Educate me on Mini Splits Please

[justsam]

My daughter just purchased an 1800 sq ft production town home built in about 2010 in Portland Or. She sent me the inspection report to review and I had a couple questions about mini splits which this town home has as built originally by DR Horton.

The units are Mitsubishi, and I understand the use of them in main areas of the home, however the report also lists "registers" in areas such as bath rooms and some bedrooms.

What is the source of conditioned air for these "registers"?

Does the outdoor compressor unit feed more than one indoor evaporator unit?

In general, are mini-splits complemented by other sources such as base board heat, infra red bath units, etc. for smaller areas?

Thanks for your insight!

 

[Climatecreator]

Sure!

All of those things.

DMS can have many other sources of "backup" heat or even sometimes AC.

They also make mini ducted splits, same condenser but has a small air handler.

Also the "head" that traditionally hangs on the wall could instead be a low wall mounted unit looks like a radiator kind of as well ceiling mounted versions.

Hard to say what they are for sure but it's possible with mini splits.

Could be for ventilation as well.

CC

 

[tapered-pin]

^^ all correct..

ductless mini splits are very efficient, you can often see a single outside unit tied to several indoor heads. (the heads function like individual systems, but share the exterior compressor)

They are a great option in smaller residences or open floorplan layouts.

they can be used in conjunction with other types of air conditioning, but typically NOT for the same room being conditioned (unless the original system was undersized for the heat loads/gains)

 

[justinjoyal]

I’d be surprised if she had a ducted mini-split system.

Are there wall units? How many?

Does she have a HRV/ERV ? The registers could be used for that.

 

[theoldwizard1]

What is the source of conditioned air for these "registers"?

Sometimes that is to get heated/cooled air to move between rooms. Not a perfect solution. Most companies sell a ceiling unit that can be ducted to more than one room. Also less than perfect.

Does the outdoor compressor unit feed more than one indoor evaporator unit?

Maybe. Check the outside compressor unit. Some have multiple pairs of ports. The most common "air handlers" are wall mount, either high or low. Ceiling fans are usually an important part of any mini-split installation.

In general, are mini-splits complemented by other sources such as base board heat, infra red bath units, etc. for smaller areas?

If done correctly, this should not be required. I could see an infra red in a bathroom for quick heat. Base board resistance means the system was not design correctly.

 

[theoldwizard1]

ductless mini splits are very efficient, you can often see a single outside unit tied to several indoor heads. (the heads function like individual systems, but share the exterior compressor)

I am a fan of ductless mini-split system, but for those who are looking for the MAXIMUM efficiency, the one air handler (head) to one compressor units have the best efficiency. They can be slaved together.

 

[justinjoyal]

If done correctly, this should not be required. I could see an infra red in a bathroom for quick heat. Base board resistance means the system was not design correctly.

I disagree.

Backup heat is needed to provide adequate heat in case of malfunction or insufficient output due to outside temperature.

 

[tapered-pin]

What is the source of conditioned air for these "registers"?

As stated above, if the "registers" are in the wall above a door (or the doors are undercut to approximately 1/2"-3/4" off the floor), then they're probably transfer grills..

it's easy to tell if your home is built with transfer grills, any grills that occur within 12" of each other on opposite sides of the wall are more than likely transfer grills. (a quick google search will yield enough information on them to determine whether they're used in her application)

 

[Jackfre]

The short cutting of the doors and thru registers are an effective way to get air circulation. Over the years I've seen this done thousands of times with the Rinnai Energysavers and subsequently with mini-splits. You will generally have a 2-3* temp difference if it is laid out properly. Tjernlund manuf the Airshare Transfer fan for room to room and floor to floor applications to provide a mechanical transfer. Panasonic, Broan and others are also making transfer fans, but I prefer the Tjernlund (btw, pronounced CHERN-lund). Tamarack Technologies makes an excellent transfer grill. It has styrofoam baffles to reduce noise and light transfer.
I don't need electric heat in my bathrooms. I have the Toto Washlet toilet seat. It is heated and planting yourself on a warm seat greatly reduces any possible discomfort

 

[Climatecreator]

I don't need electric heat in my bathrooms. I have the Toto Washlet toilet seat. It is heated and planting yourself on a warm seat greatly reduces any possible discomfort

Wow that seat https://amzn.to/2KzRsfQ is really something else! I had to go look that one up, wow! How do you manage to ever go anywhere else? Lol

 

[tapered-pin]

who wants to spend enough time sitting on the toilet to justify a $360 seat?

i guess unless you've got IBS or something..

 

[justsam]

Thanks to all for the information! I certainly knew of mini splits but it never occurred to me how to deal with heating and cooling in the non-main areas of the home. I have not even walked through the home, only seen some photos. I do believe there are two evaporator units mounted high on the walls in the main areas.

What could one reasonably expect to find in a median priced, (for the Portland Or. area), 1800 sq ft 2 story production built town home? What would supplement the mini splits? I was not aware of transfer fans, but I have to think there would still be need for base board or IR heat in the baths. Would some one that is accustomed to a properly designed central, forced air system be dissatisfied?

 

[tapered-pin]

try looking for that information on www.zillow.com

 

[theoldwizard1]

I disagree.

Backup heat is needed to provide adequate heat in case of malfunction or insufficient output due to outside temperature.

Malfunction, maybe. But millions of people live in the midwest with no back up to run their force air furnace it the power goes out.


Insufficient output = IMPROPER DESIGN !

 

[theoldwizard1]

Thanks to all for the information! I certainly knew of mini splits but it never occurred to me how to deal with heating and cooling in the non-main areas of the home. I have not even walked through the home, only seen some photos. I do believe there are two evaporator units mounted high on the walls in the main areas.

If there are no air handlers in the bedrooms, they will be hot in summer and cold in winter.

 

[justinjoyal]

Malfunction, maybe. But millions of people live in the midwest with no back up to run their force air furnace it the power goes out.





Insufficient output = IMPROPER DESIGN !

Eh?

Backup heat does not mean « in case the power goes out », it means resistive or fuel-based heat.

You don’t design a heatpump system using heating load/capacity, Even so, backup heat would be needed where temperatures fall under confortable levels.

 

[finn]

Eh?

Backup heat does not mean « in case the power goes out », it means resistive or fuel-based heat.

You don’t design a heatpump system using heating load/capacity, Even so, backup heat would be needed where temperatures fall under confortable levels.

Sounds more like supplemental heat rather than backup heat.

To me, backup implies some sort of mechanical or electrical failure.

Supplemental adds capacity when the unit is asked to operate outside of its design range or capacity.

 

[justinjoyal]

In case of a heat pump setup, I would say both terms would be correct in their own aspect.

A air handler with electric strips is less likely to fail than a heat pump and acts as backup if said heat pump fails or goes into defrost.

Then it also acts as supplemental heat when the heatpump output is not sufficient.

But to claim improper design because a heatpump cant suffice on its own is just wrong.

 

[theoldwizard1]

Sounds more like supplemental heat rather than backup heat.

To me, backup implies some sort of mechanical or electrical failure.

Concur !

My in-laws lived with a heat pump (they were clueless, it was a box in the basement that made hot and cold air) for about 10 years. The builder told them they need a backup heat solution so they had propane fired fireplaces and a buried propane tank.


They never use it to SUPPLEMENT their heat, even though it got below freezing some nights where they lived.

 

[justinjoyal]

Concur !

My in-laws lived with a heat pump (they were clueless, it was a box in the basement that made hot and cold air) for about 10 years. The builder told them they need a backup heat solution so they had propane fired fireplaces and a buried propane tank.


They never use it to SUPPLEMENT their heat, even though it got below freezing some nights where they lived.

So ? Backup/supplemental heat is often needed.

What do you do when you have a 50kbtu heat load and a 26kbtu cooling load? You don’t get a 4-ton hp..

 

[Trey T]

Thanks to all for the information! I certainly knew of mini splits but it never occurred to me how to deal with heating and cooling in the non-main areas of the home. I have not even walked through the home, only seen some photos. I do believe there are two evaporator units mounted high on the walls in the main areas.

What could one reasonably expect to find in a median priced, (for the Portland Or. area), 1800 sq ft 2 story production built town home? What would supplement the mini splits? I was not aware of transfer fans, but I have to think there would still be need for base board or IR heat in the baths. Would some one that is accustomed to a properly designed central, forced air system be dissatisfied?

The ones you saw are, what I called, basic or original flavor of "mini split" systems. Originally, these Japanese technologies were created to replace windows units, which are common in US. Today, there are many flavors that exist to fill the gap between window unit and central air system - THEY CAN BE SUPER EXPENSIVE!!!

With that being said, the mini split that you saw is generally not meant to replace a central air system. Theoretically, a proper setup using mini split systems will requires up to 5 units vs 1 central air system for a standard home (w/ various types of rooms) to perform adequately; the down side is the costs, potentially 2-3times more. The mini splits will perform better but no body in their right mind will want to spend more than they have to.

mini split have their places but generally speaking, central air is more desirable as their initial costs are low and energy prices are relatively cheap in US.

 

[Jackfre]

I use a combination of mini-splitis and the gas fired Rinnai Energysaver in my home. It is an ideal combination for "net to the space" heating and cooling and the addition of the Rinnai allows a proper sizing of the mini. One thing not discussed in this post is the benefit of modulating equipment. Modulating equipment wants to do two things for you. Number 1, it wants to make you comfortable. Number 2, it wants to do it at the lowest possible input. In other words, it wants to continue to run. Why? Because if it is oversized or the low range is not low enough it has to shut off or overshoot. When it shuts off you end up with the perfect sine wave comfort curve. Hot and cold in heat, humid, cold and hot in cooling. Extended run times also allow conditioned air to penetrate adjoining spaces. Basic physics, heat wants to go to cold. With properly sized and positioned modulating equipment transfer grills are an effective method of heat transfer.
The perfect supplement, in cold climates to the mini-splits is the Rinnai. It offers redundancy and as much as I like my mini-splits for heat, having gas fired heat at the floor level is the best. We have 2200 sq ft and the whole place is zoned and comfortable in any season and by taking the central system to the dump I gained two closets and storage under the stair case. A well designed central system that is very well installed, meaning a tight duct system, which is another story in itself, can offer great comfort. However, by the time you add the zoning and go with the modulating high efficiency equipment and pay the labor to install same, you aren't saving much, if anything, over a mini-split system install.
It is interesting watching the HVAC industry over the years. I've been in it for almost 55 yrs now and in my experience, ALL the advanced technology has come from off shore. Modulating equipment was developed in Europe or Japan. Why, because they pay a lot for their energy while we have paid little and had little incentive to develop new things for the American consumer. I introduced the first modulating gas equipment into the New England market with the Rinnai's in '91. It was like magic. People couldn't believe how well they worked and sales reflected that. All the modulating boilers came to the States from Europe initially and forced the American manuf to develop their own. The inverter mini-splits have blown the American manuf business to hell in a hand basket and deservedly so. The fight to get central cooling to go from 10-13 seer was something to watch. My mini-split is 26 seer. I remember the fight to get the regs developed in the late 80's to force, and I do mean force, equipment manuf to raise the minimum gas efficiency from the low 60's to 78% on central equipment. American manuf were dragged kicking and screaming to the high efficiency market in boilers, furnaces and air conditioners.The same is happening today in water heating. The Japanese and Korean modulating tankless water heaters are forcing the tank manuf to up their game. At last! With all of these terrific technologies available the American consumer is showing the American manuf that perhaps they should invest in new technologies. It would be nice to see us "lead" in this way for a change!!

 

[justinjoyal]

The ones you saw are, what I called, basic or original flavor of "mini split" systems. Originally, these Japanese technologies were created to replace windows units, which are common in US. Today, there are many flavors that exist to fill the gap between window unit and central air system - THEY CAN BE SUPER EXPENSIVE!!!

With that being said, the mini split that you saw is generally not meant to replace a central air system. Theoretically, a proper setup using mini split systems will requires up to 5 units vs 1 central air system for a standard home (w/ various types of rooms) to perform adequately; the down side is the costs, potentially 2-3times more. The mini splits will perform better but no body in their right mind will want to spend more than they have to.

mini split have their places but generally speaking, central air is more desirable as their initial costs are low and energy prices are relatively cheap in US.

I often read posts similar to yours and have come to think it must be a cultural thing.

Most houses in Quebec use mini-split(s). They outperform central systems and are much cheaper.

They do allow greater temperature deltas between rooms/stories sometimes, but when properly placed/used, the truth is they work just fine most of the time, often for 1/4 to 1/2 the price of a central setup.

Considering the amount of money saved, most people can live with the downside...

 

[Climatecreator]

I often read posts similar to yours and have come to think it must be a cultural thing.

Most houses in Quebec use mini-split(s). They outperform central systems and are much cheaper.

They do allow greater temperature deltas between rooms/stories sometimes, but when properly placed/used, the truth is they work just fine most of the time, often for 1/4 to 1/2 the price of a central setup.

Considering the amount of money saved, most people can live with the downside...

I agree with you. Here in CT it's way less to use ductless most of the time, especially when you consider it's true zoning nature, only use what you need not fire up the whole house but block some off. Even with blower modulation on conventional, ductless outperforms every time, plus it heats too so you have a backup or offset to your regular heating.....

CC

 

[yeldogt]

Without pictures it's not possible to understand what's in the house.

Mini split success depends on many factors. It starts with great insulation and air tightness -- a well insulated house w/ no drafts is of uniform temperature. There are many open plan homes being designed today using only one or two heads -- they can work when done correctly.

Trying to retrofit an old victorian located the coast of MA -- in the winter w/ single pane glass .... may not be happy with a couple mini splits.

Unfortunately, builders are builders -- they build homes to make money. Insulation/HVAC/Window efficiency don't sell homes .. appliances and countertops sell homes.

 

[Trey T]

I often read posts similar to yours and have come to think it must be a cultural thing.

Most houses in Quebec use mini-split(s). They outperform central systems and are much cheaper.

They do allow greater temperature deltas between rooms/stories sometimes, but when properly placed/used, the truth is they work just fine most of the time, often for 1/4 to 1/2 the price of a central setup.

Considering the amount of money saved, most people can live with the downside...

Lol.... Damn, WTF. Did you not read my response? I agree with your assessments but I'm not gonna repeat myself.,,, Lol. Keep in mind, I chose my words very carefully.

One of the downside of mini-splits is the appearance - they are almost as ugly as windows unit. Some company tries so hard to make the wall units to be integrated into a home as some-form of a furniture, but it's still a damn plastic box hanging off the wall.

Again, mini-splits has their places and limitations.

 

[OzarkMan]

I wouldn't call them ugly.... Love my unit. Doesn't even register on the bill. Don't even know its running its so quiet. Mini splits come in many flavors. Ducted, ductless, cassettes, wall mount, Art frame mount, ceiling hung...



IMG_8908 by https://www.flickr.com/photos/153164955@N06/, on Flickr

 

[eddieK]

Concur !

My in-laws lived with a heat pump (they were clueless, it was a box in the basement that made hot and cold air) for about 10 years. The builder told them they need a backup heat solution so they had propane fired fireplaces and a buried propane tank.


They never use it to SUPPLEMENT their heat, even though it got below freezing some nights where they lived.

A properly installed heat pump system with supplemental resistant heat strips can keep a place comfortable in very low climates...

The strips not only provide heat during defrost, they speed up the defrost time by adding heat to the evap (when it shifts to cooling mode in defrost)...the best way to achieve this is by proper install and using a night set back t stat(mini splits come with them)...never allowing the space to get more than 15F (10F is better)cooler at any time. Essentially you are not asking the system to attempt a 25 - 40F degree work load where it will at some point enter defrost.

 

[yeldogt]

Looks are a factor with the wall units -- no getting around it in the USA. I did two 12k cassettes on the second floor of my big cape cod -- both rooms are large with one central bathroom. They work great -- really don't notice the units as I have them off center and use three of the four outlets --- with good insulation we really don't notice the loss of the bathroom vent. This replaced a 2T AC unit that was installed in the attic for this space. Mini-split is a 30k Mutsubshi hyper heat compressor w/ three outlets -- We used a conventional 12k wall unit in a new 14x20 single story addition built at the same time. The addition was spray foamed and we updated the insulation throughout the house. The addition has a cathedral ceiling and we hid it above site line. Since its a heat pump -- we can use it to warm on occasional cold days before the hot water heat is turned on (radiant)

As they become more prevalent (and smaller) you don't notice them all that much. I'm using them in my new build as well -- part of the project is an old stone house and there is nothing else that will work/fit. They keep getting better -- companies now have units in standard air handler cases that can be installed w/ conventional ductwork and even gas furnaces. So you can have a standard system in one part of the house and separate heads in another (great for retrofitting/ upgrading) Floor/wall and various hidden units -- there are options.

If I was designing a new house -- with plenty of space -- would install VS conventional system w/ zones. I'm an old house guy -- so space for ductwork is tight.

 

[justinjoyal]

Lol.... Damn, WTF. Did you not read my response? I agree with your assessments but I'm not gonna repeat myself.,,, Lol. Keep in mind, I chose my words very carefully.

One of the downside of mini-splits is the appearance - they are almost as ugly as windows unit. Some company tries so hard to make the wall units to be integrated into a home as some-form of a furniture, but it's still a damn plastic box hanging off the wall.

Again, mini-splits has their places and limitations.

I have read your response, and stand by my reply. [emoji4]

In my experience, you do not *require* as many units as you suggest and they are not more expensive than a regular split system.

I’m in Quebec, Canada. Things may be different. Culture is different. My experience is probably different as well.

For example:

Top of the line mini-split in a new bungalow: 3500$ (main floor).

Add another mini-split in the basement, same high end unit for another 3.5k. Still « only » at 7k and you got efficient A/C and heat down to -25F. You can add say 1k for baseboards and tstats as backup/supplemental...

Average, basic split system in the same bungalow: 12000$+. And you need strips, gas or oil because the heatpump is no longer efficient under 5F.

There are up and downsides to each solution, but mini-splits are great IMO.