Furnace Run Time

[HowAboutThis]

For heating, can someone explain how the CPH works when the Honeywell has a non-adjustable temperature differential of +/- 1 degree? I'm not quite getting it. How, or does the CPH over ride the temperature differential? For instance, if it is very cold out and the temp drops 3 degrees below the setpoint but the furnace has already cycled 2 times in less than an hour, what happens?

I don't get it either. Because I'm running about 25+/- minutes now at cph of 2. Which obviously isn't half of 60. But it's better then 17+/- minutes per cycle at least.

And yeah, as I've been reading online, some people say the temp overrides CPH. Which would then seem like CPH is pointless. But it's somehow extended my interval. So, yeah, I'd be interested in learning about how CPH works, too, because it seems to have extended my cycles but is about 20% short of 2 per hour when it's set at 2 per hour. Seems like maybe it's more complicated then what I'm finding online.

 

[HowAboutThis]

What's your gas bill run? My last one was $207 staying warm.

Water heater and furnace was $145 on the bill from December 11-January 11.

 

[HowAboutThis]

For heating, can someone explain how the CPH works when the Honeywell has a non-adjustable temperature differential of +/- 1 degree? I'm not quite getting it. How, or does the CPH over ride the temperature differential? For instance, if it is very cold out and the temp drops 3 degrees below the setpoint but the furnace has already cycled 2 times in less than an hour, what happens?

I'm seeing the same things on Reddit and HVAC forums. That temp overrides. This link from Honeywell seems to imply it somehow does something but also says it's +/- 1° default and can't be changed Maybe I'll contact them next week and see if they can give me more than this kind of cryptic answer. Or maybe I'll call an HVAC place.

Thermostat Cycle Rate: What Is It? | Honeywell Home

The cycle rate setting on your Honeywell Home thermostat is a factory setting that helps the thermostat maintain your preferred temperature. Read more here.

www.honeywellhome.com

 

[Fitter30]

Thermostat might have 1° dead band cph set on 3 will over ride that 1° deadband for 20 minutes of satisfied temp

 

[HowAboutThis]

For heating, can someone explain how the CPH works when the Honeywell has a non-adjustable temperature differential of +/- 1 degree? I'm not quite getting it. How, or does the CPH over ride the temperature differential? For instance, if it is very cold out and the temp drops 3 degrees below the setpoint but the furnace has already cycled 2 times in less than an hour, what happens?

Here's a great explanation of CPH. Which makes sense why I extended my run time but it's an algorithm not directly 2= 2 cycles per hour. It just tells the brain to run the burner longer if the number is smaller. So when it was at a 5 it was maybe getting to 67.6° and then kicking on again at 67° but now at a 2 setting it might be getting to, say, 68.2° and kicking on at 67°. At least that's kind of how I understand it

 

[HowAboutThis]

Thermostat might have 1° dead band cph set on 3 will over ride that 1° deadband for 20 minutes of satisfied temp

Check the video I just posted. Supposedly smaller CPH increases potential to overshoot the set thermostat temp and, thus, will stay on longer and off longer (since overshooting takes longer to reach the degree drop to kick back on). So when it's really cold it might cycle 4 times and really warm cycle 1 time per hour at any given CPH setting. The numbers are meaningless and you just base them on what you need your system to do. But changing CPH does, in a way, change your temperature differential by overshooting (smaller) or undershooting (bigger). It seems more like variance would be a better name for it. It's just not linear it doesn't seem? So a larger CPH keeps the variance between system turn on and system turn off tighter and smaller CPH creates a wider spread in temps between when it turns on or off because it tries to overshoot the temp setting (burner runs longer) even though the temp setting is by default 1° drop kicks it on. So with my higher CPH number it was a bit under my thermostat setting when it would tell the burner to stop but then it would drop a degree faster because it didn't heat the house as hot thus starting the furnace soon after it quit. Essentially a higher CPH seems like you're creating a short cycle.

 

[hrv]

I'm seeing the same things on Reddit and HVAC forums. That temp overrides. This link from Honeywell seems to imply it somehow does something but also says it's +/- 1° default and can't be changed Maybe I'll contact them next week and see if they can give me more than this kind of cryptic answer. Or maybe I'll call an HVAC place.

Thermostat Cycle Rate: What Is It? | Honeywell Home

The cycle rate setting on your Honeywell Home thermostat is a factory setting that helps the thermostat maintain your preferred temperature. Read more here.

www.honeywellhome.com

My T 6 Pro by Honeywell is the same plus or minus 1 degree.. It shows no way to change that setting even in the install and set up book that the tech uses...I my self would not mess with it...

 

[John105]

My unscientific belief is I always heard getting too large of a condenser or furnace (over sizing) causes short cycling and less comfort. That’s because AC makes us comfortable by dehumidifying. Along those lines, I think the furnace would need time to distribute the air.

These are just thoughts. If nothing were wrong, then I wouldn’t change the dead band if that’s what it was.

Think about a variable condenser. It stays on up to 100%, but is not single stage.

My .02 is check with a pro though. I’m more or less thinking it’s not something to tinker with.

Ps in the real world our thermostat is a smart one. I set the heat to 65F. If I were to glance at it and it said 64F, something is wrong. It always says 65F when set to 65F. Always.

Furthermore, I don’t believe the temp is always 64.5000000000000001 to 65.49999999. Catch my drift. If that’s why the dead band was changed I’d put it back the way it was from the factory.

Sorry for typos iOS is horrible.

 

[hrv]

Does anyone know how to change the cph in the heat cycle on a t6 pro honeywell thermostat??

 

[tbm5690]

My understanding for Honeywell and others is that you are setting the appropriate CPH when you select the system type on setup...H.E. GFA, GFA, radiant, etc.

 

[Fitter30]

Does anyone know how to change the cph in the heat cycle on a t6 pro honeywell thermostat??

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https://digitalassets.resideo.com/damroot/Original/10011/33-00181EFS.pdf?rv=aad05089f92145a08d5059f401052464

 

[greenjp]

Some of this has been covered in the thread or maybe the posted video. On a Honeywell, the CPH is an algorithm parameter that sets the number of cycles the system will run per hour when the demand is 50%. It is neither an upper or lower limit per se. It will indirectly affect the over and undershoot. My guess is on a consumer grade type thermostat it's fixed, we have a pair of VisionPros in our home and this can be adjusted via the installer menu. Ours is set to 1 for AC (to maximize efficiency and dehumidification) and 5 (the default) for heating with a forced air furnace.

Another note, the display doesn't exactly show you the precise temperature, for the reason that Honeywell doesn't see a benefit to the consumer of being able to actually see the swing up and down as it occurs. So as long as it's close it just shows you the set temperature.

jeff

 

[hrv]

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https://digitalassets.resideo.com/damroot/Original/10011/33-00181EFS.pdf?rv=aad05089f92145a08d5059f401052464

what ISU number am I looking for??

 

[Dave9]

My unscientific belief is I always heard getting too large of a condenser or furnace (over sizing) causes short cycling and less comfort. That’s because AC makes us comfortable by dehumidifying. Along those lines, I think the furnace would need time to distribute the air.

Larger or colder AC coil pulls moisture out faster so not really a humidity issue, rather it is just less efficient and more wear to keep cycling AC on and off more often.

There is a time:distribution factor for heat, that a blast of hotter air will warm the thermostat faster than cooler air (or lower rate) that warms the surrounding objects more before the thermostat reaches the trip point.

 

[Fitter30]

what ISU number am I looking for??

370

 

[KrisZ]

Larger or colder AC coil pulls moisture out faster so not really a humidity issue, rather it is just less efficient and more wear to keep cycling AC on and off more often.

That is simply not true. The de-humidification effect is largely determined by the cycle time, not the size of the coil. An AC coil doesn't get cold enough right away and starts pulling moisture out of the air.
It takes time to fully get below the wet bulb temperature and for the condensation to take place. The larger the coil, the longer it takes for it to reach that temperature. On top of that, an oversized system will reach the set temp faster, therefore the coil doesn't have enough time to dehumidify the air because it takes longer for it to cool down below the wet bulb temp and it has a much shorter cycle time.

 

[hrv]

370

Thanks I checked mine and it is on 3....so I guess that is where it is supose to be for my gas furnace..Is the CPH kind of like what the antisipator was on the old style mercury thermostat???

 

[John105]

Larger or colder AC coil pulls moisture out faster so not really a humidity issue, rather it is just less efficient and more wear to keep cycling AC on and off more often.

There is a time:distribution factor for heat, that a blast of hotter air will warm the thermostat faster than cooler air (or lower rate) that warms the surrounding objects more before the thermostat reaches the trip point.

If a home should have a 3 ton condenser and a 6 ton is installed, the system will cool down very quickly and shut off. The inhabitants will feel uncomfortable. They feel comfortable when humidity is being removed from the air, that is when the system is running. Humidity is an issue (the above is AC). The cfm for heat is about 1/2 that of AC. This is why variable condensers run even more often at a lesser capacity. Comfort. Believe me, I watch YouTube.

 

[John105]

That is simply not true. The de-humidification effect is largely determined by the cycle time, not the size of the coil. An AC coil doesn't get cold enough right away and starts pulling moisture out of the air.
It takes time to fully get below the wet bulb temperature and for the condensation to take place. The larger the coil, the longer it takes for it to reach that temperature. On top of that, an oversized system will reach the set temp faster, therefore the coil doesn't have enough time to dehumidify the air because it takes longer for it to cool down below the wet bulb temp and it has a much shorter cycle time.

I agree. I want to call them hacks. They calculate and oversize. Oversize makes people spend more. They they lose comfort. Don’t get me wrong things may be different in Boston vs Phoenix. But oversizing imho means the condenser is running much less and the occupants feel less comfort as a result.

Another issue is if a replacement system the ducts may not have enough airflow for oversizing making matters even worse.

You’re saying what I did imho, only more eloquently.

 

[hrv]

Here's a great explanation of CPH. Which makes sense why I extended my run time but it's an algorithm not directly 2= 2 cycles per hour. It just tells the brain to run the burner longer if the number is smaller. So when it was at a 5 it was maybe getting to 67.6° and then kicking on again at 67° but now at a 2 setting it might be getting to, say, 68.2° and kicking on at 67°. At least that's kind of how I understand it

This is by far the best video on this subject...Thanks for posting it...