Question about thermostat Temperature Swing settings

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Old 12-09-10, 11:03 AM
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Question about thermostat Temperature Swing settings

Hello,

I have a Bryant gas furnace in an old house (not insulated).
I have a RiteTemp programmable thermostat with a Temp. Swing set to 3.

The problem is that because it is so cold outside and the lack of insulation in the house, the furnace has very little "break" between cycles.
Say my temp. is set to 66. When the room temp. drops to 65 the furnace kicks in and it shuts down when the room temp. reaches 67. It could be 10 minutes before it drops to 65 again and furnace starts again.

My concern is - do these frequent cycles damage the furnace, or am I worrying myself for nothing?

Thanks.
 
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Old 12-09-10, 02:45 PM
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If the swing is set to 3 then the the boiler should not kick on until 63 if t stat set for 66. Though these are not that acurrate. I am for comfort and have a 1 dgree swing but mine only go to 2 degrees. 5 times boiler cycle an hour in the cold is not that bad but others here might differ.

Mike NJ
 
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Old 12-09-10, 03:00 PM
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I don't know about your particular thermostat but many digital thermostat have a fixed "deadband", what you are calling swing. It appears that your deadband is one degree since it takes a one degree drop in temperature to initiate the furnace and a one degree rise above the "setpoint" to stop the furnace.

What you more than likely have is a "cycles per hour" setting and by having it set on 3 it means that the furnace will fire a maximum of three times per hour. Setting at a lower number will cause the furnace to fire less often but the temperature will drop more between firings.

"Short cycling" indicates a furnace that has far more heat output than is necessary for the outside temperature at any given time. Improving the energy efficiency of the house by insulating and weatherstripping is the proper way to reduce the amount of heat necessary.
 
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Old 12-09-10, 03:35 PM
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Generally speaking, furnaces become more efficient the longer they run, so having them run less often but for longer times (in other words, greater swing) tends to be the most cost effective
 
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Old 12-09-10, 04:54 PM
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Originally Posted by lawrosa View Post
If the swing is set to 3 then the the boiler should not kick on until 63 if t stat set for 66. Though these are not that acurrate. I am for comfort and have a 1 dgree swing but mine only go to 2 degrees. 5 times boiler cycle an hour in the cold is not that bad but others here might differ.

Mike NJ
I thought the swing is measured end to end, so 65 (furnace kicks in) to 67 (furnace stops) is 3 degrees, unless I miss something.

Originally Posted by Furd View Post
I don't know about your particular thermostat but many digital thermostat have a fixed "deadband", what you are calling swing. It appears that your deadband is one degree since it takes a one degree drop in temperature to initiate the furnace and a one degree rise above the "setpoint" to stop the furnace.

What you more than likely have is a "cycles per hour" setting and by having it set on 3 it means that the furnace will fire a maximum of three times per hour. Setting at a lower number will cause the furnace to fire less often but the temperature will drop more between firings.

"Short cycling" indicates a furnace that has far more heat output than is necessary for the outside temperature at any given time. Improving the energy efficiency of the house by insulating and weatherstripping is the proper way to reduce the amount of heat necessary.
According to the manual (RiteTemp 8022 or 8022C, not sure, but they are almost identical), as well as on the t-stat itself (when I enter the setup mode) it specifically says "Temp. Swing", so I am pretty sure it is not cycles per hour. It is set to the default (which is 3) and it definitely has more than 3 cycles per hour.

Originally Posted by mitch17 View Post
Generally speaking, furnaces become more efficient the longer they run, so having them run less often but for longer times (in other words, greater swing) tends to be the most cost effective
Problem is I can't really have it run in heat mode, once it hits the temp. it will shut the burner down. I can keep the fan running but this will throw cold air in and I don't want that in an already cold uninsulated house.
 
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Old 10-21-13, 06:29 PM
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Old thread, but since it didn't get all the details it deserved...

Swing is measured from set point to start point so his swing is 1F.

The OP's thermostat IS set to 3, which is the default, however it is only the default swing SETTING, not the actual swing in F.

The TempRite swing settings* (and their respective actual swings)
1= .33F
2= .67F
3=1.00F (the factory default and the OP's setting)
4=1.33F
5=1.67F
6=2.00F

* For 60XX models (although I found one reference that said 6022 default swing was .5F; what can I say?)

A small swing does run the furnace more often. More starts and stops does mean more wear. (I wouldn't go so far as to call it "damage".)

As mitch17 pointed out, longer run times are more efficient. Try using a setting of 4 (1.33F) instead?

Three data points left out:

The outside temperature
The run time (OR the total cycle time, i.e. start to start)
The outside design temperature
 
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Old 10-21-13, 06:40 PM
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Thanks for the additional feedback I-DYI. I will close this thread since it is an oldie...
 
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