Thermostat with adjustable cycle rate

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strogg
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Thermostat with adjustable cycle rate

#1

Post by strogg » Sun Jun 28, 2020 10:50 pm

As the title suggests, I'm looking for a thermostat with an adjustable cycle rate. The HVAC I have right now is definitely way too large for my place and is short cycling like crazy. Does anyone have any suggestion on reliable thermostats that'll fit the bill? I would prefer thermostats that can work as designed without wifi. I'm not a fan of the whole IOT movement.

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Re: Thermostat with adjustable cycle rate

#2

Post by 03Lightningrocks » Sun Jun 28, 2020 11:41 pm

strogg wrote:
Sun Jun 28, 2020 10:50 pm
As the title suggests, I'm looking for a thermostat with an adjustable cycle rate. The HVAC I have right now is definitely way too large for my place and is short cycling like crazy. Does anyone have any suggestion on reliable thermostats that'll fit the bill? I would prefer thermostats that can work as designed without wifi. I'm not a fan of the whole IOT movement.
If your system is short cycling due to being over sized, changing the thermostat is not going to help. How did you end up with an over sized system? Most homes are designed with the correct HVAC system size to begin with.

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Re: Thermostat with adjustable cycle rate

#3

Post by RPBrown » Mon Jun 29, 2020 7:44 am

03Lightningrocks wrote:
Sun Jun 28, 2020 11:41 pm
strogg wrote:
Sun Jun 28, 2020 10:50 pm
As the title suggests, I'm looking for a thermostat with an adjustable cycle rate. The HVAC I have right now is definitely way too large for my place and is short cycling like crazy. Does anyone have any suggestion on reliable thermostats that'll fit the bill? I would prefer thermostats that can work as designed without wifi. I'm not a fan of the whole IOT movement.
If your system is short cycling due to being over sized, changing the thermostat is not going to help. How did you end up with an over sized system? Most homes are designed with the correct HVAC system size to begin with.
:iagree: Unless you have a 2 speed or variable speed condensing unit, you could be looking at some long term issues as well.
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Re: Thermostat with adjustable cycle rate

#4

Post by strogg » Mon Jun 29, 2020 8:53 am

I'm well aware of the long term issues. Unfortunately, I had no control over the initial installation of the AC units. They are undersized because there are far fewer people living here than the house was designed for. I'm very leery of replacing them with smaller units right now because they're still working perfectly fine, and it would cost thousands to replace with variable speed units. I'd rather spend the money later if I can. Now isn't all that great of a time.

Anyhow, I was able to get the cycle rate to go higher by closing off the vents to the rooms with the thermostats and by lowering the temperature by a couple degrees. The average cycle time is now about 10-15 minutes. Before it was 5-10. I'd rather not do that for the long run because it's getting chilly in here.

I guess I'll rephrase my question. Does anyone have any other suggestions? Otherwise, I'll probably end up getting new thermostats as a bandage until the AC units finally give in. I am hoping with the new thermostats can increase the cycle rates while increasing the time between cycles. It'll save power and allow the temperature to be warmer during the summer months. I don't really care if there's a larger temperature swing inside. That's the least of my worries.


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Re: Thermostat with adjustable cycle rate

#5

Post by Archery1 » Mon Jun 29, 2020 9:25 am

strogg wrote:
Mon Jun 29, 2020 8:53 am
I'm well aware of the long term issues. Unfortunately, I had no control over the initial installation of the AC units. They are undersized because there are far fewer people living here than the house was designed for. I'm very leery of replacing them with smaller units right now because they're still working perfectly fine, and it would cost thousands to replace with variable speed units. I'd rather spend the money later if I can. Now isn't all that great of a time.

Anyhow, I was able to get the cycle rate to go higher by closing off the vents to the rooms with the thermostats and by lowering the temperature by a couple degrees. The average cycle time is now about 10-15 minutes. Before it was 5-10. I'd rather not do that for the long run because it's getting chilly in here.

I guess I'll rephrase my question. Does anyone have any other suggestions? Otherwise, I'll probably end up getting new thermostats as a bandage until the AC units finally give in. I am hoping with the new thermostats can increase the cycle rates while increasing the time between cycles. It'll save power and allow the temperature to be warmer during the summer months. I don't really care if there's a larger temperature swing inside. That's the least of my worries.
One option is have an HVAC service see where some air could be "dumped", say an unused utility room or room of some size or anything that's not mixing with the house even if the air is lost to cooling the house and can be controlled via flow/temp controlled dampeners. Zoned systems sometimes need to do this. Equipment wear aside, you run a risk of developing mold issues with the lack of humidity removal due to short cycling. Shutting down register vents is not good, as that messes with the airflow rate across your coil(s) and compounds the issue of cycling damage.


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Re: Thermostat with adjustable cycle rate

#6

Post by flechero » Mon Jun 29, 2020 9:38 am

If I had that problem, I'd partition off 1/2 the garage and A/C that for workshop stuff!


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Re: Thermostat with adjustable cycle rate

#7

Post by strogg » Mon Jun 29, 2020 11:14 am

Unfortunately, I'd have to route ducts through the living space to get to the garage. Otherwise, I'd be all over that. The only place to dump extra air would be the attic itself.

Yes, I know about the humidity thing. That's actually what prompted me to jump down this huge rabbit hole of a problem to begin with. Fortunately, humidity is stable at around 51-54% for now, with it hitting 54% when fresh air is introduced to the supply.


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Re: Thermostat with adjustable cycle rate

#8

Post by Archery1 » Mon Jun 29, 2020 12:54 pm

strogg wrote:
Mon Jun 29, 2020 11:14 am
Unfortunately, I'd have to route ducts through the living space to get to the garage. Otherwise, I'd be all over that. The only place to dump extra air would be the attic itself.

Yes, I know about the humidity thing. That's actually what prompted me to jump down this huge rabbit hole of a problem to begin with. Fortunately, humidity is stable at around 51-54% for now, with it hitting 54% when fresh air is introduced to the supply.
You could try a thermostat with a greater variance, but that's a big "if" you can tolerate the swings. Some can go up to 3-degree, which doesn't seem a lot, but it can leave times you are uncomfortable waiting till it kicks back on. It's might not be the same as constant temp where you never notice the 1-degree variance.

Closing off too many registers, much of the house, is basically like manual zoning, but without a bypass or dump they use to maintain efficient airflow across the evaporator, it puts a strain on your system, and slow air is not good for the system. Think about whether you would run with a dirty air filter to do basically the same thing, slow down airflow to make system run longer. It's not running longer now because it has less air to cool an area, it's because it's efficiency through the coil is being greatly altered, which is bad on the compressor as well.

If a thermostat with variance is your first option, try that with all registers open like system was designed to run. If that won't give you at least 20-30 minutes run time in Texas heat and humidity with a comfort level you can tolerate, I would call an HVAC and see what other options you have.

Don't dump cold air into the attic. Cold air and hot air make condensation, and you do not need that, water, in the attic.

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Re: Thermostat with adjustable cycle rate

#9

Post by RPBrown » Mon Jun 29, 2020 2:54 pm

A few years ago I gave my wife a 20x15 sunroom for her craft room. I ran 2-9" ducts int the room because of all of the glass. I replaced our system with a 2 speed with variable speed blower and up sized and additional ton to compensate for the sun room.
Now, keep in mind that I have been in the a/c business for 47 years. She has been with me almost the entire time and has heard me complain about people not changing filters, closing vents, and other things that they think helps.
Anyway, I come home and sit down to eat and the system comes on and it ramps up to gale force air before backing down slightly. I get concerned because it usually only does this when the filter is dirty. I knew i had just replaced the filter the week prior but went and checked it anyway. Clean. I blow it off, until it does it again. I start checking the static and its high. I immediately go to the attic just knowing she had put something up there and crushed a duct. But no, everything okay up there. I went and sat back down and decided to wait until the weekend to check it out. The wife comes home from whatever excursion she was on and it happened again. Then, all of a sudden it stopped. She comes out of her craft room and says "it got hot out there while I was gone so I opened the vents back up" :grumble . I asked her how much and why she closed them. She said it got cold out there so she closed bot vents almost all of the way off. After I :banghead: and I gave her the :rules: , she said she wondered why it started sounding like a jet when it started up :headscratch
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Re: Thermostat with adjustable cycle rate

#10

Post by strogg » Mon Jun 29, 2020 3:14 pm

I definitely am not planning on dumping air into the attic. The only reason I closed the registers by the thermostats is to give it the illusion that it takes longer to cool down the air than it actually takes. Once a bandaid solution is in place (ie, one that doesn't require me to purchase a 2-stage), I'll open the registers back up.

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Re: Thermostat with adjustable cycle rate

#11

Post by aero10 » Mon Jun 29, 2020 3:48 pm

Check out Honeywell VisionPRO 8000. I have a th8321r1001, but you may find newer models. It had options for how many times an hour the system can turn on and how long of a wait period between cycles. It was installed in my house when I bought it and I was skeptical of it at first, but it has a ton of customization options and has a lot of expansion options. One thing we just did, we bought a wireless remote temperature sensor. Our bedroom was the hottest room in the house, now the temperature is averaged between the sensor in our room and the thermostat. The house is more comfortable now.

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Re: Thermostat with adjustable cycle rate

#12

Post by Jim Beaux » Mon Jun 29, 2020 4:01 pm

strogg wrote:
Mon Jun 29, 2020 8:53 am
I'm well aware of the long term issues. Unfortunately, I had no control over the initial installation of the AC units. They are undersized because there are far fewer people living here than the house was designed for. I'm very leery of replacing them with smaller units right now because they're still working perfectly fine, and it would cost thousands to replace with variable speed units. I'd rather spend the money later if I can. Now isn't all that great of a time.

Anyhow, I was able to get the cycle rate to go higher by closing off the vents to the rooms with the thermostats and by lowering the temperature by a couple degrees. The average cycle time is now about 10-15 minutes. Before it was 5-10. I'd rather not do that for the long run because it's getting chilly in here.

I guess I'll rephrase my question. Does anyone have any other suggestions? Otherwise, I'll probably end up getting new thermostats as a bandage until the AC units finally give in. I am hoping with the new thermostats can increase the cycle rates while increasing the time between cycles. It'll save power and allow the temperature to be warmer during the summer months. I don't really care if there's a larger temperature swing inside. That's the least of my worries.

I was over the mechanical maintenance for one of the larger oil company facilities & the number one complaint I had to deal with was air conditioning.

I doubt that your problem is related to the thermostat. The AC should run approximately 75% of the time in order to control humidity. 10 - 20 minute cycle times are average. Less than 10 minute cycle time could mean outside air intrusion or inadequate insulation. I suggest raising the temp & adjusting the ceiling fans. Too much humidity is a mold breeding haven.

Circulate the interior air. Do not close off rooms or pinch down ducts. Have a tech air balance your ducts (well worth it) You probably have a temp imbalance from room to room. You cannot balance the ducts without a flow hood.

Seal windows and top off attic insulation. If you have a multi speed blower motor see about it being lowered. If your house is properly weather proofed & insulated you can run the AC at a higher temp & be comfortable. I would not consider dumping air.
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Re: Thermostat with adjustable cycle rate

#13

Post by 03Lightningrocks » Mon Jun 29, 2020 4:12 pm

strogg wrote:
Mon Jun 29, 2020 8:53 am
I'm well aware of the long term issues. Unfortunately, I had no control over the initial installation of the AC units. They are undersized because there are far fewer people living here than the house was designed for. I'm very leery of replacing them with smaller units right now because they're still working perfectly fine, and it would cost thousands to replace with variable speed units. I'd rather spend the money later if I can. Now isn't all that great of a time.

Anyhow, I was able to get the cycle rate to go higher by closing off the vents to the rooms with the thermostats and by lowering the temperature by a couple degrees. The average cycle time is now about 10-15 minutes. Before it was 5-10. I'd rather not do that for the long run because it's getting chilly in here.

I guess I'll rephrase my question. Does anyone have any other suggestions? Otherwise, I'll probably end up getting new thermostats as a bandage until the AC units finally give in. I am hoping with the new thermostats can increase the cycle rates while increasing the time between cycles. It'll save power and allow the temperature to be warmer during the summer months. I don't really care if there's a larger temperature swing inside. That's the least of my worries.
How long the system stays off once the stat is satisfied is a function of heat gain within the home. How long it takes to cool the home off once the system stat calls for cooling is a function of unit size. Thermostats are simply switches that automatically turn the system on and off depending on the temperature it senses. There is no such thing as a stat with an adjustable cycle rate. Your stats have nothing to do with the problems you are having. They are simply turning the system on or off based on set point. A thermostat that takes the temperature lower than the off set point and does not come on until higher than the on set point is called "broken". If you are asking about stats that will call for cooling at say 78 and then run until the temperature is 76 before shutting off, there may be a stat that does this but I am not familiar with it. Most people prefer the temperature remain at the set point they are comfortable with. Even a two degree swing would feel warm by the time it came on and cold by the time it goes off.

Second. People load is not enough to create a sizing issue with your residential system. People are figured into a load calculation at about 400 btuh per person. Even 10 people is only 4000 BTUH for the entire home. That is only a quarter ton of cooling capacity.

A few things that can cause a system to not run long enough to remove humidity are installing too large of a system for the home. From what you said, you did not do this. If it was not doing this from day one, it is not doing it now unless. You increased the efficiency of your home through the addition of new insulation that has an R value far above the original R value. Replacing all the windows with more efficient windows than the original. Sometimes a new roof that holds more heat in the attic than the original can increase humidity. This is fixed with additional attic ventilation.

Closing off some of the vents near the thermostat can help because it makes it take longer for the area around the stat to cool off than the rest of the house. This can create larger temperature swings in the rest of the home below the set point on your stat. ie. stat reads 78 but the rest of the home is 76. The other issue to keep watch on with the grilles you have shut down is condensation around the closed off grille, leading to mold or even damaged sheet rock around the grille.

All of this said I am curious as to what the actual issue you are trying to solve is. Not what you think is causing it, what the actual issue is. I might be able to point you in a direction that does not involve unnecessary repairs that don't fix the problem.


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Re: Thermostat with adjustable cycle rate

#14

Post by strogg » Mon Jun 29, 2020 4:56 pm

03Lightningrocks wrote:
Mon Jun 29, 2020 4:12 pm
All of this said I am curious as to what the actual issue you are trying to solve is. Not what you think is causing it, what the actual issue is. I might be able to point you in a direction that does not involve unnecessary repairs that don't fix the problem.
Ultimately, I'd like to maintain a low humidity household. Unchecked, this place was consistently at a whopping 60-70% RH. That started leading me down this rabbit hole that makes my brain hurt. I definitely think it would help if someone came out to take a look at my current setup to give me best practices. Unfortunately, the only callbacks I've gotten so far were from the original installers. They haven't been all that helpful. The whole short cycling thing only came up when I learned that ACs running only 5-10 minutes at a time isn't exactly a good thing.

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Re: Thermostat with adjustable cycle rate

#15

Post by 03Lightningrocks » Mon Jun 29, 2020 5:24 pm

strogg wrote:
Mon Jun 29, 2020 4:56 pm
03Lightningrocks wrote:
Mon Jun 29, 2020 4:12 pm
All of this said I am curious as to what the actual issue you are trying to solve is. Not what you think is causing it, what the actual issue is. I might be able to point you in a direction that does not involve unnecessary repairs that don't fix the problem.
Ultimately, I'd like to maintain a low humidity household. Unchecked, this place was consistently at a whopping 60-70% RH. That started leading me down this rabbit hole that makes my brain hurt. I definitely think it would help if someone came out to take a look at my current setup to give me best practices. Unfortunately, the only callbacks I've gotten so far were from the original installers. They haven't been all that helpful. The whole short cycling thing only came up when I learned that ACs running only 5-10 minutes at a time isn't exactly a good thing.
That kind of humidity increase is usually due to one or both of your systems not running properly. Some things you can check for yourself are, filters, check for dirty coils on your outdoor units and wash the crud off if they are dirty. Turn the power off at the disconnects located by your units just to be safe before washing off the coils. If you have power attic ventilators on the roof, check to make sure they are working. High heat in the attic can cause humidity to increase in your home. Especially if the insulation has settled due to age. All blown in insulation settles with age and the Rvalue drops dramatically. Check the temperature drop of the system. Using the same thermometer, check the temperature of the air coming out of a few supply air grilles. (air blowing into house). Then check the temp of the air going into the return air grilles. The difference should be 18-20 degrees. A 16-17 degree drop will work but is not optimal.

Systems that are low on refrigerant will cause humidity issues. If you are not familiar with proper charging procedures, this is something a service technician will need to check.

I am not sure what area you live in and I usually don't look for work on the forum. I come here to get my mind off what I do for a living but. we service as far north as Frisco, as far west as Carrollton, south to North Dallas and east to Murphy/Saxy area. but don't get further out than that.If you are in our area we can check your systems out for you. The easiest way is to do a maintenance agreement which is 119 per system and includes one cooling maintenance and one heat maintenance per system. Most issues can be found on the maintenance checks. We also clean those outdoor coils.

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