Daikin VRV systems in hot humid climates

[multisync]

When you are referring to American STD Air Con Market are you referring to the window rattlers that you see all over the place in America?

Or have i misunderstood?

Nope Rheem etc type wind and tin. "Union made" stickers are a clue to their quality control..

Multisync
London

[Thermatech]

NB34

appologies but the thread was side tracked trying to answer questions by Mchild.

I am also trying to uderstand the chalange of high humidity aplications & so have started another thread.

The posters so far are well known on these boards.

The Mitsubishi Electric VRF systems for example use control statagy to maintain suction pressure & evaporating temperature at indoor units which maintain the ADP & provide continual dehumidification in cooling mode. Therfore constant dehumidification even when the indoor unit reduces capacity.

The exception is when the indoor unit enters the power save mode at 2 deg C above setpoint. The indoor unit then sets a new higher target SH & the LEV valves ramps down to reduce refrigerant flow. The dehumidification at this point might be slightly reduced depending on the air on coil conditions.

Some engineers with a biased opinion & different agenda are critical.
However I have spent the last 16 years specialising in VRF commissioning & trouble shooting & I am confident that the system will perform well in higher humidity conditions than we see in the UK.
I have spent most of the last 12 years carrying out commissioning & trouble shooting site visitson VRF products & spend most days monitoring the system operation with a lap top computer.

I would suspect that critical comments come from engineers who dont have a high level of understanding about how VRF systems operate.

The small size of the indoor unit coil, low air volume & Sensible Heat Ratio all conspire to make dehumidification unavoidable even when the refrigerant flow is reduced.

As already stated in Japan high humidity is also an issue which the manufacturers have to overcome to provide comfort cooling to the staisfaction of local customers.

I wonder how many who comment here have been to Japan to see for themselves.

[Gary]

I would suspect that critical comments come from engineers who dont have a high level of understanding about how VRF systems operate.

And rightly so, Why would you expect end users to purchase expensive equipment that is not widely understood? This places them at the mercy of those chosen few who know the secret handshake.

[Abby Normal]

I wonder how many who comment here have been to Japan to see for themselves.

lol I wonder how many who comment have dealt with tropical humidity

[frank]

Why would you expect end users to purchase expensive equipment that is not widely understood?

This could also relate to computers or even motor vehicles et al

[Ross]

NB34

I am a tech in Australia previously worked for Daikin, commissioned many Daikin VRV including up in Darwin (northern Australia) where temp are typically 35degC & 80-90% humidity in summer. Some of these systems the indoor unit also introduce outside air and the systems work perfectly fine in these conditions...Go for it, you won't be disappointed!

[SUBCONTRACTOR]

That is contrary to the fact. I am an hvac engineer in florida and I wanted to get an understanding of how other people viewed these types of systems and if they have ever encountered problems when they were placed in a high humidity environment. My questions about the fan coil leaving air conditions still have not been answered.

Dude,the prblem with these system is not the high humidity,they work absolutely fine but when the humidity is very very low then you gonna have frozen coils....
The other problems that you can expect somtimes is the complicated electronics and availability of replacement pcb.

[NB34]

Thank you to everyone for your responses. I have a couple other questions in regards to the VRV III systems.

1) What is the typical condensing unit downtime for changing a leaky evap coil? (I ask because I am trying to figure out the best combination of indoor units to place on a single piping system. I want to minimize the time the other indoor units would be offline in order to fix the troubled unit)
2) Can the indoor units be isolated from the piping system by service valves so that an evap coil could be replaced without shutting down the entire system? Has anyone ever done this?

These question all stem for the use of Daikin in hotel room applications. I do not want one unit going down and in order to fix the one room 10 other rooms will have to go down for an extended period of time.

[Abby Normal]

or ask your self what kind of job some hack in south florida will do piping it up in the first place

there is a few systems installed down here, i am a good 400 miles south of you, I am keeping an eye on how it performs. I just wish they would shut the damn blowers off when they were modulated down all the way

[Thermatech]

Some contractors have fitted service valves & schreader access for gauges for indoor units. Although often this is for the option of installing extra units at a later date.

In the UK hotels use the VRV / VRF as the only heating / cooling in the bedrooms.
The really big hotels, like over 400 rooms have a maintenance engineer on site for general maintenance & 24/7 emergency cover from specialist a/c contractor.
The hotel will keep a stock of spare parts on site.
So most any problem can be resolved within a few hrs.

The smaller hotels have specialist contractor on call but dont keep any stock of spare parts so they have to wait for next day delivery if parts are required & they pay for the contractor to attend site twice.

Most hotel managers prefer the VRV / VRF systems because if there is any problem it will only affect a small number of rooms & the hotel can often work arround this.
With a chiller if there is a problem every room in the hotel is affected.
In hotter climates perhaps hotels opt for the installation of a standby chiller ?

[NB34]

I agree with you Abby, I am very leary of specifying this equipment because of that reason. The contractors have a tough time installing and trouble shooting a split dx system. I am more worried about how the system is going to get fixed than installed.

[NB34]

Typically there would be two or three chillers.

[Thermatech]

There will always be split bashers
&
there will always be chiller technicians

In between there is the VRV / VRF technician

Installation & service engineers with half a brain tend to move on from split systems into VRV / VRF systems.

15 years ago hardly any a/c engineers knew anything about VRV / VRF systems here in the UK but for quite a few years now almost every service job advert states VRV / VRF experiance required.
Thats because our market has been swamped with this kit so every a/c contractor in the country needs to be able to install & maintain VRV / VRF equipment.
It is the every day bread & butter work for most a/c contractors.

When a manufacturer starts selling this type of equipment into a new market they have to provide extensive technical support for commissioning & trouble shooting to assist the a/c contractors. Also provide extensive technical training for the installation, commissioning & service engineers.

It takes a year or two but contractors get to know the equipment & become confident with it the same as they would with any new type of chiller.
If there is any unusual problem they can alway call on the manufacturer to assist to solve the problem.

Generally I tend to find that most a/c engineers will make an effort to learn about new technology.
This week I was working for a day with a 70 year old a/c service engineer & he spent the whole day bending my ear with questions because he really wanted to understand how it works & because he knew his stuff he was asking very intellegent questions.

So your never to old to learn about new technology.

[Gary]

So your never to old to learn about new technology.

Obviously, we are not going to learn from you.

[Gary]

This week I was working for a day with a 70 year old a/c service engineer & he spent the whole day bending my ear with questions because he really wanted to understand how it works & because he knew his stuff he was asking very intellegent questions.

Did you actually answer his questions?... or did you just say "It's complicated"?... tell him to go to Japan?... and then call him a "split basher"?

[puddleboy3]

Did you actually answer his questions?... or did you just say "It's complicated"?... tell him to go to Japan?... and then call him a "split basher"?

timeout guys!!!!!! go to your corners

[Abby Normal]

I agree with you Abby, I am very leary of specifying this equipment because of that reason. The contractors have a tough time installing and trouble shooting a split dx system. I am more worried about how the system is going to get fixed than installed.

I have been stalling a job here its going to go with the mcquay version of the daikin vrv,its a larger estate home about 15,000 square feet

I am sticking to my guns, and I have a couple heat pipe BKP series in doing the big granidoise open areas of the central cores on each floor, they will work like AC most of the time, blow some warm dry air in an extreme worst case scenario of zero solar gain, 80F dry bulb and 80F dew point, and owner setting stats at 80F to save energy when not in various areas of the home. The BKPs draw in fresh air whenever they run the compressors. It is imperative here to have spaces pressurized.

But instead of going with a small chiller or multiple split DX systems the vrv is being considered as a way of dealing with the structure and the aesthetically pleasing high ceilings that leave no room for duct work.

So anyways, I am running the load like a commercial VAV system, and sizing the condensing units for whatever the building peaks at, then sizing all the mickey mouse fan coils and cassettes for what ever the zones peaks at.

I predict in my worst case scenario that can linger for days on end, it will be the dehumidifers that save the day as opposed to a system that has to function by running a fan all the time.

This thread is interesting as you see the fear of something new, resistance to change. Then on the other end of the scale you see the salesman mentality where rather than explain something you get into techno-babble.

To me if you cannot explain a concept in the terms relative to your audiences frame of reference, it is because you do not fully understand what you are talking about.

Salesmen when challenged by a question, try to make it sound more and more complicated to shame the person posing questions into feeling too stupid to persue the question anymore, when the fact is the salesman does not really have the answer to the querstion in the first place.

Whenever I start hearing 'flux capacitors' or needing 'X15 modulators' it is a red flag.

[mchild]

. . . opposed to a system that has to function by running a fan all the time.

Does the discussion here: http://www.refrigeration-engineer.co...ad.php?t=16250 resolve this issue?

[Abby Normal]

maybe when obi wan replies it will be resolved

[2498]

In each IDU there are 3 sensors, 2 for inlet and outlet of refrigerant system and 1 for return air temperature, to modulate the refrigerant flow rate to suit the required load which getting from return air sensor and desired temperature. Integration of the flow rate required from the whole IDUs in the same refrigeration circuit this will lead to call the required flow rate from CDU. Currently both refrigerant and air flow rate are able to vary in order to match to flictuated load precisely.

Piping design and charging volume are very critical. Follwing manufacturers guideline is strictly request.

[NB34]

Abby
Our firm also designs a lot of estate homes of that magnitude in the Naples florida area and have been looking at Daikin as a possible solution to the zoning problem within large estate homes. The owners of these homes want control of each space within their house and with the vrv system and there smaller sizes this is possible. This is hard to accomplish with dx systems because they do not come smaller than 1.5 ton. I just want to become more fimiliar with the product before we venture out and specify the product. A good knowledgable service tech in our area is hard to come by, so our motto is the simplier the better (to an extent). I have had conversations with the Daikin's engineers in the states and they indicate that the fan cannot be turned off (while in cooling mode)during the thermostat off condition. The other thread seems to indicate that the fan can be turned off during the cooling mode with programming. I agree with your approach of using a seperate type of system to handle the latent load and use the VRV systems to handle the sensible portion. I would not count on them for dehumidification, especially with constant fans.

Our ideal design for these large estate homes is with constant volume, face & bypass, multizone, chilled water air handlers located in a mechanical room under the house. This type of system will provide dehumidification at times while the building is in the cooling mode. The outside air is injected between the face & bypass damper and cooling coil assuring that the outside air will always be conditioned.
Combine this with an extended plenum ductwork design and use the millwork (carpenters are better at finish work then a/c contractors, plus there are no visible diffusers or grilles in the house) as your diffusers and you have the ultimate air conditioning system for florida!

[Abby Normal]

Well we get more humid than Naples, but what our worse case is here is a lingering unorganized system where it is about 80F and 80 dewpoint.

Most of these homes have the unshaded mulit-million dollar view of the Caribbean so more cooling than typical to handle that sun. They also tend to get spacious internal zones as well.

So with sky high humidity, temp not warmer than 80 and no sunshine, nothing tells the AC sized for the sun to run and the places can load up with humidity. When it is cloudy and a system is going by there is wind. Wind increases infiltration- especially in from the attic.

So in these spacious cores I like to use Heat pipes BKP systems with a remote condenser. They will blow cool air like an AC unit or, if the humidity gets high and the space is cool, they will use the hot gas to reheat the supply air like a traditional dehu.

We build primarily with block down here and that can make for a tight wall. But if you take it the step of sealing an attic, you will have an extremely tight home and no humidity problems.

I easily hold 40% RH in my own home, single speed, 13 SEER unit, PSC blower (actually running 520 CFM per ton).

When you take infiltration out of the equation you get better performance than all the variable speed, multi-stage systems, with "Comfort R" ramping, or "Dry Modes" without even trying.

[mchild]

Abby
Our firm also designs a lot of estate homes of that magnitude in the Naples florida area and have been looking at Daikin as a possible solution to the zoning problem within large estate homes. The owners of these homes want control of each space within their house and with the vrv system and there smaller sizes this is possible. This is hard to accomplish with dx systems because they do not come smaller than 1.5 ton. I just want to become more fimiliar with the product before we venture out and specify the product. A good knowledgable service tech in our area is hard to come by, so our motto is the simplier the better (to an extent). I have had conversations with the Daikin's engineers in the states and they indicate that the fan cannot be turned off (while in cooling mode)during the thermostat off condition. The other thread seems to indicate that the fan can be turned off during the cooling mode with programming. I agree with your approach of using a seperate type of system to handle the latent load and use the VRV systems to handle the sensible portion. I would not count on them for dehumidification, especially with constant fans.

Our ideal design for these large estate homes is with constant volume, face & bypass, multizone, chilled water air handlers located in a mechanical room under the house. This type of system will provide dehumidification at times while the building is in the cooling mode. The outside air is injected between the face & bypass damper and cooling coil assuring that the outside air will always be conditioned.
Combine this with an extended plenum ductwork design and use the millwork (carpenters are better at finish work then a/c contractors, plus there are no visible diffusers or grilles in the house) as your diffusers and you have the ultimate air conditioning system for florida!

NB34 and Abby Normal,

In an earlier post in this thread I asked Abby if a discussion in another thread answered the question to his satisfaction about being able to have the indoor units cycle the fan off when the call for cooling had been satisfied.

In that other thread I had been provided information in a PM that described how to program the air handlers to cycle off the fan when the call for cooling had been satisfied.

Since then it has been rather cold here so I had not switched the system to cooling in order to test it. Today I was finally able to test it and I can report that the fan can, in fact, be programed to turn off when the calling for cooling is satisfied. Thus, the fan can be off in both cooling and heating.

I understand that when the new VRVIII-S systems are available in the U.S. this feature will be one of the new field code available for general programing. With the current VRVII-S system you have to go deeper into the programing to accomplish this.

I hope this helps both of you in your understanding of Daikins VRV systems.

[NB34]

NB34 and Abby Normal,

In an earlier post in this thread I asked Abby if a discussion in another thread answered the question to his satisfaction about being able to have the indoor units cycle the fan off when the call for cooling had been satisfied.

In that other thread I had been provided information in a PM that described how to program the air handlers to cycle off the fan when the call for cooling had been satisfied.

Since then it has been rather cold here so I had not switched the system to cooling in order to test it. Today I was finally able to test it and I can report that the fan can, in fact, be programed to turn off when the calling for cooling is satisfied. Thus, the fan can be off in both cooling and heating.

I understand that when the new VRVIII-S systems are available in the U.S. this feature will be one of the new field code available for general programing. With the current VRVII-S system you have to go deeper into the programing to accomplish this.

I hope this helps both of you in your understanding of Daikins VRV systems.

Does this also pertain to the 3 and 4 ton VRV-S systems? Also could you send me a link to where this programming is explained. With no airflow, the return air sensor can no longer control the fan coil unit, so does a remote sensor have to be located in the zone to control the fan coil?

[NB34]

NB34

appologies but the thread was side tracked trying to answer questions by Mchild.

I am also trying to uderstand the chalange of high humidity aplications & so have started another thread.

The posters so far are well known on these boards.

The Mitsubishi Electric VRF systems for example use control statagy to maintain suction pressure & evaporating temperature at indoor units which maintain the ADP & provide continual dehumidification in cooling mode. Therfore constant dehumidification even when the indoor unit reduces capacity.

The exception is when the indoor unit enters the power save mode at 2 deg C above setpoint. The indoor unit then sets a new higher target SH & the LEV valves ramps down to reduce refrigerant flow. The dehumidification at this point might be slightly reduced depending on the air on coil conditions.

Some engineers with a biased opinion & different agenda are critical.
However I have spent the last 16 years specialising in VRF commissioning & trouble shooting & I am confident that the system will perform well in higher humidity conditions than we see in the UK.
I have spent most of the last 12 years carrying out commissioning & trouble shooting site visitson VRF products & spend most days monitoring the system operation with a lap top computer.

I would suspect that critical comments come from engineers who dont have a high level of understanding about how VRF systems operate.

The small size of the indoor unit coil, low air volume & Sensible Heat Ratio all conspire to make dehumidification unavoidable even when the refrigerant flow is reduced.

As already stated in Japan high humidity is also an issue which the manufacturers have to overcome to provide comfort cooling to the staisfaction of local customers.

I wonder how many who comment here have been to Japan to see for themselves.

Is there any reason for not reducing the fan speed AND refrigerant flow as the system approaches the setpoint. I think this would be the ideal control strategy.

[mchild]

Does this also pertain to the 3 and 4 ton VRV-S systems? Also could you send me a link to where this programming is explained. With no airflow, the return air sensor can no longer control the fan coil unit, so does a remote sensor have to be located in the zone to control the fan coil?

NB34,

Yes, it does pertain the the S models - I have the 4 ton unit. I also have remote sensors in each zone to more accurately monitor temps. With ducted units I think this is the best way to go.

I have sent you a PM.

[Abby Normal]

thanks for the update on auto fan capability mchild

[clubchamp5]

i wish i had the problem of living in florida with all that lovely weather although i have been there on holiday 5 times now, i am daikin trained up to vrv3 on install and commissioning but i much prefer mitsubishi city multi vrf by far the best all round systems i have just commissioned 16 outdoor vrfs serving 148 ducted/ cassettes/ wall mounts over 8 floors in an office block in Glasgow Scotland U.K. and the weather at this time of year is wet, then minus 8 hail, sleet and snow so humidiyt is never a problem