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Thread: Reliable heat pump water heater?

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    DIY Member MushCreek's Avatar
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    Default Reliable heat pump water heater?

    Does anyone know of a reliable heat pump water heater?

    These things sound like a dream come true- use the ambient heat to make hot water. Payback is as little as 2-3 years. Our basement would be ideal, with temps ranging from 60-80 degrees year-round. The problem is that the reviews are dismal. I almost bought one at Home Depot that was marked down to half price, but when I researched them, it sounds like the failure rate is very high. I'm building a new house, and need to make the WH purchase within a couple months. Perhaps I should just install a cheap conventional unit until the quality comes up?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    For simplicity, an electric WH is by far the simplest unit you can buy...now, that may be the most expensive option to run. NG, should you have it available, is usually much more energy efficient than straight electric. A heat pump could be the most efficient, but with the upfront costs and added complexity, it may not be the best in the long-term.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member MushCreek's Avatar
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    Natural Gas is not available here. It's a little frustrating that I'm building an ICF home with R-25 walls, R-49 ceiling, ductless A/C, good windows, and LED lighting, but I still have to heat water the old-fashioned way. I'm not gonna be a guinea pig- I'll install a cheap standard unit, and wait for the technology to catch up. DHW will be my biggest energy usage, I guess. I might play around with a home made solar unit to at least augment the electric unit.

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    In the trades Dana's Avatar
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    Quote Originally Posted by MushCreek View Post
    Natural Gas is not available here. It's a little frustrating that I'm building an ICF home with R-25 walls, R-49 ceiling, ductless A/C, good windows, and LED lighting, but I still have to heat water the old-fashioned way. I'm not gonna be a guinea pig- I'll install a cheap standard unit, and wait for the technology to catch up. DHW will be my biggest energy usage, I guess. I might play around with a home made solar unit to at least augment the electric unit.
    The ROI on heat pump water heaters in an SC climate goes beyond mere hot water heating, since for half the year (or more) it's doing double-duty as a dehumidifier/air-conditioner. In tight higher-R houses the sensible cooling load is often much reduces (provided you don't screw up the window placement & type), but you'll still have a substantial latent load, much of which can be handled by a heat pump water heater.

    But you may also be able to take advantage of your other HVAC equipment and equal or better ROI than a heat pump water heater, depending on how you intend to heat/cool/dehumidify the place.

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    DIY Member MushCreek's Avatar
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    That's why I wanted one; it seemed like a good fit in an insulated basement. The only ones I've found so far with good reliability are like $3000. That's a little out of my budget. A/C and heat will be a ductless mini-split unit. I'm still undecided on whether to put two heads on one, or have two separate units.

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    In the trades Dana's Avatar
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    You tend to get higher efficiency out of separate mini-splits than a 2-head multi, as long as they are reasonably well matched to their peak loads, and cost-wise it's often a wash. At 3 heads or more it'll usually be cheaper to go multi-split, with a small hit in average efficiency.

    Daikin will soon be marketing a fully split hot water heater in the Australian market, and they've been selling smaller versions in China for a few years now (don't have much details), and were one of the EcoCute (CO-2 refrigerant) split water heater developers in Japan. Their hydronic-output Altherma space heating + hot water heat pump (uses a mini-split compressor) might work for you, but it's probably not going to meet your budget.

    The in-situ tested savings of a heat pump water heater is only in the 20-35% range (see the slide on p.12 ), when only looking at the hot water heating aspects. If you have a full basement or the shower is on the second floor, you can get comparable savings out of a highly reliable and long-lived drainwater heat recovery heat exchanger, but it won't buy you anything on tub fills, only showers, and it won't be lowering your latent cooling load. But if you're a showering family heating hot water with resistance electricity, it still has a reasonable payback period- the fattest & tallest that fits is worth the upcharge, since efficiency increases with total surface areas.

    To date most of the tank-top heat pump water heaters use noise reciprocating compressors and noisier than necessary fans. My understanding is that the Daikin split hot water heaters (even the EcoCute) use variable speed scroll compressors and variable speed blowers, making them one the quietest in the bunch. Both Sanyo and Daikin have CO2 refrigerant space heating products out there now too, but none of the residiential scale versions are available in the US (yet.) As a refrigerant CO2 is a lot greener than R410A, since it's global warming potential (GWP) is only 1 x CO2 (strangely :-) ), while R410A is a whopping ~1700 x CO2, thus even small refrigerant leaks have consequences, even if its ozone depletion factor is zero.

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    DIY Junior Member floydo's Avatar
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    We bought a GEH50DEEDXX model from Lowes several months ago (cost with fed and utility rebates was simply the sales tax - wow!). These are simply a electric water heater with a heat pump on top. They can be run in water heater only, hybrid, heat pump, etc mode, so reliability for hot water is should be no different than a elect water heater.
    So far it works very well, the current model has a different heat pump heat exchanger (addressing the issue of leaky solder joints of an earlier model per GE). The fan is a bit noisy and is really "inexpensive" in terms of noise design.
    The benefit is realized if the heater is in an unconditioned part of the house (basement here is great). As stated above it dehumidifies the area which is great. So in PacNW, and the Southeast it would be a good choice.

    So in terms of reliability time will tell, and GE may have addressed earlier problems; and with a 10yr parts warranty along with all the rebates out there for the appropriate installation it can be great......

    http://products.geappliances.com/App..._Water_Heaters
    Last edited by Terry; 06-19-2013 at 09:46 AM. Reason: added link

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    In the trades Dana's Avatar
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    floydo: Where do you think the heat getting pumped into the water is coming from in that "unconditioned" basement?

    Unless your basement is so well insulated and air tight from the fully-conditioned space, it's coming from... the conditioned space (or at least mostly.) Subsoil temps WA are in the low 50s F, and unless your basement is actually at or below those temps, it's being heated by the conditioned space.



    If your furnace/ducts/boiler are uninsulated in the basement keeping the basement above those temps, that "waste" heat is heat that actually would have accrued to the conditioned space, were the hot water heater not sucking the temp down even lower. While the lowered basement temp due to the water heater reduces the heat loss out of an uninsulated foundation, it increased the heat loss from the first-floor floor into the basement. Is that really what you want?

    These beasts are best suited to areas with substantial cooling loads for at least half the year. In heating dominated regions like WA/OR about half the heat going into the hot water is coming from your space heating, at whatever fuel price/efficiency that system is running. You can't cheat the laws of thermodynamics- the portion of the heat being sucked out of the air has to come FROM somewhere, and if it's located inside the thermal & pressure boundary of the house, most of that heat is coming from conditioned space, and represents a space heating load.

    If it's out in an uninsulated garage rather than a basement it's taking it's heat primarily from the outdoors, but there may be periods in a NW winter when the garage is below the efficient operating temp (or even absolute operating temp) of the heat pump water heater. This would be less of an issue west of the Cascades than it is in the higher/drier/cooler eastern slope.

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