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Giles
12-14-2010, 06:05 PM
I have an old natural gas central unit. It is heat only and is old enough that is uses a mechanical fan control switch. I only use it, in place of my heatpump, when temps are in the 20s.
It works beaautifully--maybe to good.
I am using a new Honeywell Pro TH311OD and when the outdoor temp is in the twenties or teens, the house stays at a constant 69 degrees.
The gas unit cuts on a runs only about 3-5 minutes and cuts off.
I am not complaining but seems to me like the temp in the home should drop a degree or two before calling for heat.
I have looked at the instructions and I don't see a "heat anticipator" adjustment as it is electronic and non-programmable.
Should I just be happy and deal with the short cycling?

jimbo
12-14-2010, 06:21 PM
The cycle rate...cycles per hour...is adjustable in the system set up. see page 8 of the install instructions, to make sure you have all the right settings. Some of the factory defaults may not be right for your system.
http://customer.honeywell.com/techlit/pdf/PackedLit/69-1846.pdf

Thatguy
12-15-2010, 10:13 AM
seems to me like the temp in the home should drop a degree or two before calling for heat.

It probably does without this change registering on the display.

My furnace is only on 1/4th of the time in a typical winter. Is yours also oversized?

jadnashua
12-15-2010, 11:19 AM
Many of the newer electronic thermostats allow you to adjust how close to the setpoint you want the temperature held. the closer you want it, the more it will cycle. this isn not necessarily very good for efficiency (depends on the type of heat). Burners don't fare well in efficiency when they only run for a short time. Electrical systems are fine with it, and hydronic systems may or may not, depending on how they are set up.