View Full Version : CPH settings
10-07-2008, 12:16 AM
On a Carrier 3 stage furnace with a Infinity controller the CPH settings they I have availible are 4 or 6 and reading some of the recent post regarding this issue some recomend a CPH of 3 but since that is not a option for me is 4 CPH per hour ok or is there other factors that come into play before changing this setting ? My furnace on average runs in low fire about 60% of the time and around 15%-20% in second stage and of course about 10% on average in high fire. My run times are prestty close to that when in cooling mode which is about 20-30 minutes per cycle so it really isn;t even 4 CPH even though it not set for less than that so can I assume the controller basically takes over the settings even though it is set to 4 on the Infinity controller?
10-07-2008, 10:09 AM
CPH is at 50% load.
So it won't always be that number of cycles at loads above or below 50%.
Alsp, humidity settings will effect CPH operation un cooling.
10-08-2008, 09:06 AM
"CPH is at 50% load" Beenthere can you elaborate on this alittle more I'm not sure I fully understand what you mean by this statment. I will however take a stab at it, I am guessing you mean even though the controller only list a CPH setting of either 4 or 6 it will modulate down or up depending on other varibles like RH thru out the home, OD temps, ID temps ??? I am also guessing that this is where the modulation comes inot play with the BD. on the furnace and the controller,is that close or way off in left field ??
10-08-2008, 11:25 AM
On stats with CPH.
CPH is based on 50% run time in an hour. Which gernerally only happens at 50% of load.
Weather heating or cooling. 50% load would be the point that your home needs 1/2 of teh full capacity of the system to maintain temp.
3 CPH, 10 on, 10 off: 10 on 10 off: 10 on 10 off. In one hour.
4 CPH, 7.5 on, 7.5 off: 7.5 on, 7.5 off: 7.5 on, 7.5 off: 7.5 on, 7.5 off. in one hour.
If you have the control set to dehumidify, and it slows the blower to do this, lowering its sensible in cooling and heating. So as the time to meet set point increases. The stats timing logic increases on time and decreases off time to compensate. But, it can only alter it so much. After a point it skips an off cycle, so now your at 1 less CPH then set.
As the load increases, it will eliminate another off cycle, and so on until it is in continuous run mode.
Maintaining set temp, takes priority over maintaining set CPH.
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