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Old 06-18-16, 11:46 AM   #1
Elcam84
Apprentice EcoRenovator
 
Join Date: Jun 2013
Location: TX
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Default First 100* days with the new ac thoughts and usual minor rant...

Well we have already had a few 100* days already. Yesterday was 104*...

Man j calcs come up with a 3 ton ac for our 150 sqft house here. The problem is man j uses 100* for its calc temp which as I have mentioned before is not correct for here. Actual temp to use is 105* to 110* depending on exact location.

I ended up putting in a 3.5 ton 16 seer system. Added several returns and am going to run one to the far end of the house as well. The only way for it to get there is through the crawlspace which is better than through the attic as it doesn't get anywhere near as hot there.

I still have to run a 4" vent into the pantry and a small bathroom that's off the laundry room. They each will have a wye off the main ducts feeding those rooms. The supplier didn't have the ones I needed in stock at the time.

So far it's keeping the house at 75* but you can't do much cooking as that puts more heat into the house than it can handle and keep it 75* which is typical here. Part of living in tx is that you do minimal cooking in the summer inside. You bear the heat outside and cook on the grill.

Now when I get done with moving a wall and rebuilding both bathrooms I will be able to add more insulation in the attic and that will have an impact as back in 1960 they didn't put much up there. The old stuff is blown in rock wool made from coal slag. It has good properties except that it's the messiest insulation to use as it has lots of coal slag pellets and dust. It's worse than the dust from cellulose.


Things I would have done different if we weren't going to be moving in a year...

I would have gone with a 4 ton two stage system. Yes it's technically oversized but our summers are continually getting hotter at an alarming speed. Also if you subscribe to the global warming then you need to take that I to account which I don't see anyone in the hvac industry even giving it a thought let alone recommendations for dealing with it by increasing system sizes etc.
We are headed for another summer of 110*+ temps like we have had the last 4 years. That means easily 100+ hours over the official 100* man j temp. I do like using the man j calculator but with valid numbers.


Another thing I would do is use an indoor temp of about 70*. Just because we live in tx doesn't mean we like it hot inside. The usual interior temp is 75* which is fine nut for sleeping it's a little warm. Now with a larger master bedroom I could put in a tiny minisplit and just keep that room to 70 or less for sleeping. Remember ideal sleeping temp is around 65* according to studies.
I have spent too many summers with the temp at 78* and way too many sleepless nights because it's too warm to sleep....



Another thing I would have done if we were staying would be to put the unit in the attic instead of in the house as an upflow. It's much quieter that way. With an upflow there is no way to make it quiet because the return vents under the unit let sound from the blower right out into the hallway. You also get the slight hiss from the refrigerant when running and the low pitched sound from the compressor on startup. I hear high pitched noises very well like bad capacitors so that hiss from the refrigerant is loud to me.


I would also run the condensate to the yard if I have a good way to. The last thing to be done was to hook up the drain. So I let it drain into a bucket to see how much water it put out. Before it got hot and the ac wasn't running much it was putting out 5 gallons a day. Now with it running much more it's going to be quite a bit more.
Now that doesn't water much but hey its free water on the yard. And no pudding isn't an issue. Sandy soil and our temps it won't make a mess or run off.



For now the ac is set to 72 at night or when someone is home. If we are away it's set at 75*. Now don't get onto me how I should use a programmable t Stat and let it warm up when gone. Several real world tests including done by the DOE have shown that it does not save energy. Thus is why programmable ones no longer carry the energy star branding.
Also if I were to let it warm up it would be midnight before it cooled off to temp so it's a futile process especially if you have a "properly" sized system which is designed to maintain temp not to quick cool. However if you oversized the unit by 1 to 2 tons then you could pull it off however remember the contents of the house still need to cool as its a large thermal mass that warms up quickly but it slow to cool.

Enough ranting I guess... I'm grumpy for about 5 months of the year cause I hate being hot and getting cabin fever from not being able to do much outside. You get covered in sweat just going from car to building not to mention soaked in the car until the ac cools it off. Hint next car will have remote start...

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