Dana- in answer to the question in you last post (remember I have the the basic round Honeywell T-stat set to 3 CPH) a "normal" burn lasts about 6 to 8 minutes on average. When it short cycles it will burn for several minutes, cool for a few minutes, reignite- but sometimes the call for heat end before the re-ignition, or shortly after the re-ignition. So when it happens I am getting the 3 ignitions per hour based on the T-stat's 3 CPH and another short-cycle induced ignition per cycle, for a worst case scenario of 6 ignitions per hour, based on what I have observed.
Oddly earlier tonight while running my electric dryer, I timed a burn for 10 minutes, then the burn stopped, but the call ended before re-ignition. Another time it reignited but the call ended shortly there after. The dryer is on the heated level and must be sucking a lot of heated air out of the house - the burn lasted a bit longer than average and I would have expected it to short cycle earlier than 10 minutes into the call. I have noticed this before because the bedrooms, away from the area where the dryer is, actually get warmer (you can feel it and see a degree or two increase on a thermometer).The T-stat is closer to the laundry closet. Maybe the bedrooms have more baseboard per SF than the more open living room, kitchen & dining, and laundry closet. (Or are more isolated from the areas having the heat sucked out of them).
Jac- I'll try lowering the heating capacity further when it's a little warmer and I have time to observe it over a period. Some start ups seem fairly smooth now and some involve a bit more ramping and shifting, and the occasional flame restart. (And I think sometimes you are not sure if there is a restart or just a "shift" because I think the remote controller and the green burner light on refresh only every so often).
A T-stat does not and can not control the length of the
burns- it can only determine the length &/or number of
calls for heat per hour. The lengths of the burns during a continuous call for heat are a function of the boiler's internal controls, primarily how far above the boiler's temperature setpoint it allows before turning the boiler off, and how much below the setpoint it allows before re-ignition. With some boilers that temperature difference is user-tweakable, but SFAIK that's not the case with this series. If it's normally burning for more than 3-4 minutes per BURN cycle during a continuous call for heat, it's not a short cycle.
If as you say cycling on/off during a call for heat but the burns are always 6-8 minutes during a continuous call for heat that's cycling, but not short-cycling. When the burns are under 3 minutes and cycling at a rate way above 5 burns per hour it becomes an efficiency and longevity problem. If it's averaging burner-on for 7 minutes, burnr-off for 3 minutes and running an absolute maximum of 6 burns/hour it's less than ideal, but it's not a problem.
The difference in indoor to outdoor temperature determines the instantaneous heat load, which varies through out the day. That won't affect the cycling rates, but it does affect the length of time it takes for the thermostat to be satisfied. If the temperature of the air at the floor entering the baseboards is colder the amount of heat the baseboards put out is higher, which would affect the cycling slightly, but that won't change much with outdoor air temp.
If you replaced the Honeywell with a dumber T-stat that didn't limit the number of calls for heat per hour it would probably cut down on the number of ignition cycles per heating season by more than 10%, which will improve boiler performance & life, but not by a huge factor. (Recommended.) In your case since the min-fire output is higher than your 99% heat load and you're operating outside the condensing zone for temperature, you might get modest fuel savings using a cheap $25 programmable (eg Lux TX500E or Honeywell RTH2300 )
using modest overnight setbacks (not more than 5F or recovery ramps would take awhile), but a cheap $25 digital non-programmable would be fine too.