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re: Any HVAC Professionals?

Posted on 5/8/19 at 8:10 am to
Posted by notsince98
KC, MO
Member since Oct 2012
18099 posts
Posted on 5/8/19 at 8:10 am to
quote:

Thanks for all the responses everyone. Here is some more info.

1580 sqft house
Outside Unit:
M/N 14ACXS030-230A23

Inside Unit
Model #: CX35-48B-6F-2


OK. This one is a bit complicated. Your builder or HVAC guy may not be too helpful. Depends on how good their customer service is. There are 2 issues that matter in this situation:

1) This is a listed match in the AHRI directory. Here is a link to an AHRI certificate for one like yours. If you know your furnace model #, I can get the exact one for your system: LINK
Since this is a fully matched system, there isn't technically anything wrong with the system that is installed as far as parts go most likely.

2) This system is matched with an oversized indoor coil to squeeze as much SEER out of it as possible. Your AC unit is only 14 SEER but matched with this oversized indoor coil you are getting 16 SEER. This is great as far as energy savings go but it is TERRIBLE as far as comfort goes because it cannot remove humidity at all under marginal loads.

Possible solutions:

1) I'm going to guess the first attempt your HVAC guy will try is reducing the CFM setting. Less warm air across the indoor coil will allow the coil to get colder. The colder the coil gets, the more water condenses on it and the more humidity it will pull from the air. Depending on CFM requirements for proper air distribution throughout your home, this could work or it might end up starving an area of your home with lack of air flow.

2) To get better humidity control might require a different indoor coil. The CX35-30B or CX35-30/36B might be a better option. It should work with your existing furnace. Odds are your installer probably won't want to eat the cost of replacing the coil.

Good luck. I have been in your situation before. I had to force my builder to completely replace my HVAC system because EVERYTHING was sized way too large for my home. Credit to my builder and HVAC guys, though. They did it at no cost. They did not refund me the cost difference for going to a smaller system but at least I have a properly sized and comfortable system now in my new house.
Posted by CrawDude
Baton Rouge
Member since Apr 2019
5290 posts
Posted on 5/8/19 at 9:13 am to
Good answer/nice explanation.

OP as another poster asked does your new house have spay foam insulation in attic/walls? I know we are not yet in the heat of the summer but when your HVAC runs does it cycle frequently (i.e. have short run times)? Do you know if your builder had a Manual J load calculation done ( used to size the unit) and as I understand is now required by code. You need to ask to see the manual J load calculation for your new home to see if the unit is sized correctly.

On the HVAC-TALK forum I mentioned in my earlier post, I know a common theme among the HVAC professionals is that the most common problem they encounter in poorly preforming HVAC units, including new construction, is oversized HVAC units and undersized/poorly installed duct work. And they say builders have a tendency to over-size the units even when the Manual J load calculation tells them differently.

I’ve also seen some videos on HVAC issues associated with new installs where the problem was as simple as the unit being overcharged or undercharged with refrigerant, or as mentioned by Notsince99 where the indoor air handler blower speed was/is not properly set. Sometimes it’s 2 or 3 issues acting in concert with each other. Hopefully your problem is a simple one that is easily resolved by the HVAC installer.

When you get the problem resolved bump this post and let us know that the problem was and how it was fixed.
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