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Old 05-08-2021, 04:54 AM
 
7,076 posts, read 8,530,515 times
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Quote:
Originally Posted by Valley Native View Post
Terrible idea! Any qualified technician will tell you that anything over 85 degrees can be dangerous on so many levels. Setting the temp as high as you do adds stress to the HVAC system, and it's not healthy for your house in general. I leave periodically during the summer, but never set my thermostat any higher than 82 when I'm gone. The last thing I want is to come home from vacation and have my house feel like a g.d. sauna!
Speaking for myself, I despise spending more money on electricity. But I am going to take experts advice. I asked three people because I did not want to believe the correct answer. Lol

Analogy: A person changes their car oil every 20,000 miles to save money even when it causes stress on their system. But since they never were burnt, they repeat their own personal experience of not seeing a problem. Penny wise, pound foolish. If I wanted to “see” the problem with the air, I would put on a set of pressure gauges during a hot day and high internal house temp. Then let the temp drop inside to 85 and re-compare the pressures.

Re: humidity in AZ. I had a home on the beach in Mazatlan. No AZ monsoon storm could complete. I know I need humidity added when I turn the air off. I am less sure when I have it set to 85 degrees. But sites still recommend it. I could point you to a dozen sites that suggest adding humidity (tubs of water). Again, it is a PITA. I don’t want to. But I bought all new furniture in this place and spent a small fortune. At 75 degrees, I of course would not bother. The problem is a COMBO of high temps and low humidity.
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Old 05-08-2021, 07:24 AM
 
Location: Sonoran Desert
34,506 posts, read 44,501,261 times
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Quote:
Originally Posted by MN-Born-n-Raised View Post
Speaking for myself, I despise spending more money on electricity. But I am going to take experts advice. I asked three people because I did not want to believe the correct answer. Lol

Analogy: A person changes their car oil every 20,000 miles to save money even when it causes stress on their system. But since they never were burnt, they repeat their own personal experience of not seeing a problem. Penny wise, pound foolish. If I wanted to “see” the problem with the air, I would put on a set of pressure gauges during a hot day and high internal house temp. Then let the temp drop inside to 85 and re-compare the pressures.

Re: humidity in AZ. I had a home on the beach in Mazatlan. No AZ monsoon storm could complete. I know I need humidity added when I turn the air off. I am less sure when I have it set to 85 degrees. But sites still recommend it. I could point you to a dozen sites that suggest adding humidity (tubs of water). Again, it is a PITA. I don’t want to. But I bought all new furniture in this place and spent a small fortune. At 75 degrees, I of course would not bother. The problem is a COMBO of high temps and low humidity.
None of your AC system is within the heated/cooled space. It is in the attic and outside. So your pressures would not be any different, not that it matters in the first place. With respect to your humidity concerns you are neglecting to consider that running your AC for hours to keep it at 83 is removing significant amounts of moisture from the air. I don't know, but it is possibl that the relative humidity is actually less in the cooled space than in one that is not. During monsoon, the relative humidity outdoors is around 30%. If you cooled that air the humidity would rise, of course, but if you do it with ac it removes moisture in the process.

In fact it could be this moisture difference that puts greater "stress" on the system. It is about the only thermodynamic relationship that I can think of that might. It works like this. An AC moves heat. There are two kinds of heat - sensible and latent. Sensible heat is what you can feel - it's hot out there. Latent heat is heat that is absorbed and released as a substance undergoes a phase change - gas to liquid. It is the whole reason why AC works in the first place - the phase change of the refrigerant. But the air being cooled matters too. When moisture in the air condenses on the evaporator coils a very significant amount of heat is given up. Your ac has to remove that heat along with the sensible heat in the air. Latent heat is about 7 times per degree what sensible is if memory from long long ago remains. So it is a very big deal and why it takes an AC much longer to cool a humid space than a dry one. Well, if we start out with more humidity, because the miserly owner set the thermo at 95 then it is going to be a greater "stress" on the system getting the temp down than if the owner set it at 83, it ran all day, and the humidity was therefore pretty low. Then again, Miserly Owner's AC runs far, far less time in maintaining the temp at 95. IDK, I am unconvinced and will keep mine at 95 (and I do change my oil).
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Old 05-08-2021, 08:24 AM
 
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Quote:
Originally Posted by Ponderosa View Post
None of your AC system is within the heated/cooled space. It is in the attic and outside. So your pressures would not be any different, not that it matters in the first place.
The high and low pressures WILL be different when you are cooling the house air temp of 95 versus 85 versus 75 as compared to the outside temperature. Don't take my word for it, ask any single person in the profession. I wasn't convinced (better yet, I didn't want to believe) tech # 1 or tech # 2 and the worry about setting at a high temp. That's when I called the factory tech support that field calls from the techs in the field. As in, the expert of the expert. AND, you are a google away from seeing a dozen posts that also recommend 85 degrees. VN's tech told him the same. So do as you please.


Quote:
Originally Posted by Ponderosa View Post
With respect to your humidity concerns you are neglecting to consider that running your AC for hours to keep it at 83 is removing significant amounts of moisture from the air..
I'm not neglecting to consider that POV. In fact, I've posted that in the past. My personal guess is that it is a waste of effort by putting buckets at 85 degrees (at the same token, I think it is a mistake not to put buckets in at a set point of 95 degrees or higher). Still, google the topic until you are blue in the face and you will see a dozen people suggest turning your air down to 85 AND adding in buckets. So I'm erroring on the side of caution. As I said, I spent a small fortune on new furniture. I bought the elephant, I best have the $$'s for the peanuts.
Plus, I will be flying to visit in early July and late August for work. I'll simply fill-up the buckets. It should be common sense that the humidity level will be higher (air on or off) with buckets of water in the house. I have a lot of surface area on my tubs (storage tubs). Air on or air off, the humidity will be higher.

With both topics (humidity and hotter air), we are talking about a summer-long situation AND combined with a multi-year approach. If I had my air on for a summer at 95 F and no buckets, shy of some elastic waistbands and possibly some bad red sauces, the world will spin. Especially on a 2018 model that isn't no its last leg. But I'm not interested in jolting my tens-of-thousands worth (three compressors), 2018 Carrier units over multiple years. YMMV.

We probably both know enough on the topic to be dangerous. It's why I called people and feel comfortable with my approach. If I was you, I would double-check your thoughts under the spirit of "penny wise, pound foolish". Because your answer will match the three I got. From there, if you think the concept is paranoid, do what you think is best. I went the other direction because I feel I have too much to lose.

Now if it cost me $600 more a month in electricity, I might look into figuring out what item would need to be repaired and how much. Or go after my PITA approach and leave it off while I have 2x more buckets. I could also really hammer one air conditioning zone which would reduce the total cost of a repair to one zone. Because of this cost of energy topic, I will be doing some day-to-day experiments by looking at kWh's and temps at different set-points. I will post accordingly because I think this is an interesting experiment.

Last edited by MN-Born-n-Raised; 05-08-2021 at 08:37 AM..
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Old 05-08-2021, 05:56 PM
 
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I'm curious about this as well and have a decision to make shortly. Typically in past years we have just left the AC off, no buckets. Some of my exercise bands suffered and the inside fabric of one sofa disintegrated.

But now, we've just upgraded our AC and I wouldn't want to do anything to stress it, right out the gate. But I am having a hard time understanding what the actual stress is above 85. or what line is under pressure. Can someone point me to a link, technical is fine. Google search is not yielding anything
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Old 05-09-2021, 12:29 PM
 
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My Honeywell wireless thermostats range from 23 to 26 percent humidity inside with my water buckets while its 11 percent outside. All of my stats show around 80 degrees F (thermostats set to 85 degrees and it is 88 outside).

Once it gets warmer and the air kicks on, it will be interesting to see what the humidity measures.
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Old 05-11-2021, 01:49 PM
 
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Assuming you have a programmable thermostat.

I would drop it as low as 70 right before the sun comes up. If you have the time of use plan, turn it off during those expensive hours.

It is easier to cool at night and it is more efficient to run it for longer than having it kick on every time the temp hits 82 when you have it set to 83.

Even on the hottest days, it will take a while for it to raise 13 degrees indoors with the blinds closed.

I would think that's the cheapest way to do it.
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Old 05-14-2021, 04:57 AM
 
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Quote:
Originally Posted by ajonesaz View Post
Assuming you have a programmable thermostat.

I would drop it as low as 70 right before the sun comes up. If you have the time of use plan, turn it off during those expensive hours.

It is easier to cool at night and it is more efficient to run it for longer than having it kick on every time the temp hits 82 when you have it set to 83.

Even on the hottest days, it will take a while for it to raise 13 degrees indoors with the blinds closed.

I would think that's the cheapest way to do it.
That would be easy to program remotely (I have 4 thermostats; 3 units and one is a split zone). I will experiment by looking at per kWh consumption as it gets hotter. That split zone isn't as efficient. I would want the damper to cool all vents (both zones) when one of the two thermostats calls for cooling.

Even with a high of 98 degrees and our (still) cooler nights, the air is barely kicking on at all. Electricity usage was $2.12 yesterday. Though I'm seeing a slight internal temperature ramp-up (above my set-point) from around 6PM to 10PM? I would have thought the air usage would be the highest around 2 PM?!
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Old 06-02-2021, 12:16 PM
 
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An update as of June 1st. I've been watching my daily consumption. I turned off the casita air conditioning zone yesterday and it hit 92 degrees inside that room (Outside temp of 103F high/ 78F low). So the house doesn't seem to warm up very quickly.

For the other three zones, in order to maintain them at 85F, I used 21 KWH of power yesterday. I am on the basic plan (almost 3,000 square foot one level home). So that's about $3 a day all in. I suspect it will cost me $100(ish)/month in June. I have my lights automated and I left the Fridge and wine cooler on. That sounds much more reasonable than I thought. The jury is out once those 115 degree days are more common.
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Old 06-03-2021, 06:16 PM
 
Location: The Grand Canyon State
6,820 posts, read 3,591,217 times
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The damage caused by turning the AC off would that not cost less to replace things over a few years when compared to the cost of running the AC even at 85F.

I live in a smaller home so I use a shed have had several plastic items damaged from the past metal shed 2 summers ago I had a custom shed built on a concrete slab with radiant barrier. This helped a lot where the metal shed was more like a oven. I did think about installing a solar fan but I don't want to draw in the dust I like the shed sealed keeps the dust out. I have thought about adding small window AC unit which would allow me to store more sensitive items in there. Not sure it's cost effective when you add it up it took a few summers to damage the plastic even in the steel shed.
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Old 06-04-2021, 12:09 PM
 
7,076 posts, read 8,530,515 times
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Quote:
Originally Posted by kell490 View Post
The damage caused by turning the AC off would that not cost less to replace things over a few years when compared to the cost of running the AC even at 85F.
Working the math, it's better to turn it off and add a bunch of water buckets.
When you use that approach, you have to:
1. Really clear out your cupboards. A lot of the sauces go bad. So there is mental energy trying to do your best not to waste. As in, the wind-down process takes a couple of months of semi-planning. And often, I would haul food back to MN. A small PITA.
2. Emply your Fridge/freezer and then turn it off. All of those condiments need to get tossed including freezer items that would normally be able to make it through the summer.
3. Remove battery items (automatic wine openers, battery phones, etc). I have been sending them to neighbors.
4. Add more buckets of water to make sure you are covered. It's a PITA. Plus you need to store those buckets.
5. Risk damaging your elastic (underwear, trunks, and bedding), and leather items. Especially any bonded leather is highly susceptible to damage. Ask me how I know.
6. Worry about some alcohol items. Especially wine. I'm not sure how well a wine cooler would do in super hot conditions. But we had to toss various spirits as they taste funny.


Big picture, getting out of town (and reopening) is much simpler at 85 degrees. I did it 10 years in a row using my approach above. Also, techs tell you that you should really run your air at least once a week. I was told to run the air every so often for "lubrication" reasons. I could do that remotely. But again, you need to mark your calendar.

In the end, having two places sounds glorious. But it's mental energy and it is wearing. I've had 2 or 3 homes 25 years. It's getting really old. For $400(ish) a season in power, it's a no-brainer. Though I do feel a bit guilty using power when I am not there.
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