Mini-Spits? I got questions

[383 240z]

First up, a little background on my situation. No natural gas in my area, My only options are electric and oil for heat. We put in a new better quality furnace when we moved in 8 years ago, and band-aided the AC system, it works but wont cool the second floor. We have no issues with heat.

The house was built in 1817, 2 story about 2500 sq ft, 6 rooms down, 6 up. When we had the A/C fixed I asked why the second floor would not cool. I was told the A/C unit was large enough, however we needed ALL new ductwork. The basement is a MAZE of fixes, patches, repairs, and mods. It *****! Feeding the second floor, all I can find is one 8" vertical, and NO returns. I don't know much about air flow, but I figure if I want to put cool air in a space, I need to get the hot air out, right?

Any way after reading about replacing all the duct work, and laying out a new system, I'm going to be cutting LOTS of holes in my hardwood floors, and walls. The floors I have no problem with, however most, about 90% of our exterior walls are concrete over expanded metal, and plaster and wood lathe. Interior walls are covered with some form of early sheet rock. However the early parts of the house are built in frame and timber style, and running ducts in them will be VERY complicated.

This brings me to the point of my rambling. Mini-splits. After looking at the basic concept I have a few questions I don't want some salesman answering for me.
First up, do I need one unit for every room? One for each floor? How does this zoning system work?

Thanks for any input guys, I'm sure every answer I get will give me 2 more questions to ask. Keith

 

[green.bubbly]

I am not sure how many rooms you are trying to cool upstairs or if all the rooms need to be cooled all the time. Certainly sounds like you are a perfect fit for for a mini-split system. Generally you need one indoor unit for each room similar to a window unit setup.

There are multi zone mini-split systems that will probably work well for you. A three zone would give you three indoor units and one outdoor unit. The systems are variable speed and can be controlled independently. Lets say you needed all three rooms cooled at the same time. The outdoor unit would run at full capacity feeding all three indoor units. You could only need two rooms cooled. You could shut down one indoor unit and the outdoor unit would run at a slower speed/capacity.

The beauty of these systems is that you can really customize them to fit your needs. You could get three individual systems or one two zone system and one single zone. Just think about what rooms need to be cooled and what would be the best combination.

There are even multi sized units. For example you may may have one large room and two small rooms. You could then get a three zone system with one 18,000 btu indoor unit and two 12,000 btu indoor units.

Best of all, you are not running one large central unit trying to cool off the entire house even when nobody is upstairs. No need to run duct work. It may be a little more upfront cost but in the long run, you will have a more efficient system and a lot less headaches.

 

[Jackfre]

Go to Fujitsugeneral.com and Mitsubishi and read. Fujitsu's Hybrid Flex Inverter unit is 48 kbtu and you can connect from 39kbtu-62kbtu worth of evaporators (indoor units). Max output is still only 48, but that is more than adequate for your sized place. That said, do a heat loss/gain to ensure sizing. You can put up to 8 Evaps on that unit. Or you can do the multi 18, 24or 36kbtu units. Depending upon how the floor plan lays out you may be able to do the first floor with an evap on either side to the first floor. They are variable speed and will project the air into adjoining spaces much better than the single stage type systems. If you do this and run them on heat rather than running your oil, you will reduce your bill by probably 60%. You can also look at this as the ultimate in zone control. You could do the upstairs or down this year and the other later. You do want them on the first floor though to get off your oil bill. That is what will pay for this system. I had a lot of customers in ME, NH &VT who did this and I am comfortable with the 60% savings figure. Btw, I'm a peddler

 

[pseudorealityx]

This brings me to the point of my rambling. Mini-splits. After looking at the basic concept I have a few questions I don't want some salesman answering for me.
First up, do I need one unit for every room? One for each floor? How does this zoning system work?

Thanks for any input guys, I'm sure every answer I get will give me 2 more questions to ask. Keith

1) You need a unit in any room you actually want to actively cool. I would suggest exterior rooms, bedrooms, living room, kitchen, dining, etc. Open floor plans help in that air can blow through multiple rooms and mix. Houses with lots of rooms with doors...not the best.

2) You don't need 2 condensers for 2 floors. In fact, if you get a heat pump system, it would help you to NOT do 2 units per floor, at least under certain circumstances.

3) Each evaporator works independently. It's refrigerant is then pumped back to the outdoor condenser. The condenser pays attention to what conditions the refrigerant comes back at, and does its thing, be it heat or cool. Unlike most standard split systems, it can modulate capacity, which is a nice feature, and will save you $$.

4) You will still need your oil heating system, even if you get the heat pump option, but I would suggest it anyway, because of the savings quoted above. You'll want to take a look at oil prices vs. electricity prices, but I'm still confident that until you get to ~40 degrees outside (probably lower, depending on prices), the heat pump will be the easy winner. The oil will be a nice solid reliable back-up.

5) These systems are a good fit on a case by case basis. For certain applications, they're perfect. For others, they're terrible.


<--- HVAC engineer, not selling anything.

 

[Falcon67]

Having owned several old houses, most built in the 20s~30s AND having looked hard at this, I say "good luck". It may cost you 2-3 times as much to do the split stuff as to do conventional. Old houses with small walled off spaces are just not suited for mini-split systems. Bitty bed rooms, bathrooms and narrow hallways make it hard enough to balance a conventional system. Line set runs on your upstairs rooms will probably have at least one outside unit sitting on a shelf 8' off the ground. Maybe not as noted above, but you're still going to have $20 million in copper tubes running all over LOL.

 

[pseudorealityx]

Having owned several old houses, most built in the 20s~30s AND having looked hard at this, I say "good luck". It may cost you 2-3 times as much to do the split stuff as to do conventional. Old houses with small walled off spaces are just not suited for mini-split systems. Bitty bed rooms, bathrooms and narrow hallways make it hard enough to balance a conventional system. Line set runs on your upstairs rooms will probably have at least one outside unit sitting on a shelf 8' off the ground. Maybe not as noted above, but you're still going to have $20 million in copper tubes running all over LOL.

That's a good point. These are NOT cheap systems. Fortunately, things like balancing aren't an issue with these systems either. It's a compromise system for sure, but it is an option.

 

[383 240z]

small rooms are not going to be a problem living room is 19x28 dining room is similar. 9 1/2 celings on both floors.

Lots of good points both ways. Looks like I will be trying to get some HVAC guys out to give me quotes. I'm guessing that I'll be doing all the tear out work, to save a bunch of labor. Then let them start running new duct work. The furnace most likely stay and new A/C unit fitted if we go with a central system. I'd like to say that I would be taking the oil furnace out and putting it in the shop, however it would stay in place as a back up sytem. Keith

 

[brewchief]

If you are keeping the oil furnace go with a heat pump instead of a straight a/c, it will save a lot in the spring and fall.

Sent from my SPH-D600 using Tapatalk 2

 

[ormachine]

Would these mini-splits be good for an open floor plan? Say for instance a 27x54 shop that has R19 in the walls covered by 3/4" OSB, and the ceiling having R30 covered with 1" foam insulation board..

Ron

 

[jkeyser14]

I used to be in the same situation as you. I paid a local company to install geothermal. It was $27k before all the tax credits, $16k after. This included the company installing all new duct work throughout the house. We used to have heating bills of $600 in the winter with oil and $150 in the summer with the AC. We're now $200-300 in the winter and $100-125 in the summer. We also run the AC from May through September where before we used to just run it in July and August. Payback time will be about 7 years. Warranty on the geothermal coolant loops is 50 years, warranty on the furnace is 10 years. We're very happy.

 

[Falcon67]

small rooms are not going to be a problem living room is 19x28 dining room is similar. 9 1/2 celings on both floors.

Lots of good points both ways. Looks like I will be trying to get some HVAC guys out to give me quotes. I'm guessing that I'll be doing all the tear out work, to save a bunch of labor. Then let them start running new duct work. The furnace most likely stay and new A/C unit fitted if we go with a central system. I'd like to say that I would be taking the oil furnace out and putting it in the shop, however it would stay in place as a back up sytem. Keith

That's good, not all are like that. Most stuff around here is one step removed from farm houses. Even the "big" old houses typically have 10x10 bedrooms with 4x4 closets. 1817 big and formal - sounds nice.

 

[brewchief]

One option that might work is to fix the ductwork in the basement so it's not a patched up mess then add a couple mini-splits to the second floor only, use the existing furnace and a/c(or replace the a/c with a new heat pump) for the first floor and for some heat to the second. With this approach the existing a/c may be to big so if you decide to replace it make sure it is properly sized for the changed load.

 

[Jackfre]

In looking at this again, for the second floor, you might look at a 24k condensing unit and depending upon room lay-out, two or three of the compact concealed air handler units. They are very low static units so great care must be taken in duct design and installation, but I think they would be ideal for your "old house" retrofit.

For the downstairs, without an idea of lay-out, it is hard to say what would be best for you. Do you have a floor plan?

 

[383 240z]

I'll try to draw one up here in the next few days. I'm working 12's this week so please bear with me. Keith

 

[Jackfre]

I'll try to draw one up here in the next few days. I'm working 12's this week so please bear with me. Keith

Pretty sure the correct response in light of the 12's is, when you are ready!

 

[Highbeam]

Thing is, the indoor units are fugly. An earlier post mentioned that the mini splits work like a seperate window unit in every room. Well, they look like it too. Looks like something you would find in an RV trailer. I don't want to live in a trailer.

 

[wrigh003]

Replying because I’m looking at these as well. In our case, our main AC unit is getting older, and remodels done to the house before we bought it are putting more load on the AC than it was meant to handle. Our place is a ranch, so one level, but there’s a converted carport at the end of the house that gets super hot- because it’s tacked onto the main AC trunks, it faces due west, and gets **** for air circulation. 2 vents in a 400sqft room, and they don’t supply much air (again, I think they were just tapped onto the existing ductwork).

Considering adding a 1-ton unit just for that room, or maybe a dual-zone one so I can eventually cool the garage with it as well. The outdoor unit would be right there by our electric panel and right next to the room that needs cooling, so it could work easily enough that I could probably manage 95% of the install, then call a buddy to come help me evacuate the unit and get it charged and running.

As for how they look, yeah. Not pretty. If we go the way I’m considering I’d be devising a cabinet/built in (probably made to look like a storage cabinet/ bookshelf over the TV) to hide the indoor unit.

 

[pseudorealityx]

Don't put a garage on the same system as your house.

1) There's no need to cool it 90% of the time.
2) In order for it to work, you'll need a return there also.
3) If there's a return, now whatever smells/odors/chemicals/dust is in the garage, is now being spread throughout the house.

 

[pseudorealityx]

As for how they look, yeah. Not pretty. If we go the way I’m considering I’d be devising a cabinet/built in (probably made to look like a storage cabinet/ bookshelf over the TV) to hide the indoor unit.

Remember they have to get air in (return), and then blow air out (supply). You can't just completely block them.

 

[Jackfre]

Replying because I’m looking at these as well. In our case, our main AC unit is getting older, and remodels done to the house before we bought it are putting more load on the AC than it was meant to handle. Our place is a ranch, so one level, but there’s a converted carport at the end of the house that gets super hot- because it’s tacked onto the main AC trunks, it faces due west, and gets **** for air circulation. 2 vents in a 400sqft room, and they don’t supply much air (again, I think they were just tapped onto the existing ductwork).

Considering adding a 1-ton unit just for that room, or maybe a dual-zone one so I can eventually cool the garage with it as well. The outdoor unit would be right there by our electric panel and right next to the room that needs cooling, so it could work easily enough that I could probably manage 95% of the install, then call a buddy to come help me evacuate the unit and get it charged and running.

As for how they look, yeah. Not pretty. If we go the way I’m considering I’d be devising a cabinet/built in (probably made to look like a storage cabinet/ bookshelf over the TV) to hide the indoor unit.

If you are going to try to conceal the evap then do not use the high wall unit. there are ceiling cassettes and concealed mini-air handlers. In my experience, or opinion at least, the high walls are best.

You could put an evap in the converted car port area and the other in the garage, but I agree that unless you are going to cool the garage regularly, it is not the best system. They would run independently, so my comment is based upon efficiency. My 4 yr old dual system (30 amp) is 16.5 Seer and about 8.5 HSPF. My single 12 (15 amp) is 25 Seer and 12 HSPF. Big difference and worth considering separate systems, depending upon power availability. Run the numbers. I think I would put the most efficient system I could find in the converted carport. The high efficiency systems are going to be high wall only evaps, generally, although models change frequently.

When I was representing Fujitsu and training contractors on mshp and living with them at home and in the office I used to ask the guys to follow up with some of their customers who didn't like the appearance and let me know how things went over time. Based upon performance, comfort and economy I have found that my saying, "The longer you live with them the better looking they become," is true.

When you think of the things we live with and get used to, the garbage cans, gas meter, lp tank, air conditioners, gas grills and the things that support our life style the mshp just becomes another piece of the puzzle.

Over the holiday I was at a friends house and he heats/cools his 3 story home with a quad (4-9's) and an 18. His sister was visiting from NYC. She is a decorator in the City and commented on the evaps in a rather disparaging way. Four days later she was going to call contractors to get them installed in her home, right away. They just work!

 

[Highbeam]

When I was representing Fujitsu and training contractors on mshp and living with them at home and in the office I used to ask the guys to follow up with some of their customers who didn't like the appearance and let me know how things went over time. Based upon performance, comfort and economy I have found that my saying, "The longer you live with them the better looking they become," is true.

She is a decorator in the City and commented on the evaps in a rather disparaging way. Four days later she was going to call contractors to get them installed in her home, right away. They just work!

This is like dating an ugly girl because she has such a nice personality. You've still got to turn the lights off to enjoy it.

 

[Jackfre]

I think, if I was you, I'd do something other than put in a mshp

 

[Highbeam]

I think, if I was you, I'd do something other than put in a mshp

The proper answer is, "it is like riding a moped, until a friend sees you".

I'm hoping to someday see some great examples of how to hide these things and integrate them into standard interior home decorating. The best I've seen to date is a nice hutch (tall freestanding shelf type cabinet) that comes up near the bottom of the high wall unit.

 

[rlitman]

The proper answer is, "it is like riding a moped, until a friend sees you".

I'm hoping to someday see some great examples of how to hide these things and integrate them into standard interior home decorating. The best I've seen to date is a nice hutch (tall freestanding shelf type cabinet) that comes up near the bottom of the high wall unit.

Go to Europe. People are much more concerned with fashion and how thing appear over there, and yet mini-splits are seen in most every room.

Oh, and newer ones are getting more and more "designer" looking.

 

[SilverHVAC]

Before spending a lot of money on upgrades and new equipment, there are a couple of low-cost solutions that may make your system more effective.
1: Install a thermostatically controlled attic fan to help remove built up heat (they are a couple hundred dollars, and a good idea regardless)
2: Ask your HVAC contractor about installing an in-line booster fan, wired into the cooling terminal. This will draw more cool air off of the coil as well as push the air at a higher velocity to the upstairs
3: Ask your HVAC contractor about installing a "scoop" or "diverter" this is a piece of metal installed in the plenum the guides air towards the intended take off
4: Seal your ductwork and change your air filters regularly
I often see companies that jump to offering entirely new systems when there are other solutions that will make them less money

 

[383 240z]

Sorry for the delay on getting that floor plan, been super busy. Silver, I do have an attic fan and they do work wonders. Thanks for the few things to ask about. I'm pretty sure that I need new ducting, the bulk of what we have is VERY convoluted, and dis-organized. nothing like in a new built home. From what i understand from the history of the house, it went from wood, to coal, to oil heat. I have only 3 heat vents on the second floor and no returns. Keith