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Outside temp reset, when steam used parallel to heat pump?

agurkas
agurkas Member Posts: 238
in Strictly Steam
Right now I have 4 bedroom heated with single pipe steam. In couple weeks I should have heatpump installed with four heads in each of those bedrooms. I understand it is cheaper to run heatpump up until outside temps are 35F or so (I am getting Mitsu Mr. Slim) and heat with steam, when temps outside drop below that.

I have now Carlin conversion gas burner being controlled by Nest. Should I get outside temp reset that won't let the burner kick in, until it is less than say 38 or 40 outside, so place gets heated by steam an I don't have to mess with heatpumps?

Comments

  • Mark N
    Mark N Member Posts: 1,115
    Are you getting the split minis for the a/c mostly? They are very expensive to install to possibly save a few dollars on heating above 35 degrees. Also a BTU is a BTU and natural gas is way cheaper than electricity per BTU.
  • Mark N
    Mark N Member Posts: 1,115
    A person named JPF who used to post installed split mins with his steam system. Hopefully he is still around a can answer your question.
  • agurkas
    agurkas Member Posts: 238
    edited December 2014
    Yes, I am getting mini-splits. With rebates and state incentives it was worth it. Yes, primarily for AC, but in my research I was finding that 75% efficient steam (at least for my converted boiler) was more expensive per BTU above 35F. That is considering $1.4 per therm for NG vs $0.30 per KW
    That is with 8.9HSPF mini-split
  • Mark N
    Mark N Member Posts: 1,115
    edited December 2014
    There are 3415 Btu's per kilowatt. So there are 29.28 kilowatts per 100,000 btus, so electricity comes out to $8.78 per therm.
  • agurkas
    agurkas Member Posts: 238
    edited December 2014
    Right, but that calculation assumes HSPF of 1, not 8.9. No?
  • Mark N
    Mark N Member Posts: 1,115
    edited December 2014
    From what I just read on HSPF a heat pump can deliver 1.5 to 3 times heat energy to the building than the electricity it consumes. What were you told?
  • Mark N
    Mark N Member Posts: 1,115
    How many kilowatts will the unit use to supply 100,000 btu's per hour?
  • agurkas
    agurkas Member Posts: 238
    I think HSPF translates to roughly 2.6COP
  • Bug512
    Bug512 Member Posts: 52
    30 cents a kw ! WOW Where are you located ?
    Gene in Northern NJ
    NJ HVACR License 19HC00537600
  • agurkas
    agurkas Member Posts: 238
    I am getting two MXZ-2B20NA-1. Rated capacity at 47F is 22K BTU. If am reading spec correctly, to deliver that it need anything between 520 and 2,620Watts
    http://www.mitsubishielectric.ca/en/hvac/PDF/m-series/Cooling-Heating_MultiIndoorUnit.pdf
  • Mark N
    Mark N Member Posts: 1,115
    Use that to figure it out. I come out with $3.38 per therm for electricity if your getting 2.6 times the heat energy per kilowatt.
  • agurkas
    agurkas Member Posts: 238
    Bug512 said:

    30 cents a kw ! WOW Where are you located ?

    Well.... right now it is like 9cents for distribution and 14 cents for generation. But they are trying to get state to allow for higher rate (in MA)

  • Bug512
    Bug512 Member Posts: 52
    agurkas said:

    Bug512 said:

    30 cents a kw ! WOW Where are you located ?

    Well.... right now it is like 9cents for distribution and 14 cents for generation. But they are trying to get state to allow for higher rate (in MA)

    Ouch ! I thought NJ was high. I am at 11 cents generation / distribution.

    Here is a Fuel Cost Calculator

    I just switched to natural gas this summer and so far so good.

    For almost fourteen years I burned around four tons of coal in my Keystoker stove.

    Good luck with the splits. You will love them come summer.

    Gene in Northern NJ
    NJ HVACR License 19HC00537600
  • agurkas
    agurkas Member Posts: 238
    I am planning on installing large array of solar panels, since I have a lot of roof space, so it will really make sense to do heatpumps for heat, once I got that setup going.
  • Bug512
    Bug512 Member Posts: 52
    Have you seen the value of a SREC's ? They are in the tank compared to a couple of years ago.
    Gene in Northern NJ
    NJ HVACR License 19HC00537600
  • Mark N
    Mark N Member Posts: 1,115
    Has there been a heat loss and a heat gain calculation done to properly size the split minis? I don't know enough about them to comment on how the heat, I find my steam heat to be very economical to operate. I leave the thermostat at 1 setting from November to April.
  • agurkas
    agurkas Member Posts: 238
    Mark N,
    Yes, in order to get state rebates and incentives, you are required to do manual J

    Bug512,
    I know, but those incentives will be back. Just watch. Plus panels are getting much cheaper to make.
  • Bug512
    Bug512 Member Posts: 52
    agurkas said:

    Mark N,

    Yes, in order to get state rebates and incentives, you are required to do manual J



    Bug512,

    I know, but those incentives will be back. Just watch. Plus panels are getting much cheaper to make.

    It has nothing to do with incentives. it is what the energy markets are willing to pay the suppliers (people with panels).
    So for example I have a relative (residential) that generates around 4 SREC's a year, a couple of years ago that worth was around $2,600 ($650.00 a SREC), now since 2011 that have been around $165 (and as low as $70 !) So now beside their monthly savings their SRECS are only cashing in at around $650 a year.

    In my place of employment we have over 35,000 panels, over a year ago we would turn them off because our mainance fees were more then what we were getting back in SREC's. We can generate as much as two a day.

    I'm just saying watch the solar market. Especially with fossil fuels dropping. Dare I say we might have too much energy one day ?

    I attached the historical SREC data for Massachusetts.

    Again I think you will love your splits come summer.
    Gene in Northern NJ
    NJ HVACR License 19HC00537600
  • agurkas
    agurkas Member Posts: 238
    Bug512,
    Have couple of friends who are energy trading quants. Listening in to them about factors in play, I am not putting all my heating eggs in fossil basket. What you are seeing right now is temporary. Europe and Asia get back on growth and you will want to have other options.
    I like having hot backup of my systems.

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