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  1. #14
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,346
    Minisplit heat pumps are available.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  2. #15
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by soylentgreen View Post
    No, but that's because you left out 80% of our electricity usage!

    My Math:
    The PV system will be about $19k after rebates & tax credit, and should generate 7800 KWH/year. Our average utility bill with electric car usage and (estimated) heat pump usage will be about $150/month. PV system + Heat Pump should knock that down to about $15/month (mainly natural gas for the clothes dryer and water heater). So the savings is something like $130/month or about $1500/year. This implies a 12 year payback on the system. I've run the numbers, and you can make this payback period go up or down substantially depending on the values you plug in for cost-of-money vs. expected increases in electricity and gas prices, and estimates of how much more electricity we will use - we have one electric car but only drive a few days a week on average. So overall I'm pretty confident the PV system, as a pure investment, ranges from "mildly bad" to "screaming great!" depending on the assumptions one uses.

    I'm intentionally not including the cost of the heat pump, but I'm not sure it's fair to include that entirely in the calculation, since (A) our furnace is 25 years old and probably needs replacing soon anyway, and (B) there will be a substantial quality-of-life increase.
    See what I mean now?

  3. #16
    Quote Originally Posted by Tommy knocker View Post
    See what I mean now?
    Tommy, I've asked the moderators to look into your posts, as so far you've been 100% snark and 0% content. I'm happy to entertain a strong disagreement if you bring facts and data, or even if it's just plain old crusty old-fart opinions to the table.

    But you are just doing content-free sniping here. I'd expect better on a "professionals-only" forum.

    I would love for you to explain what you think, and why you think it. I'm here to learn.

  4. #17
    Quote Originally Posted by Shophound View Post
    Minisplit heat pumps are available.
    I thought that all minisplits were heat pumps... am I misunderstanding something? Are there non-heatpump minisplits?

  5. #18
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295

    Thumbs up

    Several alternatives exist in the mini-split area.

    For example,
    two of Several Mfgs,


    http://us.sanyo.com/HVAC-Multi-Split-Systems

    http://catalog.mitsubishipro.com/cat...s-heat-pumps-2
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  6. #19
    Quote Originally Posted by dan sw fl View Post
    Several alternatives exist in the mini-split area.
    For example,
    two of Several Mfgs,
    Ok, I think I understand my confusion : although technically all Air conditioners are "heat pumps" in the thermodynamic sense, in the industry the terms have special meanings, e.g.
    • "Heat Pump" : a heat pump that works in both cooling and heating modes
    • "Air Conditioner" : a heat pump that works only in cooling mode.

    (which brings up the question: is there a "heat pump" that only works in heating mode? If so, what would that be called? Off topic I know...)

    Now I think I understand Shophound's original comment - they meant that I could use a minisplit for heating, not just cooling.

    I agree, and it's a good comment, though in this house the office is upstairs, so I think in the winter a minisplit used for heating wouldn't do a good job of heating the whole house. I suppose that might be workable - just heat the office during the day and leave the downstairs unheated.

  7. #20
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by soylentgreen View Post
    Tommy, I've asked the moderators to look into your posts, as so far you've been 100% snark and 0% content. I'm happy to entertain a strong disagreement if you bring facts and data, or even if it's just plain old crusty old-fart opinions to the table.

    But you are just doing content-free sniping here. I'd expect better on a "professionals-only" forum.

    I would love for you to explain what you think, and why you think it. I'm here to learn.
    Ok. My professional opinion is its a waste of money, the solar thing. Your #s may be good, didn't actually look, in a perfect world where stuff don't break. In my opinion your probably closer to 20 years on the ROR. Now you will disagree and though out a bunch of previously researched data you have there in front of you. My point was it seems you already have the data and made your decision. And I doubt anyone here is going to change your mind.

  8. #21
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,290
    Another thing to consider is going all electric and dropping the monthly gas meter fee. In our area it's $28/month just for the meter to sit there no matter if you are using gas or not. We need to save $336/yr by using gas vs. electric before the meter pays for itself. For us we have almost everything gas, because once you pay the meter fees, the gas itself is relatively cheap. If we had electric or heat pump heat the gas meter fees wouldn't be justified.

  9. #22
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,179
    Quote Originally Posted by Tommy knocker View Post
    Probably don't matter what we tell ya. You got it all figured out.
    Let's keep it professional. This wasn't called for.

  10. #23
    Quote Originally Posted by Tommy knocker View Post
    Ok. My professional opinion is its a waste of money, the solar thing. Your #s may be good, didn't actually look, in a perfect world where stuff don't break. In my opinion your probably closer to 20 years on the ROR. Now you will disagree and though out a bunch of previously researched data you have there in front of you. My point was it seems you already have the data and made your decision. And I doubt anyone here is going to change your mind.
    Ok, fair enough and thanks for clarifying that. How about we agree to disagree on the question of Solar panels?

    What I really came here for was advice on HVAC, specifically whether a heat pump makes sense in a mild climate like San Diego, and if there are any things to look out for, whether my calculations of converting Therms to BTUs to KWh etc. are in the ballpark, stuff like that.

  11. #24
    Quote Originally Posted by 54regcab View Post
    Another thing to consider is going all electric and dropping the monthly gas meter fee. In our area it's $28/month just for the meter to sit there no matter if you are using gas or not. We need to save $336/yr by using gas vs. electric before the meter pays for itself. For us we have almost everything gas, because once you pay the meter fees, the gas itself is relatively cheap. If we had electric or heat pump heat the gas meter fees wouldn't be justified.
    Ouch, sounds like you all in OK are getting the raw end of that deal! Here in California, in SDGE territory at lest as far as I can tell there's no "meter fee" at all. For gas I get billed per therm (11 therms for $10.44 last month). On the electric side, it's not so clear on the bill, but I see one source saying it's only a few dollars per month minimum billing.

    As for the future, anything's possible - they could change the rules, and the prices of Gas and Electricity could change. As you may have heard, our local Nuke plant (San Onofre) is having a bit of bother in the "series of tubes" and may or may not reopen. I understand that we are pretty close to an all-time low in natural gas pricing, too. Long-term, I can see the advantage of keeping the ability to use either gas or electricity as the market changes.

  12. #25
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by soylentgreen View Post
    Ok, fair enough and thanks for clarifying that. How about we agree to disagree on the question of Solar panels?

    What I really came here for was advice on HVAC, specifically whether a heat pump makes sense in a mild climate like San Diego, and if there are any things to look out for, whether my calculations of converting Therms to BTUs to KWh etc. are in the ballpark, stuff like that.
    Yes. A heat pump would work very well in the moderate climate.

  13. #26
    Join Date
    Mar 2010
    Location
    Morgan Hill Ca.
    Posts
    1,219
    Just curious if you have had anybody look into potentially going air to water?

    Radiant heat in the floors and heat pump generated domestic hot water..... You could still use water in a small air handler for heating and cooling also.

    I love cooking with natural gas, but some of the induction stoves that have come out lately are off the hook cool.

    Have you checked out these guys? Sun Run http://www.sunrunhome.com/?_nw=googl...FY6DQgodG1UAkA

    Curious to see how this thread progresses, I am somewhat in the middle of coming up with plans for an off the grid "forever house" and have looked into some systems that have me more than a little motivated.

    Good luck
    If a day goes by and you have learned nothing, I hope you got a lot of sleep.

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