Mini Split or Conventional Forced Air

[DetachedGarage]

Hey Everyone,
I've got a few key decision points to make in the scoping of the garage. Conditioning/HVAC is one of them. I am planning on doing a Hydronic heated floor with PEX, but I'm debating how to condition the work out area and also the bedroom, bathroom, and storage area's in the loft. I've got a few questions for the forum.

1. Can you do multiple mini split units off of the same exterior condensor unit?​

2. If so, how many is reasonable?​

3. At what point does it make sense to go forced air?​

I'll be doing fans in the shop area of the garage, but need conditioning in the work our room right away. I'm wondering if I just bite the bullet and go with a conventional forced air HVAC system right away, or if I can do one mini split for the workout room and then add additional units in the future as funds and time become available.

Cheers!
Sean

 

[Jim greengo]

Depends on the size of the mini split.

 

[rlitman]

It depends on what you want. Mini-split can be very efficient, because there are no duct losses, and because you put the cool (or heat) exactly where you want it and nowhere else.

There are multi-head mini-split units, but most require a fixed number of head units, so it isn't like you can just tack on one or two at a later time.

 

[tim9lives]

I think you’re going to find the single mini splits are considerably less expensive than multi-zone units. For a shop.... I’d go with lowest price generic units on EBay. A single zone generic heat pump @ 600.00 on EBay. The multiple zone units are around 2000.00
If you need more cooling capacity just get 2 of the 1 ton units.

 

[jjrbus]

Not sure of right way? I'm in Florida and want redundancy so I put 3 single units in. Nothing worse that the AC going out in a heat spell and all the techs are super busy!

Plus the multi head units are more expensive which also influenced my decision.

Not sure if you are aware that minis require more maintinence/cleaning than central units?

 

[Notgrownup]

You can put up to 5 units on 1 condenser...look at www.alpinehomeair.com

 

[2012 LML]

I just installed a 5 ton forced air in my 40x60. We stuck the AH in a corner that basically just dumps air out at the unit. Big *** Fan moves the air around very well. I ended up using the old unit from my home after installing a new one for preventative reasons.

 

[theoldwizard1]

1. Can you do multiple mini split units off of the same exterior condensor unit ?

Yes, but you lose efficiency. How big of a space are you trying to cool ?

2. If so, how many is reasonable ?

2-4, but you really need to check the efficiency.

3. At what point does it make sense to go forced air ?

For EVERYTHING or just cooling ?

Forced air is almost always the cheapest INSTALLATION solution ! You lose the comfort of a warm floor and the efficiency of a mini-split.

I'll be doing fans in the shop area of the garage, but need conditioning in the work our room right away. I'm wondering if I just bite the bullet and go with a conventional forced air HVAC system right away, or if I can do one mini split for the workout room and then add additional units in the future as funds and time become available.

It will cost you more in total installation, but you won't have any ductwork to look at/hide and the cost of operation will be less.

Run the mini-split on heat mode down to about 40F, then switch over to the hydronic heated floor. The 40F-90F range is where they are most efficient.


Segue - In other parts of the world they sell mini-split systems that have a heat exchanger to heat the water for the hydronic heated floor. These still have not caught on in the US, probably because they are for aimed at building with <1500 sq ft.

 

[theoldwizard1]

There are multi-head mini-split units, but most require a fixed number of head units, so it isn't like you can just tack on one or two at a later time.

Not true !

The multi-head units usually start with about 4 ports. You CAN add "air handlers" as required. Some can add a "distribution" box and go up to 8 ports. I am not saying this is the "best" solution, but it is an option.

 

[theoldwizard1]

I think you’re going to find the single mini splits are considerably less expensive than multi-zone units. For a shop.... I’d go with lowest price generic units on EBay. A single zone generic heat pump @ 600.00 on EBay.

If you can really get a decent quality unit for that price, it is actually FEASIBLE to buy more than 1 complete system ! Most can be slaved so when they are installed in the same room, one is the master and the other(s) slaves.

 

[kj_mustang]

Keep in mind you will have to access and clean all those mini-split filters fairly often vs. one filter on a central system.

 

[Jackfre]

It is difficult to advise without knowing the lay-out. In my experience "biting the bullet" is definitely going with the mini-splits. I'm done with ductwork. Cleaning the filters on the 4 evaporators I have in the house is about a 5 minute process and I don't have to crawl into a confined space to do so.

 

[rlitman]

Not true !

The multi-head units usually start with about 4 ports. You CAN add "air handlers" as required. Some can add a "distribution" box and go up to 8 ports. I am not saying this is the "best" solution, but it is an option.

There are all sorts of options out there. Daikin makes systems with distribution boxes, where you can even heat in one room and cool in another. But a 2-head unit for example will have two ports, and will absolutely not work with a third head added. There is communication between the heads and the compressor, and just as you cannot add a second head to a 1:1 unit, the simplest multi-head units don't have much adaptability either (except for mixing and matching capacities).

My point is, if you buy a 4-head unit, don't expect that it will automatically work with 3 or 5. Yes, that option many be available in some models, but it is not across the board.

I think you’re going to find the single mini splits are considerably less expensive than multi-zone units. For a shop.... I’d go with lowest price generic units on EBay. A single zone generic heat pump @ 600.00 on EBay. The multiple zone units are around 2000.00
If you need more cooling capacity just get 2 of the 1 ton units.

Yeah, the 1:1 units are a LITTLE cheaper per inside head unit than the multi-zone systems. But then you need space for multiple compressors outside. If you've got the room, and don't care about the appearance, then that may be the least expensive route.

 

[Coach James]

Not sure if this is any help, but I have ten 1 ton units for our gym, ~12,000 sq. ft.. I have to clean the filters every week, but we also are using a great deal of chalk.

Coach

 

[DetachedGarage]

Great feedback guys! Thanks so much. I think you are right, probably best to do the layout first and then really dig into this. I'm hoping the land sale can move forward quickly into July so I can officially get with the designer/architect.

I think I'm leaning towards multiple mini splits though. I think the Hydronic slab will do most of the heating, but it will still be colder up in the loft.

I'll get a concept floor plan out in SketchUp as soon as I get better with it

 

[GRivera]

Any idea what size mini split unit I would need to heat/cool an insulated work shop 30x40x12'? R19 walls, R30 ceiling.

 

[Jim greengo]

Probably 2.5-3 tons,depending on number of heads.

 

[danb35]

@GRivera, I have 24k in my 30x40x14 shop with less roof insulation, and it's working well so far--but I haven't been through a whole summer yet.

 

[DetachedGarage]

@GRivera, I have 24k in my 30x14x14 shop with less roof insulation, and it's working well so far--but I haven't been through a whole summer yet.

Good to know as my shop area will be 30x40 and then the other areas will be the loft and the workout room.

 

[GRivera]

Probably 2.5-3 tons,depending on number of heads.

looking at the single head Mr Cool from Costco for $1500 - Costco has lifetime warranty on most items it sells

@GRivera, I have 24k in my 30x14x14 shop with less roof insulation, and it's working well so far--but I haven't been through a whole summer yet.

Is that a typo- 30x14x14?

 

[danb35]

Is that a typo- 30x14x14?

It is, thanks; I've fixed it. 30x40x14.

 

[nsula_country]

I used forced air in our 40x60x17. I have a build thread on the HVAC in signature. I did all the installation.

CT

 

[Jim greengo]

looking at the single head Mr Cool from Costco for $1500 - Costco has lifetime warranty on most items it sells



Is that a typo- 30x14x14?

That's going to be a lot of air to move with a single head ststem.
I normally figure between 450-500 sf per ton around here anyway for cooling,towards the lower end with higher ceilings.

 

[SALIV8]

Hey Everyone,
I've got a few key decision points to make in the scoping of the garage. Conditioning/HVAC is one of them. I am planning on doing a Hydronic heated floor with PEX, but I'm debating how to condition the work out area and also the bedroom, bathroom, and storage area's in the loft. I've got a few questions for the forum.

1. Can you do multiple mini split units off of the same exterior condensor unit?​

2. If so, how many is reasonable?​

3. At what point does it make sense to go forced air?​

I'll be doing fans in the shop area of the garage, but need conditioning in the work our room right away. I'm wondering if I just bite the bullet and go with a conventional forced air HVAC system right away, or if I can do one mini split for the workout room and then add additional units in the future as funds and time become available.

Cheers!
Sean

1.yes. The most I've done is 4 off the same condenser but some systems can go as high as 7.

2.well that would be up to you, your budget, and design.

3.good question. The cost difference and added efficiency is what sold me on mini splits. Forced air was almost double the cost of mini splits (for both of my projects) and the efficiency was also lower. I installed the systems myself with Justin joyals (a pro on this forum's) help and couldn't be happier.


Mini splits will have Linesets, drains, condensing unit, and electric visible from the outside but no ductwork is inside. If you are cool with the indoor heads and the outdoor setup I recommend mini splits.

Multi head options offer many different high seer options (even though some responses seem to think not) and they offer individual temp controls per indoor unit/space as well.

 

[DetachedGarage]

1.yes. The most I've done is 4 off the same condenser but some systems can go as high as 7.

2.well that would be up to you, your budget, and design.

3.good question. The cost difference and added efficiency is what sold me on mini splits. Forced air was almost double the cost of mini splits (for both of my projects) and the efficiency was also lower. I installed the systems myself with Justin joyals (a pro on this forum's) help and couldn't be happier.


Mini splits will have Linesets, drains, condensing unit, and electric visible from the outside but no ductwork is inside. If you are cool with the indoor heads and the outdoor setup I recommend mini splits.

Multi head options offer many different high seer options (even though some responses seem to think not) and they offer individual temp controls per indoor unit/space as well.

Summed up perfectly! I think I'm leaning towards the mini split route!

 

[EdT]

I put 2 mini splits in my two story 24 x 36 shop building. I seldom use the upstairs one since I don't go up there much. I use the downstairs one a a fair amount and it cools fine in the Georgia summer. It is also a heat pump unit and will work well down to about 25*F which seldom occurs around here. All in all, I've been pleased with the performance. Since it was new construction, I ran the line sets inside the walls making careful note of where they are, but I've not needed to know yet. One additional benefit is that both the condenser and evaporator units are very quiet. Much quieter than the conventional units in the house. It may vary by geographic area or other factors, but most of the installers around here don't like mini's. You have to twist their arm to get them to install one. I think it's because there is so little involved they don't make enough money on the install. I installed mine and had my AC guy "commission the system which was required by my warranty. One tip, on my units the controls run on line voltage which means that the remote cut off things that some utility companies offer to manage peak loads will not work. Also, on my units, you have to maintain the L1, L2, N relationship throughout the system or it won't work. That is, the hots in the condenser and the evaporator must be in the same positions on the terminals.
AFA the hydronic heat thing. You may want to investigate the time for the system to warm the space from a cold start. Unless you plan to keep it warm all the time, you may need to turn it on yesterday to work in the shop tomorrow. The thermal inertia of the slab is pretty high and the heat input is fairly low so it can take a while to get up steam.

 

[Fixin'Stuff]

I've had my Mr. Cool Oasis ES in a 480 SF garage for almost a year now. I freakin' love it! I keep the garage at 76-78 all summer, yet I haven't noticed enough change in the power bills to even know its running. It also did a great job of keeping the garage warm during what passes for winter around these parts. By keeping it warm I don't have to worry about the humid Houston air condensing on everything inside when the door gets opened.

 

[theoldwizard1]

I put 2 mini splits in my two story 24 x 36 shop building. I seldom use the upstairs one since I don't go up there much. I use the downstairs one a a fair amount and it cools fine in the Georgia summer. It is also a heat pump unit and will work well down to about 25*F which seldom occurs around here.

Efficiency numbers drop off quickly for units that can handle multiple (even just 2) air handlers. Your initial cost is higher, but you will recover it !

 

[Jackfre]

I have found that from a pricing and performance standpoint you have to look at the individual spaces and the projected use of those spaces when choosing mini-split systems. For instance, in my home. Initially I was going to go with a 36k system that could handle 3 evaporators. Todays 36's can handle 4. I ended up going with a 26 seer/12hspf), 12kbtu single and a 24 dual 16seer/9.5hspf) for the two upstairs bedrooms with individual evaporators. The pricing came out almost the same as the 36 system and I have better comfort and economy. I laid it out this way to obtain the max efficiency in the commonly used area. I have never run the heat in my bedroom but do run the cooling in the summer. All the spaces are zoned and individually controlled. Once we remodeled I added another 15k high efficiency unit for that area. I had the panel space to handle this set-up. Look at your use and lay-out and be very careful in equipment selection. Do not assume one manuf has the same specs and lay-outs. Yes, you can run up to 7 or 8 headed units but costs go up substantially for those systems. They are very cool however.

 

[DetachedGarage]

I have found that from a pricing and performance standpoint you have to look at the individual spaces and the projected use of those spaces when choosing mini-split systems. For instance, in my home. Initially I was going to go with a 36k system that could handle 3 evaporators. Todays 36's can handle 4. I ended up going with a 26 seer/12hspf), 12kbtu single and a 24 dual 16seer/9.5hspf) for the two upstairs bedrooms with individual evaporators. The pricing came out almost the same as the 36 system and I have better comfort and economy. I laid it out this way to obtain the max efficiency in the commonly used area. I have never run the heat in my bedroom but do run the cooling in the summer. All the spaces are zoned and individually controlled. Once we remodeled I added another 15k high efficiency unit for that area. I had the panel space to handle this set-up. Look at your use and lay-out and be very careful in equipment selection. Do not assume one manuf has the same specs and lay-outs. Yes, you can run up to 7 or 8 headed units but costs go up substantially for those systems. They are very cool however.

Great advice! Thanks