Fixed!

[perrybucsdad]

...I think.

Okay, well we had someone come out and they replaced the coil on the unit (see previous post (http://hvac-talk.com/vbb/showthread.php?t=607822) for history) and it seems to have fixed the issue. I have a ton more airflow at the registers that I had before, and nice cold air coming out. The house in maintaining temp, but in all fairness the temp outside is not really HOT... just warm.

The old coil looked okay, but for some reason, it was really resctricting the airflow. I didn't see any crap built up on it when the guy took it out, but maybe it had drywall dust or something in it that was blocking it. I duno... or maybe it was just a poor design.

We had a 13 SEER coil put in (old was 10) and it is a bit taller.

Anyhow, big question is this. In the winter, my setback themostat works great and saves us money. In the summer though, is it just better to set it to one temp and leave it that way 24 hours a day, or will it be able to handle the setback? I know it's harder to cool than it is to heat, so I'd like to see everyone's thoughts.

Thanks,

John

[bmathews]

You have to experiment with the setback to see what works best. It depends on a lot of factors. Such as outside temperature, what you like it set at, the building envelope, is it properly sized or maybe over or undersizsed. The warmer you keep your house the lower the bill will be. There is no such thing as a seer rating on a coil by itself. It is rated with a particular condensing unit. I'm curious about how you get better airflow with a coil. Did you go from an "A" coil to a slab coil perhaps? It sounds like it may not have been installed correctly or was freezing up due to mismatch of condenser to coil.

[skippedover]

You're quite right about not having as much extra capacity with a properly sized AC system as you might have with a properly sized heating system. One of the reasons is that not all of the capacity of the AC system is used for cooling. Some is used for wringing moisture out of the air. The amount of moisture in the air determines how much will be spent removing moisture and how much will be spent cooling the house. Running a higher temperature consistently will save you some money over the full season. Going up and down with temperatures will save little because of the need to dehumidify to a lower relative humidity (RH) with each lower temperature selected. My recommendation is to set one temp and let it be. That way you'll always have the same RH and temperature.

[beenthere]

Setting back temp in cooling mode will save you money. But often it will take longer then you like for it to recover.

[bmathews]

Setting back temp in cooling mode will save you money. But often it will take longer then you like for it to recover.

Therein lies the answer. Don't run it much during the day so it can run all night while you're home and potentially be uncomfortable. Or let it run off and on all day and be comfortable when you're home. I did a little experiment on my house years ago. I set it at 80 during the day while I was gone. I got home and sweated. I set it at 76 all day while gone and turned down to 71 at night to sleep. I was comfortable and the bill was the same. 6 of one and half a dozen of the other.

[perrybucsdad]

Thanks gang... that's what I figured. We used to use the setting where we would let the house heat up while we were at work and come home and be miserable. I set it yesterday to be the same temp during the waking hours, and just a tad warmer at night (I like it cool at night, but not cold)... I'll see what happens.

As far as the SEER rating, what I meant was that the coil that he installed was for a 3 ton unit (which I have) that is 13 seer. It looked a bit more open than the old one, but not that much different. Both were/are an A frame type coil.