Mini-Split help

[Spfrancis]

So I"m trying to put in a mini-split into a back cottage that is pretty straightforward. I am trying to avoid just turning it over to a contractor, as the price seems to go up very quickly. Here is some of the specifics. I have pulled a 220 wire from the panel over to the location that will be outside of the cottage. I will probably need about a 20 ft line run, as I will have it coming into a shed, and then run that over to the wall that will have the air handler. Talking to the companies that will sell you you a Heater/AC mini-split, with the linesets, it looks like I can spend about 1200 for the actual unit. When I spoke to a couple of contractors over the phone, they are all talking about $3200, or higher for this project. That will includes the equipment costs. In my mind, this seems like a project that they can knock out in a day. I know that I probably don't want to mess around with the work to vacuum the refrigerant lines, and check the low side and the high side and fill as needed. I know that there are certain things that I should have a certified HVAC person do. I wanted to see if anyone on the forum has dealt with this type of problem, or would offer some ideas on how they kept costs low.
Thanks for any help.
Sony

 

[Dana]

It's not clear what your problem is. If you read the manuals and follow it very carefully you can install the whole shebang up to the point of the final pump-down & refrigerant charge & test, paying the refrigerant tech for their expertise and use of the tools that you probably don't want to own.

There are DIY mini-splits out there that come with pre-charged linesets in that price range if you don't mind that they are the most super-efficient available. If you have 11 left thumbs and screw it with leaky lines you'd be in for hiring somebody to re-charge it for you, but that's no worse than buying all dry hardware, installing it, and have a tech commission it for you. If you want a top tier Japanese vendor's model with a longer warranty and higher efficiency you'd have to spend nearly twice that for just the hardware.

Have you run a heating/cooling load calculation of any type on that cottage? Which model were you thinking of installing mostly-DIY?

 

[Sponsor]

 

[Spfrancis]

It's not clear what your problem is. If you read the manuals and follow it very carefully you can install the whole shebang up to the point of the final pump-down & refrigerant charge & test, paying the refrigerant tech for their expertise and use of the tools that you probably don't want to own.

There are DIY mini-splits out there that come with pre-charged linesets in that price range if you don't mind that they are the most super-efficient available. If you have 11 left thumbs and screw it with leaky lines you'd be in for hiring somebody to re-charge it for you, but that's no worse than buying all dry hardware, installing it, and have a tech commission it for you. If you want a top tier Japanese vendor's model with a longer warranty and higher efficiency you'd have to spend nearly twice that for just the hardware.

Have you run a heating/cooling load calculation of any type on that cottage? Which model were you thinking of installing mostly-DIY?

Dana,
Hey, thanks, that is the type of information I was looking for. I worked with one of the guys at an online seller of mini-splits(ecomfort.com) for the load calculation. We came up with 9000BTU This cottage used to be a garage, that someone put a bay window in, and plumbed a bathroom. It is only 21x16 in size. The guy at ecomfort was pushing "Gree", as he was stating that for the price point, they provide the best value. They are also one of the biggest sellers of Mini-splits in the world. I had never heard about that brand, but I guess they are bigger overseas?
So I am thinking that it may be better to buy dry hardware, and hook it all up, and then having someone come in and commission it for you? I assume that when you buy linesets from a company, I would have to bend the coolant lines to get it from the compressor to the inside air handler. I would also have to put fittings on the ends to plug in to both sides. Is that difficult/prone to error? Once it is all hooked up, then a refridgarant tech could come out and fill the system, and perform a test to see that it is maintaining? Is that what I should be asking for? How many hours do these type of things typically take?
Thank you for the quick response. It makes it easier for me to pull the trigger.

 

[Dana]

Gree is the largest air conditioning equipment manufacturer in China, and make equipment under contract for many other brands. (A number of second & third tier vendors' units are rebadged Gree units. I believe Carrier's mini-splits are all Gree designs.) Even the big orange box store sells Gree mini-splits.

Saying that it doesn't need to be bigger than 9000 BTU doesn't really say what the loads really are, and it matters. Most manufacturers don't make mini-splits smaller than 9000 BTU, and your actual loads are lower than that. A 336' house that has at least some insulation probably has a cooling load of no more than 4000 BTU/hr, maybe 5000 BTU/hr if it has a single pane west-facing sliding door or only R13 in the attic (which is a comfort problem worth fixing if it's that poorly insulated.) Your heating load is probably also less than 5000BTU/hr.

A differentiating factor between models would be the MINIMUM modulated output rather than the maximum. The most efficient (and comfortable) operation of a variable speed "inverter drive" mini-split is when they are modulating at part load rather than cycling on/off at it's minimum speed. If you only need 5000 BTU/hr of cooling at design condition and the minimum modulated output is important- it's not going to be as efficient or comfortable as equipment that modulates down to ~1000 BTU/hr. So, the exact model matters- Gree makes at least 3-4 different 9000 BTU mini-splits.

The highest efficiency 9000 BTU Gree is the CROWN 09HP , but it's priced, more like $1600, not $1200. ($1575 at eComfort) It has a lower minimum-modulation than most of their others at about 1500 BTU/hr, which isn't bad at all.

But that low min-output is is still not as low as the ~$1300 9000 BTU LG ArtCool Premier at ~1000 BTU/hr, and which also an even higher rated heating efficiency than a Gree Crown despite 10% lower cooling efficiency.

The Gree Terra is about the same money as the LG, but only modulates down to 3500 BTU/hr in cooling mode, 2200 BTU/hr in heating mode. The Terra has comparable in cooling efficiency to the ArtCool Premier, but 25% lower heating efficiency.

For first-tier Japanese mini-splits the Mitsubishi -FH09NA would be the ticket, due to it's ~1600 BTU/hr minimum output, which is lower than the Fujitsu & Daikin competition, priced at $1,629 at eComfort, more efficient than the Gree Crown, and only $54 more (at eComfort).

The recently released half-ton Mitsubishi FH06NA could almost certainly cover the loads for a 336 square foot cottage, and it's even cheaper ( $1519 @ eComfort) , with the same ~1600 BTU/hr min-mod output numbers of the FH09NA.

So...

... if it were my project (which it isn't) I'd be inclined to go with the either half ton FH06 if going first-class, or the 3/4 ton LG LA090HYV1 if the $200-300 price difference was important for my budget, and not the Gree Terra, which has a minimum cooling output comparable to your design cooling load and would thus never actually modulate.

 

[Spfrancis]

Gree is the largest air conditioning equipment manufacturer in China, and make equipment under contract for many other brands. (A number of second & third tier vendors' units are rebadged Gree units. I believe Carrier's mini-splits are all Gree designs.) Even the big orange box store sells Gree mini-splits.

Saying that it doesn't need to be bigger than 9000 BTU doesn't really say what the loads really are, and it matters. Most manufacturers don't make mini-splits smaller than 9000 BTU, and your actual loads are lower than that. A 336' house that has at least some insulation probably has a cooling load of no more than 4000 BTU/hr, maybe 5000 BTU/hr if it has a single pane west-facing sliding door or only R13 in the attic (which is a comfort problem worth fixing if it's that poorly insulated.) Your heating load is probably also less than 5000BTU/hr.

A differentiating factor between models would be the MINIMUM modulated output rather than the maximum. The most efficient (and comfortable) operation of a variable speed "inverter drive" mini-split is when they are modulating at part load rather than cycling on/off at it's minimum speed. If you only need 5000 BTU/hr of cooling at design condition and the minimum modulated output is important- it's not going to be as efficient or comfortable as equipment that modulates down to ~1000 BTU/hr. So, the exact model matters- Gree makes at least 3-4 different 9000 BTU mini-splits.

The highest efficiency 9000 BTU Gree is the CROWN 09HP , but it's priced, more like $1600, not $1200. ($1575 at eComfort) It has a lower minimum-modulation than most of their others at about 1500 BTU/hr, which isn't bad at all.

But that low min-output is is still not as low as the ~$1300 9000 BTU LG ArtCool Premier at ~1000 BTU/hr, and which also an even higher rated heating efficiency than a Gree Crown despite 10% lower cooling efficiency.

The Gree Terra is about the same money as the LG, but only modulates down to 3500 BTU/hr in cooling mode, 2200 BTU/hr in heating mode. The Terra has comparable in cooling efficiency to the ArtCool Premier, but 25% lower heating efficiency.

For first-tier Japanese mini-splits the Mitsubishi -FH09NA would be the ticket, due to it's ~1600 BTU/hr minimum output, which is lower than the Fujitsu & Daikin competition, priced at $1,629 at eComfort, more efficient than the Gree Crown, and only $54 more (at eComfort).

The recently released half-ton Mitsubishi FH06NA could almost certainly cover the loads for a 336 square foot cottage, and it's even cheaper ( $1519 @ eComfort) , with the same ~1600 BTU/hr min-mod output numbers of the FH09NA.

So...

... if it were my project (which it isn't) I'd be inclined to go with the either half ton FH06 if going first-class, or the 3/4 ton LG LA090HYV1 if the $200-300 price difference was important for my budget, and not the Gree Terra, which has a minimum cooling output comparable to your design cooling load and would thus never actually modulate.

Okay, thanks for all the data. I definitely want to select the unit that would be the best fit for the space. I am going to get something that has "heat" as well, even though it will probably get used maybe once a year. This is definitely a summer usage place, as it is close to the shore. But I figured that since we are putting this in, we might as well get heat for the odd chance that we end up down there during the winter. The other concern I have is having to do with worrying about warranty work, if I take the approach of DIY, and just get someone to fill the system/check it out. I'm sure many of the problems that crop up are from poorly designed solutions, that have the system coming on too much. Is the warranty period worth much for these type of systems. I figured if the whole system is being sold at 1200-1600, then parts have to be fairly cheap, if things need to be fixed. I would guess that Japanese brands are better for parts?

 

[Tom Sawyer]

Well, you get it all installed and I'll (and most other licensed installers) will come in and tell you all the things you did wrong, vac and charge it and hand you a bill that about covers what it would have cost to have it installed in the first place. Or, you can find some unlicensed handy hack on Craig's list.

 

[Dana]

Don't count on repair parts being particularly cheap or available. Parts and debug expertise availability is higher if there is a local distributor and lots of installers of that brand. In my area there is great distributor support for Mitsubishi & Fujitsu, less for Daikin. YMMV. For Gree or LG it's crap-shoot, you'd almost be better off buying a replacement system when some internal component fails, especially if the unit is more than 5 years old (which is usually the case). The evolution of models & components is pretty rapid, and in the world markets served by second tier vendors the whole notion of a warranty is pretty vague.

Having a licensed installer doesn't guarantee that it'll be done right, but a licensed bonded installer is at least somebody you can file a claim against if/when they screw it up. As a DIY it's important to read and understand the installation manuals before diving in, including investigating the installation manuals for units & manufacturers other than the one you're installing.

Even when it's installed by the book, the book doesn't necessarily factor in niceties such as installing the compressor well above the historical maximum snowpack depth so you don't have to dig it up after every winter storm. A common flaw I see in New England is that they treat it as if it were an air conditioner that would never need to work in a snowstorm, sometimes even mounted in the drip-line of the roof to guarantee that it experiences extreme icing-up or gets destroyed by a falling icicle or roof avalanche.

These were installed by licensed professionals too:

Bracket mounting it on the wall, above the snow-drift line also keeps it from sucking in weeds that might otherwise be growing around it too:

I can't tell you how often I get push-back from installers when insisting on that- they're all paranoid about the potential for some vibration coming through the walls or something. When wall-mounted you'll usually be able to hear it, but it's quieter than your refrigerator, which you can also usually hear.

Mounting it where it can be protected by roof overhangs is best practice- under the rake is far preferable to under the eaves, unless you have 2'+ roof overhangs at the eaves. Be sure to leave more than the bare minimum of clearance to the back side of the unit.

On the interior heads, don't stuff it in a corner at minimum clearance from the ceilings & walls, which would be a recipe for short-cycling the thing into lower comfort & efficiency. (I've seen installs by licensed pros commit that sort of idiocy too.)

If you have to install it near a corner, figure out which end of the unit the temperature sensor is located, and put the sensor side away from the corner. They'll often work fine at min-clearance to the ceiling during the cooling season, but giving it ~18" of clearance makes it less prone to short-cycling during the heating season.

You might want review this handy list too. (You can take a free trial subscription to see it. It didn't used be be behind the pay wall, but apparently it is now.)

 

[Spfrancis]

Dana,
Thanks for all the information. You definitely gave me a lot to think about. I'm definitely going to sticks with one of the big companies(as you recommend). I'm still working through some of the details, as I figure out how to move forward. I will keep all posted as I progress.
Thanks.

 

[Spfrancis]

So question about preping the area for the compressor. I see some folks that just mount it on a couple of 4x4's. I don't think I want to mount it on the wall, as the one picture shows. Is there much that needs to be done to prepare an area for mounting the compressor. I'm probably going with one of the 2 Mitzu's that Dana talked about above. I figured I could prep the area, to remove any non-hvac work that is required. One additional question is about making 90 degree turns with the linesets. I am hoping that I could run the line sets through the interior walls of a shed(to make less visible from outside). The shed has standard 2x4 studs, and there would be 3 turns required. If we went on the exterior wall of the shed, it could be one less turn. Is there something to worry about with regard to turns.

 

[Dana]

If you're not going to mount it on the wall above the weeds & snow, mount it on riser blocks on a raised condenser pad at least 5-6" above grade, with a 1' or larger perimeter of the pad that is vegetation controlled with landscaping fabric and washed gravel/stone

Feel free to get creative about what constitutes the pad, but make sure it's not going to be sucking in vegetation, and has sufficient clearance to walls or other obstacles per the manufacturer's installation instructions.

This one is probably a bit too close to the porch, but the elevation above grade and the weed-control around it is pretty decent:

This one is susceptible to weed growth behind it, and sucking in leaves with nothing to control vegetation, but at least the pad is somewhat elevated, and it's on riser blocks:

This one is somewhat better, but should be a bit more level:

This one is guaranteed to suck in grass & weeds, with no weed perimeter:

These should remain pretty clear & clean without a lot of maintenance:

Purpose-made wall mounting brackets are not very expensive, and makes keeping the coils free of crud a bit easier. Landcaping fabric & washed gravel under this unit probably would be better than the bark mulch under this bracket-mount, but at least you can weed the mulch easily:

I'm not sure how you would install refrigerant lines in walls with three turns short of gutting the walls. There are minimum bend radius constraints, and equivalent-length calculations to apply to those bends (though it's unlikely you would end up exceeding the maximum length specs.)

 

[Spfrancis]

Hey, thanks for the education on how the outside unit can be setup. This was exactly what I was looking for. I did some research on the things you mentioned about bend radius. This information will help when I meet the one guy on Sunday regarding the Mini-split setup. I thank you for all the help.

 

[Dana]

Be sure to set it up so that you can gently brush & vacuum out the back side of the outdoor unit at least once every year or two, even if you're keeping it well clear of vegetation. If you install it at minimum clearance on the back side it's nearly impossible to clean it out without bending up the fins. The back side is pretty much fully exposed finned coils, as seen in this rear view of a Mitsubishi -FHo9 compressor unit:

 

[Spfrancis]

Hey, a follow-up question about certain models of Mitzu's. I was looking to put in the FH-09NA, but the guy who came out Sunday was talking about a model that I don't even see on the ecomfort site. MSZ-GEO9NA. I can't tell if this is just an older model, or something where the model numbers for the certified technicans, are different than what I would see on sites like ecomfort. Does anyone have any experience with the different Mitzu units?

 

[Dana]

The GE09NA has been around a long time (15 years?) is cheaper and SFAIK is still in production, but has crummier (but still respectable) SEER & HSPF efficiency than the FH09NA. Furthermore, it only throttles down to 3800 BTU/hr in cooling mode (more than 2x that of the FH09 or FH06).

That minimum modulated output could be pretty close to your 1% outside design temp cooling load in a 350' cottage, which means it won't modulate much, and may not hit it's SEER efficiency due to cycling on/off. To hit their numbers mini-splits need to have an average load above the minimum modulated load, but below the max capacity, and a "rated" or "nominal" capacity at least as big as the peak load. When sized correctly once the thing turns on as the outdoor temps rise it'll cycle on/off maybe once or twice before running nearly continuously until late in the day. When it's oversized it'll cycle on/off all day just as the compressor on a window-shaker would.

 

[Spfrancis]

So thanks Dana "yet again" for all the help on this purchase/setup. I really like that the FH09 over the FH12NA, since it is a little cheaper, and modulates a little lower. The HVAC guy is wanting to go with the bigger unit, as he figures it is always safer to go with a bigger unit, as you will never have the situation that it can not keep up, and the room never feels cool. I get that. The price difference is only about $150, which is pretty minimal delta. I like the idea that it will be more efficient, and when running for the hot part of the day, it will probably save me money, and it will be a better user experience( not cycling), which drives me crazy. I see that 9000BTU/cooling would be fine for 350-400sqft. I don't have western exposure window. Basically the only window is a bay window that is south exposure. This is a pretty dense area, so there are a number of shade spots, where the house will not big baking in the sun. The ceiling is 7.5 feet, and there is a minimal crawlspace attic roof. I attached a picture of the cottage. My pln

My plan is to put the outside unit behind the shed there in front. I have cleared out that back area where this pictures shows a bush. I was going to run the lineset on the back wall of the shed, and bring it into the main living area. The air handler will be on the wall where the outside light is. Probably about 3 feet to the right of that light. The linesets should only be 15-20 feet. I'm hoping a pretty straightforward setup.

 

[Dana]

There's no WAY that place would need a 1-ton even if it had no insulation whatsoever! (And even then, the FH09 can deliver 12,000 BTU/hr of cooling = 1 tonrunning at full speed, albeit at lower than it's rated efficiency.) Your peak load is almost certainly under 5000 BTU/hr, and even the FH09 has the capacity to cool down pretty quickly when needed.

Crusty old-schoolers in the hot sticky gulf states typically use a "one ton per 500 square feet of space" rule of thumb, which reliably oversizes it for a tar paper shack with single-panes at 110F in a sunny humid swamp, and that includes duct losses from uninsulated duct in a 130F attic, and some oversizing to be able to cool it down quickly from a high temp (the "...come home from work to a 90F house and crank it up..." scenario.) For 2x4 framed houses with R19 in the attic and insulated ducts some will begrudgingly use a 750BTU pwer square foot rule of thumb. With the ducts inside of conditioned space reality is tyically on the order of a ton per 1000-1500 square feet, even in those minimally insulated houses.

With a modulating system like a mini-split there are no duct losses, and you'll use less power if you "set and forget" approach rather than turning it off when you leave for the day forcing it to cool down quickly. Cooling down an overheated hot house means it runs at full blast at it's lowest possible efficiency during the recovery ramp, whereas when modulating at part load all day it'll sip power at extremely high efficiency unless it's so oversized that it's cycling on/off most of the time. To get a handle on just how efficient it when modulating in cooling mode, check out the medium and low speed efficiency plotted against outdoor temp for the 12RLS2 in figure 14, p20 of this document.

The FH series Mitsubishis are more comparable to the Fujitsu RLS2s in cooling mode than the older FE series Mitsubishi that was also tested. The FH is actually more efficient than the RLS2 in an SEER test. Running at full blast at 95F outdoors it just clears a COP of 3, but during the day it's cooler running at part load with a COP between 6-9 , which is 2-3x as efficient as running it full blast during the hottest part of the day. At your likely oversizing factor it'll probably run a COP north of 5 even at 95F if it's modulating rather than attempting to cool down an overheated house.

 

[Spfrancis]

Yeah, that was what I was hoping you would say. I was hoping that the smaller unit would be enough, as I think the space is really pretty small at 336 sqft. Thanks for the additional input.