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retrofit for outdoor sensor

We have a conventional Hot Water Boiler 80% gas fired heating a large Victorian House with cast iron rads. I am wondering about a cost effective retrofit for an outdoor sensor setup to get boiler to respond to rapid change in temp outside. As is it can be up to 4-5 hours for thermostat to respond to sudden temp drop, house is pretty tight for old house. Thanks for any info

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 17,832
    Think about this for a moment. All an outdoor sensor would do is alter the setpoint for the circulating hot water. It has nothing to do with whether or not the thermostat inside the house responds. If parts of the house are chilling off before the thermostat gets the word, that's really a problem with thermostat location. There are thermostats available which can use multiple inputs and average them -- or it may simply be that the thermostat you have could be more advantageously sited.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,560
    edited December 2019
    "Heating a large Victorian House"! That says Cast Iron Radiators to me! My experience in Cape May NJ is; those houses have an eclectic, missed-matched, system of radiators from over the years of renovations and additions from original installation to today!
    That said... I saved a customer over 2000 gallons of fuel by installing the thermostat in the coldest room in the building. Then add thermostatic zone valves to any room that overheats.
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,560
    Another solution was outdoor reset with constant circulation. I needed to add a bypass to keep the return temperature up. That was so long ago I forgot how I did it. They have since removed the Oil Boiler and installed a Mod/Con boiler
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
    SuperJ
  • SuperJ
    SuperJ Member Posts: 605

    Another solution was outdoor reset with constant circulation. I needed to add a bypass to keep the return temperature up. That was so long ago I forgot how I did it. They have since removed the Oil Boiler and installed a Mod/Con boiler

    This is good, but requires primary secondary piping on a old CI boiler. With a modcon it's bliss. I run constant circ with TRVs to a buffer which is maintained off an ODR. It works very well. There is a always a hint of heat everywhere to take the edge off, and the cold rooms can take as much as they want. I have the ODR turndown set fairly aggressively so nothing can overheat even if a TRV gets cranked wide open.

    Great article...
    https://www.phcppros.com/articles/7804-when-old-tech-meets-new-tech

    Regarding thermostat placement
    Many thermostats are placed too far interior in a building, and won't kick the heat on until much of the house is too cold. This leads to energy hogging high set points to compensate. The problem is the amount of compensation varies hourly depending on conditions. People have it ingrained not to put the stat on an outside wall, which is correct. But, in my experience it should be in a room with some outside walls, and not too far from an outside wall. It will pick up the heat loss before things get uncomfortable and cycle the boiler/furnace on before you get to the point of feeling like you need to go and mess with the stat. If it's a warmer sunny day, with no wind. It can be left at the same set point, as a cold windy day it will just cycle less but always maintain comfort with no messing around.

    EdTheHeaterMan