Waterfurnace Envsion NWT for hot water?

Discussion in 'Quotes and Proposals' started by JFLame, Oct 21, 2012.

  1. JFLame

    JFLame Member

    I've decided I'm going with the Waterfurnace system, and with that finally out of the way I'm focusing on which hot water option(s) to invest in.

    The current quote is for a DSH with buffer tank, and electric finish tank.

    I've started reading up on dedicated geo hot water solutions, and Waterfurnace offers the NWT which could perform that function.

    I have sent an email to my Waterfurnace installer asking him, but in the meantime I thought I'd post here and see if I could get some information.

    Can anybody lay out for the me the nuts and bolts of dedicated hot water? PLEASE, if somebody could give me an idea of the costs involved I would REALLY APPRECIATE IT. My rough understanding so far is that the NWT is a new unit that will still need a finishing tank and will use the same flow center as the 5-series unit. So at a minimum the new unit would be needed, but I'd save the cost of the DSH and the final water heater.

    My rough calculations using 3.7 COP based on a usage calculation done through GeoLink are giving me a rough savings of about $200 a year. I'm wondering if with the additional $1000 Waterfurnace rebate and the30% tax credit that a dedicated solution might be cost effective, but at this point I have no idea what to expect for the cost of the NWT unit.
  2. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Piping costs should be the same, but you save one tank and the desuperheater itself. Now you need the 2nd heatpump, and an additional pump or a zone valve and a boiler control. Don't know for how much you will be charged for that.
    Last edited: Oct 21, 2012
  3. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    How many full time residents?

    Water heating energy highly depends on number of people in the home.

    There is no doubt in my mind that a dedicated geo unit will provide domestic hot water at highest COP and therefore lowest operating cost.

    I'm guessing the dedicated unit will cost $2-3k more than the DSH option with its own preheat tank. Payback on that incremental cost may be decades unless there are a dozen residents in the house.
  4. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    I haven't heard of the NWT unit?

    But I'm thinking you are talking about using a heat pump for dedicated hot water? On its own, this is an expensive way to go. This is a fully operationally heat pump (ie has a ground loop or such). You know what you're paying for an HVAC requirement. So you can see that it doesn't make much sense economically unless you are a car wash or such.

    Other than the standard desuperheater setups, other options include:

    - if you are using radiant, you can plumb as such (through a heat exchanger) additional loads for the domestic from your radiant heat pump. An indirect tank is an option.

    - if you use a hybrid unit (water and air) you can use the water side for a hot water.

    Keeping in mind, the upwards limit of heating for geo might not be the domestic finishing temperature you want. Most domestic water should be run through a double-walled heat exchanger - so the plumbing can be a bit complicated.

    edit - costs. I don't recall what your ground loop options were, but off a well system might be the cheapest. If you are having to add geo loop for the increased load, I wouldn't even consider it. You'd be starting at around 10k I'm thinking. I've never had a client put in geo for dedicated domestic hot water if that gives you an idea of the economics:)
    Last edited: Oct 21, 2012
  5. zacmobile

    zacmobile Guest

    What he said, but I did do a dedicated domestic water system once before. It was in a seniors extended care facility that already had two water to air units for heating on an open well system so it was a pretty simple matter to add the water unit. I don't know why more people don't use the Climatemaster THW, I know it's expensive but it's not THAT expensive and it sure simplifies the hot water & controls set up.
  6. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    It is THAT expensive for a 3 ton unit, now you are stealing capacity away from it. Usually, houses needing high temp are less efficient (older baseboard heat or radiators). That is why Waterfurnace hit a void with the new 7 ton high temp unit. Water-Water units with 100% DHW design via indirect tanks, we usually charge $4000 for 108 gal Stiebel Eltron and controls and labor, but you safe $2000 for DSH and also minus the 2 tanks. So for $2000 ($1300 after tax credits) more you have 100% DHW all year around. The increased load on the loop is insignificant. Keep in mind you would steal 10% for a DSH anyway.

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