20 Most Recent Mitsubishi MS-A09WA Split System Air Conditioner - Page 4 Questions & Answers

Notes: "ductless" heat pump refers to the mini-split heat pumps ASSUMPTION: You have an existing forced air system that uses a heat pump for heating and cooling and the heat pump needs to be replaced. You are trying to decide if you should simply replace the existing heat pump with a similar unit, or install a ductless mini-split system and abandon (or remove) the existing ductwork. Make sure you have addressed any deficiencies with insulation, windows and doors, etc., that have had a significant impact on your homes overall conditioning requirements prior to installing the new system. Doing this will reduce the size requirement of the new heat pump. This article includes more general suggestions for heat pump installations General:

·Ductless (vs replace existing) will probably cost more to install due to the addition refrigerant piping and electrical that goes to each indoor unit. ·Ductless systems have a substantially better efficiency vs your existing unit for several reasons such as: energy losses with the ductwork which can be up to 30%; each room is individually conditioned and has its own remote thermostat so you are not using energy where it's not needed. The thermostats are usually programmable, so you can program the system or just specific indoor units (modules) to provide minimal conditioning during unoccupied periods. ·Ductless mini-split systems are the norm in Europe where energy costs are very high. ·You'll need a separate indoor modules in each room that you want conditioned, unless rooms have significant openings between them. ·One downside to ductless systems that is usually overlooked or not addressed adequately by contractors is the need for fresh air into the spaces, which would normally be supplied with a ducted system via the main air handler. This is important. Your house needs an adequate supply of fresh air to ensure a healthy environment. If you decide to install the ductless system, consider retaining your existing ductwork and use this to provide a minimal amount of fresh air into the home if your house has no other means for fresh air introduction. You should evaluate this carefully. There are guidelines available for determining how much fresh air should be introduced (generally, about 20 cfm for each occupant) and exceeding this amount will place unnecessary load demands on your heat pump, especially during very low or high outside temperatures. ·I am not intimately familiar with all residential manufactures so cannot make specific recommendations. However, Mitsubishi was a pioneer in ductless systems and I believe sell far more than any other brand. Their units are virtually everywhere in Europe. In the last 5-10 years, many other HVAC manufacturers have entered the market including Trane, Carrier, Fredrich, York, etc. I have used only their commercial and industrial units, and have found them all to be relatively equal in quality. Watch for compressors that use inverter technology vs reciprocating. Inverter-type compressors are far superior in terms of longevity and energy efficiency. ·Watch the energy ratings on the units. Some jurisdictions that offer rebates/tax incentives require a certain minimum SEER rating. ·Watch carefully the length of the refrigerant pipe runs. The unit manufacturer will provide a recommended maximum length of pipe run. ·Installation is a crucial factor if going ductless mini-split. The contractor MUST be very good, or you'll have problems that could include a much-reduced system life. The refrigerant lines that run from the outdoor unit must be sized properly, plumbed perfectly (the slope of piping is crucial in refrigerant piping) and the unit commissioned properly. Choose the contractor carefully and make sure they have a history of successful installations of systems similar to the one you will install. The installation warranty (and manufacturers warranty) is important. ·It's important that the ductless system be sized appropriately. If it's too small or too large you will have problems. Air vs ground (geothermal) source heat pumps: I am not well-versed in geothermal. In general, the geothermal is superior in terms of efficiency due to the year-around constant "favorable" temperature of the heat source/heat rejection medium. However, it gets complicated when determining the cost/benefit due to several major variables and the relatively high cost of installation (significant costs due to excavation and underground piping). A consultant is probably needed if you get serious about it. Here's a few things to consider:
·Soil type is important. Some soils provide better heat transfer than others, and the length of the underground pipe run depends on this variable. Also, the longer the underground pipe runs, the less efficient the system is. ·The presence/lack of water has a major influence on length of underground piping. I would imagine that a home located in an area with a very high water table would have a huge benefit over a dry soil location. I love the concept of geothermal, but it's an option that needs careful analysis. It isn't used very much, so there are probably good reasons for staying with air source.