Need HVAC advice

[BuickMike]

I think I have a duct leak somewhere. My AC blows cold (55 degrees), however it is taking noticeably longer to cool the house off and it almost seems like there may be less air flow. I believe my returns are fine. If I remove something from the ceiling I think I have air movement while the AC is on above the ceiling.

The problem is that I have a flat roof house which means no attic. Is there any creative way to find the leak other than hiring a guy with a special camera?

 

[xrunner123]

If you had an airflow meter you could meter the inlet cfm vs outlet cfm of all of your ducts. If there is *no* leak they should be equal.

 

[georgewe4]

Not seeing the house or being there I am at a big disadvantage. But..I'll give it a shot.
If the system is off for a long while does it blow hard when you first turn it on? Or does the airflow slow down after run time? Is it condensating or draining humidity.

I'm just wondering about the refrigerant charge.
A system low on charge may blow out cold air. But the indoor coil is running below 32 degrees. The longer the system runs the more humidity freezes to the indoor coil therefore restricting airflow. I've been on calls where the complaint is similar to yours. They even go so far as to thinking the indoor blower is not running due to NO air flow. I go to the indoor coil to find the system froze up. Low charge, dirty filter, dirty indoor coil, or bad indoor blower motor is the biggest reasons I find for systems freezing up. Im sure you looked at the filter and indoor coil when you noticed this.

If its not freezing up the best way to find the problem would be a flow meter as mentioned above. Do you have sheet metal ductwork or duct board?

 

[BuickMike]

My house is only 3 years old. I checked the coil and the filter. They are fine. The air flow seems constant, not stronger at any point. I noticed towards the end of last summer that it seemed like the AC was running longer and the electric bills were a bit more. My gas bill was more last winter too (same air handler). I was having a hard time figuring out if something was wrong becuase it was colder than before and the gas rates went up.

I found a AC / mechanical place that a couple friends recommended and they do free estimates. I'll probably just call them out and see what they say.

Thanks for the replies

 

[BuickMike]

I talked to a guy at my work in our facilities department and he said he will let me borrow his flow meter over the weekend. :biggrin: Hopefully he'll give me a good idea about how to use it. Any tips georgewe4?

 

[CHARGED]

It all depends on how the ductwork was run in your attic. IF there is 1-2 pieces of main supply duct off the air handler and then flexable duct attached to that which runs to all the rooms, they should all have dampers at the main duct which would mean if one has a leak it would be somewhat isolated to that run only not the whole house, which means the leak would have to be on the main supply duct(s)
If one of the returns has a leak it would be pulling in hot air from the attic in the summer and cold air in the winter.
Again I have no idea how you ductwork is run.

 

[georgewe4]

Sorry this is late...12:24 AM friday morning here...Worked late today just catching up...With the last post of not cooling well toward the end of the summer and the heating problem in the winter I would check the return. It may be drawing in air from the attic. One good way to check this is on a hot day see what your indoor temp is in the house and then check to see what the return air temp is going into the furnace/air handler. Use a probe type thermometer prefer digital. If there is a good increase in temp from the return temp compared to the house you could be sucking in attic air. Wait for a sunny warm day to be for sure.
Hope this helps

 

[turbosam6]

I found a AC / mechanical place that a couple friends recommended and they do free estimates. I'll probably just call them out and see what they say.

Thanks for the replies

Free estimates are for equipment replacement, not repairs. They should charge you a diagnostic fee for coming out.

I'd do what George said, measure the air temps coming in the return. You should also see about a 20 degree split between the return and delivery temps. If its 75 going in, look for 55 going out. This varies, but 15-20 degrees is usually right.

I'd consider having a routine maintenance performed, that way everything is cleaned and if there is a problem with the performance of the system a good tech should be able to pinpoint it.

 

[georgewe4]

I second the routine maintenance!
I know around here you can get a visit for 59.00..
Thats about what you get is a "visit".
We acid clean indoor and outdoor coils, new pleated filter, blow out condensate lines and a bunch of other stuff. Also Our tune-up includes up to 1 pound of refrigerant if needed. Takes us about 1 1/2 to 2 hours depending on how things go. We are at 129.00 for a cleaning/tune-up.
If you get a routine maintenance performed ask them what you are getting for your money and if they are actually cleaning things or just checking.
Like turbosam6 said a good tech should be able to pinpoint the problem.