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New to modcon heating

28W Member Posts: 141
As we move into the New England heating season, I'm looking for advice.  Up until this year, I've had an oil-fired hydronic system, so I've been used to the house heat up very quickly when I turn up the thermostat (180 degree water to the radiators).  Since my new modcon system (Vitodens 100 with outdoor reset) will generally be sending lower temperature water to the radiators, does this mean that I should expect it will take longer to raise the temperature in the house?

I've done a careful heat loss analysis and emitter output analysis, and have set the boiler curve accordingly, but it seems amazing to me that, for example, my house will stay comfortably warm on a 32-degree day, with 113-degree water flowing in the radiators.  My house has a single heating zone, and is mostly Beacon/Morris convectors, plus one room with baseboard.


  • SWEI
    SWEI Member Posts: 7,356
    outdoor reset radiant

    the goal is to dial in the reset curve so you don't have to adjust the thermostat - in a single zone system, the thermostat should function basically as a high limit control and should not call for heat unless you have an additional source of heat (solar gain, woodstove, etc.)
  • 28W
    28W Member Posts: 141
    I should have mentioned . . .

    Just updated my post above.  House has mostly Beacon/Morris convectors, plus one room with lots of baseboard.
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,483
    does this mean that I should expect it will take longer to raise the temperature in the house?

    Not if you don't lower it! You can use ODR or you can use thermostat setback,but you can't use both!
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • 28W
    28W Member Posts: 141
    OK, but

    I like the house a bit cooler while sleeping. If I set my programmable thermostat to drop down to 65 at night, but want the house back up to 68 at 7AM, will the boiler be able to do it?
  • JStar
    JStar Member Posts: 2,752

    You can make your system do anything you want, if you do it correctly. Don't expect any system to heat up 100% in a few minutes. If you want to setback overnight, program it to come on about an hour before you wake up, so it'll be the temperature you want.
  • 28W
    28W Member Posts: 141

    I didn't expect the modcon to raise the temp as fast as the old oil boiler did. I just wanted to be sure that it could be used in this manner. I have one of those Honeywell "adaptive learning" thermostats that, over the course of a few days, figures out when it needs to turn the system on in order to hit the desired temperature at the specified time. I've had it for years and it has proven to be very good.
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