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Outdoor reset and baseboards

First off, thanks to everyone for the knowledge on this forum.

I moved into newer house last year and am looking to optimize the heating a little bit. This is in northern Wisconsin, zone 4B. Design temperature looks to be -16 Farenheit.
House was built in 2004, 2x6 construction, reasonably well sealed. Two floors on insulated slab.

This has a propane mod/con boiler. Triangle tube prestige solo 110.

First floor is hydronic in floor. There looks to be one zone, with four loops that each has a manual flow control. This is controlled by an air temperature thermostat. There is also a wood fireplace which gets used often but I don't want that to be a requirement. 1050 square feet, 9 foot ceilings.

Second floor has 34 feet of baseboard heater on one zone. 550 square feet, 8 foot ceilings. This also has an air temperature thermostat.

Originally the boiler was set to 160 F water temperature so it wasn't condensing. No outdoor reset. There is a manual mixing valve that was sending lower temperature water to the in floor heat on the first floor.

I've since added outdoor reset. I haven't really dialed in the temperature setpoints yet because we're just getting into the start of the heating season.

I have three questions:
1. The outdoor reset on the boiler is set for 0 degrees as the low setpoint temperature. Does anyone know if it's possible to change that? I need it to be somewhere around -20.
2. So far while using the reset, the upstairs has been a few degrees below the setpoint with the boiler circulator running full time. This is set to the medium speed. I feel that I might not have enough baseboard upstairs if I'm going to use a lower water temperature. I think the heat delivery in the first floor is better than the second floor. What are my options? Add more baseboard, replace with high output baseboard, or add air source heat pump (for AC in summer too). Am I missing anything?
3. I want to do my temperature control on the first floor off the slab temp instead of air temp. What are my options? The thermostat has 5 wires to it and currently has a Nest which works poorly because it's air temp.



  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 3,824
    edited October 2022
    There are a few renditions of the Solo. Do you have the Trimax control or something else? Take a picture of the front of your boiler or give us the serial number.
    1. The outdoor reset on the boiler is set for 0 degrees as the low setpoint temperature. Does anyone know if it's possible to change that? I need it to be somewhere around -20.
    As far as I remember, you choose a reset curve when programming the boiler which will dictate water temperatures at whatever the outdoor sensor says. I don't think there's a place for design temperature to be recorded.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Thanks for the response. It has a Honeywell MCBA14201D controller inside. Serial number of the boiler is PS18864.

    I just found the answer to my question for the design temperature... From the documentation at https://cdn.triangletube.com/wp-content/uploads/2021/08/13141651/2011-1-Prestige-Solo-110-Installation-Maintenance-Manual-.pdf page 51, I need to change parameter 11. I didn't see this when stepping through the parameters, but I see now I need to enter an MCBA access code.

  • And regarding the MCBA access code, I can get through all the steps in their documentation, but it still doesn't give me access to the hidden parameters. But I think that's a different issue so I'll take that up with their tech support.