Some stats like honeywell controll within a degree, so they will never move from setpoint. EX 75.0-75.9*
I have a quick question on my TStat (for Trane XV95/XL15i system).
I had not focused on it because I have been distracted with static pressure and small duct issues.
I watched the Tstat (T803) yesterday and it was set at 75. It never moved off 75 as the AC cycled on and off every 6-10 minutes. I thought the compresser was only signaled to come on if the Tstat temp reading changed and thus a call was made to bring it back to the set point?
If I manually set it to 77 the compressor will go off and stay off until the room goes to 77 (even if it takes an hour or 2).
If I manually set it to 73 it will come on immedialtely and stay on until the temp gets to 73....then stay at 73 as the unit cycles on and off.
Can the unit be set less sensitive so that it only comes on if the temperature reading on the tstat goes above the set value a degree or 2?
I have no confidence in my installer as he originally under-wired, then mis-wirerd the tstat. It has been corrected thanks to this site. When he corrected it with the info I provided from this site he admitted he does not know much about these Tstats.
Thanks in advance.
Key1
Some stats like honeywell controll within a degree, so they will never move from setpoint. EX 75.0-75.9*
You can I think using the installer's menu options, but doesn't that kind of defeat the purpose of having these types of AC's? I don't know if the XL15 has a multiple stage compressor or variable speed fan, but I know the XL16 does. So instead of wide swings of indoor temp, when the AC runs full speed to cool the house down to 1-2 below setpoint, then wait to 1-2° above setpot to come back on full speed, it runs more often in slower speeds maintaining a nice comfortable +/-1° of setpoint while providing very good energy efficiency.
Honeywell/Trane stats has a nice tight temp control, and you will not see the swing... Example. 75.1˚ to 75.9˚., Just set your temp you want and enjoy the new equipment.
If you want the A/C to run longer the CPH (Cycle per Hour) can be set to a lower # like 2 vs 3 that the manual suggest.
There are 2 settings that can change that operation slightly.
1 is to set the CPH to 2(or a number lower then the current setting).
The other is to set the cooling to aggresive. It will tend to over shoot set point.
Comfort stat, don't let the temp go up more then a few tenths of a degree before they bring the system on.
Just curious if your AC is possibly oversized? I am having the same setup from Trane installed next week and 6-10 minutes on seems really short. They are putting in the XV95 60,000BTU and a 2 Ton xl15i AC for an older 1250SQ house in Northern NY.
Teddy
Teddy,
I think you are OK with those size.
The house is 2800 sq. ft. in central NJ 4ton 15i and 100k btu XV95. No manual J ever done. System is set at 350CFM/ton and does a good job lowering humidity and cooling (even if I leave it off all mornig and cut it on at about noon). Problem is static pressure is high due to ductwork and that is being addressed.
Key1
I wouldn't think the compressor should be turning on and off every five minutes. Doesn't the cycles per hour setting default setting and the "Wait" feature prevent this? What's the "Wait" time when the compressor can't come back on after shutting off... it's something like 7 minutes isn't it.. meaning if the compressor shuts off, it won't come back on for 7 minutes even if you adjust the tstat set temp down. Not sure why your system is cycling every 5 minutes.
I frankly can't hear my system when it comes on, only when the blower goes to full speed and I'm near one of the returns can I the blower starting (or late at night when the house is dead silent, or next to the one window next to the outside unit). Maybe mine cycles more than I think, but I don't hear the relays in the tstat triggering that often, that's for sure.
Factory default wait time is 5 minutes.
Thanks for the comment mayguy. I did have a manual J done and it came to 51,000BTU heating and 19,000BTU cooling or so. I am a little concerned with the possiblility that in 10 years I could add an addition of another 500 or so SF. But I only currently have 8 inch insulation in my attic which I plan on icreasing in the next few years. I hope that will give me the headroom in case I add on. Of course the next size up Trane is 80,000BTU which seemed kinda large for my house. So I am going with the smaller one. Also the company will gurantee it.
Key1cc sorry for stealing your thread. I am curious your outcome because I plan on having the same thermostat (Possibly the 802) installed. I am no expert, but I would think you would get some cycling when it is mildly warm outside (like 75-80) and long run times when it is (90-100). What is the outside temp when you notice this short cycling? Thanks
Teddy
Yesterday it was 90 degrees outside....and I'm not sure 6-10 minutes is defined as short cycling. I took the advice of this site and set my cyles per hour from 3 to 2 today at lunchtime. Afterwork I will monitor it closely this evening to see how it does. The temp will be in the low to mid 90's.
My compressor protection time is set at 5 minutes.
Key1
Key,
I've got the 803, too. Do you have humidity control enabled on the stat along with comfort-r? ? How well is it doing?
Thanks. Please keep us posted. Just curious, are you using the Comfort-R feature? Where it runs at 50% fan for a minute, then 80% for 8.5 minutes, then if it still needs cooling 100%? From what I have heard it can give longer run times.
Teddy
I have some results....but 1st I will answer your questions.
I do have comfort R enabled (which is only a timer that runs the blower on low for 1 minute then 80% for the next 7 or 8 minutes then 100% if needed....I think). I am not using the dehumidification feature that dehumidifies by over cooling 3 degrees lower than the set point.
Now the results. I took the advice from the pro's given in this thread and it appears to have worked. (I changed the cycles per hour from 3 to 2 earlier today). At 5:45 PM I begin monitoring as the condenser had just shut off. It was 92F/ 40% humidity outside. Inside was 75 and 44%. The Tstat was set at 75.
It stayed off for 9 minutes then came on for 23 minutes then off for 12 then on for 19 then off for 23.
When i first started the test.....the wife had just finsihed cooking so there was extra heat load from the oven....also the temp outside dropped to 86F/46% by the time I had finished as thunder clouds were approaching.
With all the variables it is still better than the on/off every 6 to 10 minutes I was getting when it was set at 3 cyles per hour (not sure why that is the reccomended setting in the owners manual). I will try monitoring again earlier in the day tomorow hopefully without all the variables.
Key1
They base that on the unit being sized right for the house.
Over sized systems will tend to short cycle at 3 CPH.
Question 1. If changing the cph from 3 to 2 is good ....would changing it further from 2 to 1 be better?
Question 2. Isn't it better for the compressor to run longer? and have long off times rather than quickly on and off trying to stay within 1 degree?
Question 3. If I do set it on 1 cycle per hour and during the off time the temp changes more than 1 degree. Would the unit condensor come on even if it ment it would have to run more than 1 cph?
Key1