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Mixing valves and gypcrete

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by SteveJ, Jan 9, 2008.

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  1. SteveJ

    SteveJ Member

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    With radiant floors using gypcre under carpet and hardwood floors, how important is it to keep the water temp entering the floor around 110?

    What happens with a higher temp?

    I currently have the water going straight from the wood boiler in series with a propane boiler going into the floor - temps around 170F.

    For efficiency and power consumption, would it be best to use a mixing valve (tempering) or to use four way mixing with another circulator?

    Eric - you mentioned four way mixing in this thread. Could you provide a quick diagram or detailed description? Would it be something like this?

    Thanks,
    Steve

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  2. Eric Johnson

    Eric Johnson Mod Emeritus

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    That looks like a 3-way valve, but it's too early in the morning for me to focus on the details, especially since my understanding is a big hazy to begin with.

    Craig told me about 4-way mixing valves. Here's my basic understanding, though I've never used one. Funny thing about that webpage: They say to oversize the valve by one size, but a heating pro told me to undersize a 4-way valve by one size to keep it from "hunting."

    Anyway, as I understand it, 4-way valves work best on big zones with continuous circulation. A thermostat on that zone constantly adjusts the valve to maintain a water temp in the baseboards or floor radiant or cast iron radiators, etc. that keeps the living space at the desired temp. So instead of pumping 180-degree water into the house radiant periodically to keep the temp within the range, the four-way valve keeps, say, 130-degree water circulating through the zone at all times to maintain room temp. As the outside temps drop, the valve creeps open a little more, allowing the temp in the circulating water to rise accordingly.

    The results, as I understand it, are twofold: First, you get more consistent, even heating and your radiators are always warm enough--but not too warm--to keep the house at the set temp. Secondly, especially with zones with big water capacities, such as those with cast iron radiators, you can store more heat, because it's spreading it throughout the system and maintaining it. It's no substitute for a storage tank, but it does allow you to keep more heat in your system than a conventional "bang, bang" arrangement.

    Four way valves are big in Europe. When I was pricing them, you could get a new Honeywell 1 1/4-inch 4-way mixing valve for around $100 (valve body and actuator) plus another $100 or so for the thermostat. You can also use an outdoor stat with these valves.

    That's about all I know. You'd probably want to get someone like Craig, who really understands the topic, to correct or elaborate on what I've said.
  3. Eric Johnson

    Eric Johnson Mod Emeritus

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  4. SteveJ

    SteveJ Member

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    Eric,

    Thanks for the info and thanks for sugar coating RTFM ;-)

    Steve
  5. Eric Johnson

    Eric Johnson Mod Emeritus

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    It's one of the many services we provide.

    BTW, in this business, I've found that most of the FMs are NFG.
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