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HVAC Guy[_2_] HVAC Guy[_2_] is offline
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Default Honeywell MagicStat thermostat - questions about jumper settingson the back

Daniel who wants to know wrote:

The manual for mine, a Honeywell RTH221B1000 that I got 3 of for
$5 each from the Orscheln Farm and Home bargain bin makes no
mention of cycles per hour.


Of course not.

Because the number of cycles per hour will depend on

- the temperature span or hysteresis around the desired set point
- the heat loss of the space being controlled
- the BTU capacity of the furnace

If the stat has a setting for cycles per hour, then you're going to have
a variable hysteresis, and the stat is going to take some time to learn
what that's going to be for a given set of conditions.

To make it more complicated, the heat loss of the space is going to be
affected by ambient outside weather (wind and temperature) and how well
the space is insulated. As that changes, the thermostat will have to
re-learn how to control the furnace to keep the desired set-point while
maintaining the desired cycles per hour.

It's far simpler to set the hysteresis (2 or 3 degrees instead of 1
degree) and live with what-ever cycles per hour you end up getting,
rather then aim for a set or fixed cycles-per-hour.