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.
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Variable Refrigerant Flow (VRF) systems experiences? 2
- Thread starter GMcD
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2
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AbbyNormal
Mechanical
Lol, I am still waiting for them to give me some success stories in Florida or PR, etc.
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.
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.
It seems like a good idea on paper. My concerns are refrigerant piping running tru walls, ceilings etc. If the system is not properly piped and has leaks, once the building is finished it will end up like a supermarket job with technicians gassing and going.
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
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
gregreader
Electrical
WE were interested in using this type of system but found them not conducive to handling our Outside Air requirements.
- Thread starter
- #5
Gregreader- the VRF system still needs a dedicated outdoor air unit/supply (DOAS) just like a four-pipe fan-coil system, packaged hydronic water to air heat pump units etc.
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.....
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.....
I have seen dozens of these systems installed in the UK. It comes down to this, you need to have a reputable and competent installer. I’ve never had any problems with the physical systems but on one occasion the control package did fall over and as you have noted needed to be replaced. Fortunately this was still in the warranty period.
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- #8
Lilliput: Hmm, letting the supplier/manufacturer design the system, yet I would take full responsibility for it's design and operation when I seal the drawings....Doesn't sound like good practice to me, unless I get the Supplier to seal and sign off his documents. Doesn't leave a lot of "design" or "engineering" in my court, so why would an Owner hire me to design one of these systems if the supplier is going to do it?
AbbyNormal
Mechanical
Well how good are you at designing refrigeration piping, especially piping for variable flow, sizing it for peaks etc.? You draw up much 410A yet?
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.
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.
- Thread starter
- #10
AbbyNormal- Yeah, I am Not a refrigeration expert, and would leave this to a design-build style specification for sure, and yes, I DID do my own PEX tube layouts under the tutelage of an old hand using the old Polytherm system back in the early '80's. I did spend a lot of time on a steep learning curve for radiant systems back in the day, and it's something I can do easily, accurately and confidently now. Same with sprinklers, I can design them easily based on the mentoring I got in the industry early on. But Refrigeration has always been a "black art" and my only exposure has been to take the heat reclaim connections off Supermarket refrigeration systems for the Air Handling stuff that I was responsible for.
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
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
AbbyNormal
Mechanical
Wasn't implying that you or myself can't do hydraulic calcs.
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.
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.
Let the manufacturer design the system because they would defintetly know the system better than you. They may have some trade secrets. While they are doing their design, question them. Check out the design to your satisfaction. A lot of salesmen complaints that engineers sometimes think they can get what they want just by by specifying anything. Actually the manufactured products are what they are and it is difficult and usually not advisable to modify them to suite a particular project. So you should first let them work on the project to the extent that they are comfortable they can meet the reasonable requirement.
In the right situation I have no issues with VRF systems and have designed Daikin and Mitsubishi systems in the past and all worked with no issues. For a smaller commercial type project where you might need 2 or 3 systems they seem to make sense and give good energy efficiency.
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?
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?
The advantage of these systems is that they do use the same amount of energy as conventional systems. They also allow you to use the heat removed from one area, (perhaps a server room) and dump it into another room (such as office space) rather than just dumping it to atmosphere.
In the right application they work well, cheap to install, and energy efficient. Also they can handle very long refrigeration pipe runs (up to 150m) which can be helpful at times.
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.
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.
- Thread starter
- #17
Redgdon: but I fail to see how the VRF system would be any better (energy efficiency and maintenance-wise) than a system of packaged hydronic heat pumps and a 2-pipe hydronic circuit with a small boiler and fluid cooler setup- trades the same heat and cool through the hydronic system, you can pick and minimize the amount of refrigerant you need to deal with, by using small water source ceiling mounted heat pumps. Is the energy efficiency all that better? besides, the best efficiency works when you have heating and cooling going on at the same time so you can trade the energy around the circuit. But what if one has an all-cooling or predominantly heating application? What's the energy efficiency difference then?
KiwiMace
Mechanical
- Feb 2, 2006
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I saw a lot of these working in Singapore. Daiken is a very well respected brand, and the green spec manuals were a staple in every design office. One suited application is 24hr multiple server rooms in office buildings. The VRV serves these spaces efficiently and independent of the much larger central plant.
aussiehvac
Mechanical
The main advantage is the saving in space and the diversification of the load as stated. Say on a 50kW system with 10 indoors the first condenser ramps up to 100% ( a variable capacity unit) before the second single speed condenser starts and the first one backs down to 10%.
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
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
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