronic leak. The reason that the coils form ice is that when the system is short on charge part of the coil runs very cold and ice starts to grow. Once the ice starts to grow it is in insulator and keeps on growing until the coil and the refrigerant lines are one block of ice. If the coil is very dirty then the ice will form out to the outside unit (cooling mode) very quickly.

 

[BoomerD]

Have you cleaned the outside coils yet?

Being a noob about this stuff when we bought our first house 10 years ago, I had no idea I was supposed to do this...

My neighbor who is an AC tech, came over and gave me "the 411" on proper AC maintenance to avoid having to pay for needless service calls.

That unit outside is a huge dust/dirt magnet. The fan sucks tons of dirt and debris into the cooling fins in the cabinet...and you need to hose them out. I do mine at least 2x /year.

Ideally, you'd rinse them from the inside to the outside, but with most boxes, when you take the cover off the fan, you also open up the electrical connections...and they're not very water-friendly... So...take your garden hose with a good nozzle on it and rinse from the outside, starting at one top corner and work down, then move to the next panel, and so on. Odds are, if it hasn't been done recently, you'll get a ton of crap out of it.
the people who lived in this house previously, had a red pomeranian...and the only shade at the time was behind the AC unit. The first time I rinsed this one out, I got enough dog hair out to weave a large rug...and amazingly, the AC worked FAR better than before.

Take your time, be thorough as there MAY be a lot of debris lodged in the cooling fins.

 

[BUTCH1]

Originally posted by: BoomerD
Have you cleaned the outside coils yet?

Being a noob about this stuff when we bought our first house 10 years ago, I had no idea I was supposed to do this...

My neighbor who is an AC tech, came over and gave me "the 411" on proper AC maintenance to avoid having to pay for needless service calls.

That unit outside is a huge dust/dirt magnet. The fan sucks tons of dirt and debris into the cooling fins in the cabinet...and you need to hose them out. I do mine at least 2x /year.

Ideally, you'd rinse them from the inside to the outside, but with most boxes, when you take the cover off the fan, you also open up the electrical connections...and they're not very water-friendly... So...take your garden hose with a good nozzle on it and rinse from the outside, starting at one top corner and work down, then move to the next panel, and so on. Odds are, if it hasn't been done recently, you'll get a ton of crap out of it.
the people who lived in this house previously, had a red pomeranian...and the only shade at the time was behind the AC unit. The first time I rinsed this one out, I got enough dog hair out to weave a large rug...and amazingly, the AC worked FAR better than before.

Take your time, be thorough as there MAY be a lot of debris lodged in the cooling fins.

Some good advise there but with one added step, turn off power at the breaker first!. I'm going to get adventurous on the long weekend and crawl in my attic for a resealing of my ducts along with an evaporator coil cleaning. I think I'll add the outside coil cleaning to the list too..

 

[Bateluer]

Thanks for the replies guys. Don't have a hose yet, but I imagine its quite dirty. So just kill the power at the breaker and hose it out?

Edit - Doesn't seem to be working this morning. No airflow from the vents though I can hear the unit running. Haven't checked for ice yet this morning though. I've turned the thermostat up a few notches. I had the AC set at 77 last night, never got below 80.

 

[BUTCH1]

you might have ice on the evaporator coils (the part of the AC that's inside) blocking your airflow. Might not be able to see it if you can't get a view of the coil (like if it's in the attic), best bet there is to run the system on "fan" only mode to let the ice melt, if you try to continue to run the AC it will ice up more. Call a tech though, sounds like a freon problem and it won't go away

 

[BTA]

No air flow at all probably means the blower motor isnt kicking on with the condenser. You're probably only hearing the condenser noise. If you turn the AC off for 15min or so (maybe longer) and turn it back on I bet the blower comes on fine, and then wont kick back on the next time it cycles.

If your blower motor isnt starting up then the condenser coils can ice over like you're seeing.

It may just be old and need a kickstart kit (I'm sure there are multiple terms for them) to get the blower motor going reliably. It's basically a relay. The AC tech would probably charge you $100 or so to install one.

I imagine it still does need a good cleaning though as well. Not cooling well even when the blower motor is kicking on, is usually dirty coils. Sometimes you'll have leaks in your duct work (have anyone in the attic running cables lately?)

The AC tech will be able to check for correct temperatures coming from your vents and such though.

 

[drnickriviera]

Turn off the A/C unit. You're doing nothing but wasting electricity. Leave the blower on to defrost the evaporator. You're low on charge and the evap has frozen over. or Where is the inside unit located? Up in the attic, on the same level as ground floor? If it's on ground floor and you haven't been changing the filters regularly, then you need to have the tech look at and possible clean the evaporator. It may be caked with dust and dirt.

 

[BUTCH1]

Originally posted by: BTA
No air flow at all probably means the blower motor isnt kicking on with the condenser. You're probably only hearing the condenser noise. If you turn the AC off for 15min or so (maybe longer) and turn it back on I bet the blower comes on fine, and then wont kick back on the next time it cycles.

If your blower motor isnt starting up then the condenser coils can ice over like you're seeing.

It may just be old and need a kickstart kit (I'm sure there are multiple terms for them) to get the blower motor going reliably. It's basically a relay. The AC tech would probably charge you $100 or so to install one.

I imagine it still does need a good cleaning though as well. Not cooling well even when the blower motor is kicking on, is usually dirty coils. Sometimes you'll have leaks in your duct work (have anyone in the attic running cables lately?)

The AC tech will be able to check for correct temperatures coming from your vents and such though.

What you are referring to is a start/run capacitor, it's not a relay. Good luck getting anything done for $100, they charge $79 around here just to roll the truck and that only covers the 1st 1/2 hour..

 

[Eli]

No air from the vents would either mean that the evaporator has completely iced over, or the blower motor has died. I wouldn't assume its low on charge if it was working well just days before.

 

[iGas]

It could be low on refrigerant, dirty/clogged filter, blocked return air vent, or dirty outside coil. My hunch is a combination of all of previous conditions, however the likely cause is low refrigerant and/or blocked return air supply.

Shut off the AC unit, and wait a few hours for the ice to completely melted in the line. Wash/Spray the outside coil with water, and you may speed up the thawing out of pipe with a hair drier.

 

[iGas]

Originally posted by: Eli
No air from the vents would either mean that the evaporator has completely iced over, or the blower motor has died. I wouldn't assume its low on charge if it was working well just days before.

It is possible that the blower failed, but one would hear loud hum from it. The culprit could be dirty filter, jammed blower, or blocked return air supply.