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Flow control valves

I have high efficiency house in central Vermont. It has radiant tubing in the floor for heat. I am trying to get the on demand propane fired hot water heater, a Takagi, and the circulator pumps to run as little as possible. Electricity is the biggest obstacle, not propane. The house is a second home and I hold the them when the house is empty at 50 degrees. I have a sealed combustion wood stove to provide the majority of the heat when I'm there. The house is off grid with PV and batteries. Both are a little on the small side. The house has 6 zones with flow valves on each. No zone is over 400 feet. Tubing is 1/2 inch PEX. Current Delta T when three or more zones are open is 10 degrees. With one zone open the delta is maybe a degree. The current set up is one loop from hot water heater through through Stainless pump and heat exchanger. Second loop with one pump feeds all the zones on other side of heat exchanger. I currently have all flow valves wide open. I wondering if I should slow them down to allow the hot water to spend more time radiating heat into the floors? I could also raise the temp of the water. Any ideas would be most appreciated. Thanks


  • SWEI
    SWEI Member Posts: 7,356
    First, you are using a tankless water heater where a mod/con boiler should have been installed. It's going to take some work to make it perform even moderately well.

    Am I reading above that you have loops of 1/2" PEX that are longer than 300 feet?

    Has anyone done a heat loss calculation on the house?
  • hot_rod
    hot_rod Member Posts: 14,748
    If the goal is to lower power consumption perhaps changing the circa pumps to ECM type or 12VDC would be one step.

    Assuming the system was designed, installed and sized properly on a design (coldest) day the boiler would run non-stop. Any condition less than design the boiler would operate less, of course.

    Depending on what you have currently, and what you want to spend, adding a buffer tank can lessen the cycling of the heater.

    Not sure the cost to do that would offset enough operating dollars?

    Of course what ever you can do to upgrade the structure and lighten the heating load, weatherstripping etc, is the very best place to spend $$.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • icesailor
    icesailor Member Posts: 7,265
    I always looked at heating systems like my computer GIGO. Garbage IN, Garbage OUT.

    You need enough heat coming IN (Garbage IN) as you need going out into the system (Garbage Out). If you are off the grid, your money might be better spent on more recovery and storage. Solar Panels have come down in price. If you don't have to deliver your own LP, a better generator with better exercising schemes might be in order. Whatever you do will cost you, But the need for power and BTU's for heat won't be changing because you spent money elsewhere.

  • olsonphoto
    olsonphoto Member Posts: 4
    SWEI,,, The heat loss is 15-18,000 BTU. It's a very tight house. The Takagi water heater is a highly efficient condensing/modulating unit.

    HotRod... I have thought about the tank for tempering water. seems like it might make everything run more smoothly. It seems like the quickest and easiest thing to do is change the circulators. Do you have a suggestion for the Stainless Steel pump on the DHW side of the heat exchanger. The BumbleBee ECM pump seems like a good one for the radiant floor side of things. I'm still curious about the amount of flow on the individual zones. Do I want the water flowing faster to deliver more full temp heat or do I try and slow it down so the water spends more time out in floor doing the magic and coming back cooler?

    IceSailor... More PV panels are in the plans.

    thanks all for the excellent responses.
  • hot_rod
    hot_rod Member Posts: 14,748
    I'm pretty sure the Grundfos Alpha is available in a stainless version. I like the B&G Vario also, not sure of volute choices.

    If you can work with the size that small solar 8-24VDC B&G/ Laing comes with a brass body. That would be the best as you would not take the inverter hit if you powered directly from the battery bank.

    Yes, faster flow moves more heat from an emitter. But you don't want to grossly oversize a circ to get that extra floret necessarily.

    Tune in the Coffee with Caleffi tomorrow, we have a two part webinar on pump selection, sizing, troubleshooting, and the how and why of high efficiency delta circa. Noon CST.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • icesailor
    icesailor Member Posts: 7,265
    Will the added/new circulators add more heat to the system so it gets hotter than before? Or will the friction of cash leaving your wallet be the source of extra heat?

    A very old goal of invention was "Perpetual Motion". Changing circulators sounds a lot like perpetual motion. Something that has never been invented.

    Even the tides need the moon to work.
  • olsonphoto
    olsonphoto Member Posts: 4
    icesailor,,, I think the heat will be the same but the draw from my batteries will be much less, maybe as much as 20% of my current pumps. Compared to batteries, circulators are a bargain and making the sun shine longer seems like something beyond my control, not that I ever had any control over anything. Here is the current system.
  • Harvey Ramer
    Harvey Ramer Member Posts: 2,215
    icesailor said:

    Will the added/new circulators add more heat to the system so it gets hotter than before? Or will the friction of cash leaving your wallet be the source of extra heat?

    Sometimes you crack me up, Ice. lol
    Ramer Mechanical
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Rich_49
    Rich_49 Member Posts: 2,563
    edited December 2014
    Glad you made it .
    The stainless pump Rod mentioned for the boiler/water heater side makes alot of sense . Get rid of the differential pressure bypass and use an ECM circ of your choosing . This should really lower your electrical consumption for the heating by possibly more than half . Hope you found what you needed here . It would have taken too much time over the other place besides people calling you foolish for not abandoning what you have . Sorry that happened .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • icesailor
    icesailor Member Posts: 7,265
    "" It would have taken too much time over the other place besides people calling you foolish for not abandoning what you have . Sorry that happened . ""

    I hope that nothing I said was considered me saying it was foolish.

    My comments are based upon 40 to 50 years of working in a very isolated place. There were few "Off the grid" houses, but ones that depended on someone to be sure that all was well is something I personally consider "Off The Grid". The fuel supply could never be too big. If you are using Solar and batteries, you can never have enough batteries. They hold less with age. You only get so many hours of sunshine. You only get so many hours from a battery. The more batteries, the more panels, the more stored energy. Like your Propane.

    When I was living on Cape Cod, they had a really big Northeast winter storm. There must have been a lot of Micro-Bursts or Mini Tornados. It blew down a lot of really big trees along Route 6A. Until the trees were cleared, the power crews couldn't get the power back on. In some areas, it was over 5 days before the power was back on. No one with Generators had enough fuel for 5 days, so they ran out. And they were trying to figure out how to drain their houses without power. If someone could even get there through the downed trees, power lines and snow.

    Its a choice, Either, Or, or Both.
    I think it is a fine idea to use ECM circulators. They're as slick as baby poo. They just don't run well without adequate electricity.

    That's all I was saying.
  • olsonphoto
    olsonphoto Member Posts: 4
    Icesailor.... I "get" you. You're OK in my book. I was reading the end of your last post and it occurred to me that sentence might have ended, "They just don't run on sunshine." but wait, in my case they do! heehee... well, in VT there is little sun but it seems like just enough to get the job done. Rod.. Thanks for the ideas. I will look into the pumps and keep by flow valves wide open.
  • icesailor
    icesailor Member Posts: 7,265
    I've always been intrigued by the clouds forming in the trees on the sides of the mountains when going up 89. All those clouds and moisture gets returned back to all that cow corn grown in the Champlain Valley and waters all that cow corn so the cows can be fed in the winter time.

    89 is always interesting. I'd be driving up and think I was driving down a hill. And look at my GPS and it would show I was driving up in elevation. Then a few minutes later, I'm thinking I'm driving the other way around. Strange. Especially at 2:00 AM in January or February going to Mallets Bay to go sailing.

    Why is it when driving North on 89, there are plenty of places to stop and relieve one's self. But driving South toward New Hampshire, there's no place to stop. Does Vermont have something against New Hampshire or something? It can be a long way between pit stops.
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