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Thread: Old Heat Pump - New Options??

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    DIY Member devans175's Avatar
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    Default Old Heat Pump - New Options??

    I live in Maryland. I own a large rancher. Most of the main floor is heated by a hot water boiler. I also have a 12x30 addition that is heated and cooled by a heat pump. The heat pump also has a 10 inch return and 2 6 inch supply ducts running to the basement. This set-up has done a good job thus far of cooling these areas and removing humidity from my basement. My complaints are, like most people I talk to, I hate the heat pump for heating. It's noisy, uncomfortable and expensive!! It's really old and I think the fan went bad before I left home this past summer for Afghanistan (I'm in the Air Force).

    Are newer heat pumps any better than the 10-15 year old "Comfort Maker" that I've got? If I do replace it with a new, high efficiency model (should I), what are some low cost, yet efficient means to add supplemental heat to the rooms when the temps drop? I was thinking of adding some electric baseboard heat, but I can't get a feel for how efficient they are compared to the heat pump. Does this make sense? I'd love sume ideas from you all before I search for contractors when I get home next month!!!

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    Retired Defense Industry Engineer jadnashua's Avatar
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    A heat pump is generally in the order of 2-3x better at generating heat than a straight electric baseboard heater...IOW, for 1Kw to run the pump, you get the equivalent of 2-3Kw of heat out from the heat it can extract from the air (or ground or water, depending on the type of heat pump).

    The fan speed used for cooling may often be to high for comfortable heating, adding to the noise, and preventing the air from warming as much as required to feel good coming out of the ducts.

    You might consider one of the newer split systems which are both quiet and efficient.
    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 devans175's Avatar
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    I'm familiar with the split units, I like them and I will definitly consider them. The one place I think they fall short is that they don't move the air around as much. I like the idea of turning the air over in the basement, which is all below grade.

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    Plumber jimbo's Avatar
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    Your old unit is at best 10 SEER. A newer unit will be 13 SEER minimum, and 14 to 20 SEER are available. A heat pump is the least expensive heat often, but is not always a "comfortable" heat.

    To upgrade to a new Heat Pump, you will have to also replace the indoor air handler, as a proper ARI match probably cannot be achieved...meaning you won't be able to set subcool for proper operation.

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    DIY Member devans175's Avatar
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    I was afraid of that. It's probably best to replace them both anyway. The old system was put together pretty pooly. If I do go with the heat pump option, is there a good option for suplemental heat.. is there such a thing as a "High Efficiency" electric baseboard?

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    Plumber jimbo's Avatar
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    Quote Originally Posted by devans175 View Post
    .. is there such a thing as a "High Efficiency" electric baseboard?
    Electric heat is virtually 100% efficient....all the KW are converted directly to heat. It is just that electricity is so costly compared to nat gas, or even oil.

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    In the trades Dana's Avatar
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    Combining the heating & cooling functions with a ventilation function may save something on up front cost, but isn't always rational and costs more to run over time. If the basement and addition are basically two relatively open spaces you can heat & cool/dehumidify them with a 2-head ductless at extremely high efficiency and low noise. Ducted air heating & cooling systems exchange the air, sure, but they also drive outdoor air infiltration at uncontrolled rates, which adds to the heating & cooling loads.

    Ventilating with an energy recovery ventilation system (with it's own small diameter ducts) is a lot quieter and guaranteed more effective way to remove indoor air pollution. In most homes a complete whole-house ERV system will run $2-4K- not free, but the difference in air quality in the home is almost immediately noticeable, and if properly installed as a balanced system, only moves air through the heat exchanger, not random leakage places in the house the way unbalanced and leaky ducted heating/cooling systems do. The sizing of your existing ducts may be amenable to using them for the ERV, with adjustments.

    In a MD location a good inverter-drive ductless will have average a coefficient of performance over 3, (maybe over 3.5) during the heating season, and may be cheaper than running a gas fired boiler (depending on your actual gas and electric rates.)

    There is no such thing as a high efficiency electric baseboard. They all run at a 100% (COP=1). A ductless will use less than 1/3 the amount of power. Your existing heat pump may be only averaging a COP of 1.5 in a sub-optimal implementation, and it's more than likely not well balanced in heating mode between the basement and the above grade addition. With a 2- head ductless you could zone the basement and addition separately, and you may be over-heating the basement much of the time on a single-zoned system, since the heat loss characteristics are so dramatically different from above-grade rooms.

    You could just ventilate the basement as part of the ERV system, and use a room-dehumidifier if it's ever necessary, leaving the basement only semi-conditioned, and go with a much cheaper single-head ductless. A 3/4 ton or 1-ton single-head ductless mini-split can run under $2K as a DIY install, under $3.5K if you hire a pro, and is probably sufficiently sized for the task. (There are people who heat their whole house with a 1-ton mini-split in comparable climates to yours, but it really depends on how the addition is built.)

    Oversizing a ductless by more than 50% for the actual loads isn't advisable since it'll lose efficiency to cycling and they'll be louder, but at 1.25 oversizing they do quite well, since they modulate with load and run every long cycles a very low compressor and blower speeds, and very low power. To get the most out of them you "set and forget" the temperature rather than turning them off or setting back, since they would have to run at higher speed/lower efficiency on the recovery ramps, using more net power than the savings from an overnight setback. Heating with ductless is nice- very comfortable. Once you've done it you'd never go back to a ducted air source heat pump solution (except maybe the best-in-class fully modulating versions.)

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