Honeywell Pro 3000 Tstat set to 5 CPH and running just once?

[shovel99]

Hi guys,
The smart pills are getting better already. I found that my HW Pro 3000 Tstat is programmable for cycles per hour... am trying to get the system to run more often. It is so oversized that it is cycling every 50 minutes at 30 degrees outside, on lowest first stage. When I got inside the Tstat setup, it was set for 5 cycles per hour heat... for my 95% furnace.. and only running once per hour. What is up with that? Why is it only running once?

Thanks, Paul

[skippedover]

Ah, perhaps because the t-stat is satisfied and doesn't command the furnace to run? Basically the t-stat doesn't care how much the furnace runs, it's just going to control the maximum number of times it can cycle in an hour. It's primarily there for heat pumps and ac systems to keep the equipment from losing efficiency with short run cycles.

[shovel99]

Thanks skipped over. Makes sense.

Did I see that White Rodgers stats may be adjustable to get my system to call for heat before a full degree drop?

Thanks,

Paul

[skippedover]

Yes, there are many t-stats that have all kinds of adjustments, including off-sets to you can fool yourself into thinking it's warmer than it really is. Do your research and find the one that meets your demand. If it's a single stage t-stat you might be intrigued by the NEST thermostat. You can control that one using WiFi and your smart phone. How cool is that?

[motoguy128]

You can control that one using WiFi and your smart phone. How cool is that?

Not so cool... since in my house, my wife is the one with the i-phone.. so it would be hotter than he** all the time.:grin2: Well, maybe not since she pays the bills. I'm more the spender. I'm scheming now how repalcing the hot water heater can be an excuse to go for a tankless WH that can in the future be tied to a hydronic air handler to replace the upstairs oversized furnace and then some day the downstairs as well.

[Gunnery Sergeant Hartman]

You're not going to fix an oversized furnace with a thermostat...

[beenthere]

The 3000 should be sensitive enough. Its just your house isn't losing heat fast enough for it to need to come back on quickly again.

[shovel99]

You're not going to fix an oversized furnace with a thermostat...

No real cure, for sure, but maybe enough benefit from experimentation with programmable fan circulation, controlled temperature differential for $ before I dump another $2500+ into replacing the furnace.

Three "highly regarded local industry "professionals" bid my job without even breathing a word of "load calculation".. and I was screwed from day 1 because of that. The one I chose put in a furnace that delivered 89k that only needed 55k of heat... 62% oversized.

I have just ordered a Braeburn 5000 TSTAT for $ that has a programmable fan circulation function .... variable from 1/6 of the time on up to half of the time... that users rave about. It also allows choosing a .5 degree settable temperature differential... initiates the call for heat/cool when .5 degree up or down.... which may or may not be as tight as whatever spec Honeywell is using, which is "Widely Undisclosed".. not even available from their tech support.

We'll see.

Paul

[shovel99]

The 3000 should be sensitive enough. Its just your house isn't losing heat fast enough for it to need to come back on quickly again.

Thanks BT. My 89k is idling, even at 30 degrees OT. With the additional insulation I added a week or two ago, my revised load calc is 55k btu at an Atlanta design temp of 22 degrees, delivering 72 indoors.

[SBKold]

The CPH setting is not a maximum allowable CPH.

The setting should have direct impact on the frequency and lenght of each cycle, with the higher CPH settings keep a tighter "swing"

[superfittertech]

nothing is gonna work with a 62k furnace with a 55k load. Live with it or bite the bullet:angel:

[shovel99]

The CPH setting is not a maximum allowable CPH.

The setting should have direct impact on the frequency and lenght of each cycle, with the higher CPH settings keep a tighter "swing"

That is what I expected... but it doesn't appear to be happening. When I broke the code (and broke the rules as a homeowner setting a Pro Stat), HWell Pro 3000 was set on 5 cycles per hour on... (should have been 3 for my 95% unit according to the HW documentation). But on that day, the furnace was coming on for 9 minutes (63k first stage) and then shutting off for 27 minutes.... one cycle per 36 minutes... or 1.66 cycles per hour. That confirms what Beenthere stated: stat not calling for heat until temp differential... so "maximum CPH" not engaging.

There seems to be programming in a all these digital devices. Do you suppose this has to run a number of hours, cycles, days to build up a "history" before it "knows" to cycle? I will continue to observe its observation and report anything interesting.

[beenthere]

CPH is only truely accurate when the homes heating loss or heat gain is at 50% of the equipments capacity.

So from your description of operation. When it was doing the 1.66 cycle per hour. The outdoor temps still weren't low enough for you to be at 50% of your furnaces first stage capacity.

While the thermostat will take a little time to completely adjust to the new CPH setting. It won't change much, as it can't compensate for gross over sizing.

[shovel99]

CPH is only truely accurate when the homes heating loss or heat gain is at 50% of the equipments capacity.

So from your description of operation. When it was doing the 1.66 cycle per hour. The outdoor temps still weren't low enough for you to be at 50% of your furnaces first stage capacity.

While the thermostat will take a little time to completely adjust to the new CPH setting. It won't change much, as it can't compensate for gross over sizing.

Thanks BT. Disappointed but not surprised. I am hoping that the air circulating TSTAT may help out a little.

Paul

[EYEKUTR]

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[jpsmith1cm]

EYEKUTR

This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

You can find the rules for posting and qualifications here (http://hvac-talk.com/vbb/showthread.php?t=957002).

Additional infractions may result in loss of posting privileges.