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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
    Lancaster PA
    Posts
    67,922
    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
    1,373
    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
    Lancaster PA
    Posts
    67,922
    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

  7. #7
    Join Date
    Jun 2007
    Location
    ohio
    Posts
    73
    You might want to run your pumps lil longer then your boilers on shut down to get the extra btu's...out or your water...

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,922
    My want to use a sensor in the slab.
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  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,922
    Quote Originally Posted by Mrcyber07 View Post
    You might want to run your pumps lil longer then your boilers on shut down to get the extra btu's...out or your water...
    If the boilers on an OD reset, they isn't going to be much in the way of extra BTUs.
    If the circs run too long on a nat draft boiler, you can pull heat from your mass back to teh boiler.
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  10. #10
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    2,006
    With that amount of free gas, I myself would be looking at some form of Cogen setup. Heat my house and produce electricity at the same time. No energy bills 12 months out of the year not to mention the potential for selling excess electricity back to the grid and maybe getting a paycheck. Use the paycheck from the electrical company to maintain the cogen.
    Ok.......... time to quit dreaming.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,922
    3000 therms isn't enough for co generation.
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  12. #12
    Join Date
    Jun 2008
    Location
    Western Pennsylvania
    Posts
    6
    Quote Originally Posted by firecontrol View Post
    With that amount of free gas, I myself would be looking at some form of Cogen setup. Heat my house and produce electricity at the same time. No energy bills 12 months out of the year not to mention the potential for selling excess electricity back to the grid and maybe getting a paycheck. Use the paycheck from the electrical company to maintain the cogen.
    Ok.......... time to quit dreaming.
    I have plans for the extra natural gas. The house is 1650 sq ft on main floor, same for basement, heat load calculates to about 55,000 btu. Won't even come close to 300,000 cu ft. I will also have radiant slab in 28'x32' garage, and in 10'x30' breezeway. Also, will use to heat hot tub, and likely a pool. Might even use some outdoor gas lights to light up my 500' driveway.

    What would be the best way to heat the garage/breezeway and the hot tub/pool? Use a seperate boiler from the house with antifreeze for the garage/breezeway and use that boiler with a heat exchanger for the hot tub/pool? I think I would want to keep the chlorine away from any PEX, correct? Or, should I run everything from one boiler in the house? Heat load in the summer would be much lower, with only the indirect DHW, hot tub, and pool heat when it is chilly. The pool would be closed in the winter.

    Again, thanks for any info,

    Mark

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