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different zone temps

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keyote
keyote Member Posts: 659
in Radiant Heating
my situation is ive finished renovating the top floor of my four floor brownstone the top floor now has radiant floors which eventually the entire house will have, in the meantime the rest of the house still has the old dragon in the cellar and old hydronic radiators I was going to simply install a new modcon and indirect DHW and run both systems. I once added a radiant zone to another house using mixing valves etc i forget it was a long time ago it worked fine but ....Im wondering if doing it in reverse is easier now , can i simply connect the big old circulator to the new modcon at 180 d while the radiant zones are at whatever 90D and the indirect is whatever it needs to be or does it all need to be mixed down.I guess another issue is the radiant is all oxygen proofed the old system not so much can a strainer at least keep the particulates out of the boiler. Im considering for now buying this slightly used used baxi that modulates from 105-35kbtu. the top floor is my priority to heat for tenants im living like a refugee in the rest and dont really care about conditions several rooms had radiators removed for work or clogs so its not perfect but ive run extra rads with pex where i camp out. this baxi and a used stor45 tank both with all the trim will only cost me 1200 while i save for the dream units. I can live with running both units if need be but be nice to not have to.

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  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
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    So what's the question? Run the modcon at 180* or whatever the rest of the building requires and use a mixing/thermostatic valve for the radiant zone... till you switch over to all radiant.
  • keyote
    keyote Member Posts: 659
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    i dont know i guess i was hoping i could fire the boiler at different temps for the different zones,i suppose im hoping to keep the fluids separate some how but i cant really see how to completerly do that.
  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
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    Lochinvar modcons allow for up to three independent temp/loop demands. However when multiple "zones" call for heat, it'll fire the boiler at the one with the highest set-point.

    So say a baseboard and radiant zone call for heat at the same time... BB set to 180* and radiant set to 120*. The boiler will fire at 180* till the BB loop is satisfied and drop to 120* if the radiant is still calling.

    Depending on how the circulators are wired... the lower temp zone might circulate while the hotter one is running. You could get fancy with electronic mixing valves, separate circs, etc... However ultimately you'll still have to run at 180* (or whatever the BB demands) often.

    Separate the fluids? Two boilers :)

    Since the majority of the house is BB, just set the radiant with a mixing valve... run at higher temps. When you get around to doing radiant everywhere else, then you just remove the mixing valve and run the boiler at much lower temps.
  • keyote
    keyote Member Posts: 659
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    yeah i cant see how to separate the fluids short of running the radiant through the indirect hot water instead of through the boileror something crazy with the combi hot water side which i was going to just ignore. theres no way im running that 110 year old dragon blood through my new manifolds and tubing. guess ill just run two systems for a year. thanks guys

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