Infinity system-not keeping up in cooling 2nd floor
I have a brand new Infinity system with two 25HNA6 3-ton units. Last two days have been brutal here in Philly. Temps around 95-98F. First floor system is cooling well and keeps the temp at 77F, which is my setting. The 2nd floor system is not keeping up. The setting is 77F, but the t-stat is reading 80F indoor. The air out of the vents is coming out very cold. It's running in high stage cooling, but can't seem to catch up until the nighttime, when the outside cools off a bit.
What can be done? Is that a sign of improper sizing? How should the system behave in such hot weather anyway?
Check for restrictions in the return air, although you stated its a brand new system the problem could be a very dirty air filter or a return grill being blocked by a dresser, etc. Also you stated that the air coming out is very cold... is the air blowing strongly from the supply registers or just a small amount of really cold air? Also how is the insulation in your attic?
Yes, the system is new (installed in April). The air is coming out strong from the registers and it is cold. I can control the speed of the fan by Infinity t-stat. No returns are blocked by furniture. The air filter is Lennox media filter MERV 11 (I think). It's an accordion style, wide media filter. It's also new (from April of this year). Our house is not particularly dirty, so I doubt it's clogged. So, unless such thick filter is just a bad idea to begin with, I don't think it's that.
The insulation in the attic is blown in type. It's for the most part up to the top of the joists, which are 12 inches tall, I am guessing.
ok... so do you have lots of windows letting the sun shine in on the 2nd floor?
Sounds like your attic insulation is sufficient, hard to look what's in the walls.
There are only so many things you can do as a homeowner to help your A/C cool your house... then its time to call a service technician to do a complete system check.
What did your contractor say about it.
How big is your second floor.
You can control air flow from the Infinity controller, by why would you, let it do its job.
If your duct isn't designed for a MERV11, it can be slowing down your air enough to cause this.Philly has a lower design temp. Hopefully he didn't use it.
How big is your 2nd floor compaired to the 1st? Did the installer run a heat load calculation on your house before designing it?
It could be due to many things, including being too small. However, there is no way anyone here can tell what the problem may be without looking at it. Call the installer and have them check the system, they are the ones you paid to do this, let them do their job.
By the way, you can not control the fan speed from the thermostat. The fan settings (Auto, Low, Med, High) are only for continuous fan operation, they have nothing to do with the fan speed on a call for conditioning.
If all else fails....Try reading the directions!
Tell it like it is and let the chips fall where they may.
Any views or opinions stated here are strictly my own.
Yes, they did the heat load calc's and came up with close to 3 ton need for each floor. 2nd floor is smaller than 1st, but about 600-800 sq ft, I think, due to the two story foyer and living room. I am not sure if the ducts are designed to handle MERV 11 filter. That's a good point. The old system had electrostatic filters only (those that make snapping sound).
But in any case, this is NOT normal even in such extreme temps to have a 3 degree difference, is that correct?
If it was designed for 77° indoors or less ,then it's not correct to be at 80°.
Okay I see how far above outdoor design it is ,so depending on the actual indoor and outdoor design,it may be doing fine.
Last edited by dash; 06-09-2008 at 06:14 PM.
Even though you don't have use of that open space. Its still part of the load for the second floor.
Do you remember what size the old unit was for the second floor.
Even if the the new one is the same nominal size. The condenser and air handler match may not have the same sensible capacity as the old one.
I would want the system checked. Plus I'd ask the contractor what temp he design/sized it to maintain at what OD temp.
It is normal.
Originally Posted by dafreerider
Systems should not be designed for historic heat waves like we are having.
Philly has a design temperature around 90°F. Loosing 3°F at 100°F is normal, your contractor should be congratulated. The only thing he forgot was to properly educate (you) the homeowner.
Do you want a system that is running at its best 2 or 3% of the year or 70 or 80% of the year? Sounds to me like you got the 70 to 80% system in your home .
Saturday philly was 98, Sunday 97, and today 97. According to PWS.
A fair amount above normal.
But, that Merv11, may be slowing the air down enough, to be the difference between 80, and 77. And, it may be set to 350 CFM per ton instead of 400, which makes a big difference.
Having it checked is the only way to know.
Thank you, guys. I will have them check it out.
But I guess, it is possible for the system not be able to catch up in some extreme temps (like in last 3 days), especially if the house is either losing cold air or being heated up via many windows and skylights...