Variable Refrigerant Flow (VRF) systems experiences?
Variable Refrigerant Flow (VRF) systems experiences?
(OP)
North American HVAC Engineer here, looking for other world views on installation and operational issues related to VRF systems. These are relatively new to North America and I am concerned about the general operating pressures (what happens with 400 psig+ leaks of R-407 or R-410??) as well as the real operational issues that anyone has encountered. I understand that the controllers for some of the proprietary VRF systems are "black-box" technology that any Tom, Dick, or Harry controls guy can troubleshoot or modify, so the only choice if one of these fouls up is a replacement plug-in new black box. Doesn't sound that user friendly.





RE: Variable Refrigerant Flow (VRF) systems experiences?
They seem to be coming in about the same cost as chilled water, they will include an ERV system and dedicated ductwork.
You give them loads similar to what you would use to pick out VAV boxes and they claim to lay out the piping, the Mitsubishi reps claim to do it, supposedly Daikan will too.
Daikan stuff was popular here years back, then they pulled out of North America and left you holding the bag. They seem a little more comitted to trying to make a go in North America this time, and bought MCQuay from the Malaysians
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Variable Refrigerant Flow (VRF) systems experiences?
Its a given that if you ever go to renovate the building or a tenant fit out, some knuckleheads going to cut a line thats in their way. I've seen it happen on an aplication where Carrier was trying this type of aplication over 25 yrs ago. A 50 ton condensing unit with 10 5 ton AHU's. Exposed refrigerant piping all over the place during renovations, what a nightmare. JMHO
RE: Variable Refrigerant Flow (VRF) systems experiences?
RE: Variable Refrigerant Flow (VRF) systems experiences?
Also- just wanted to correct a typo in my initial post- I meant to say that the VRF controls system is a "black box" controller that the normal controls types CANNOT access or modify or fix, and it's my understanding that if the VRF controls pack up, you gotta get the original maker/supplier in to replace the black box(es) as required.
Thanks for the responses so far, sounds like my gut feelings are a common issue - high pressure insulated refrigerant pipes running all over a building, with the piping installation at the mercy of the field installer's expertise (or lack of it). Running low pressure water for a packaged heat pump system sounds like a heck of a lot less risk in my mind.
Also- any comments about the HFC phase outs? R-407 and R-410 are HFC refrigerants and I understand that Denmark is banning all HFC installations with over 10 kg of refrigerant as of Jan. 1, 2007. That would virtually eliminate many VRF systems.....
RE: Variable Refrigerant Flow (VRF) systems experiences?
RE: Variable Refrigerant Flow (VRF) systems experiences?
RE: Variable Refrigerant Flow (VRF) systems experiences?
RE: Variable Refrigerant Flow (VRF) systems experiences?
I would be tempted to weasel out and take a performance specification approach on the first one or two, maybe like drawing up sprinklers quickly based on a pipe schedule scheme, then putting the onus on the contractor to provide engineered shop drawings. It is no more lame than the stuctural engineers saying "pre-engineered roof trusses, submit stamped shop drawings"
If you read a book or take a course on how to layout this piping, would you really feel professional competent to stamp that drawing on your first shot?
Maybe cut your teeth on a couple take the seminar, and get some experience before you stamp it yourself.
You layed out all the pex tubing on your first infloor job or did you make wirsbo do it for you ?
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Variable Refrigerant Flow (VRF) systems experiences?
I'm just having qualms about this type of proprietary system with high pressure, expensive refrigerant running around an institutional type building. The Owner/Client isn't pushing it, but one of the other parties on the design team is, and I'm being asked an opinion. I wanted to get some feedback from anyone else who has experience with these systems to be able to assess some realistic issues.
I don't think it would do an Owner/Client any big favours to have them buy a proporiteary system and be locked into a supplier for support and maintenance afterwards
RE: Variable Refrigerant Flow (VRF) systems experiences?
The VRF has been around for sometime in Asia and they are using it in the UK, but not established in North America.
Back in 2002, I had a substantial project and an european head office was pushing for an 'argonite' clean agent supression system. At that time there was perhaps 4 systems in place on the western side of the Atlantic.
The argonite was a similar system to inergen, however most of the contractors here were experienced only with FM200. I had a good ally on getting argonite 'suppressed', the Fire Marshall refused to accept it.
I was glad because the faciloity was supposed to withstand a Category 5 hurricane (which it did) but I would have been forced to design numerous pressure relief vents in walls which were other wise a fortress.
It would have almost defeated the purpose.
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Variable Refrigerant Flow (VRF) systems experiences?
RE: Variable Refrigerant Flow (VRF) systems experiences?
Items to take note of:
- Refrigerant charge in the system and potentially all of this could leak into a small single room if there is a leak.
- Zoning of the system, especially if it is a cool/heat unit without simultaneous heating and cooling.
- Let the supplier size up the pipework, they have software for this.
- System will be a proprietary system, ie controls/fcu's etc cannot be added on by a third party as per chilled water system.
- Lifespan of the system. I wouldn't expect the condensers and fcu's to have the life span of a chilled water system. New generations of system seem to come onto the market every few years so long term support may be an issue?
RE: Variable Refrigerant Flow (VRF) systems experiences?
RE: Variable Refrigerant Flow (VRF) systems experiences?
RE: Variable Refrigerant Flow (VRF) systems experiences?
Typically for a project with maybe up to 200kW cooling they are certainly cheaper to install than a chilled water system with FCU's. Project where I have installed them include offices, expensive residences, and schools.
RE: Variable Refrigerant Flow (VRF) systems experiences?
RE: Variable Refrigerant Flow (VRF) systems experiences?
RE: Variable Refrigerant Flow (VRF) systems experiences?
RE: Variable Refrigerant Flow (VRF) systems experiences?
You can have only two offices being served and the compressor will match the load.
The black box black box controls with the electronic TE valves allow you to get a report on the amount of heating /cooling the sytem has done for that ROOM.
Main draw backs, thicker wall copper in Australia, blend of refrigerant that has to be totally recharged if you have a leak, because which part leaked?
The problem with the electronics and system is the 450 page fault decoding book. The code is show on the control panel or the condenser.
The nessecity of an interface for BACNET and LON BAS systems.
The FCU's/condensers may not have e retrofit in five years if one fails and a new one is required, different operating system, controls
There is a case in Sydney Australia where the running costs of a seven level building were cut by 35% over a old chiller and boiler system with AHU's.The VRV was successfull in a floor by floor retrofit.
The refrigerant leak into rooms has been addressed with leak detectors required in the smallest room near the end of the loop and alarms etc.
The pipe distance with the Daikin units is limited in that, from the first refnet to the last fan coil is 40m.
They work but there is drawbacks
Daikin, Hitachi, Sharp, Carrier/Toshiba, and a couple of more are on the market in OZ.
regards
RE: Variable Refrigerant Flow (VRF) systems experiences?
If you get a refrigeration leak you will need a lot of new refrigerant to replace it all!
RE: Variable Refrigerant Flow (VRF) systems experiences?