Whole House Minisplit System

[jserr68594]

I am looking for opinions on my proposed minisplit layout. I am trying to decide whether I should go with 3 condensers or 2. I am not considering anything other than minisplits for this project, so I just want opinions on the best minisplit route to go.

If I go the 3 condenser route (As pictured) Unit 1 would be a 3 zone 28K conditioning the main floor bedrooms. Unit 2 would be a single zone 24K for the living/kitchen area. Unit 3 would be a 3 zone 36K would be for the basement and garage.

If I go the two condenser route, I would have a 48K unit conditioning the 1st floor living/kitchen, basement living and garage. Then I would use a 36K unit for the 4 bedrooms upstairs and down.

My goal either way is to have redundancy on the first floor. If one unit were to go out, I would have the other unit as a backup. I appreciate any advice!

 

[dcg9381]

I don't know your location, but we just finished a "small house" (1400 sqft) with a single unit. It's in a northern climate. The bathroom gets very humid, so I think you're going to run into that issue potentially without and ductwork or HVAC intake functions. But maybe just the baths, everything else is covered.

I think it could be potentially handled by installing through-wall forced air venting. Something to consider.

About 4 years ago we did our primary residence. I got bids on ductless AC and it turned out to be more expensive (turn key) with the number of heads required.

I like the redundancy thinking. But other thing with these is that they are much more "disposable" units than traditional ducted HVAC.

And advantage is you can shut entire rooms down if you're not using them....

 

[ericm]

It seems like the bathroom and kitchen exhaust fans should address most of the humidity problem. Mini splits remove humidity as well, at least when they're in cooling mode.

 

[nadogail]

We just finished the installation of a 5 ton heat pump with 4 line sets and 4 air handlers. It is about 1500 square feet, three bedrooms and 2.5 baths.

 

[manwithtools]

We just finished the installation of a 5 ton heat pump with 4 line sets and 4 air handlers. It is about 1500 square feet, three bedrooms and 2.5 baths.

Gail, that seems significantly oversized for your temperate location on Coronado Island?

 

[Jackfre]

Orientation N/S is always helpful in these questions Usually to ensure the late afternoon low sun doesn’t beat you down. Check out Tjernlund Airshares. They will help in some locations

 

[chinboys]

Your design seems reasonable. I did the same design upstairs at my home.
I used an LG 48K mini split driving a 4-port manifold in the attic. The 1-inch suction line and 3/8-inch liquid line run about 50 feet from the condenser up 2 1/2 stories.
I use 3 - 12K ceiling cassettes plumbed with 3/8 inch suction lines and am 1/4 inch liquid all under 20 feet in length.
The 4th 12K connection drives an induct unit which has an ERU (energy recovery unit) circuit in it.
I chose this configuration as I didn't want multiple suction and liquid lines on the outside of my home and my design allowed everything to be done from inside and from the attic.

I believe other mini-split manufacturers also have central or multi-manifold offerings.
LG also makes an 60K unit that can drive 2 multiple port manifolds.

For my ground floor LG setup, I have a 36K unit that drives 4 wall units each with their respective liquid and suction lines.

I was introduced to a copper line set alternative during my HVAC certification studies last year.
We were told that the head USA LG engineer in Cali used it for his own home and will start to recommend its use.
The only problem is whether or not your local building inspection department will allow it to be used.
The product is PEX-based and is offered from Python Line Sets.
My class and I have used it in our lab and it is very easy to install with minimum splicing. The connections are pricey but worth it due to ease of installation.

 

[ratflinger]

That looks interesting. Liked the kink resistance of it. Just like PEX I bet these PERT lines end up taking over.

 

[pcmeiners]

Gail, that seems significantly oversized for your temperate location on Coronado Island?

Gail I suggest you read as many previous post in this sub forum related to minisplits as you can bare, you are definitely way over sizing your minisplits, about twice as much as needed. As you research the brand/model, SEER is your important number NOT HSPF, as it is not relevant in your area. Research single zone vs multi zone efficiency. Living room/kitchen, garage are candidates for a single zone units

The next linked tool is a spreadsheet download....

https://www.energystar.gov/sites/default/files/asset/document/ASHP_Sav_Calc.xls

Product Finder — ENERGY STAR Certified Heat Pumps

Compare ENERGY STAR Certified Heat Pumps, find rebates, and learn more.

www.energystar.gov

SEER Energy Savings Calculator for Air Conditioners

Use our free SEER Energy Savings Calculator to instantly see how much energy you save by upgrading to an air conditioner with a higher SEER / SEER2 rating.

www.seerenergysavings.com

Mini Split SEER Savings Calculator (+Operating Cost)

How much can you save with a more efficient mini split ductless heat pump? Will choosing a higher efficiency be worth the extra money? This calculator gives you clear, accurate results about costs and savings. Note for calculator: This calculator is based on EIA Residential Electric Rate...

www.pickhvac.com

Examples of very efficient units, the units to the right of the chart are extra low temp units not needed in your area.
...

https://www.goodlifehvac.ca/images/Fujitsu_LZ_Series.pdf

Thermal load calculator.....

HVAC Load Calculation - Maunualj - Whole House Loadcalc

ManualJ load calculator, HVAC calculation, Whole house, - www.loadcalc.net

www.loadcalc.net

If you put a heat pump[ water heater in the garage, a minisplit head on a thermostat will rarely turn on as the water heater provide dehumdification and a good deal of air conditioning at very low water heating cost. If you ever decide to get a heat pump water heater, oversize the capacity, recovery is slower than a gas unit.

In San Diego, hope you have an abundance of attic insulation.

"Check out Tjernlund Airshares. They will help in some locations" from Jackfre's post, very good idea, especially for bathroom due to humidity.


Lastly floor units (mounting like radiators) are much more esthetic for living room and bedrooms. My living room units are Fujitsu, quieter than wall units, look better, but a little less efficient. I mounted them recessed between the studs (about 3-1/4 deep) with only 1/8" clearance around entire unit's fascia, less conspicuous.

 

[brit vet]

We had a cooling requirement to 5 bedrooms and a lounge on the ground floor and I went with a Toshiba mini VRF 2 pipe system including 6 wall mounted fan coil units. It's a heat pump so it does also provide heating but that mode rarely gets used. The big disadvantage is you cannot have simultaneous cooling and heating but that wasn't a concern to us. Big advantage is only one external condensing unit and one pair of pipes that tee off to each of the fan coil units. Just about the most efficient system out there and works down to an ambient of -20C

 

[fitter30]

Has anyone run load on this house per room? Have you looked at on you tube what it takes to clean indoor wall units? Having two systems in my house 1900 sq ft 3 bed two bath with 5 wall and a fan coil. 2 down stair beds and a bath and utility rm. Second unit loft bed / bath and kitchen / living. Both units 2 ton 3 head can cool house with one unit and heating both.