I was wondering if anyone has any experience using VRF (Variable Refrigerant flow) systems? I understand they are supposed to be very efficient. I am wondering about the amount of Refrigerant piping going all through the house. What happens if there is a leak of refrigerant, how is it found? Any advice or experience would be helpful.

Most leaks would be the result of impact. Once installed and properly tested little else could make a lineset fail. I use Daiken; very nice but pricey.

Nearly all modern ductless mini-split & multi-split heat pumps utilize variable refrigerant volume technology, as do some of the better ducted air-source heat pumps.

Slow refrigerant leaks will cause the system to under-perform, which will eventually become obvious. Fast leaks will be discovered by that large hissing sound and frost formation where you just sunk that nail or screw into the refrigerant line. :-)

R410A (the most common refrigerant in these systems) isn't very dangerous to humans or houses unless it displaces a large amount of the air. It doesn't burn at temperatures of any consequence in a house (if any part of your house hits temps above 750C it's already on fire) and isn't very toxic at slow-leak exposures, or even high leaks of short duration. http://www.refrigerants.com/MSDS/r410A.pdf

Are these a good investment and idea to place in a residential home? I am building approx 5000 sqft home that will have all the "best" insulation, solar shading, windows, etc... I understand that these can operate several airhandlers at once. Looks like Daikin can do 8 and Mitsubishi 5 at once. But if you place a vent in every room (Bed room, Bath room, Kitchens, living, etc..) That is like 20 airhandlers that need filter changing, maintenence, motors taht can go bad, etc.... Can these be connected as in 1 airhandler covers 3-4 rooms?

Fast leaks will be discovered by that large hissing sound and frost formation where you just sunk that nail or screw into the refrigerant line. :-)

It's a chilling sound.

Can these be connected as in 1 airhandler covers 3-4 rooms?

That depends on a lot of things. Most important is your room by room heating or cooling load. Not only does the capacity of the airhandler need to be matched to the room combination, there has to be a way to effectively circulate the air. For example, I have a single airhandler covering a suite of rooms comprising Master BR, Office, Master Bath, walk-in closet and an anteroom. The walk-in closet was the farthest room out and we had to remove a north-facing window because we just couldn't get the heat needs in that room down enough. We also furred the room in an additional 2" for more insulation. The ventilation system draws air to the very back of the closet so as to facilitate circulation.

Are you speaking of a VRF system? So you have one Air handler that covers one wing of your house that connects via refrigerant line to your VRF condenser outside?

Also what is the overall cost compared to a standard 18 seer system where I need about 8 Tons?

A ductless head or cassett in every room would be both a huge upfront cost and a huge hit in efficiency. The smallest ductless heads are rated about 6000BTU/hr cooling, and a bit more than that for heating (depending on your actuall 99% & 1% design temps output will vary.) The peak room loads need to be at least 2/3 the output rating of the head to stay in the highest efficeincy & highest comfort range. A 6000 BTU head for room with a 1500 BTU/hr peak load will literally never modulate, only cycle, and uses power while standing-by.

Mini-duct cassettes can split the output between adjacent or nearly-adjacent rooms with very short duct runs. I've yet to see anybody split the output between 4 rooms, but 2-3 are common enough.

If you haven't calculated both the room-by-room and whole house loads, you have no basis for deciding what makes sense. What makes you think it needs anything LIKE 8 tons of heat pump?

Eight tons of cooling load would be extremely high for most that will have all the "best" insulation, solar shading, windows, etc... Even code-min 5000' homes would have cooling loads on the order of 5 tons these days (even in cooling dominated climates), and 5000' home that has been optimized for load reductions could easily come in at 3 tons.

Depending on climate and load these can be a GREAT way to go, but when you're looking at a gazillion heads and splitters, etc the cost is high, and may even be higher than ground source heat pumps of similar (or sometimes better) efficiency.

OK. I have searched high and low for answers on this type of AC system (VRF) and am having trouble getting the needed answers as I cannot find a single contractor that knows these things inside and out from a RESIDENTIAL install. Here are my questions:

1. Can I use a ductless VRF system for my TOTAL ac system in a regular residential home with 6 rooms, 6 bathrooms, closets, kitchen, etc....?
2. What will that look like in real terms? Will there be a bunch of individual air handlers in every single room with a spider web of refrigerant tubing gong everywhere?
3. Can I use just a few air handlers (ducted into other rooms) with 1-2 outside compressors to supply the Whole home?
4. Is it a nightmare to have that many air handlers, that can break and need filter/drain maintenance?
5. Am I better just going old school with 1-2 split system/airhandler units for the whole house?


Thanks

1) Maybe (depends on the envelope, the type of VRF you use and building codes)
2) Depends (If you buy a multi-head unit then you will have multiple outlets)
3) Maybe (same as #1)
4) Everything need s maintenence but yes you may have multiple filters
5) Depends on what you want

One of the reasons you might be having trouble getting answers is the questions you are asking and the amount of info available. A super high performance envelope may be heated with one minisplit unducted and one head.

A code minimum envelope may need several units.