Ask Me Help Desk - New A/C, but humidity is high.

Quote:

Originally Posted by KWBum

So, if I'm understanding all of this correctly, the main issue is the fan speed?

I need to get the fan to run at the right speed, for the right time, to remove the humidity.

That is, I shouldn't worry about the pistons, or about installing a TXV?

Also, the whole-house dehumidifier would be overkill?

Every one here is taking a guess about what can be done about your system. We are not there to take pressure, humidity,air in and air out and other readings and see the install and the house.

There might have to be a combination of item done to help correect your problem and then after you do all of that it could also fail to make you happy .

First off get a professional that knows what they are doing and let them look at your system. They may be able to reduce the blower speed without causing other problems and yes lower blower speeds can cause problems with the system the is why you need to have guages on the system to see what is going on especially on the suction side. You do not want to loose a compressor from slug back especially since you have a piston system.

The fanhandler that I mentioned has done wonders on systems with problems like yours but if the system is one to two tons oversize there is a limit as to what corrective items can do to help you.

I believe we have all tried to be helpful but besides trying to give you a crash course in this business I have no other answers that you do not already have.

It is jobs like this that give our industry a bad name because someone did not know what they were doing to start with. Good luck with your project.

So, thank you all for all the advice and comments. It's really much appreciated.

hvac1000, you are absolutely right about getting a professional. But, that's the main reason I'm posting. Thus far I've had 3 people look at the system, and I've gotten 3 completely different opinions about what needs to be done.

Until I posted here, much of what I was told I had no idea about. All of the comments above have been really helpful. Yes, they've been a crash course on air conditioning. Hopefully now I'll be able to make a decision as to which professional... well... "knows what they are doing," as you say.

At least now I have an idea of what might be wrong, and what might be done to fix it.

A new system is out of the question simply because of price. But, from what you all are saying a reasonable fix is possible. It might not be ideal, but better than it is.

Thanks again!

So, here is where I'm at with all this. I'd really appreciate any comments as to whether I'm taking the right approach.

Thus far I've had both fan speeds lowered to "medium." And my upstairs unit took 9lbs of freon. (Which seems like an awful lot. However, it's apparently due to the mis-matched pistons.)

Humidity is acceptable downstairs, but upstairs continues to even hit 60% and more.

I'm considering proceeding by getting TXV's installed on both units. Also, the pro I'm working with should be able to measure static pressures, and lower the fans even more.

The fans are three-speed, with the lowest speed taken up by the heat. So, to get the A/C to run on low, I will need to have a 'jump' installed so as to be able to run both A/C and heat on low.

But my big question is this, should I even spend the money on the TXV conversion?

The units both cool very well. It looks like they are oversized. The upstairs unit, with short cycles, isn't even touching the humidity.

Installing two TXV's will cost about the same as an installed Ultra-Aire 90H. Though, it will be a tricky and difficult install because of the design of the house.

My reasoning is that the A/C has to be RUNNING to dehumidify. So, slowing the fans, TXVs, and so on, are all trying, in a way, to make the unit less efficient. And, what about days when it's nice and cool outside (like today), but still humid? Maybe not comfortable inside due to the humidity, but too cool to run the A/C.

The only thing I see as being worth it, would be two FanHandlers, one on each unit. Then, the run-time would go way up, and (hopefully) the humidity down.

But, combined with the TXV conversion, two FanHandlers installed are an expensive overall project. Probably twice as much, all told, as one Ultra-Aire.

I'm leaning toward the Ultra-Aire as it can run independent of the A/C and, if connected to the A/C ducts, provide air circulation. If one U-A can knock the RH down an extra 10% it would be great. 15% would put it at 45%, and would be perfect. But, I don't know it an U-A unit is capable of that.

What do you all think? Two TXV's, plus two FanHandlers?

Or, one Ultra-Aire?

Thanks!