Owner Building installing Mini Splits in New Construction, Help Please.

[MaryS]

Hello All,
This is a great site you have here and I hope I'll be able to discuss my planned mini-split adventure with you a bit. My husband and I are fulfilling a dream we worked on for many, many years and finally broke ground this past July; owner-building our home. I've been the lead person on planning, budgeting, procurement, hiring subs and on-site general contractor. On his days off from work and on weekends, we both work on the house. A long ways back in our design decisions I choose to go with a mini split for heat/AC (zone 6, south central PA) ... and then I stumbled on to this site and got the idea that we could also do the install ourselves. I paid someone to do a Manual J for me and had planned to buy the mini split on-line. My husband is an experienced and skilled machinist with pretty much every tool known to man and a willingness to aquire more and has assured me he feels comfortable doing the install. It is my job to select and purchase the system.

And here in lies the problem. I should have purchased already, but I'm having a pretty hard time deciding. And it isn't even the money, so much. Its the idea that I want to "get it right" and have a comfortable home (or at least a reasonably conditioned one) and I'm just scared about making a big mistake. I've tried to read as much as I can on-line, but I would really like to bounce some ideas around ... and this seemed the right place.

I guess the order of my priorities is something like this:
- comfortable home (heat/ac) for our zone 6 climate
- efficient operation
- decent install documentation and/or tech support
- cost

House Stats:
1600 sq ft 1st floor (main living area, master bed/bath, office). The kitchen/dining/living area is all open on the south side of the house. The master bed/bath, the laundry/mud rm, the office, the 1/2 bath are all separate rooms (not very good air distribution) and are not nearly as sunny.

600 sq ft 2nd floor (two bedrms, full bath, small sitting area) for short and/or long term family guests

We are building the house very tight and will have mechanical ventilation (that we're also installing).

The best location (really the only location) for the outdoor equipment is on the windy north side of the house, next to the garage. I'll put in a temporary wind break this winter and then a better fence for it after final grading, but I am concerned about operation given this location, and the distance to the indoor heads (about 44' 1st floor and 55' 2nd floor).

FIRST FLOOR Manual J calc (in BTU)
heat load, entire 1st floor 18,292
cool load, entire 1st floor 13,696

1st floor: one head in main living area
heat: kitchen, dining, living area: 3712 + 3744 + 2140 = 9,596 heat
cool: kitchen, dining, living area: 3838 + 1287 + 2408 = 7,533 cool

1st flor: one head in master suit area
heat: master bed/bath/closet: 2218 + 1518 + 665 = 4,401 heat
cool: master bed/bath/closet: 820 + 449 + 305 = 1,574 cool

The 1st floor rooms of office, 1/2 bath, laundry/mud would rely on passive air circulation, or possibly some supplemental heat source.
heat: office, 1/2 bath, laundry/mud: 2272 + 74 + 402 = 2,748
cool: office, 1/2 bath, lundry/mud: 1297 + 25 + 695 = 2,017

SECOND FLOOR Manual J calc (in BTU)
heat load, 2nd floor 10,912
cool load, 2nd floor 5,729

2nd floor: one hd in open sitting area, just outside two bedroom doors and about 3 ft from bathroom door

I like the hyper heat mini splits for my peace of mind (in cold weather) and their efficiency. But if I understand correctly, they're only for one indoor head, is that right?

I welcome any comments, suggestions, advice, or words of encouragement.

Thanks!

[AC_Hacker]

Originally Posted by MaryS

I welcome any comments, suggestions, advice, or words of encouragement.

Good going MaryS, you did a heat load calc!

That shows considerable wisdom on your part.

It would help to have to have a drawing (nothing fancy) of the floor layout, but here's my opinion.

A lot of the dealers will quote you SEER ratings when they try to sell you a unit. For your purposes, you want to know the HSPF (AKA: Heating Seasonal Performance Factor) because that's the figure of merit for choosing a mini-split for heating, SEER is the figure of merit for choosing a mini-split for cooling. If your dealer doesn't know what HSPF is, or can't find the HSPF of the unit you are interested in, you need to find another dealer.

First of all, do your own research of the various mini-split units available to you and learn what is the minimum operating temperature they specify... because they're not all the same. Then you need to know how often the temperature gets really low in your area, and what that low temperature is. This is important because when it hits that temp your mini-split might not only not work very well, it might shut off entirely. If there's a threat of that, it's good to have a supplemental heat source you can fall back on... something like a wood stove comes to mind, or a pellet stove with a battery, or a propane heater that does not require electricity (you can still find them).

There's always the possibility that you could lose electricity in the middle of a cold snap... that could be quite uncomfortable.

With HVAC heating, your best economy is to size your heating system slightly smaller than what would be required for the 2% worst scenario, and make provision for using supplemental heat for that situation. That would be an unusually cold snap that may happen every year, or so. If you size to the maximum heat load, you'll pay more for your heating than if you sized a bit smaller.

Where you locate your outside units is pretty important, Your mini-split(s) will kick out a very large amount of cold air, because afterall, that's where they get their heat from. I have mine by the front door (not the best location) and when the weather is chilly, it's really chilly coming in the front door. But maybe more importantly, you certainly don't want to locate it on the side of your house where snow drifts are likely to occur. If you were asleep and it started to snow and drifted until your mini-split was buried, both you and your mini-split would be grumpy... that is unless your husband shovels the snow in your family, then you, and your husband, and your mini-split would be grumpy. Your best bet would be to locate the outside unit(s) on the side of the house where the hard winter winds are NOT pounding... The down-wind side would be perfect (thank me later).

Then it's a matter of choosing the minisplit either single-head or multi-head that would be slightly smaller than your Manual-J heat load.

Personally, I think you will get better efficiency with several smaller single head units, than a bigger multi-head unit. You will also have redundancy, so if one of the units goes out, you still have other units to see you through.

Of the brands, I own a Sanyo, which has worked just great for me, but if I were buying another, I would buy a Fujitsu Halcyon RLS series, because it has the highest HSPF that I am aware of.

Here's a link to some info... notice that they move more BTUs in heating mode than in cooling mode. For your purposes, it's all about heating.

Best of luck!

-AC_Hacker

[MaryS]

AC Hacker, thanks for your reply. I stayed up very, very late (like 'till early) looking at specs for different mini splits and working out a plan (or two) for how I might heat/cool the house. I hate staying up that late because then the next day (like now) I'm really beat. But sometimes, that's the seems the only way to ramp myself up and get somewhere in the problem solving. So, anyway, I've got a 1.5 ton (no pun intended) of stuff to do today and will post back with my plan to see if anyone wants to comment, or if it has holes in it so big you could drive a truck through, or anything like that.

Thanks for the kudos on the Manual J, but just so you know, I hired it out, I didn't do it myself.

We're in agreement on the importance of the HSPF and I like the Fujitsu too, for its efficiency. I had been thinking multiple heads ... but after reading your post and looking over the specs - I also agree with you that there seems a lot of merit in multiple outdoor (very efficient) single head units. I'm working out some cost compares too.

I've checked into the winter average temps, but need more time looking on that to get a feel for lowest temps, and how frequent.

All in all, I'm feeling a good bit better about being able to decide and move forward than when I made my original post. Thanks so much, and... I'll be back (said in my best Arnold S. voice).

MaryS

[AC_Hacker]

Originally Posted by MaryS

...but just so you know, I hired it out, I didn't do it myself.

I understood that you hired it out... But my kudos were based on knowing that doing a Manual-J is important.

Too many people skip this most important step, it's to your credit that you recognized the importance.

Best,

-AC_Hacker

[hotwire]

One web site that I've found helpful for comparing ductless mini splits is the Air-Conditioning Heating and Refrigeration Institute.

Being able to compare specs like HSPF and Btu output at 17°F might help you in making your decision.

When doing a search, I will usually select the search option for active systems only, it will help narrow down the field of equipment so that you're not looking at older discontinued equipment.

Hope this helps,
Kenny

[Xringer]

"got the idea that we could also do the install ourselves."


I've done two simple Sanyo Mini-split installs and found it a little nerving racking when placing the orders.

http://ecorenovator.org/forum/geothe...l-project.html

http://ecorenovator.org/forum/geothe...ct-2011-a.html

Because, I didn't know if I would be able to do the job (without a rescue)
and I didn't know if these things would work in cold weather..

When you DIY install these systems, you need to check things with your supplier.
My supplier had a big page covering everything they will and will not do for you.

Some vendors want a professional installer, or else all bets are off.
Others think DIY is fine, if you have an HVAC pro come in and do the
final checks and turn on the system.
My warranty form had a place for the HVAC installer company name.
I sent it in, But I'm not sure if they even looked at it, when I needed a new
out-door unit (my first one leaked after working fine for over a month).
Once I convinced the support manager I had located the leak in the ODU
beyond any question, he instantly agreed to ship out a replacement unit.

I was able to repair that leaky unit and it's running again today..(My second install).
http://ecorenovator.org/forum/geothe...r-project.html

Now, I almost feel like I could install these things for a living..

There are a lot of DIY install videos on Youtube these days..
Check them out. Some are very good. But mostly, read your install manual.
That will help you to decide, how much of the install you want to do.

[MaryS]

Here is my general strategy.

Provide heat/cool with three single head min split units, to be located in the:
- main living area
- upstairs (guest area)
- master bed/bath/closets area

I'm looking at either of the two systems below. If I read the specs correctly, the Fujitsu is more efficient in operation while I think the Mitsubishi operates better at lower temperatures. The efficient Fujitsu operation appeals to my thrifty (some would say cheap) side. The low-temp Mitsubishi operation appeals to my ultra-planner (some would say worry wart) side.

- Fujitsu 9RLS HALCYON Wall Mounted Mini Split Single Zone Heat Pump 26 SEER - 9,000BTU
- Mitsubishi MSZGE09NA+MUZGE09NA Mr. Slim Wall Mounted Single Zone Heat Pump -9,000BTU

The three separate systems will provide higher efficiency than a multi-head (indoor) system, and as ACHacker mentioned, redundancy if one of them goes down. So that's good.

On the not so great side, the 9K BTU system for the master bed/bath/closets area is significantly more capacity than needed for that area. It would be better matched if I included the laundry/mud room and office as part of that 'zone'. But the floor layout isn't going to help me. The office & laundry are only a wall away in a birds eye view ... but with no ducting they're actually out the bedrm door, down the hall a little bit and through another door. I'm not sure, but I don't think open doors are going to be enough to share out the heat/cool form the master bed/bath/closets area.

Our house should be rather tight. I've paid particular attention to that issue in materials and construction details. We're going to have mechanical ventilation. Will that help even out conditioning between zones? I don't really know. I am toying with the idea of 'jumper ducts' or something like that between the closets and the laundry room, and laundry and office (?). Not sure...Time will tell on that.

The over capacity issue, if there is one, would happen with any mini split system, single head or multiple head. I didn't see much in the way of lower capacity indoor heads. I know the compressor can ramp up and down, so there is a range of operation, so maybe it will be just fine.

So, I was thinking of buying one of the three systems we need. We can install it and use it, and see how things go. I'm thinking this will be installed in the main living area. It could provide some heat as we finish up our rough plumbing, ventilation duct work and then turn to electrical wiring. Then blown cellulose and drywall. Since we're doing the work ourselves, and my husband only gets a couple of days a week on-site - our schedule is pretty slow going.

Ok, so that's the general plan, Any comments? Thanks for your input and help in posts above.

[Xringer]

Hi Mary,

"The over capacity issue, if there is one, would happen with any mini split system, single head or multiple head. I didn't see much in the way of lower capacity indoor heads. I know the compressor can ramp up and down, so there is a range of operation, so maybe it will be just fine."

Our Sanyo #2 is way over-capacity for our Den. But, with the doors open to the rest
of the house, it's not really an issue. It does run less and at lower power.
Even with the Den doors shut tight, there is no problem.
It might last a few years longer than our living room Sanyo..

My first run-in with a mini-split was a 24,000 BTU Cool-Only Sanyo.
It was installed in 10'x20' conference room.
It worked fine, even if the demand was only for 4,000 to 7,000 BTUhs.
While I worked in the room, I used it in Quiet Mode and didn't sit right under it.
When I say Quiet, I mean Quiet... I felt the cool air, read the manual and fell in love!

Because cool air runs on the floor, we have found our living room Sanyo
cools our bedroom (down the hall), much quicker than it heats.
However, we only use the master bedroom at night, and my wife likes it cool.
Keeping the bedroom to her liking is not a problem.
We shut the door during the day, so in won't get too warm in there (from solar gain+the Sanyo twins).

Because an inverter type mini-split will throttle up and down, and sleep
at very low power while the room is at setpoint, over-capacity not a prob.
The only worry seems to be under-capacity, and you've already done your homework there.

I would not use wall mounted outdoor units, put them on a ground pad.
It might be okay to use wall brackets, if the wall was remote from
the active areas of the home. Like the far side of a garage.
Wall mounts have appeal for those of us living in snowy areas.
They are very common in upper floor installs in Europe.

[AC_Hacker]

Originally Posted by MaryS

If I read the specs correctly, the Fujitsu is more efficient in operation while I think the Mitsubishi operates better at lower temperatures.

As you plan your system, also consider your axillary heating sources. I'm not sure what axillary sources you have available to you, so that must influence your thinking. For me, I have natural gas, which is reasonably priced, so I am considering something like one of these:

It is direct-vent, so it gets it's combustion air from outside and it vents exhaust gases to the outside, also. The reviews look pretty good, and also mentions that a fan (not required) is available to help spread heat around. It does not require house power to ignite or to operate (the fan would need power). This heater has a propane adapter kit available. There are many different models and sizes of this style of heater from different manufacturers, and different prices.

> the Mitsubishi operates better at lower temperatures.

If you can get some weather statistics for your area, and can find out what percentage of heating days you could expect those low temperatures, it can make your decision more of a calculation and less of a guess.

Originally Posted by MaryS

On the not so great side, the 9K BTU system for the master bed/bath/closets area is significantly more capacity than needed for that area.

If you do some absolutely relentless searching, you will discover that there are units that are smaller than 9k BTU (12k BTU heating). Not widely advertised in the US, but they exist.

Originally Posted by MaryS

We're going to have mechanical ventilation. Will that help even out conditioning between zones?

It might.

Your HRV should be really high efficiency. There are European (German) models that are state of the art, and there are also some European 'combi' units that are HRV combined with some active heating ability, too.

This unit (UltimateAir) seems to be the most efficient I have come across in the American market.

Good luck with your project!

-AC_Hacker

[Xringer]

That gas heater would have been great for my daughter last month when her grid failed.
I just emailed her the URL.

That UltumateAir unit looks good too. But, after cleaning the our Sanyo's filters
every 3 or 4 weeks, I get the feeling they are doing a pretty good job
of cleaning a lot of gunk out of the indoor air.
They worked great during the tree pollen season this past summer.
Normally, I would have some seriously red, itchy eyes for a few weeks.
But this time I needed very little in the way of eye-drops..

Mary FYI, if your house is really tight, getting fresh air indoors will be important.
Our 1956 home has fresh air designed into it..