Ductless Mini split a/c systems
Hey all. Tryin to decide on an a/c system for my house. I’m doing a roof raise and the house is now 3 stories plus the basement. I was thinking of using the ductless mini splits since they would basically zone every room and I would not have to cool the entire house all the time. I have a couple of concerns though. One is cooling areas that don’t have an indoor unit like bathrooms or hallways. Also, how efficient r they compared to traditional ducted central air. If I was to leave all the units on all the time using the thermostats in each room would it cost more than ducted units cooling the whole house. Like I said the zoning is a big plus cause the kids could each set their rooms to the temp they like but if it’s gonna cost a fortune to run then forget it. Has anyone used them for a whole house? Any advise or sharing of ur own experience is welcome. Thanks. Richie
Replies
I've installed quite a few of
I've installed quite a few of those but that was about 10 years ago so things might have changed since then.
I seem to remember that you could have only 2 evaporators (the cold part) per condensor (outside part). Uless they have increased the number of evaporators per condensor you are looking for a lot of condensors outside.
One of the big problems of ductless is that it is one thing to run the pipes and wiring to just about any location(box in) where are you going to run the condensate water that every evaporator produces? It must flow down with gravity. Water doesn't go up hill very well. Inside wall installs have this problem. An outside wall is easy.
I think they are great but we used to say they were "location specific" in that if you had a room or an area that got excessively hot where existing a/c either cool enough or physically couldn't.
3 story house to a/c is going to very expensive anyway you look at it.
Just curious, why would you want a/c in the bathroom?
roger
roger
Generally, you may find the EER/SEER lower on the small split systems, so if you cool the whole house, it will be more energy. However your concept is right ... cool only the areas you need to cool ... that would be somewhat more efficient than doing the whole house. Generally not the approach of choice for an entire house ... more like a situation where you would 'pick up a loose end' w/out upgrading your furnace or extending your ducts. What do you have on the existing house? The mini split may be your option of choice for the addition, but maybe not as a replacement for the existing central air.
Thanks guys. The existing house does not have central air. I'm doing hot water baseboard for heat and some type of a/c for the house. It's not that I want a/c in the bathrooms I just don't want them to be 95 degrees either. As far as indoor to outdoor units, now they have ones that can supply 4 indoor units with 1 outdoor unit and they have pumps that pump the condensate out of the house so you don't need gravity to do it.
there are mini splits with SEER up to 26, choose wisely....
There's only one path to
There's only one path to follow if you really want to know how/if the system will work: You must have someone who is thoroughly familiar with doing room-by-room load calculations do a load calc for the house.
But if you choose not to do that, and are content with guessing, then, by all means the mini-split with 4 cassettes will be a better choice.
1) Your 3-story house with basement will have many very incompatible spaces, that is, spaces having very different heating or cooling needs. So, having the abilily to place the cassettes where they're most needed is good.
2) A single ducted system would never handle such incompatible spaces unless you installed a zoned system, which besides being expensive, would not function at its rated efficiency anytime certain zones were closed off. You get the rated efficiency only when the airflow across the evaporative coil is high enough. This can't happen when only one zone is open, even though there is a bypass damper that allows air to short-circuit back thru the blower--the bypassed air is already chilled, and will not assist in unloading the coil.
3) Duct systems are notoriously inefficient due to leaking air and the pressure imbalances they create. A mini-split with a lower SEER rating will actually deliver that efficiency because of no duct losses, but an AC unit with a high SEER rating installed in a ducted sytem will have an actual system efficiency far less than it's rating.
It seems you know about a/c systems. What u said was my thinking as well. The first floor of the house is gonna be living room, dining room, kitchen. I can use one system with three cassettes but my concern is the 3/4 bath on that floor. Will the cool air naturally diffuse into the bath or will it be like 90 degrees in there? The second floor is 4 bedrooms and a bathroom. Again a system with 4 cassettes would do the job but will the hall and bathroom cool off or no? Finally the third floor is a workout room, office, master closet and master bath. A 3 casette unit would cool the whole thing no problem. I love the idea that I don't have to cool the whole house all the time especially the lesser used areas (office, gym,etc) but don't want to be stuck with halls and baths that are hot as sin. I also like the fact that each bedroom can be set to individual temps so the kids can keep their rooms at the temp they like.
To put your mind at ease about the baths and halls:
Think in terms of how the cooling load is generated in any house. The biggest source of heat gain is usually the windows, especially those with E or W orientation. Next come walls, ceilings and ventilation air; which is largest depends on insulation and airtightness. My point is that, probably the halls and baths have very little if any exposure to these sources of heat gain. They may well be surrounded by interior walls/ceilings of other rooms. If these other rooms are cooled, there is no significant source of heat to make the halls/baths uncomfortable.
Also, I assume the baths have exhaust fans, so that when they run, cooler and drier air will be drawn into the baths from adjacent spaces.
The top floor will probably have the greatest heat gain because of the hot attic above its ceiling, and because the warm air from lower floors will tend to drift upwards, while the cooled air of the top floor will sink, especially if there's an open stairwell connecting floors.
Is this new forum really editing things MID WORD - or is that just an assumption?
Thanks...I'm gonna go with
Thanks...I'm gonna go with the mini split. Ifound a room to room air exchanger that i'm gonna put in the 2 baths. They pull air from the conditioned room to the baths. I'm gonna put the fan on a thermostat to turn it on and off. Again thanx 4 the help.
yeah, its called the exhaust fan.
I think you worry too much.