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  1. #1
    Join Date
    Jun 2008
    Location
    Western Pennsylvania
    Posts
    6

    Radiant- injection or mixing valves?

    Hello. I am building a new house, a ranch style with radiant in the concrete basement floor and under the subfloor for main floor. I plan on using a condensing boiler with an indirect hot water tank. Now, my issue involves the different temperature requirements of the two different radiant applications. In a house I built 9 years ago, I just used a Slant Fin direct-vent cast iron boiler with two manual mixing valves to mix down the temperature for the basement concrete slab and the under-subfloor heat. No outdoor reset, just two thermostats. Did run the boiler at only 160 degrees, always had plenty of heat.

    With my new system, I want to take full advantage of outdoor reset and lowest possible boiler temperatures. With manual mixing valves, the temp in the loops won't go below the setpoint of the mixing valve, unless of course the boiler temp goes below the setting of the mixing valve. To do it correctly, I find that I will need a mixing solution that will also take advantage of outdoor reset. As I see it, the best ways are to either have two seperate injection pumps or two controllable mixing valves for the two different temperatures required. Am I correct? Any other suggestions? I am finding that the controls for dual injection systems can be quite expensive, 30 to 50 percent the cost of the boiler. Taco makes a nice mixing valve that connects directly to an outdoor reset. Many condensing boilers have outdoor reset and DHW priority built-in. None have mixing valve/injection pump controls that I know of. Would the Taco mixing valves with built in outdoor reset be a better option than a Tekmar control or similar control?

    Thanks for any help,
    Mark

  2. #2
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,769
    Taco OD reset circs. If one fails, the other still works.
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  3. #3
    Join Date
    Jan 2002
    Location
    East Grand Forks, MN
    Posts
    1,375
    To make it simple, go with the TACO iSeries R, as long as they are big enough to handle the load. I recommend one per zone; like one for the basement and the other for the main floor.

    Something to think about would be your minimum OD reset for your boiler! will it be higher than the main minimum floor water temp? and at what temp? is it low enough?

  4. #4
    Join Date
    Jun 2008
    Location
    Western Pennsylvania
    Posts
    6

    Any other controls needed?

    Ok, the iSeries R circulators look like just the ticket. Now, since the circs have OD reset, and the boiler has OD reset, would there be ANY need for any other controls? I am building in Western Pennsylvania. I will be having the system professionally installed, with me doing most of the PEX tubing.

    Some other information: the land I am building on is leased for natural gas. If/when they drill, I will receive 300,000 cu ft per year of free gas (my father will receive the royalties as he owns the gas rights). Until then, I will use propane then convert to NG. Knowing this, would you still install a condensing boiler, or save the cash and go with a cast iron boiler likely to last 30+ years?

    Thanks for the information,

    Mark

  5. #5
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,769
    How long before you can use the nat gas. If its 4 or more years. Well, LP is real expensive.

    Other then that, it doesn't make sense to get a mod/con boiler if the gas is free.
    Especially with all the filter and drier system you will have to install. That gas won't be clean of dry.
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  6. #6
    Join Date
    Jun 2008
    Location
    Western Pennsylvania
    Posts
    6
    Quote Originally Posted by beenthere View Post
    How long before you can use the nat gas. If its 4 or more years. Well, LP is real expensive.

    Other then that, it doesn't make sense to get a mod/con boiler if the gas is free.
    Especially with all the filter and drier system you will have to install. That gas won't be clean of dry.
    In this area, they generally will install an alcohol drying system before the low pressure regulator/meter. They drilled 3 wells on adjacent properties last year and are drilling 2 right now. Most likely, we will have a well this year or next. We are building a chimney and will have a woodburner to supplement if we have to use propane a year or two. On a ranch style house, a decent size woodburner can almost do the entire heating job. Plus, I would not have to pay for wood, just cut and split.

    I think I may have just convinced myself to go with a cast iron boiler.

    Still, is there any need for any more controls than the OD reset on the circs and the boiler?

    Thanks,
    Mark

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