I have just installed the honeywell RTH8500D Tstat.
The first thing I have noticed is that thet tstat tursn on much more
often that my old analog tstat. Is this normal? And is this bab for
my system? I have a heat pump with air and aux heat.
It could be several things. It could be that your old system was too
slow, it could be that both were within norms and it could be that the new
one is anticipating too much.
A couple of questions. It is the heat or AC that is cycling more often?
How much of a temperature swing is it allowing. How much did the old
Have you check the instructions for it to determine how to check the
adjustments for this?
Did you go into the installer setup,0170, and set your algorithm to 7?
If not, its wrong. 7 is for a dual stage heat pump..what you have.
How about setup 0530? Is it on 1, or 0?
0 is the AR, or adaptive recovery mode. Its going to take 6 to 9 days for
this to adjust itself properly and will create some odd run times until it
learns how your system reacts to your home.
Also keep in mind that this stat, unlike your old one, has a 1F
deadband...not a 2-4F deadband. its going to run more, but use less power to
maintain your homes temps.
Its not going to hurt a thing.
Question: It is the heat or AC that is cycling more often? Answer: AC
Question: How much of a temperature swing is it allowing. How much did
one? Answer: 1 degree, the old one i'd say closer to 3
Question: Have you check the instructions for it to determine how to
adjustments for this? Yes and it's set correctly
My 170 is set to 7 and 530 set to 1 (1 in my book is AR on).
With that said you think my AC coming on about 5-6 times an hour is
perfectly normal and poises no damage to me actual AC unit?
Here is my current wiring for review (2 stages of heat, 1 stage of
Red wire on R
Orange on O
Yellow on Y
Green on G
Blue on C
White (Was w2) TO AUX & E jumped
Thanks again to both,
Thank you Steve. I though some of my problem might be athe AR as it's
only be running A/C now for about 10 days (Runing the heat on and off
for a couple of months, more of then on though). My concern was people
telling me that a cycle rate of 5-6 per hour could damage my
compressor, that's why I wanted to be sure about the cycle rate.
Just out of curiosity: What size unit would be proper for my house?
And can you advise if my wiring looks OK as I did it myself.
1700 heated sq ft
1 story concrete home with vaulted ceilings 9 on the low end 12 in the
11 return units all different sizes
Thanks Steve no need to do all that work I just thought there was a way
to give a rough idea.
As for my cycle rate, I know that the tstat has a "built in compressor
protection" feature built in it per the manual. Is this what you were
Also some people have advised to upgrade to the VisionPro in order to
control the cycle rate, but according to HW my Tstat is set to a
standard cycle rate of 3 but can still cycle more based on all the
other factors involved. So even if I upgraded (to the visionpro) and
was able to change the cycle rate to 3 what's the point if it can still
run more cycles then that, or am I misunderstanding something?
Thank you for all your help Steve, I "REALLY" appreciate it!
I'm going to ride it out with this Tstat for a while and see how it
goes, for all I know my old Tstat may have went on just as much but I
did not realize it as there was no "click" when going on and off.
As long as I now know that 5-6 cycles will not ruin anything that puts
my mind at ease.
Now that you have a stat that will maintain a 1F degree setpoint....its
BTW..cycles have alot to do with the insulation of the home, the
construction of the home, and if the unit was sized correctly.
However, I would expect that your cycles will start to wane a bit over the
next couple of weeks.
It is IMPOSSIBLE to tell you over the internet what size unit your home
needs, or if the one you have is sized correctly without tons more
A manual J, or T is required. While it is possible to get a rough idea, if
you are willing to take all the measurements and send them to me that would
be required, a rough manual J could be done....it might not be dead on, but
you would be close.
If you are interested, let me know, and get ready..you will be measuring,
and writing down stuff for about an hour before you can even think of
sending the mail to me.
As far as the cycles go...I would not want more cycles per hour, and I
prefer mine to be about 2-3 per hour. 5-6 wont kill it, provided that its
getting proper time between cycles.
Not really..that is why a legitimate contractor will take the extra couple
of hours and size one right....do the work, and do the math.
Thats part of it..its a built in break on make timer.
That means, lets say, you come home, and the wifes had it up to 75, and the
unit JUST shut off as you head for the stat thinking...DAMMIT..she has it
TOO high AGAIN, and you go and turn it down to 70, the unit will NOT come on
right away. The blower might start, but the compressor will be delayed up to
Umm..ok..keeping it real simple..thats an anticipation device..an algorithm
that is programmed in.
You can have it set on 2, and it still cycle 6 times..depends on more
factors than just the anticipation factor dialed in.
So here is what I have noticed going back to the analog Tstat.
Tested for 2 days analog vs digital (basically same temps for 2 days).
Tsat Temp was set to 75, outside temp was mid 80's very sunny &
Analog tstat, stats:
Runs for around 40 minutes at a time then shuts down for 12 minutes or
so then repeats.
Digital tstat, stats:
Runs for around 15 minutes at a time then shuts down for 7 minutes or
so then repeats.
Based on this over the course of a 12-hour day my digital would run for
495 minutes (off for 231) my analog would run for 560 minutes (off for
168). Digital wins!
I guess over all I'm better off with the digital tstat, runs less
minutes, cycles about 3 times an hours and keeps the house much closer
to the set temp.
Glad I tried this I learned a lot.
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