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Posted by Warm Canuck on January 12, 2006 at 13:50:37:
In Reply to: Re: Buderus/Air Handler short cycling posted by Heatpro on January 12, 2006 at 13:07:53:
Interesting and good answers from my perspective, assuming I'm not falling into the "hearing what I want to hear" trap.
Many people worry about 6 cycles per hour and low boiler temps, though the Buderus seems to be made for that with a 104F lower operating point. All the duct work runs in the conditioned basement, which is also ICF and so any heat that escapes from the uninsulated ducts is no big deal, it just goes into the basement. Ditto for any heat losses from the boiler. I used spring loaded check valves at both the inlet and outlet of the boiler. At 150F it only loses 7F in an hour, so Buderus has done a good job insulating it.
If I had a large buffer tank, the boiler might only run 3 times per hour for 10 mins each instead of the current 6 times per hour at 5 mins each. But it sounds like other than an igniter that might need to be replaced a bit faster, there is no particular efficiency loss otherwise. The boiler has outside air intake, as the house is far too tight to provide combustion air.
I might put an indirect tank on the AH return to the boiler some day and heat the tank water with solar. Beyond that it sounds like I should just relax and enjoy the savings. Most opinions suggest 180F supply for an AH, but running in continuous mode doesn't require anything near that clearly.