How well do single mini-split units cool multiple rooms?

[zarandle]

Can mini-splits efficiently cool more than just the room they are installed in?

I have a 1,800 sq/ft cape with 4 rooms downstairs [1,000 sq ft] (2 bedrooms kitchen/dining, and living room) and 2 rooms upstairs [800 sq ft] (bedrooms on each end of the house).

I have explored duct vs ductless and am leaning toward fujitsu or mitsubishi mini-splits for the house. For the upstairs I am thinking a 9,000 BTU for each bedroom and downstairs I am thinking 1 15,000 BTU for the living room and 1 9,000 for one of the bedrooms.

Entire house is hardwood floors and all doors to all rooms are open 95% of the time.

I am curious as to cooling distribution/range of the unit. My concern is the room with the unit will be ice cold and the unit will shut off before the adjoining rooms are cooled. I would hate to have to install a 9,000 BTU unit in each room as I'd have way to many BTU's then I need and the units would be starting and stopping all the time.

Any experience with using strategically placed mini-splits to cool an entire house without having to install one in each room is appreciated. BTW, I'm not interested in heating just cooling as we heat the house in the winter with a soapstone wood stove :)

I live in north central Massachusetts.

[beenthere]

Should work as good as using a window unit.

[wahoo]

As Beenthere said, they'll work about the same as a window unit in that if you close the door (for privacy), then the room with the mini-split in it will cool. Just compare them to window units. Multiple units will give you cool in numerous places, however remember these are not heavy duty built units, so don't expect them to be working 15 years from now. Does anyone on this board have experience with these Mini-splits for 15 years? Based on what I've seen and installed, they are pretty lightweight in construction. My concern would be coverage, warranty, and lifetime.

[Jesus"]

Should work as good as using a window unit.

I think beenthere was taking the piss. Sounds like if you want to do multiple rooms, get a unit that is designed to handle the load correctly and not be undersized, causing lower than expected life, and also higher runnig cost due to continueous compressor running.
But I might be wrong

[flange]

i have done many condos at the beach with vrv systems using multiple indoor units and a single outdoor unit. have many happy clients. been putting in some form of ductless since the late eighties. biggest issues is the appearance for some people. they definately work better than window shakers.

[zarandle]

Thanks for the replies thus far. Still not getting the 'experience' I was hoping for in that what I'm looking for is this:

If the unit is in one room and an adjacent room separated by a short hall/door does not have a unit will it also get cooled? Or would the one room get cool and then the unit shut off before the other room gets any air?

Again I can live with a 3-5* or so temp difference between rooms but won't live with 6+* or so.

Would love to hear some experience from a home owner that has multiple rooms and does not have a unit in each room.

[Jesus"]

sounds like you have already made up your mind zarandle. If you want to cheap it out short term, a single unit placed in a direction to distribute air down a hallway into adjacent rooms can give you what your temp alowences suguest. But as I have allready stated that long term cost will be an issue not to mention the visual image of an off centred split can be somewhat ill disired. depends on your budget from the sounds of it, it's not allowing for the correct unit for the application. maybe look into a heat extraction system.

[beenthere]

If you want to use one unit, go ahead.

You already subconscously know that it won't work right.

But your trying to convince your subconscious that it will.

It won't.

Unless your going to set a box fan in the doorway of the room with the unit, to blow the air to the next room. And keep the doors open all night.

[Some Dude]

This may not be the place if your looking for homeowner, most of us are techs or business owners.
Try amazon or someone who rates these products all we can tell you is what we know and what our customers tell us.

[KB Cool]

If you want to use one unit, go ahead.

You already subconscously know that it won't work right.



Well, he can always add another one later. :D

[Some Dude]

Im sure well hear about it.

[KB Cool]

Thanks for the replies thus far. Still not getting the 'experience' I was hoping for in that what I'm looking for is this:

If the unit is in one room and an adjacent room separated by a short hall/door does not have a unit will it also get cooled? Or would the one room get cool and then the unit shut off before the other room gets any air?

Again I can live with a 3-5* or so temp difference between rooms but won't live with 6+* or so.

Would love to hear some experience from a home owner that has multiple rooms and does not have a unit in each room.

Since i installed a 9000 btu unit in my daughters room. I decided to see if it'll cool the adjacent bedroom a few minutes ago. I must say my daughters room is nice and cool right now. But the adjacent room isn't doing so hot. The hallway seems a little cool though. :D

[Jesus"]

Since i installed a 9000 btu unit in my daughters room. I decided to see if it'll cool the adjacent bedroom a few minutes ago. I must say my daughters room is nice and cool right now. But the adjacent room isn't doing so hot. The hallway seems a little cool though. :D

See how ugly this install looks, now his daughter can't shut her door due to daddy wanting next door to get some air. Also it takes longer to cool the room cause your throwing air out the door and not delivery to the room.

[marvin]

See how ugly this install looks, now his daughter can't shut her door due to daddy wanting next door to get some air. Also it takes longer to cool the room cause your throwing air out the door and not delivery to the room.

thats an easy one . frame in a box fan in the adjoing wall & paint it to match each room. actually had a customer do that a couple years ago.

[HeyBob]

I have a ductless mini split in my place "up north". What it is is actually a Park Model trailer with a three seasons room, mine is a heat pump, during the summer I prefer to use the mini split because it is quieter, and I do have it installed directly across from where the sliding glass door used to be, it does partially cool the trailer to a decent degree, cools the room it's in like a walk in if need be, in heating mode, if I turn it up to like 75 it will keep the trailer about 60-70 degrees, but not the front of it.

Sooooooo, ya know what, it's just a big extremely quiet window unit.

[zarandle]

Thank you for all the feedback regarding mini-splits for my application, especially the constructive criticism. The whole reason I even considered mini-splits is because of the wildly different system configurations and estimates I have been getting for traditional duct systems. I have had 5 contractors come in do a walk through and give an estimate. Of those only 2 seemed to have a clue and yet even they differ on their recommendations.

Some say I only need one return for the whole house, others say it is ideal to do one return per room, one says to put in one big compressor and run a main trunk while others say run two units one per floor, one says running duct in the basement will be a bit difficult but doable b/c of pipes etc, another says it won't be a problem at all . . . then with all this conflicting information I get quotes ranging from $9,000 to $22,000 and yet no two recommendations/systems are even comparable. The equiptment is comparable but how they want to run the duct work is now at a comical stage, each wanting to do it completely different.

All except one of the contractors had good recommendations and have been in business for more than 10 years so why such differing recommendations?

How the heck to I work to sort this out?

[mchild]

Thank you for all the feedback regarding mini-splits for my application, especially the constructive criticism. The whole reason I even considered mini-splits is because of the wildly different system configurations and estimates I have been getting for traditional duct systems. I have had 5 contractors come in do a walk through and give an estimate. Of those only 2 seemed to have a clue and yet even they differ on their recommendations.

Some say I only need one return for the whole house, others say it is ideal to do one return per room, one says to put in one big compressor and run a main trunk while others say run two units one per floor, one says running duct in the basement will be a bit difficult but doable b/c of pipes etc, another says it won't be a problem at all . . . then with all this conflicting information I get quotes ranging from $9,000 to $22,000 and yet no two recommendations/systems are even comparable. The equiptment is comparable but how they want to run the duct work is now at a comical stage, each wanting to do it completely different.

All except one of the contractors had good recommendations and have been in business for more than 10 years so why such differing recommendations?

How the heck to I work to sort this out?

As flange mentioned in an early post, you may want to consider VRV/VRF for your house. These are somewhat like mini-splits in that they have inverter compressors and can use either ductless or ducted or a combination of both for your indoor units. Up to nine indoor units can be connected to one outdoor unit. This would allow you to have one unit for each room/area if you wanted to go that route.

The ducted units are very small and can fit in a space that a typical air handler could not. As an example you could have one ducted unit for the two upstairs rooms and have it located in the attic area above the rooms. Short duct runs to ceiling registers with a common return. This would provide the cleanest appearance on installation. Since you have a basement you could do a similar set up for the first floor. By having multiple smaller capacity indoor units you resolve the issue of having all the duct work having to go from one location to all the different areas of the home. And if there is no way to do duct work for a particular area use a ductless indoor unit there.

The beauty of the VRV/VRF (Variable Refrigerant Volume/Flow) systems is the outdoor unit adjusts its capacity to the load and each indoor unit does the same. It easily resolves the zoning issues that elaborate and oversized duct work makes difficult and costly. Each indoor unit can be set to maintain its own temp and completely turned off if desired.

You can check them out here:

http://www.mehvac.com/Products/subCategory.asp?ProductCategoryID=5&ProductSubCategoryID=145

http://www.daikinac.com/commercial/productsUnits2.asp?sec=products&page=55

http://www.sanyohvac.com/products.php?id=CHX05052

[motoguy128]

Since i installed a 9000 btu unit in my daughters room. I decided to see if it'll cool the adjacent bedroom a few minutes ago. I must say my daughters room is nice and cool right now. But the adjacent room isn't doing so hot. The hallway seems a little cool though. :D

9000 BTU for a single bedroom??? Wow, I wish I had a 500+ square foot bedroom. Does anyone else think thats just a tad big?

I could see a large unit like that for a meeting room or fitness center with a occupancy of 30 people. I'd guess it must cycle for no more than 10-15 minutes even on the hotest day. How do you drain the water off the indoor coil?

These are the things I think of.

Mini-splits aren't cheap. Ductwork isn't either, but keep in mind that if you live in a neighborhood where most all the other houses have central air, it can really hurt your resale value. Likewise, central air can be a sealing feature to set you apart from other homes in your area.

It won't payback as well as maybe granite countertops... but you'll get more enjoyment and comfort out of it.

[zarandle]

9,000 was picked b/c that is the smallest unit that Fujitsu, Mitsubishi, etc makes. I live in New England so our summers are really on very hot for about 3 months (mid June to mid September); with a few other hot days thrown in. Most homes in the area do NOT have central AC (except for newer subdivisons).

We'd like to get a central system to get rid of the pain and expense of the 6 window shakers but I can't get a consistent proposal from any of the contractors i've spoken to. They all differ on where to run the duct and how many returns are really necessary. I thought for sure 2-3 of the 5 or 6 contractors I spoke to would have some consistency in their proposal but am surprised that just isn't the case.

I really want to give someone my business and install AC but have to continue research and dreadfully maybe even bring in another round of contractors to try and find some common ground with an approach.

[mchild]

9,000 was picked b/c that is the smallest unit that Fujitsu, Mitsubishi, etc makes. I live in New England so our summers are really on very hot for about 3 months (mid June to mid September); with a few other hot days thrown in. Most homes in the area do NOT have central AC (except for newer subdivisons).

We'd like to get a central system to get rid of the pain and expense of the 6 window shakers but I can't get a consistent proposal from any of the contractors i've spoken to. They all differ on where to run the duct and how many returns are really necessary. I thought for sure 2-3 of the 5 or 6 contractors I spoke to would have some consistency in their proposal but am surprised that just isn't the case.

I really want to give someone my business and install AC but have to continue research and dreadfully maybe even bring in another round of contractors to try and find some common ground with an approach.

You can match indoor units (both ducted and ductless) to the VRV/VRF systems with capacities as low as 6,000 BTU - plus they can modulate way below that when the load is lighter. If you used a ducted unit for the second floor rooms they both could probably be done with one that size. Need a good load calc to know for sure.

[motoguy128]

I really want to give someone my business and install AC but have to continue research and dreadfully maybe even bring in another round of contractors to try and find some common ground with an approach.

Well there's more than one way ot skin and cat and as you've seen on this board, each pro will have a different opinion as to what will work best.... and every set-up has advantages and disadvantages. Sounds like you're willing to spend some money to do it right, but need help finding the right contractor.

You might want to make your own post for some aded guidance. It might also be worthwhile to do the legwork your self and purchase software to do the load calcs and ductwork calculations yourself. They you can tell the constractors exactly what you want and know that it will work properly.

[jeff520]

One of the major benefits of a minisplit is that the indoor units will throttle down to as little as 10% of their rated capacity. A 9,000 BTU unit may be producing less that 1000 BTU of cooling if that is all that is needed to maintain the set temperature.

If you want the minisplit to cool an adjacent area you will have to arrange for some sort of airflow between the areas so that the mini can respond to the warm air from the other area.

[KB Cool]

9000 BTU for a single bedroom??? Wow, I wish I had a 500+ square foot bedroom. Does anyone else think thats just a tad big?

I could see a large unit like that for a meeting room or fitness center with a occupancy of 30 people. I'd guess it must cycle for no more than 10-15 minutes even on the hotest day. How do you drain the water off the indoor coil?

These are the things I think of.

Mini-splits aren't cheap. Ductwork isn't either, but keep in mind that if you live in a neighborhood where most all the other houses have central air, it can really hurt your resale value. Likewise, central air can be a sealing feature to set you apart from other homes in your area.

It won't payback as well as maybe granite countertops... but you'll get more enjoyment and comfort out of it.

The water drains out the back through a little drain tube that follows the line set down the wall. I could care less about it affecting my re-sale value (probally not) as it way down anyways. In fact i bought my house to live in and pay off. Not, to use it as a piggy bank. And no, Granite counter tops would probally cost way more than this little cool gift i gave my daughter. Also loads here in the Phoenix area are greater than where your at. But, as other's said 9000 btu is the smallest i could have got. And besides it didn't cost me anything anyways, except a saturday morning of work. I also have central air. But, its nice knowing if my compressor takes a dump in the middle of July at night. My family can all just camp out in my daughters room and remain cool until the parts house opens. But, if that happens i'll probally just replace my whole system instead.:D

[jjou812]

were any of the 5 or 6 contractors NATE Certified? visit www.hvacradvice.com. request a tech who is certified in both A/C and Airflow. the tests are no joke, they are tough.

btw- the minisplit heat pumps heat surprisingly well. the small additional install cost is worth it.

[motoguy128]

The water drains out the back through a little drain tube that follows the line set down the wall. I could care less about it affecting my re-sale value (probally not) as it way down anyways. In fact i bought my house to live in and pay off. Not, to use it as a piggy bank. And no, Granite counter tops would probally cost way more than this little cool gift i gave my daughter. Also loads here in the Phoenix area are greater than where your at. But, as other's said 9000 btu is the smallest i could have got. And besides it didn't cost me anything anyways, except a saturday morning of work. I also have central air. But, its nice knowing if my compressor takes a dump in the middle of July at night. My family can all just camp out in my daughters room and remain cool until the parts house opens. But, if that happens i'll probally just replace my whole system instead.:D

I didn't realize this was a supplemental system.

But I fully agree, homes aren't piggy banks, but life's little curve balls sometimes dictate moving. I'm guilty of over improving my HVAC system for the size and value of my home. But that's because we plan to stay here and I wanted a comfortable and efficient system to provide good IAQ.