Home A/C system help/advice

[turbopete]

I had a new Ruud A/C 1.5 ton, 10 SEER compressor installed last July in my 10 year old, 2000 sq ft house in Suffolk, VA. The cooling coils in the attic were cleaned at that time instead of being replaced. I have recently noticed that the humidity in the house is very high (50-60%). The repair guy is supposed to come over this week, but I want to be ready with my own knowledge when he shows up. What problem am I looking at?

And the GN A/C is dead. Waiting on an appointment to convert to 134a. Heat index is consistently 100+ every day!

Thanks.

 

[BandAid]

if you have the indoor fan set to "on" then that can reintroduce the humidity back into the air

 

[turbopete]

I keep the fan "on" all the time to even out the temperature in the house.

 

[TurboDave]

1.5 ton for 2000 sq ft. You need another ton and a half. I can't imagine running less than 3 tons for that square footage.
I'm running a 5 ton unit in my 2000 sq ft. and I'm glad!!!!!!!!

 

[turbopete]

Wrong number

Since you were surprised at the tonnage of the unit, I double checked...3.5 ton.
The Ruud website recommends the replacement of the cooling coils with the outside unit, but I am curious as to the common causes of why the A/C does not remove the humidity from the air.

 

[TurboJim]

Since you were surprised at the tonnage of the unit, I double checked...3.5 ton.
The Ruud website recommends the replacement of the cooling coils with the outside unit, but I am curious as to the common causes of why the A/C does not remove the humidity from the air.

Because the evaporator isnt geting cold enough to cause water to condense on it, or its clogged with dust etc and air isnt flowing thru it, but rather around it. No different than a car, just bigger.

Oh, have you looked at the condensate drain? Maybe its simply real humid and the system cant keep up? You can tell by the amount of water coming from the drain. Not sure about a house, but in a car, a 30-40 degree drop from ambient is about it.

 

[Big Stu]

Because the evaporator isnt geting cold enough to cause water to condense on it, or its clogged with dust etc and air isnt flowing thru it, but rather around it. No different than a car, just bigger.

Oh, have you looked at the condensate drain? Maybe its simply real humid and the system cant keep up? You can tell by the amount of water coming from the drain. Not sure about a house, but in a car, a 30-40 degree drop from ambient is about it.

I agree, sounds like the coil is dirty. There are a lot of hacks out there that work in the hvac field. Maybe the duct wasn't sized properly for the coil or vice versa. People like to run as big of a condenser and coil as they can, and force it through too small of duct without enough return air. Static will make parts fail quicker than $hit. Back to the subject, if you can, look at your coil and see if it's clogged with dust or hair, things of that nature. I'm sorry I don't have a dead set answer to your problem.

 

[turbopete]

There is condensate coming from the PVC piping on the side of the house. I will get into the attic and at least check out the coils. Until the A/C guy gets out here I am going to buy a dehumidifier. 50-60% humidity can't be good for too long...

 

[BandAid]

Did I miss rading that the filter has been checked...

Dennis

 

[turbosam6]

You can also look for causes of moisture getting into the house. One house we did the HVAC system on had inexplicably high humidity, until we found out they broke a water main during construction and it took forever to dry stuff back out.

Also what temps are you keeping the house at? Perhaps turn the thermostat down. You guys are way off base for your sizes too, 5 tons in 2000 sq. feet is waaay too big. 3.5 tons is a little big too, depending on construction. If you go oversize on a system what happens is it cools too fast and the unit doesn't run long enough to remove moisture from the air. In such situations many people find they have to keep their house cooler to keep the humidity down. However I don't think 3.5 tons is too far off. If the system is keeping up temperature wise, try turning it down some.

Also heres a real basic test to see how its working: 1, change the filter. 2, measure the return air temperature and delivery temperature, there should be a 15-20 degree drop on a properly working system. If you have this most likely the tech isn't going to find anything wrong. Around here if you don't turn the A/C down at night you will have high humidity in the A.M. People don't understand, if the A/C's not running its not going to dehumidify! Let us know what you find.

 

[TurboDave]

My 2000 sq ft and 5 tons sounds way off, but I didn't mention that I also have an unfinished basement under the house (which also includes an over sized 2 bay garage and all that is air conditioned and A/C ducting into my upstairs attached 2 car garage

So I'm looking at close to 5000 sq ft of air conditioned space.

 

[acoen]

As mentioned before, make sure your condenser is clean. Chances are since you recently replaced your compressor you have a small leak in your system. A low refrigerant charge will cause your system not to cool and remove moisture efficiently. I bet you need to have some refrigerant added to your system. You should have around a 30 degree drop (from ambient) across the evaporator if I remember correctly. They sell a good sealer for small undetectable leaks, its kind of expensive, but its worth it to stay cool.

HTH

Aaron

 

[turbosam6]

As mentioned before, make sure your condenser is clean. Chances are since you recently replaced your compressor you have a small leak in your system. A low refrigerant charge will cause your system not to cool and remove moisture efficiently. I bet you need to have some refrigerant added to your system. You should have around a 30 degree drop (from ambient) across the evaporator if I remember correctly. They sell a good sealer for small undetectable leaks, its kind of expensive, but its worth it to stay cool.

HTH

Aaron

30 degree drop is too much, running a 30 degree drop with an indoor ambient of 70 degrees would give you a 40 degree air temp and would mean the coil is too cold which will cause it to freeze. Thats why 15-20 degrees (depending on humidity) is the proper drop. Ask any manufacturer. The other day I was troubleshooting a system and we had mild temps and high humidity and a 17 degree drop was obtained on a properly running system. Remember, cooling the air too fast will not allow the unit to run long enough to dehumidify the space.

TurboDave, that makes much more sense.

Also as stated, a low refrigerant charge will cause your symptoms too, but usually won't allow the system to maintain temperature as well. You only mentioned high humidity, so I ASSume the system is maintaining your temperature setpoint OK?

 

[turbosam6]

I was also going to mention that 50% humidity is far from "high" when your outdoor humidity levels are in the 90's.

 

[acoen]

I apologize guys, couldn't remember exactly what the temperature drop across the evaporator should be. For some reason 30 degrees crossed my mind. Wow outside humdity in the 90% range OMG!!!! I live in Ca. we only see 90%+ humidity in the rain!!!! What is the temperature outside? No wonder your AC unit can't keep up....Wow!

 

[turbopete]

The update

After telling the A/C tech that the humidity was so high (60+%), and that I was concerned about mold with all the new furniture, carpet and big buck kitchen, he came over...after commenting that the air was "thick" he put some freon in the unit. He also recommended that I set the temp lower for a while to let the system run and pull some of the humidity out of the air. The air is alot crisper. Humidity is down to 49 percent, and the temperature drop between supply and return air is about 18 degrees.
I still need to go into the attic and make sure the coils are clear. In the fall when I have the heating system checked, I am going to have him change the coils. The manufacturer recommended it, but I just didn't have the money when the compressor was installed.
Thanks for all the help.