4 Zone Mini Split with just 1 head attached?

[HamAndEggs]

I got myself a dual zone Daikin mini split for my office and bedroom. Its an 18K outdoor unit with 2 x 9K indoor units

Damn, this thing is AWESOME. It has literally halved my electric usage some days, and it makes the room much more comftorble, as you just set it to a setpoint, and it sits there all day. It also gave me redundancy in my cooling and heating

Now I want one for my living room. But I don't want to get a single unit, only to then want one down the line in another room and need a whole extra unit

If I got this 4 port 36K BTU unit - https://www.daikinac.com/content/as...ts/Multi-Split/4MXL36TVJU-Submittal-Sheet.pdf

And just attached a single 12 or 18K BTU indoor unit. Would it cause much issue?

 

[yeldogt]

Have to look at the specifications --- they all have min. My guess is it may be two or even three.

Remember --- the idea with the multi is to base the compressor on the overall load. You don't take the heads and just add them up.

More often than not the heads will be greater than the compressor -- both of my three head systems are 30k compressor and 3 12's heads

 

[Yankeefarmer]

You definitely need to check the detailed specs. Several years ago, I contracted with a very reputable local HVAC dealer for a 36k multi split where he had quoted a 24k head for our great room and a 12 k head for our master bedroom. Only problem (for him, that is) was that when he ordered the equipment, he was told by the distributor that the outside 36 k unit could not handle the 12 + 24 combination. He had to upgrade the outdoor unit to the hyperheat model in order to feed those two inside units. (I know this is true, because I had looked up the installation instructions for the unit he quoted and saw that it was not an approved configuration.) Being a reputable company, they honored their original price.

 

[yeldogt]

You definitely need to check the detailed specs. Several years ago, I contracted with a very reputable local HVAC dealer for a 36k multi split where he had quoted a 24k head for our great room and a 12 k head for our master bedroom. Only problem (for him, that is) was that when he ordered the equipment, he was told by the distributor that the outside 36 k unit could not handle the 12 + 24 combination. He had to upgrade the outdoor unit to the hyperheat model in order to feed those two inside units. (I know this is true, because I had looked up the installation instructions for the unit he quoted and saw that it was not an approved configuration.) Being a reputable company, they honored their original price.

Most have a lack of knowledge -- even the Mitsubishi Diamond dealers. So if Mitsubishi (hyper heat) guys don't fully grasp them .... you know there are a lot of bad systems out there.

The heads are the same -- it's just a heat exchanger anyway. All the action is happening outside. Couple things to remember/ note what doing a multi. What's the lowest output of the compressor -- take this number and look at your smallest head. Understand that the output range on the head is not the same as if it was on a single set -- read the manual and look at the chart (as you found out) . The last --- remember that the heads are never fully off with a multi head mini .... It's not water flowing around in those tubes. A small amount of refrigerant must always flow to all the heads.

One of my recent projects illustrates the issues. It's an unusual project with a two story kitchen addition and a very high loft in the old original structure. The place has radiant heat as well as duct work ... but, I was not able to duct the addition as I would have liked. Addition open on three sides and the HVAC unit is in the old building. It actually works better than I thought it would. In the planning stage my thought was three heads --- one for the loft -- one for the kitchen -- one for the lower level of the kitchen (walk out mudroom bath). One compressor. After looking everything over (my builder got estimates) I called Mitsubishi engineering (not easy). They confirmed my fear. Since the loft would be rarely used -- you don't want some far flung unit attached to a multi. The refrigerant must flow to that unit whenever it's running another head. My other problem was the kitchen ... kitchens are the only regular room in a typical house where you may have to plan on some over capacity -- especially one open on three sides/ big stove and set up to entertain (people). The multi 18k specifications were not as good as the 15k unit on a single compressor .. so I worried about top capacity ... and I was going to have to get an outside unit that was never going to run low enough for the lower level 9k or 12k head. The best solution -- 3 single units.

Now I have other multis -- one at my beach house with three 12k heads on a 30k compressor. Prefect. The heads are always on and it's able to ramp around perfectly to provide what is needed

 

[HamAndEggs]

Thats some good information guys!

Yeah, looking at the 4 zone, once I attach 4 zones its going to not be able to go low enough

I think best idea is to get a dual zone, and then maybe another dual zone down the road

 

[dlwilson]

I don't know anything about AC, but last year I put a 36 ton mini split with two indoor units in my garage, and I'm very happy with it. I got it on Amazon, and you can also buy the same compressor with one, three, or four units. Here's what I got: https://www.amazon.com/gp/product/B00UV3LLB8/?tag=atomicindus08-20