Return Air problem??

[beenthere]

Don't think you can ask for a precise x" static pressure. But a pressure low enough to allow use of a normal air filter for 30 days with out losing your cooling or heating. That pressure would be under the highest static rating your blower has that still delivers teh CFM your system needs.

Booster fans are a band aid, but have their place. Sometimes they take air away from other supplies, and then make those rooms lose temp.

[perrybucsdad]

Okay... I had a feeling you were going to say that. So if the blower performance data reads from .20 to .90, should I assume that is the operating range? What if the HVAC guy says he wants to install a bigger blower that can deliver more CFM? Should I accept that or resist it? My ultimate goal is comfort, but I don't want my furnace or compressor to suffer or wear out sooner either.

What could cause this high pressure though? Dirty coil, plugged ducts, body parts , bad design?

Since the house is only 2 years old, I can't imaging dirty coils would be the problem, but what if the builder ran the fan when there was no filter in and the air was dusty. Could that cause high static pressure? To me it would seem logical. Wouldn't I see icing of the coil though?

[beenthere]

The coil could have got dirty, and that would cause high static also.
Undersized ducts will cause high static.
Spare body parts in the duct can do it to.

A larger blower would move more air. But could also make your system too loud.

Best to see what the static test reveal, and what that contractor recommends.

The coil won't freeze up right away, and the air flow can be low, but not low enough to cause freezing.

[perrybucsdad]

I just received a call from my son and he told me there is a small damp spot to one side under the furnace (yes, it (the AC) is running).

My first thought is icing, but could this be anything else? Should I have him shut the unit down?

[beenthere]

Could be icing, or a clogged drain line.
Never hurts to shut it down and have someone come out and check it.

[knthms]

Why are we guessing about airflow problems?
Could be in need of a charge. Icing on coil is good indication. Possibly drty a-coil. Is unit outside clean? Lots of guessing without checking the obvious!

[beenthere]

We're not guessing. She has someone coming out to check system.

[hvaclover]

purchased a new home two years ago and I have been having problems with the AC in the house. The house is 3400 sq feet, has a 3 ton AC (or it may be 3.5... I forget), and no matter what we do, we can not comfortably cool our house. The front of the house faces east, and the rear of the house faces west. Lots of windows on both sides.


3-3.5 ton for 3400 sq ft??? Lots of windows on both sides? If i had to guess i would say its undersized....

The gent might as well live in a terrarium with all that glass. The radiant load is massive.

[perrybucsdad]

Okay... had a service tech come out yesterday and he tested the static pressure. It was 1.2. According to the blower info, that is off the charts and that could be the whole problem.

I did tell him that the builder wants to send out the installer to fix and he pointed out a few things. He said to make sure the installer checks and cleans the coil and drain tube, but to also point out to him that it is being starved for air.

As you may remember, the night before I had removed the door infront of the blower. Well, I had run the unit all day yesterday with the door off (I placed a filter vertically over the door and duct taped it in place so as not to suck any cats or dust into the unit), and the house stayed nice and cool (72 degrees in the heat of the day .. I think we were 88 yesterday). So adding more air on the return side really helped. He felt that a whole new return duct needed to be done. He said the return lines just seemed too small. He also said that the blower was quite strong and that I should not need a larger blower as that would just be a band aid on the problem.

Anyhow, the guy really seemed to know his stuff, and was very professional. Not once did he criticize the installer, but just made constructive remarks on how the system could be improved. I wish I could get my builder to use him as opposed to the installer that we have. I would much rather go with quality over low bid any day.

[beenthere]

Keep his phone number. You may still need him after the builders guys are done.

[perrybucsdad]

Keep his phone number. You may still need him after the builders guys are done.

That's what I was thinking too. If the installer just can't do it right, I would think the builder is still liable to get it working correctly. If so I will push him to use this guy.

It was just refreshing to not hear "well whoever installed this crud didn't know what he was doing." It was more "well, here are some things that could be optimized" and "this is a bit small, but can be fixed". That and the fact that even though he knew he wasn't getting the job to repair it, he took the time to tell me what needs to be done. That I thought was really classy.

One question I didn't ask him though was this. If air is entering the blower box from the return side now, and also through the front, that basically means I need to double the air supply ( or maybe more since he said we still should have more airflow). If that is the case, how can you do that with only using the existing opening? Would the single opening be able to handle more air coming from a much larger return duct?

[beenthere]

A larger return duct will allow air to return to the air handler easier.

But, if that 1.2" is with the blower getting air from both the regular return and with the blower door off. You need supply duct corrections.

Do you know what the individual static reading are.

[perrybucsdad]

The 1.2 was with the cover on the unit. He did not do a reading with the door off.

As for the individual readings, I have those at home. But no, I don't know the individual readings right now. Will that tell me if it is more a supply or deliver side issue (or both)? He seemed to concentrate on the supply side with all of him recommendations (other than his comment about inspecting the coil and cleaning it).