Any HVAC experts here? Honeywell Thermostat hysteresis

Serendipity

Was wondering if any HVAC experts could chime in on this problem: We have a Honeywell 7 day programmable thermostat with the "smart learning" feature that adjusts the run time based on the time it takes to heat the house (time from heater cycle to set temperature). Recently, the thermostat has been overshooting the set value and overheating the house several degrees, then allowing it to cool 2-3 degrees. Sometimes it will not even run the furnace for several hours after a long run cycle!

Is there any way to adjust the hysteresis of a Honeywell 32207626 programmable thermostat?

We have a steam system.

Thanks!

Serendipity

Well, the unit is on a wall that's got nothing on 3 sides (you could call it a peninsula), and not near any exterior walls of the house. I pulled the thermostat off and couldn't feel any cold drafts coming through the wall. Yes, it has started doing this recently, and I was the original installer of the thermostat. Made sure that it's set to "Steam" instead of "Forced Air," recovery is set to "Auto", and I haven't messed with the service menu yet.

jimsvm

Was there any home improvment going on to create alot of dust? The stat temp senser may be dirty. Blow it out carefully. If this does not fix the problem go into the sub program and "reset" the stat to its factory settings.

jimsvm

Honey mod # would help. I have info for all.

Serendipity

anonymouse wrote: »

Ok... does the thermostat register the set temperature and still not shut off? i.e. if you set it to 70, does it just keep the heat going while the display reads 70, 71, 72 through 73 and then shut off?

Yes, but it doesn't change that fast. If you set it to 67, it will go up to 69 and at that point, all of a sudden it displays 70 and the heat shuts off.

Also no home improvement or dust in the house. I just pulled the unit off and cleaned it!

Not sure of the model number. Will find it.

obieone

jimsvm wrote: »

Honey mod # would help. I have info for all.

+1. The # listed doesn't come up at the Honeywell site. 3220 brings up the Chronotherm tstat's. Not 100% sure that's the right one?

obieone

looking at the 'Adaptive Intelligent Recovery' feature of what I assume is your tstat, it's designed that way.

Serendipity

obieone wrote: »

looking at the 'Adaptive Intelligent Recovery' feature of what I assume is your tstat, it's designed that way.

I think this is the problem. Is there a way to erase the "Adaptive Intelligent Recovery" memory?

If set to 67 degrees the stat doesn't even display 68, it will go from 67 to 69 and then before you know it the room temp is at 70 with the heat off!! The heat turns off only AFTER the display reads 69!

disneyjoe7

I have Honeywell Thermostat also, and it does some weird also. When it recovers during cooling it also states the temp is 81f when if it was under 81f to start. Really weird, I have think its a bug in the software of that thermostat. Not sure if that is a problem with you but....

Serendipity

disneyjoe7 wrote: »

I have Honeywell Thermostat also, and it does some weird also. When it recovers during cooling it also states the temp is 81f when if it was under 81f to start. Really weird, I have think its a bug in the software of that thermostat. Not sure if that is a problem with you but....

Exactly! At one point I had "Adaptive Intelligent Recovery" set to OFF, and I don't recall any of this strange stuff happening. With my early morning schedule, and having to leave sometimes at 6:50AM, I set the wake time very early this year. Much earlier than before where the delta between Cold --> Hot is much greater (i.e. 60 to 68 degrees).

jimsvm

Is the t-stat a touch screen?

Serendipity

jimsvm wrote: »

Is the t-stat a touch screen?

Nope.

Thinking back to when I installed it, I believe it may be an early (push button) version of the 7600 series.

Runs an embedded system, programmable, with "Adaptive Recovery" and LCD screen.

obieone

I know what t-stat you've got- it's the HAL9000, "What are you doing, Dave?":cheesygrin:

Sorry. If you've lost the owners manual, you can get it off the Honeywell site. Either view it, or download it in PDF.

jimsvm

Do you have a red manual and a white installers manual

Serendipity

obieone wrote: »

I know what t-stat you've got- it's the HAL9000, "What are you doing, Dave?":cheesygrin:

Sorry. If you've lost the owners manual, you can get it off the Honeywell site. Either view it, or download it in PDF.

Haha, will do. Disneyjoe's post was the best explanation of the problem, it states the temp is xx when it's under or above that to start when it recovers during heating. I constantly have to fiddle with it otherwise it will overshoot by a big margin.

jimsvm

To much night set back will cause problems with Adaptive Recovery. Does it only overtemp after night set back?

Serendipity

jimsvm wrote: »

To much night set back will cause problems with Adaptive Recovery. Does it only overtemp after night set back?

It overtemps pretty much after any set back, and I don't think a night temperature of 58-60 is unreasonable.

jimsvm

No its not. Have you tried to set it back to Forced Air. The differance is in the anticipation of temperature, steam has a very high recovery rate, and seems like the stat can not react fast enough to shut down. Are your rads the older cast iron type?

disneyjoe7

It seems to be worst when I set it higher then 2f from where I like it. If more then that my AC / cooling needs to work harder and longer to bring it down. That is when it goes to 81f, where the its only 80f in the house and needs to go 79f.

My AC set is this.

3am -7am 78f
7am - 5pm 80f
5pm -11pm 79f
11pm - 3am 77f

I call that my 2 -3f setback, works best for me.

Serendipity

jimsvm wrote: »

No its not. Have you tried to set it back to Forced Air. The differance is in the anticipation of temperature, steam has a very high recovery rate, and seems like the stat can not react fast enough to shut down. Are your rads the older cast iron type?

Haven't tried to set it back to Forced Air. It has always been set to Steam.

The radiators are the older cast iron type built after WWII. From the late 40's I would imagine.

jimsvm

What s the day time temp?

Serendipity

67 F.

So you are saying steam has a fast recovery time? I always thought Forced Air (like those in central AC/heating systems with duct work) were faster at heating the room, I may be mistaken though...

jimsvm

I was comparing to the same system on water. If no other settings have been changed and all is set to as before and worked ok. The stat has lost its ability to anticipate temp. 7 to 9 degree set back on slow recovery system is very large and should be rethought. 5 max.

Serendipity

Thanks! So I should set the thermostat to Steam?

From what I understand, hot water is a "baseboard" type heating system that is low to the ground. We have radiators that are about 2 feet tall with an air valve on one side and a knob on the other. I mistakenly thought that turning the knob to the full closed direction will eliminate a room like a "zone", but that's not what happened. I've also never touched the air valves either.

These things hiss, knock, and bang in the morning like the old houses in NYC.

jimsvm

Yes to steam or a high mass setting which is for the cast iron rads. What are all the choices?

Serendipity

1. Gravity
2. Steam
3. Hot Water
4. Forced Air

Serendipity

Now I'm confused. The paperwork for this house says we have "Hot Water" but I think that is incorrect.

There's one pipe going into the radiator, a black knob on the left, and this thing on the right:

Edit: Sorry for the blurred picture but this is a steam system right?

jimsvm

Steam, and try no large set back for a week with adapt recov on. Large setbacks do not save on slow recovery systems. 3 to 5 degrees max.

jimsvm

Can u take a pic if the boiler and surrounding piping

jimsvm

of the boiler

Serendipity

Yes, here goes: