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Multiple temps with mod con H. E. Boiler

ed med m Member Posts: 65
Wanted to install new h e mod con boiler

3 zones


2- baseboard

3 - radiant heat

Question due to the lower water temp needed for radiant and the higher temp needed for radiators and the fluctuation of temps due to outdoor reset how can I set up boiler to satisfie both if they are both calling at same time. Set point mixing vale? Which boilers would work best for this application was looking at burnham alpine or lockinvar night? Thanks for the help



  • IronmanIronman Member Posts: 3,525
    Lochinvar Knight

    It can control 3 temps with separate outdoor reset for each. They have an add on control that will control up to three electronic mixing valves so the temp in each zone can be maintained.

    The Alpine doesn't have that capability; you would have to install samrt valves or use injection mixing for the radiant.

    Domestic hot water control is a separate function that any mod/con can control. The Knight offers control of it by a sensor or aquastat; the Alpine by aquastat only.

    The Knight has the most advanced control of any mod/con and a superior heat exchanger with its fire tube design.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • clammyclammy Member Posts: 1,996
    edited March 2013
    triangle tube

    Try triangle tube prestige solo with the trimax controller ,fire tube design and set up for 2 seperate reset curves w outdoor reset .installed one with radiant and baseboard worked out very nice .Run  at radaint temps until secondary stage kicks in and then runs at higer temp reset curve  when higher temp calls it run at that temp ,you still needed mixing valves on the radiant but nice boiler with a good 2 temp curve built in .peace and good luck clammy
  • ChrisChris Member Posts: 3,056
    edited March 2013
    Vitodens 200

    Figured I'd throw that in the basket. Boiler can run two independent heating circuits utilizing the plug and play mix valve for the radiant. Boiler has a lifetime warranty on the HX, uses a combustion system that monitors for optimum operation and efficiency which none of the others do and is competitively priced.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • Steve WhitbeckSteve Whitbeck Member Posts: 669
    H. E. boiler

     I would go with the Knight WHN also.

    I don't recommend ANY gianonni style boiler. The new fire tube heat exchanger is a much better design.

    I would use the tekmar injection control on in floor radiant loop.
  • Jean-David BeyerJean-David Beyer Member Posts: 2,532
    I am sure the answer to how to do it depends dramatically on what boiler you select.

    Wanted to install new h e mod con boiler

    3 zones


    2- baseboard

    3 - radiant heat

    I have a (W-M Ultra 3) mod-con boiler set up just like that. And my system is set up with no mixing valves. (When the money tree blooms, I intend to install one at the output of my W-M indirect (actually, T.T.) and run it at around 145F instead of the 125F I run it at now. Zoning is done with circulators, though if I were to do it over, I would probably use a delta-T ECM circulator for zone 2 and 3, and zone valves instead.

    The controller on an Ultra-3 has three on-off thermostat inputs, and three 120V AC switched connections coming out. Zone 1 is the highest priority, and Zone 3 is the lowest. Each priority has its own reset curve (user programmable), and each priority can use none or more of the 120V AC connections.

    So when the dhw asks for heat, it runs  the boiler and turns on the circulator to the indirect. I have it programmed to run at 175F for that. Recovery is not as fast as it would be were I to set it at 190F, the default, but it is fast enough for my limited hot water use.

    Radiant is connected to Zone 2. When that gets control, it uses the radiant reset curve that puts out 76F to 120F water depending on outside temperature. It turns on only the boiler circulator (P-S piping) and the circulator to the radiant zone.

    Baseboard is connected to Zone 3. When that gets control, it uses the baseboard reset curve that puts out 110F to 135F water depending on outside temperature.It turns on the boiler circulator, and a separate Honeywell relay turns on the circulator to the baseboard zone.

    There are some subtleties I have not yet described.

    1.) If the baseboard zone calls for heat, the Honeywell relay turns on that zone's circulator and leaves it on until the thermostat is satisfied, even if the boiler is ignoring it because a higher priority reset curve is in effect. If the dhw is getting heat, the boiler circulator does not run, so 175F water does not go to the baseboard zone in that case. The result is that if both the heating zones call for heat at once, the radiant wins the priority game and that reset curve is used. But the baseboard will get heat, just not as much as it needs. But it is better than nothing. The heat loss of the baseboard zone is very low and this is enough for me. This would not work if the baseboard zone consumed most of the heat.

    2.) The priority scheme of the controller is quite sophisticated. If a high priority demand lasts too long (30 minutes, by default, but user programmable), the controller examines the other to thermostat inputs and if one wants heat, it gets control for a limited time (15 minutes by default). Now for dhw, that never happens because my hot water usage is low, and I can always recover in about 10 minutes. If I were washing cars with hot water in winter, I suppose it might stay on though. Once control is given to any priority input, it keeps it until its thermostat is satisfied, or until its time is up, whereupon it relinquishes its request. So if dhw was insatiable, it would run 30 minutes, radiant would run for 15 minutes, then dhw would get another half hour, etc.

    3.) If an input requests heat for "too long" (user adjustable), the controller can switch the reset curve up 10F in an effort to recover more quickly. I have this feature turned off except for the baseboard zone. I do not use setback except in the baseboard zone). If it does not recover in two hours, boost goes into effect.

    I do have the reset curves very tight. I.e., the boiler puts out barely enough heat to keep up with the loss. Consequently, it would recover very slowly from a setback. But I cannot use setback on my radiant slab anyway, and if I abandoned the setback in the baseboard, I could disable the boost feature altogether.
  • ed med m Member Posts: 65
    Knight boiler with multi temp control

    If I use the knight with multi temp control do I still need an I series mixing valve? And if so a 3 way? I've installed plenty of cast iron boilers with mixing valves for radiant and also installed some mod con boilers but never with multiple temps for radiant and baseboard. Just trying to figure out I I will do this so I can come up itch a plan and a price. Is there any sites with layouts or specs on this? If I called lockinvar will they be able to help me? I can't even find a price on that multi temp loop control. Thanks

  • ChrisChris Member Posts: 3,056
    edited March 2013
    These Should Help You

    The first is a great read for Mixing in Hydronics from our friends at Caleffi the second is a piping diagram for Viessmann which will be similar for pretty much any condensing boiler. You can substitute the low loss header for pri/sec piping if you wish.

    The motorized valve in this diagram is controlled right from the boiler control. I believe you can do the same with the Lochinvar. If not and you chose a Taco I-Valve you would have to run its outdoor sensor outside and program it correctly for your application.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
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