talk to me about multi-split ductless heat pumps or alt heating
Shauna Black
last year
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Charles Ross Homes
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split-ductless heat pump question
Comments (4)"the overall unit would cost less not being a heat pump model" true, buy only very slightly. The heat pump version costs around $250 more than the cooling version. The amount of savings on your electrical bill will pay this back in a couple of months. "easier to install because its not a heat pump" completely not true. There is no difference between installing a mini-split heat pump and a cooling only one. In a traditional ducted system, the heat pump does require extra wires to be hooked up, but even that really isn't too difficult. "it would be a project that you could probably do yourself" not really for either straight cool or heat pump. You need to have a vaccuum pump to evacuate the lineset/evaporator, guages to check the pressures, and possibly extra refrigerant if the included amount is not correct. To the OP: Get a unit with an Inverter compressor. Such as the MSZ-XX-NA line. They heat better at colder temperatures. They are also very efficient. Heating at 47 degrees will cost 3.3 to 3.7 times less than baseboard, and heating at 17 will cost 2.5 times less than baseboard. For example, the MSZ-09NA modulates from 5500 BTU to 9000 BTU in cooling, 5200 BTU to 12600 BTU in heating at 47 degrees, and 7700 BTU in heating at 17 degrees. You will have to keep the baseboard for supplemental heat when the heat pump can't keep up on really cold days, however the electrical savings when the heat pump is running on the 30 degree days that are majority of the winter season will be substantial....See MoreMini-Split Heat Pump for Basement Condo?
Comments (7)First off, 4 stories sounds like a big vertical head for residential mini-split equipment just from my casual notice of those requirements. I would check that out first. I am testing a whole-house mini-split installation right now (Mitsubishi, 7 in, 3 out). I will let you know in a year or so if I like it ;-) On paper they are more efficient due to inherent efficiency and the inherent zoned nature. We have been having pretty hot weather and with my wife out of town this week, I have been pretty much been cooling the bedroom and the kitchen with some intermittent cooling in the utility room where the exercise machine lives. Note that I am not much of a sit and watch TV type. You are really a leg-up over lots of others on this decision as you have experienced mini-splits. One thing to think about is that, IIRC, most of them don't have back-up heat so you will not have any heat while they are defrosting. (Maybe none of them have electric resistance back-up, but I think I ran across at least one brand that does.) You also have to pay close attention to cold weather performance for the mid-Atlantic region. I know that with Mitsubishi's current residential equipment, the 1:1 systems have better low temp performance than the multi-splits. They are more efficient too. Even if they do have back-up heat, you can kill the efficiency pretty fast if you need back-up very often. Keep in mind that there are lots of options to the wall-hung indoor units. They cost more, but there are units that can be dropped into ceilings and others that sit on the floor. There are also short, ducted units that would solve that big room problem by splitting the supply and return. (You could also install more than one indoor unit/room.) Condensate needs to be dealt with using pumps. I am not an HVAC or building pro, so take my observations with a grain of salt. After replacing a ducted system with mini-splits, and talking to my install guys a lot, here are some observations and conclusions. Installing a mini-split through outside walls, as is it usually promoted, is pretty quick and straightforward (read fast and cheap) compared to installing a new duct system in an existing house with no central AC. My install was done through interior walls running the lines/cables under the raised house and out to the side which was much more complicated. If I were doing this over and I had a good duct system within a house envelope, I would stick with it. The trouble is, what is a good duct system? More often than not, they are outside of the living space. In addition, they are considered good when they leak 5% of the air and they only get worse as they age. My system was in the attic with parts of the duct system in the attic and partly in a furred-down space over the hallway. The worst part was one duct that started at the AH in the attic, dropped down under the house in a chase and ran for about 30 feet before it reached the first floor register in an addition with a flat roof (thus no attic). It then reduced in size and ran another 25 feet under the house. That part might have been mini-splitted even if the rest of the house retained a ducted system. By your description, your duct system was not installed very well, but if the design is sound, it could be revamped less expensively than installing minis. In general, I think that ducted systems are trickier to design and install than mini-splits so there is more tolerance for less than careful and knowledgeable installers with mini-splits. Due to their ability to handle variable loads, choosing the right size is not as critical either. (I had 4 tons cooling plus a gas furnace before, now I have about 106% of the cooling and 60% of the heating. The heating was way oversized.) My system will handle cooling fine with the house the way it is, but I should not have trouble after I make improvements to limit infiltration and add insulation. My installer is knowledgeable, smart, very workmanlike, and experienced (he has taught the trade for 30 years). He would have installed new ducts and a two-speed system for a slightly lower price than the chosen mini-split equipment. I doubt that he would do it for the same price if doing it on a similar home going through interior walls. He did not have much mini-split experience and brought in a collaborator that does, on this project because he was looking forward to a learning experience. I don't think that he lost his shirt, but I don't think he made as much as he usually does....See Morenew natural gas furnace or mini ductless heat pump?
Comments (10)You are right on the cusp with a 20 yr old gas furnace of when the codes changedand the requirement of all gas equipment was for a minimum of 78% efficiency. That was '93. The question is, is yours one of the newer units or did they put in the older style. If the older, then you may be looking at a 60% efficient unit. Also, those being new designs there were some problems with those "new" units at the time. l guess after 20 yrs we can call your ok;) Although the previous owners remodeled I would make my mshp/furnace decision almost solely on the condition of the duct system. You need to have it pressure tested for leakage. Google "doeductleakage" to see what I am talking about. If the duct system passes muster then the new furnace is a choice. If it doesn't then it is not. It is not worth spending the money to repair it. I pulled all my ductowrk out and went mshp and Rinnai Energysaver (all Net to the space heating/cooling with no duct or duct losses) As a result, with the elimination of the ductwork I found two good size closets and a large storage area under the stairs and we are very comfortable....See MoreDuct Heat Pump vs Mini-split and in-floor electrical
Comments (9)Jsbjab118, Congratulations on having started your build - exciting and stressful times! We will be building in the Truro area. House likely to be 1 and 1/2 storey with about 1400 sq feet on the main floor, built on a slab, no basement. The builder who recommended the electric infloor suggested using that in the slab, with either electric baseboard or a minisplit upstairs. Although he said we could do infloor upstairs also, in a layer of mud. In our current house we use geothermal and haven't totally ruled that out. I don't think we have much need for air conditioning, just a few weeks of the year. We will face southeast. Too many decisions! Good luck with your build....See MoreShauna Black
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