VRF Pros and Cons

RayWohlfarth

Hello all,
I will be teaching a class for the local ASHRAE chapter on the benefits of hydronics and comparing it to VRF. I was hoping to have some real world experiences both pro and cons of what you found when working on or installing Vrf. Perhaps what you think some of the differences are. I have never worked on or installed a VRF system but installed a serviced plenty of hydronics. I got some info from the smart people at RPA Thank you so much.
Ray

ratio

We've been bit really, Really, REALLY hard right on the you-know-what installing multi-head heat pumps, as opposed to a true VRF system with branch boxes. Unhappy customers wonder why their new system doesn't work—at all—just because someone put a head in fan-only mode. Of course, they "couldn't afford" the VRF system, but expected the heat pump system to perform identical but cost a lot less. <smh>

EBEBRATT-Ed

I have no experience with vrf. I could see it being a nightmare to leak test and repair leaks and wonder about the large quantity of refrigerant in an occupied space if there was a fire.

RayWohlfarth

Thanks Ratio and Ed. I understand the EPA just reduced the amount of allowable leakage which will increase maintenance

ratio

The mfgr required 24 hours under 400# N₂ followed by 15 min at 650(!)#. We didn't have any leaks.

The rep even gave my guy an attaboy for the work, but the heat pump was pitched too far for him to get one from me.

Once we figured out the different-mode issue the systems seems to work pretty good. They should've sprung for the VRF system. It would have been a lot nicer I think.

Still not a fan of heat pumps in our climate though. Right when you need heat the most is when they're all done heating.

hvacfreak2

There is one looming shadow hanging over the VRF industry ( at least in the US ) , ASHRAE Standard 15. This has to do with the total system refrigerant charge of a connected refrigerating device versus the allowable area in which it resides. An example would be a 30 ton VRF system with a 009 small wall hung unit in a small 10 x 10 office as a violation of this standard. The design options become much more limited when Standard 15 is enforced.

Initial cost , system complexity ( repair costs ) , lack of true redundancy ( subjective ) for a few more negatives for VRV / F systems. An example would be losing power to a branch selector can drop the entire system. The piping and control arrangements on the outdoor units is downright scary on the larger systems.

-When installed correctly they do seem to perform as advertised , no doubt about it.
-They integrate to building control systems .
-The manufacturers do a fantastic job of support and training .
- By default they work well with other systems ( mechanically ).

ratio

hvacfreak2 said:

-The manufacturers do a fantastic job of support and training .

Uhhhhh...

The training I has was pretty nice, that's true, but I've had less than stellar support from the mfgr. In fact, regarding the latest issue we've had, the rep quit calling us back as soon as he found out that there wasn't a sales opportunity. He actually asked that. And then quit returning calls. Uncool. We had to go laterally to the person we deal with regularly to get assistance. They came through this time, but it was a chore getting them to.

njtommy

We've done a couple Mitsubishi city multi systems at work. Haven't had any problems with them at all. The oldest system we've done has been running for 5 years now. They are not an easy sales job, but offer a lot of value and comfort to the customers.

I was in a Daikin class not to long ago the say they have less then a 1% failure rate and the majority of the parts returned for warranty are still good. They of course offer a tool to plug into their units and Daikin said it will work with all manufacturers units to. It will diagnose to see which board or sensor is bad including the compressor.

Not VRF systems have branch boxes either which I find odd. Even the Daikin VFR 4 in large commercial or schools the offer it without a branch box to save money install. They you a special T or Y to send refrigerant to the heads. It just seems silly to me this way.

RayWohlfarth

Thanks Ratio wow thats a scary test 650#
HVAC Freak thanks I could use that.
NJ Tommy That is why VRF is gaining acceptance everywhere. Kinda scary

ratio

I was more worried about pushing N₂ through the valves & into the unit—that would have been a real nightmare! My Old Guy claims that's happened in the past, but the factory said it's never been an issue, so hopefully with modern valves it won't happen. Copper with the right solder (no more 95-5, <sigh>) is good for 1000# or more I believe. I actually order 650# on the copper run vertically through walls. I want to know when the hangers stick a nail in one! You just have to remember that it's only the copper itself (& apparently the valves) that can withstand that kind of pressure, the units themselves, indoor and out, can't.

RayWohlfarth

Good points Ratio Thanks

Jack

Mini-splits and VRF are disruptive technologies. They are also excellent. I think most metropolitan areas are using much less unitary equipment especially in high rises. An owner can rent out a floor and the tenant can install their own system to meet their needs with very limited space and better control/comfort. When that property turns over the new tenant can do the same.
I can only imagine the amount of lobbying going on to limit the amount of refrigerant in a building. The safety issue is being used to save the unitary business.
I remember when we introduced the 410A/inverter equipment (I was the Fujitsu rep back then). Everyone was up in arms on the pressures that the systems were working at. It has not been a problem and the performance of the systems is terrific compared to the old R22 units. Whenever I discuss mini-splits/VRF vs unitary I always look at the unitaries biggest problem and that is the ductwork. On a commercial system, if you blow the duct pressure test you are in a jam. Residentially, we are only beginning to test and actually seal ductwork. The DOE says that the average residence looses 15-40% of its energy in duct losses. There are all kinds of ways to debate that, but what it means to me is that between the homeowners comfort and the unitary manuf equipment is a totally deficient duct system. The unitary folks can put all the technology they want in the box. They simply can't deliver it. Everywhere I am traveling I talk to contractors and all of them say they can't get the help they could use. How do you keep good people when you tell them that today they get to go out and crawl into an attic or crawl space to seal up old crappy ductwork? That is difficult, dirty, unrewarding and expensive work.
Six years ago when we moved west my new old house had a 5 yr old hvac system in it. Hurricane in one room, no air in the other. Loud and wheezie! There was no reasonable way to improve and save it. I took it all to the dump put in a couple mini-splits and Rinnai DV's and everything is zoned, net to the space and utility bills are low and we are very comfortable. I also got two closets out of it. I think a lot more of that is going to take place.

RayWohlfarth

Jack
You are not helping my case here LOL Thanks for the input
Ray

Jack