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minisplit ductless heat pump

Post in 'DIY and General non-hearth advice' started by Highbeam, Feb 6, 2013.

  1. brogsie

    brogsie Feeling the Heat

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    Highbeam,
    I just installed a Fujitsu 18,000 with a 9,000 and a 7,000 inverters. I'm a general contractor so I have all tools and experience for most of the install. I ran the line sets, drain lines and the wiring between outside and inside units. Had my electrician tie into the panel. Had HVAC contractor do the line set connections and start up. Pretty easy to do even the electric and HVAC is easy. I didn't have the tool to vacuum out the line sets. The heating is great and seems pretty economical so far. I put the interior units on inside walls down to the basement to outside. It's very quiet and not so bad looking. I found a site that was helpful. I will pass it on..
    velvetfoot likes this.

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  2. brogsie

    brogsie Feeling the Heat

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  3. brogsie

    brogsie Feeling the Heat

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  4. baratta930

    baratta930 New Member

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    I bought a Klimaire inverter based unit (from heatandcool.com) for a studio I built for my wife. I partially installed it myself and then had a local hvac company do the final. It's a gimmick because they sell them as complete self install kits but no warranty if you self install them ... they did say that if the HVAC guys did the final hook ups and "approved" the install then it would have full warranty.

    It's a really nice unit and came well packaged. The copper lines are a little thin but no worse than the name brand units (according to the HVAC guys). It's supposed to work down to 5 deg F, I haven't tested that but it has worked well into the low teens without issue. It barely runs to heat the space (the inverter tech is pretty nice but I don't know if it's worth the price difference). The space has 3 inches of closed cell foam in the walls, with more in the ceiling and an insulated slab so it really doesn't take much to heat the space.

    The Klimaire units are from China and apparently they make some of the Japanese models now. I have family in Montreal, Canada that has used Klimaire for years without issue. I figure if it's good enough for Canadian winters, it's good enough for me :)

    Hope this helps ...

    Berardino
  5. eclecticcottage

    eclecticcottage Minister of Fire

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    Interesting..I wish we would get rebates for stuff like that around here.
  6. pen

    pen There are some who call me...mod. Staff Member

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    Just received confirmation this week from our electric company that we would should be looking for the $400 rebate check in the mail any day. Filled the paperwork out with them in July, guess they weren't real anxious to pay.

    Our Jan and Feb electric bill average out to 139 dollars each month. I have kept the heat pump at about 65 degrees full time, and bumped it up when things were really cold and the wood stove couldn't keep up w/out having to be run full boar so that the house stayed at 68.

    Had I run one 6 foot electric baseboard at about 1/3 as supplement for 1 week each month (which I used to do in the coldest weather), our electric bill would have been higher.

    So far, I'm impressed with everything except for the automatic fan (but I think I mentioned that already).

    In all, I figure it's been costing us about 12 dollars a month for Dec, Jan, and Feb and cost us about 15 a month in July and August last summer. Small price to pay for what I've been getting.

    pen
  7. begreen

    begreen Mooderator Staff Member

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    Awesome pen! That's better than I expected for your climate zone. Thanks for the update.
  8. pen

    pen There are some who call me...mod. Staff Member

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    I'm extremely happy. The house is warmer than it's ever been on average on the winter, and it's costing us less than it used to monthly. The wood stove caries the vast majority of the load but it can't warm the house up from 60 as quick as the fisher could so I try not to let it get that cold and supplement when real winter sets in. At such a small amount of cost, and being less than what I used to pay to supplement at a lower average temp, I couldn't be more pleased.

    In the summer, our house never used to be cooled and would simply get miserable/unbearable. Now, part of the reason it's only costing 15 bux to cool the house is that while the heat pump is running and obviously cooling, it's removing the moisture from the air and the dehumidifier in the basement is hardly running at all, where it used to run solid all summer long, just adding to the heat problem.

    For us, it was a perfect fit.

    pen
  9. Highbeam

    Highbeam Minister of Fire

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    To be fair, I am currently spending nothing on my mini split. Both Pen and I burn wood for heat. If Pen was using the mini for full heating then it would of course be higher.

    Gotta admit, the cooling would be nice for about a week in the summer.
  10. begreen

    begreen Mooderator Staff Member

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    I think you will find the cost of running that unit will be surprisingly low. Have a friend down the road that I recommended getting a mini-split system. He ended up with a Fujitsu 3 ton with 2 head units. He is almost out of wood this year and running about 80% on the Fujitsu with the house at 70. He only lights fires on some weekends. His 1900 sq ft house is leaky and has giant windows facing north. So far the worst monthly electric bill was about $140. He has to buy his wood. At local price of $250/cord, that is much cheaper than wood heating for him. Needless to say, he loves it.
  11. Highbeam

    Highbeam Minister of Fire

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    That is awesome. We had a decent cold snap this year too.
  12. pen

    pen There are some who call me...mod. Staff Member

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    On two nights we went below 0::Fby a few degrees I did a small fire, just enough to still have a few coals in the morning for the overnight load and set the heat pump to 69 to see what it could do. Woke up to a 69 degree house. By early morning, the heat pump would have been carrying the vast majority of the load.

    I was very impressed.

    pen
  13. semipro

    semipro Minister of Fire

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    So what is it about mini-splits that makes them so darned efficient when compared to standard central HVAC systems?
    The rave reviews here and elsewhere have me considering installing one in our master bed/bath area. We can handle the temp extremes elsewhere in the house.
  14. Highbeam

    Highbeam Minister of Fire

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    One thing is the variable speed inverter motors. A regular heat pump is usually one or two speeds so it is generally working too hard where the variable speed can constantly run at the proper output to maintain a temperature. Think of it like city driving vs. freeway driving and the mpg effects on your car.

    The other is duct losses. Your central system loses 15-30% of the energy through duct losses.

    I think that the manufacturers of the central units should be ashamed of themselves for not making improvements to the evaporator/condensor/blower that fully utilize the improvements that the minisplit market has pioneered. Duct losses are not their fault.
    pen likes this.
  15. woodgeek

    woodgeek Minister of Fire

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    Highbeam is right.....the major thing is variable speed. Duct losses are avoidable with conventional split systems (but often are a problem anyway). The blower on my split ASHP uses 500W...all that ends up as heat in my conditioned space, but it reduces COP by 10% or so.

    One other thing is defrost....the mini's don't call a honking big resistive element during defrost, and (I think) many have smarter defrost controls. The way mine (non-mini) was set up, the defrost was killing the COP, from 2.7 to ~1.6 at temps near freezing. I rejiggered the control myself, and got it back to 2.2-2.3.
  16. semipro

    semipro Minister of Fire

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    I think I recall someone reporting that the defrost mode on their mini-split was just the system running in cooling mode for a short time.
    woodgeek likes this.
  17. RustyShackleford

    RustyShackleford Minister of Fire

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    How's that ? You mean by obsessively careful attention to sealing with mastic etc ? Even so, the insulation on flexduct ain't that great, plus it seems to be compomised a lot by being compressed in bends and by hanging materials. I think the only way to really minimize the losses is with the encapsulated crawlspace approach - so the temperature on the outside of the ductwork is much higher - and that seems to be one of the most compelling reasons (for closed crawlspace).
    You're empirically measuring your COP ?!? Cool-o. How ? I'd love to do that.
  18. begreen

    begreen Mooderator Staff Member

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    Great duct sealing, good trunk ducts and plenum insulation and high grade flex duct insulation all help, a lot. This can be measured by checking the heat loss. Compare the temp at the plenum or closest outlet vs the farthest run. Ours used to be be horrendous. Now it is pretty good, though I don't remember the numbers. Running the ductwork through a conditioned space also helps keep duct loss down.
  19. velvetfoot

    velvetfoot Minister of Fire

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    woodgeek likes this.
  20. woodgeek

    woodgeek Minister of Fire

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    As BG said, with short R-8 flex, thick FG blankets over the trunks, and careful airsealing (a PITA) duct losses (conduction and leakage) can be <=5%. Not a deal breaker.

    running geek flag up pole.....

    If you know your BTU/h load versus outdoor temp, and log your HP run hours, you can estimate its BTU output per hour at different temps. If you measure its power consumption (e.g. with a home energy monitor), you can compute your COP from (kBTU/kWh)/3.414. Quite tedious, but if you are logging the data anyways, not that hard to sit down and bang out. You need to use a second heater (e.g. resistive aux) with known output to get BTU loads. Switching to aux (emergency mode) for a few selected days to get data costs money.

    In practice, I do it the other way.... The module COP, BTU and kW versus outdoor temp are tabulated by the mfr, (using an ASHRAE standard test regimen). You can also check the kW in the table and for the blower while you are at it. The table does NOT include blower power in the kW or those BTUs, as far as I can tell. On a spreadsheet, you can predict HP run hours versus outdoor temp from the tabulated BTU numbers, and the daily run hour log matches the model when defrost is not active. Data is noisy, you need to throw out very windy days, etc, but the model matches.

    During typical 'dry' defrost conditions, the unit runs ~18% more than the model prediction, suggesting COP is reduced by 1-1/1.18 = 15%. Under 'heavy frost' or wet snow conditions, it has to run close to 50% more, suggesting a 33% reduction in COP. Before I rejiggered the defrost control, the COP hit was closer to 40% under dry conditions! At 30°F and dry, I would have had COP=1.5 as installed. Now it is 2.1-2.2 or so.
  21. RustyShackleford

    RustyShackleford Minister of Fire

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    Ah well, I'm going with encapsulated crawlspace, for a variety of reasons. Chief might be moisture, here in this sub-tropical southern climate. I reckon the area of my foundation wall perimeter is about half my floor area, so with half the R-value, it's about break even. But then the obviation of duct losses is a big plus on top of that. Of course, the big unknown is that the crawlspace floor is now part of the insulation envelope. A huge plus in the summer I'm sure; dunno about winter, but summer is a bigger deal here anyhow. Mainly, I like the idea of being able to crawl around down there without fiberglass drooping on me and being able to see all the mechanicals clearly :) But I guess this is really all for another existing thread ..



    Damn, and I thought *I* was a geek. I'd love to try some of this. I like the idea of getting the btu/hr per degreeF empirically with some kind of aux heat. But my aux heat is propane, so pretty hard to measure the consumption of that, over a day'ish-long test period, with necessary accuracy.
    You talk about versus outdoor-temp, but shouldn't btu/hr per degreeF be more or less independent of outdoor temp ? I guess you mean HP performance depends on outdoor temp.
  22. woodgeek

    woodgeek Minister of Fire

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    Yep.
  23. woodgeek

    woodgeek Minister of Fire

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    You could buy a run hour timer, and attach it across blower... :p
  24. velvetfoot

    velvetfoot Minister of Fire

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    It doesn't apply to me because I have a single stage oil boiler, but, my new thermostat (that I'm still playing with)can apparently track the run times of the different stages of heating and cooling. You can either view it on a built in chart or download the data. The analyzing stuff they call Home IQ resides on the company's server. http://www.ecobee.com/solutions/home/smart-si/
  25. woodgeek

    woodgeek Minister of Fire

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    You are tempting me to switch out my nest for the EcoBee. Both multistage control and logging stink on the Nest.

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