Mini split or central air? Be gentle, I'm a newbie
pjs755
11 years ago
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tigerdunes
11 years agopjs755
11 years agoRelated Discussions
I'm so confused over Mini-Splits, Central A/C and Heat Pumps
Comments (5)heat pump, central air and heat and a mini split as far as cost of operation? heat pump same as central air and heat except that the heat pump provides the bulk of the heat. this is what I recomend to my clients based on savings compared to electric strip heat. with heat pumps the electric strip is emergency heat and for when temps are 30 degrees..which is not that often for us. central air is electric strip heating only. the most expensive way to heat your home. (espically if you have entergy for your utility provider) mini splits are pretty cool. expensive but fit a lot of needs and great for tight retrofit spots. the condensing unit goes outside like with any set up, but this is where it changes. in each room the air is provided by a wall mounted air handler unit. the condensing units are up to 3 tons. each room would have the ahu..this is what they are calling zones. cost is higher, but you don't have ductwork, so it evens out a little better. with the foam insulation & low e windows your tonnage of ac required will be less. although I don't recomend 'rule of thumb' sizing instead of the ususal 400 to 500 sq ft per ton, your house will be more in the range of 600 to 700 sq ft per ton. oversizing will cost more to operate, wear the equipment out sooner, and will NOT dehumidify. be diligent in finding out what is being spec'd for your home and what options are available for you. some systems will qualify for tax credit, and it is always a good idea to do better than the legal minimum allowed by law (code). in what part of La. are you building? best of luck....See MoreMini split vs central heat and air
Comments (9)I have no experience with heat pumps in an area that cold. I understand that they are getting better all the time, but I don't know how they will do in your coldest weather. Cost will depend a lot on how many rooms you have. If it is an open floor plan, cost will be lower. If you have lots of walls and doors, the cost will go up as the number of units increase. Ducts are bad when they are outside of the house envelope. Design your house with indoor ducts if you go that way. Ducts are bad when returns are inadequate causing pressure differentials between rooms. This, just like leaks in outdoor ducts makes an air handler into a power vent. Mini splits are inherently zoned, but what does that get you? Zoning is not going to save you that much energy with a well-insulated house. Heat transfer between rooms will be much faster than from inside to outside. Zoning for comfort and control might be worth it. I have seven mini splits inside on three systems for nearly 5 years. I live in a hot, humid environment in a home that was retrofitted with central and had ducts in the attic and crawl space. The original central system was done right with a dropped ceiling (9 to 8 foot) in the central hallway. Later is was messed up with outdoor ducts added. The mini splits perform beautifully for humidity control. Maintenance is higher with mini splits. At minimum, you need to clean filters for each unit instead of one, two or three. I am finding that maintenance of my Mitsubishi units is greater than that. Lots of dust gets stuck in the "coils" despite regular cleaning of the filters. The back side of the coils is difficult to reach if the units are near the ceiling. In addition to that, the blower cages get dirty as well. I am trying to figure out how to get the cages out to clean them without largely dissembling the whole thing. There are some characteristics of mini splits that some to not think of. Their performance measures are hard to compare to single speed central systems. My understanding is that they are locked into a constant chosen frequency (speed) and measured like that. In real operation, at low output, variable speed systems are more efficient than at high output. This can be a factor in choosing to use set backs, which can be counterproductive. My belief is that the manufacturers could fix that by allowing a set back recovery at less than 100% output with more sophisticated controls. My mini splits run very well on portable generator power. There is no start-up surge as seen with on-off units. They spool up very smoothly and slowly. If you have more than one system, you will never be totally out of heating or cooling. You might find this study useful. It was an eye-opener for me: Long-Term Monitoring of Mini-Split Ductless Heat Pumps in the Northeast Building America Report - 1407 December 2014 Kohta Ueno and Honorata Loomis...See MoreNo central air possible? Xpost w/ heating & air conditioning
Comments (5)I know nothing about why your home is not set up for central air. I can speak knowledgeably about split a/c units. We installed them when we lived in Thailand. They are remarkable, in that they usually feature a dehumidify setting, to get the moisture out without making it too cold, as well as a cooling setting. If they worked at 17 degrees from the equator during monsoon season and hot dry season they ought to work well in Washington state. We went with small units in each bedroom, so that we were only cooling the area we were in, and one larger 20kbtu unit for the entire downstairs....See MoreMini splits vs central heat/air new build
Comments (24)I'm not sure I understand how advanced you are in your planning, but some input: Ontario Hydro rates are here (may not be exactly right for where you are): http://www.ontario-hydro.com/current-rates Note the peak times change between winter and summer, and nighttime (from seven) to morning (to seven am) and weekends are all off-peak and lowest rate. Peak rate in summer is peak a/c time. So depending what your loads are, 'timing' your usage can make a big difference. Investing in some more sophisticated controls to favour using electricity at off-peak might be worthwhile, and possibly some 'heat storage' (e.g. heat your water at night, and even more complex arrangements). Since you won't have access to natural gas (the cheapest), what really makes sense is to figure out how well insulated you can make the house. The better insulated, the less need you should have for both heating and air conditioning. For southwestern ontario, depending where you are, the a/c season can be pretty short (although this year was exceptionally long), and with judicious use of ceiling fans, shade (in summer) in rooms where you spend most of your time, you may be able to get by with minimal a/c. Hydro's rates may seem pretty high but it's possible that some solar could make sense, if you can 'self-consume' all of your solar (which is always going to be at peak or mid-peak rates). (I don't know anything about feed-in tariff situation in Ontario). One comment, be cautious about putting a fireplace in the basement, draught/draw can be poor unless carefully designed. And if you go for a 'tight' house, they may recommend against wood-burning fireplaces....See Moreionized_gw
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