Mitsubishi Mini-split short-cycling
DavidR
2 years ago
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klem1
2 years agoRelated Discussions
Mini-Split Cost and Payment Question
Comments (32)Woa, Tippi, you have a serious and expensive moisture problem. It has to be leaks or infiltration of moist air. Is it very humid where you live? Do you have dry indoor air in the winter? My experience with mini splits indicates that potential and existing customers are very confused by the manufacturers' language ca. dehumidification. Yes, there is a dehumidify setting, but there is only one coil in the indoor unit. They can only be biased to water removal over cooling by running the fan at the lowest speed and keeping the coil at the lowest practical temperature. This is a very nice feature and is very effective in humidity control when only a little cooling is needed or a little can be tolerated. It is not as effective as a dedicated dehumidifier when one of those is desirable. The commercial units might have two coils in the indoor unit. I have not seen that, but I am not an HVAC pro. They'd also need two sets of lines, one for each coil. What I know they can do is cool and heat adjacent units in the same room, or in adjacent rooms at the same time with the same outdoor unit. This would be an effective dehumidification device in lieu of a dedicated dehumidifier. BTW, this link was posted in a current thread. I thought you might find it of use: Here is a link that might be useful: Roof in FLW-like house...See MoreDo mini split systems come cooling only
Comments (2)Yes, they can be had in cooling-only. I think that the heat pumps are a little more expensive than cooling only, but not much. I can not comment on the relative efficiency. The heat pumps are mechanically more complex so they have more failure modes. I have three multi outdoor units for my seven room house. The reversal valve crapped out on one of mine just before the one-year warranty date. (Note to you AC guys, it stuck in heat mode and would reverse if I tapped on the valve with the butt end of a screwdriver.) I do not think that is a big consideration, but you might want to discuss that. What is the advantage of heat pumps to you? Maybe a lot and maybe none. Do you heat with oil, gas or propane? You can compare your heating costs with your current fuel and electricity rates and decide if you want to heat with heat pumps in relatively mild, but cool, weather. There is a cut-off temp where they fail to perform well when it gets colder. You can zone your heat when you are using them, adding more economy, heating only the rooms are sitting in to comfortable temp and leaving your main t-stat set lower. (This gets a little complicated if the t-stat is in a room that you are heating with the mini split.) Tip: when heating with high wall or ceiling units, you will probably want to turn up the blower manually higher than its programmed speed to keep the heat near the floor and not accumulate near the ceiling. On the other hand, your ceiling paddle fan will take care of this as well if you have them. One thing you might want to keep in mind. I can say that the Mitsu (and perhaps all brand) multi are less efficient than the 1:1 units and they do not do as well as the single units with heating at low temperatures. For the former, I think it stems from the fact that the compressors only throttle back to a certain percentage of max. For example, a single unit might be rated at 9000 BTU. If you only need a little cooling, and assume that they throttle back to 10%, you can efficiently get 900 btu out of them running constantly with no on/off. Your tri unit is probably 22,000 btu and can throttle back to 2200 btu with the same assumption so your compressor will be flicking on and off more often which yields poorer humidity control and not as even cooling. Please, keep in mind the relative nature of my comments. These things all work really well compared to window units and compared to central forced air. Be sure to consider all of your alternatives for the installation. In addition to wall-hung, you can have floor mounted, short ducts to hidden units and ceiling-mounted. That all costs more though. You have probably seen the pictures of installations with the plumbing straight through the walls to the outside of the house. Mine are run inside the walls to underneath the house. Again it might cost you a little more, but talk about it with your contractor. You should look at the MItsubishi, Sanyo, Toshiba and perhaps, other web sites to get some more information about their equipment alternatives. Your contractor should be willing to discuss all of this at length with you since you are making a big investment. I hope they can evaluate your cut off point for economical heating with the heat pumps vs. your hydronic heat. They should be able to estimate for cooling only vs heat pumps. The price difference might be trivial, however....See MoreAny Mini-Split Brands to Avoid?
Comments (24)I realize there's a lot of love/hate perspectives based on brand, but after seeing prices of the big boys (Mitsubishi, Daikin, etc) at least 2-4x the cost of the DIY systems that have continued to get easier and easier to install and maintain it's an increasingly hard proposition to avoid modern HVAC over concerns of a $15-20k installation overhead when a comparable DIY install can be had for $5k-8k. As an example... After seeing my neighbor drop his electric bill 30-40% with a partial DIY Senville minisplit who had nothing but great things to say about it over his first two years of use, I took up his offer to help with install on 28k dual-head Senville system after extensive phone and email-based conversations with their sales teams on proper size, location, and acessories. The "trick" to ensuring your system's covered by most manufacturers' warranties (in Senville's case their 10 year warranty) is splitting out the "Bob Villa busy work" vs the professional stuff that could void a warranty or burn your house down. For example, all the interior work of drilling applicable wall holes, mounting interior head units (easier than a TV), filling those holes with foam, and installing the line set covers back to the compressor can easily be handled by anyone with even modest DIY XP. Just make sure you've measured out the total line set length, aren't crimping those metal lines, and (if you aren't comfortable with any of that) just leave any/all exterior lineset and/or cover work to the pros to run back to the compressor and cover up. Lineset covers are effectively glorified gutters: easy to install, not as easy to ensure they're not creating sharp angles or crimps in the lineset. Pro Stuff: checking system pressure, running new 220v/40amp electrical service with applicable cutoff(s), and ensuring that (even on systems that come pre-charged) that pressure is correct and the system starts, works to spec, and you have that warranty form filled out and signed by a professional that knows what they're doing. All in all I paid: $5,150: $2600 complete mini-split system w/covers (dual-head, 28k Senville SENA-30hf-d) $1200: electrician running new 220v/40a service (panel to compressor) $500: plumber connecting/testing line set pressures/operation $850: handyman mounting exterior compressor + buying/installing line set covers after factory covers were found not have necessary right angles) In just first winter heating costs dropped by 50% (prior pellet stove + electric baseboard so worst case scenario) and early spring/summer air conditioning has been even more impressive. The system's almost completely inaudible, the 2x10 house construction's transmitted zero reverberation through the walls (a common concerns for those wall-mounting their exterior compressor), and Senville's mobile app (which also works with the Midea app since apparently Senville's just a rebrand of Midea systems) allows fully remote, Alexa-compatible, and multiday schedules that are easily configured. I know all the existing professionals lament the fact that these DIY/quasi-DIY systems can disappear overnight and often won't touch them due to concern over future parts availability, but when costs compare at $5k vs $10-20k for even a modestly sized system it really calls into question how many inefficiently heated/cooled homes are left in the cold (no pun intended) over fear of extensive capital costs when systems like these can be the best of both worlds: an opportunity to work with local pros to understand how modern heat pump technology actually works, take a bit of the busy work off their plates and still make a living ensuring the more advanced work is not an unforced error on the part of the homeowner willing to exercise a bit of elbow grease to cut costs by 50-75% off traditional installations. Hope this helps....See MoreThinking about a mini-split
Comments (19)RIGHT SIZE MINI SPLIT. https://www.minisplitairconditioningsystem.org/ 9000 Btu|3/4 Ton|(under 400 Sq Feet) 12000 Btu|1 Ton|(400-600 Sq Feet) 18000 Btu|1.5 Ton|(600-800 Sq Feet) 24000 Btu|2 Ton|(800-1200 Sq Feet) 30000 Btu|2.5 Ton|(1200-1500 Sq Feet) 36000 Btu|3 Ton|(1500-1800 Sq Feet) 48000 Btu|4 Ton|(1800-2000 Sq Feet) 60000 BTU|5 TON|(OVER 2000 SQ FEET) BENEFITS OF A DUCTLESS MINI-SPLIT. https://www.airconditionersductless.com/ EASE OF INSTALLATION In most cases, you can connect the air handler with the compressor/condenser by running the electrical conduit through a three-inch hole in the wall. The outdoor unit can connect to the air handler from as far as 50 feet away, allowing you to place it in a less conspicuous area even when connecting to rooms that face the street. Also, mini-splits are ideal as a retrofit add-on for old homes without preexisting ductwork. They are increasingly being found in homes that: Have a costly heating system but no cooling option Have an outbuilding that ducts cannot reach Are located in areas with high fuel costs ZONING CAPABILITIES Chances are you need more than one room heated and cooled, and fortunately, one outdoor unit can power as many as four air handlers. You get the option of zoning, then, without the need for cumbersome ductwork, dampers, and so on. Each room, or zone, can have its own thermostat, letting you condition the air only when those rooms are occupied. There are smart thermostats available that are compatible with mini-splits. LOWER ENERGY BILLS Energy loss through ductwork accounts for more than 30% of all HVAC energy consumption, according to the Department of Energy. Mini-splits bypass this concern altogether. They also transfer heat rather than generating it through electric resistance or the burning of fuel, so they are very energy-efficient. This will translate into lower bills....See MoreDavidR
2 years agoAustin Air Companie
2 years agoDavidR
2 years agoklem1
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2 years agoKJ Sosa
2 years agoDavidR
2 years agoklem1
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2 years agolast modified: 2 years agoDavidR
2 years agoAustin Air Companie
2 years agoAustin Air Companie
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