Troubleshooting home air conditioning

[Jonathan]

So I don't think my central air is working as it should.

It has been fairly hot and humid here in the last month, but not as much as it has been in the past. I don't think the air flow out of the room vents is cold (cool at best) and it doesn't do much to cool the house down. It will also rarely shut itself off from achieving the temperature set point, and mostly would only do so at night when it had cooled down outside.

A couple weeks ago, I think I also first noticed there was condensation water dripping off the outside of the drain piping. This is the 1" plastic drain pipe which comes from the bottom tray on the A-coil and channels away condensation to the floor drain. I had thought perhaps something was plugged in it like 3 year old construction debris or something else. The sides of the ducting around the A-coil also seemed much sweatier than I had remembered them being.

Within the last week, I noticed the air flow was back up where I felt it normally had been. I also could feel a steady air flow out of the atmospheric drain line opening on that pipe, which I'm not sure was there before. Still though, the air isn't cold.

Yesterday I opened up the ducting in front of the A-coil to get a look. On the top, or cold side of the air flow, there appears to be nothing out of place. The condensation drain track also is clear and I tested it by pouring a little water down it and I could see and hear it travelling out the drain and to the centre of the floor. Inside the A-coil, on the warm side, it is spotless. I had thought maybe it would be covered in filth and that was why it wasn't cooling. Not the case. It was as clean as it might have been on day one.

The filter is also in good shape and has been checked and changed a few times. It is on the lower end of the ducting before it enters the furnace portion and nothing seems blocked or dirty in there.

I buttoned everything back up and turned it back on. Air flow is good again but it is not cold. It seems cool, but might only because air moving by you seems cool, but isn't any colder than the rest of the air in the house. As expected, the house didn't get cooler over the next hour or so, and it didn't shut itself off.

I checked the compressor unit outside and it appears ok and nothing is rattling or shaking. I had seen a clip online of a suggestion to put your finger on the larger/insulated copper pipe near the compressor and check to see if it is sweaty and cold. The guy mentioned it should be 45 degrees or so. Mine is not cold, it is the same temperature as outside, and it was not sweaty at all. Conversely, I checked my neighbors unit as it kicked on while I was out there and sure enough, it was cold and sweaty. The suggestion mentions this check can rule out whether your freon is low. In my case, I would say it points to my freon actually being low and needing a recharge.

Couple questions:

- Do home A/C systems not have a low pressure cut off switch like our cars do? In the car, if the freon is low, the compressor won't kick on. I would have thought the home unit would have a similar switch?

- Do home systems need recharges once in a while? What I'm getting at is, if they need to be recharged, should I be expecting to find a leak somewhere that needs to be repaired (much like our car systems)?

The home is 3 years old and the system was working, but maybe it wasn't originally filled with much over the bare minimum?

My next step is to call an A/C repair company and ask him to measure the freon charge and recharge as necessary. Sounds good?

[Bitsyncmaster]

The system should not leak so no it's not normal to need a recharge. But it does sound like you're low on freon. The service company will just put gauges on it to determine if it needs a charge. They should recommend a leak check but that only finds leaks that are accessible. Cost to leak check about $100 and charge to add coolant is $100 or more.

[Dangermouse]

I have had two AC none-operations in the past couple of years.

The first was when a landscaping crew sliced through the thermostat wires at the compressor - may be work checking that you are getting a signal on these at the compressor as they could be loose in the thermostat also.

Second was when some enterprising neighborhood kids opened the valves at the compressor and let the freon out. That time I had done all my testing and called the AC guy. When he arrived, he diagnosed that my A coil was leaking while he sat in his car in the driveway. My system was 10 years old. I got him to put his gauges on the unit at the compressor and that's when he noticed that the valves were loose. He told me that system can loose a little freon around the compressor seals but that's about all as most of the rest is hard pipes. A sudden loss is usually a hole in the A coil from condensation rust.

[DMCMW Dave]

Agreed - it is low on Freon. It should never leak as the system if properly installed is sealed, the motor and compressor are one sealed unit and all the lines should be sweat or compression fittings. I've never noticed service valves on a home A/C but apparently (based on Dermot's post) some may have them. I believe that there is a low pressure switch to preserve the compressor in the event of Freon loss, but that may not be universal, and is probably inside the compressor. There is often a high temp switch on the compressor that serves the same function.

It could also be compressor failure but that is unusual on a system less than 10 years old, especially in a climate like Canada where you don't really run it very much (compared to, say, Houston).

Being a modern system you probably have a variable speed fan which could account for the low air flow at times, but that should vary with the heat load. It is hard to check but see if you can look at the input side of the a-coil, they can plug up with dust if your filter isn't kept clean, and even if it is after a long time. Access to this may mean opening up some of the sheet metal work.

We had a new unit installed several years ago and after one year it quit working. The installer came back and found a tiny leak, fixed it, and we have never looked at it again (probably 10 years later now).

Time to call the A/C man. . . .

[Dangermouse]

The valves on my system are supposedly intended as isolation valves. They are normally open but you can close them to keep the freon in the lines to/from the A-coil if/when you change the outside unit to minimize wastage.

The AC guy demonstrated (with his leak tester) that they seal well in both the open and closed position but may leak if they are in an intermediary position. An odd occurrence that he had not seen before.

[Kenny_Z]

I just went through this. My 2 year old system rusted through and I lost freon. It had these same symptoms. Thankfully it was still under parts warranty but labor cost me 600 bucks.

[Jonathan]

Thanks for the feedback guys.

Dermot, I inspected the wiring in and out. Other than the two copper lines (one going and one coming), there is the main power cable and the signal cable. The signal cable may have additional wires within it, but from the outside it is one insulated bunch. It looks to be connected okay and no obvious signs of damage. When I turn the A/C on via the thermostat in the house, it does roar to life outside and the fan on top starts spinning. I have not taken the cover off the electrical connections to see if an individual wire is loose, but it seems like it is at least responding to being told to turn on ok.

I agree with the system shouldn't leak idea. Similar to our cars. The system did work well in the first two summers, so clearly something changed. It worries me a bit getting the A/C man over and getting hosed, so I put it out to some local friends to recommend someone trustworthy. Various things on new homes in Ontario come with a warranty, such as your roof, or foundation, etc. I looked at the part about A/C coolant leaks and it is 1 year only, so I'm likely on my own for this one and not going back to the builder. Might ask Cory about this one......

Dave is right about the climate here... we might have ours on for 30 days of the year in Ontario, whereas our home in Florida might have the A/C off for 30 days per year.

The thing with the sweaty pipes idea was that prior to me thinking it wasn't cold anymore, I had quite a bit of sweat on the copper line in my laundry room ceiling where the lines get routed indoors. The larger one with the insulation had a couple spots where the insulation was gapped and I actually saw and felt a bit of a piece of ice on the outside of it. Closer towards the furnace and A-coil, as it bent down, the large copper line insulation had started to sag and it had water dripping out of the bottom of the sag. Not sure if this was dripping back from the condensate line possibly being plugged at one point, or pipe sweat. Anyone know what to make of the ice chunk on the outside?

After seeing this, I redid the insulation in those areas and sealed it up so there were no gaps anywhere in the insulation between the wall coming in and the edge of the duct at the A-coil. About this time I saw a lot of sweat on the outside of the duct in the boxed area where the A-coil is. Again, had not seen this before, but may just not have noticed it.

When I was out this morning looking at the valves and the wiring at the compressor, the connectors look and feel tight. Also nothing visible in the fan area blocking anything.

Have a look at the photos I took yesterday when I got in to the ducting and inspected the A-coil. It was very clean and I honestly thought it was going to be plugged. It did not look as though it had been.

On the smaller line, the one not insulated, there is a gauge of some kind that I don't know what it is telling me. It says DRY-WET-CAUTION in three equal thirds around the circumference. You would think it would be the sort of thing to have a needle or indicator of some kind pointing at one of those three words, but I cannot see one. Anyone have one of these and know what they mean? I don't have any documentation on it nor do I know how it is supposed to be read.

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[Dangermouse]

Now that I think about it, there was a LP switch on mine, located inside the electrical connection compartment on the outside unit. IIRC there was a red button that popped up.

Might be worth a look and resetting it if it has popped out. If it activates again, then you have low pressure and a leak.

[Jonathan]

Ok, no luck on the LP switch being located in the electrical connection spot. I think if there is one, like Dave mentioned, it is built into the compressor and not accessible. Doesn't look like it is a reset switch popped up, unfortunately.

Not many other ideas at this point... 1-800-FIX-MY-AC looks like about it.

[Bitsyncmaster]

That looks like a sight gauge like some cars use to use. I've never seen one on a home AC system. But as your system is running, if you see bubbles than your low on freon.

[Spittybug]

Join Angie's list and you'll get some good deals on local A/C companies.

[Jonathan]

That looks like a sight gauge like some cars use to use. I've never seen one on a home AC system. But as your system is running, if you see bubbles than your low on freon.

Thanks for pointing this out. I definitely see bubbles. Definitely calling the A/C man. Will post back here what we find out. Thanks to all for the help!

[Dangermouse]

weeeeeeeeeeeeeeeeeelllllllll ???

Don't keep us in suspense...............

[Bitsyncmaster]

I got sick of paying the AC guys to add 1 to 2 lbs. of R22 to my old downstairs unit. That would cost about $200. I bought a 30 lb tank of R22 on ebay for $285 shipped (got my 608 certification online).

[Jonathan]

weeeeeeeeeeeeeeeeeelllllllll ???

Don't keep us in suspense...............

Hehe... oddly enough he is coming over this morning. I called yesterday (finally) and he dropped by just to take a quick look on his way home. He put the pressure testers on it and saw the numbers lower than expected. Today he'll evacuate/reclaim the freon that is in it and then pressure test (possibly overnight). If there are leaks, we'll tackle that next. If none are found, then it gets recharged as is. He was aware of the cookie cutter homes certain builders in this area put together from past experience and both of us felt it may have never been filled up adequately in the first place. He was also looking for any evidence of oil somewhere that might show where the leak is/was, but there wasn't any (nor can I think of a time I cleaned any up). We'll let the leak test find out for sure...

EDIT: He also mentioned my unit does not have a low pressure cut off switch like our cars have and that my model isn't the base model... he said it might be a notch below the base model. So much for negotiating freebies to be included when you build a home.

[Dangermouse]

EDIT: He also mentioned my unit does not have a low pressure cut off switch like our cars have and that my model isn't the base model... he said it might be a notch below the base model. .

Basement model?

[Jonathan]

Basement model?

Base model, more like "basic" model. Like the "cheapest model we can install to satisfy the contract requirements." I think it means it just doesn't have much in the way of special features, or extra features, isn't overly large and maybe doesn't have the best components. His comment about the builders in the area was hinting at cutting corners. I got the A/C system included in the purchase price, but they picked the specs. Live and learn I guess. It's definitely not the Cadillac, that's for sure. Maybe the Chevy Cavalier, at best.

[Dangermouse]

No, I got that. I was trying to make a funny.... What's lower than base - a basement.

nevermind :)

It's also known as contractor grade, where a big contractor can negotiate a fantastic price on a stripped out item.

[Jonathan]

No, I got that. I was trying to make a funny.... What's lower than base - a basement.

nevermind :)

It's also known as contractor grade, where a big contractor can negotiate a fantastic price on a stripped out item.

LOL, no worries. Lost in translation. More reason to use Farrar's [/sarcasm] type idea on our messages. Dear Internet, please go away and bring me back my telephone.

... the contractor grade description pretty much sums it up. Not the quality you would choose if doing your own shopping at Home Depot, but in the big business of building homes, this is what we get. Sad state of affairs the world is in :(