radiant heat system questions

Discussion in 'Boiler Forum' started by rrekih, Oct 5, 2009.

  1. rrekih

    rrekih New Member

    Oct 4, 2009
    Hi There
    I plan on installing a boiler etc. to heat the main floor with stapled up underfloor radiant heat and the basement with baseboard type heating.
    The main floor would have 5 zones.
    The basement would have 3 baseboard zones.
    My thoughts for the main floor is to have the kitchen, living room and bathroom operate at the same temperature and the 2 bedrooms being turned down more than the other rooms at night.
    The basement would have 3 individual heating zones.
    This sounds like a 8 way manifold?
    Just what parts do I need to make it work like I want?
    I understand that I need a separate thermostat for each individual heating zone.
    Does each thermostat connect to a actuator on the manifold?
    Thanks for any info that you can help with.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    This is more than can be covered on an on-line forum here!

    Some theremostats can control more than one zone valve, but yes, you could have one for each zone. If the length of pipe isn't the same for each, then you need to carefully balance them, or you may not be able to achieve the heat transfer needed. Keep in mind that the baseboards will likely need higher temperatures than you should supply to the radiant floor system, so you'll need a means of tempering that. Some boiler systems can handle that with options, but you may have to roll your own. Plus, given the huge discrepancy of flow when one verses maybe all zones are open, you may need other controls to adjust the volume and pressure. you could go with one pump per zone, but that gets expensive, too.

    You need someone familar with radiant design to help out on this to tailer it to your individual needs...and, I don't think other than general info, you can get a viable, economical system design from here.
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  4. nhmaster

    nhmaster Master Plumber

    Jul 30, 2008
    Tech. Instructor
    S. Maine
    Correct, for a system of this complexity to operate to your expectations it will need to be properly designed as well as installed. There's a lot going on here for a first time radiant job. Staple up operates at temperatures close to baseboard temps. You should call in someone with experiance
  5. Dana

    Dana In the trades

    Jan 14, 2009
    Also note, with a gazillion micro-zones system, the heat load of the individual zones are likely to be a small fraction of the lowest modulated output of any modulating/condensing boiler (and a TINY fraction of an old skool cast iron boiler sized for the entire system.)

    In this scenario to keep from cycling the boiler to death, and to avoid killing off all hopes of meeting it's AFUE rating it'll need a buffer tank (most likely a single tank, maintained at the temp demanded by the highest temp zone.)

    With enough baseboard length you can get it's design-temps down to under 100F if need be. The heat loss of insulated basements is usually lower than upper floors, so if all other zones are staple-ups designing to single relatively low water temp is possible, saving on mixing valves & pumps.

    But this is way too messy in it's details for "design-by-web-forum". Either hire a pro, or do some in-depth study of hydronic design or you're unlikely to get both efficiency & comfort out of it.
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