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How does number of heating cycles setting work?


befast's Avatar
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04-15-18, 08:19 AM   #1  
How does number of heating cycles setting work?

I upgraded my simple Honeywell Deluxe thermostat to a Vision Pro 8000 and am now getting some temperature overshoots by 2-3 degrees, whereas before that never happened. Wondering if this has anything to do with the number of heating cycles per hour setting. Can someone explain what this setting does for a hydronic system, and how it interacts with the temperature reading?

On the old thermostat, as soon as temperature went below/above the heat setting it would turn on/off. Very simple, if not entirely efficient. Is the Vision Pro 8000 doing more behind the scenes?

 
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04-15-18, 11:38 AM   #2  
Sounds like the system type is set wrong. It has nothing to do with CPH.

 
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04-15-18, 06:45 PM   #3  
The installer set up for hot water heat is located at setting #240 in the thermostat's settings menu.
It says set the thermostat for conventional heat, then at #240 it should be at 3 - 3 cph.

At setting number 240 you are actually able to set the cph from between 1 and 12.
They recommend 3 but when doing so can not know what type of rads you have and how long they retain heat.
Unfortunately your will have to experiment to find a setting that works best with what you have.

 
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04-15-18, 07:11 PM   #4  
I set it for Radiant Heat, as that happens to be the system it's controlling. I also left it on the default setting of 3 CPH. What I am wondering is what is the meaning of the CPH setting: does it force 3 exactly cycles? Does it limit at 3? Does it keep it running a little longer to try to get to 3 cycles?

 
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04-15-18, 08:16 PM   #5  
It will allow the heat to run longer and be off longer so that the cycles fit into a 1 hour time period. I would think that would make for larger temperature swings. Like Greg mentioned... it's experimental. You can try adjusting the cycles up to see how the system responds.


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04-16-18, 04:50 AM   #6  
I don't have experience with the model of thermostat you have but other similar Honeywell digital controls have a learning period where the thermostat learns approximately how long the heating source has to run in an hour to satisfy the load.
It then cycles the on/off cycles to satisfy whatever cph the thermostat is set for.

I would suggest you try reducing the cph to 2.
This would increase the off time and maybe remove more heat from the radiant panel before it cycles on again.


GregH.........HVAC/R Tech

 
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