Cycle Rates on my new Honeywell Dig. Thermostat

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  #1  
Old 11-25-05, 05:21 PM
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Cycle Rates on my new Honeywell Dig. Thermostat

Just installed a new Honeywell Programmable Thermostat (RTH7500D). Anyways, it works great, but have one concern. We have it set to 70'. Well the thermostat kicks in every 10 or 15 mins, and runs for about 3 or 4 minutes. I read on Honeywell's website that a normal cycle rate is around 6 per hour. So I guess I shouldn't be too concerned, but I still wonder if this is normal. I've been timing it the past few times. It kicks in at 6:47 pm and runs until 6:51. Then it kicks in again at 7:01 and runs until 7:05. Then again at 7:15 and runs until 7:19, and so on. I tried to find a way of setting the degree difference within the thermostat, but couldn't find any setting for that. Any advice? Or shouldn't I worry? Thanks. Ryan
 
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Old 12-01-05, 04:32 PM
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If you think it runs too much, You can change the CPH settings.. You can shorten it up if you feel you need to.

I think most people end setting it up to 4 or 3.
 
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Old 12-02-05, 01:32 PM
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Are you sure I can change the settings? I don't see anywhere within the thermostat's interface to do that. Thanks
 
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Old 12-03-05, 07:07 AM
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You won't see it right away.. Get your install mauual, and have to go into the "Advance set up" screen, and go to the set up CPH. if you don't have the books, let me know.
 
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Old 12-08-05, 06:05 PM
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I have the books and have looked through it again and do not see anywhere where you can change the CPH. I even went through the demo on the CD that came with it, and didn't see anything. Any help is appreciated! If you have the install manual and see where you can change it within that, I'll take a copy of it. (I have the Honeywell RTH7500D Programmable Thermostat)

-Ryan
 
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Old 12-08-05, 08:46 PM
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It's in the install manual. I put this in for a friend, I don't recall off hand.. but you have to go into advance set up menu.
 
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Old 12-09-05, 12:18 PM
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Well I went through every single possible area that you can go through on the interface and didn't see anything. I re-read the book 10 times and didn't see anything. Maybe I'll give Honeywell a call tonight.
 
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Old 12-09-05, 02:42 PM
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Well I talked with Honeywell, and they said that it's not possible to change the degree differential with their thermostats. They all work within +-1 degree. But you can change the Heating Cycle Rate depending on how efficient your furnace is. So I'm assuming this is what you are talking about. Maybe I'll have to take a look at that. Thanks for your help!

-Ryan
 
  #9  
Old 12-09-05, 03:24 PM
jerry814
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i'm having the same problem with the heat cycling on and off too quickly, with a honeywell RTH7400D. i e-mailed them and got the same basic answer you did, rbanse, that you can change the CPH. they don't recommend it, saying those cycles are best left with the default setting, but that changing it would cause the heat to cycle less frequently. of course, that will lead to wider temperature swings, unless your house is really well insulated.

you can change the CPH, using the Heating Cycle Rate setting. when you initally set up the thermostat, after you plugged it in, you went through the installer settings. on mine (and i'm guessing it's the same for yours), the Heating Cycle Rate is setting 240. mine said to set it to 9 for an electric furnace, which means 9 cycles per hour according to the e-mail. that particular setting is on page 33 of my manual.

my question is, is it really efficient to run the heat that often for a short amount of time? i would think that the heating coils would take longer to heat up than the heater is actually on for. but i'm going to search the forum to make sure someone else hasn't addressed that, and then post a new thread if i can't find any info.

here's the e-mail from honeywell, if it helps at all:

Please make sure the cycle rate is set according to your type of heating system. Your thermostat is calibrated to hold temperature within one degree of your set temperature to maintain an even room temperature. Because of this, the thermostat may seem to cycle more often than older thermostats that had a wider room temperature swing. Many people can feel a temperature change as low as two degrees. Since your Honeywell thermostat holds the temperature within two degrees, the room air temperature remains steady and comfortable. The energy savings come from using the programming to set back the thermostat to energy savings temperatures when there is no one at home or at night when everyone in the home is asleep.

Normal cycling for an electric system is about 9 cycles per hour. The actual amount of time that the cooling system is on or off will vary as the load on the cooling system varies.



You can go ahead and reset the cycle rate but it is possible that you will not have very good temperature control. You need to enter the installer set up to change the cycle rate.



For a hot water system or a high efficiency furnace the cycle rate is 3 cycles per hour.

For an Gas/ Oil furnace it is set for 6cycles per hour

For Steam or Gravity it is set for 1 cycle per hour.



If this does not resolve the problem then there are other reasons for the furnace to cycle too often to maintain the set temperature.

These are:

1. If the set temperature is at extreme from the temperature outside.

2. The insulation of the house. Old house are less insulated hence heat is lost quickly. To maintain the set temperature the thermostat starts the heating.



Also check if the thermostat has the word HEAT ON every time the heat comes on. If HEAT ON is not there on the display then the thermostat is not calling for heat but the furnace is coming on, on its own. In this case please contact your contractor. You may use the following link to locate a contractor in your area:



For your convenience, these additional on-line resources are also available:



Programming or Wiring assistance:

http://yourhome.honeywell.com/Consum...ard/Wizard.htm

Frequently Asked Product Questions:

http://yourhome.honeywell.com/Consum...AQ/Default.htm

Honeywell Contractor Locator:

http://yourhome.honeywell.com/Consum...torLocator.htm

Do-it-yourself Retail Store Locator:

http://yourhome.honeywell.com/Consum...ailLocator.htm
 
  #10  
Old 12-10-05, 05:11 AM
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Looks like honeywell did a good job tell you what to do.

Go ahead and change the cycles.. And you can be the judge yourself on the temp control.. Most system I do set it at about 3.. A longer run time is better on the equipment as well.
 
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