New to VRV - want to understand more

[mchild]

I came across this forum while trying to find out more about inverter driven systems. I live in the U.S. and information is very limited, as these systems have yet to gain significant market presence. Also, we have fewer manufacturers to choose from. The ones that I can find are Daikin, Sanyo, Mitsu, and Fujitsu with each primarily focused on the mini-split market.

I am interested in a complete system for my home. Currently, I have two old systems, one for the upper level and another system for the lower level. Typical, both are separately ducted systems with single speed compressors that bang on and bang off frequently. I want to retain the ducts and use any new system with it.


I am interested in what I believe is called a multi-split system where there will be a single outdoor variable capacity unit such as the Daikin VRV-S and two indoor ducted air handlers that will provide cooling and heating.

With such a system it seems like the compressor will be running much of the time as it constantly conditions the air, either a little on mild days or a lot on extreme days. What is the overall life expectancy of these systems if properly installed and maintained? Here in the US, it is common for US manufacturer warranties to be up to 10 years and sometimes more. For the above manufacturers it is much less, around six years.

I have not found much discussion on Sanyo on this board. What are the thoughts in comparison to Daikin? For the units I have been reviewing, the Sanyo units have a higher level of efficiency.

Thank you for candid remarks.

[Krondor]

Hi mchild,
As far as i know, Daikin and Mitsubishi electric considered to be the best systems in the market, regarding its performance and reliability. However there are also Sanyo and Toshiba (that belongs to the Carrier group). We have those systems for over then 5 years and they seem reliable as promised by the manufacturers. Those systems are usualy supplied with 3 years warranty, however, their life period is expected to be over 15 years.
From my experience with VRV/VRF systems they are very reliable and much less power consuming comparing to conventional splits.

[mchild]

Hi mchild,
As far as i know, Daikin and Mitsubishi electric considered to be the best systems in the market, regarding its performance and reliability. However there are also Sanyo and Toshiba (that belongs to the Carrier group). We have those systems for over then 5 years and they seem reliable as promised by the manufacturers. Those systems are usualy supplied with 3 years warranty, however, their life period is expected to be over 15 years.
From my experience with VRV/VRF systems they are very reliable and much less power consuming comparing to conventional splits.

Thank you Krondor for your thoughts.

The lower power consumption is one of the features that has been considering such systems. I can not understand why these systems have not been more widely used here in the US.

If I can get 15 years from the equipment I will be happy.

In reviewing the operating manual for the Daikin controls it states that the "Dry" mode is set from the factory and can not be changed. What percentage of relative humidity does the system maintain? Does it over cool to reduce the humidity?

[Brian_UK]

The 'dry' mode on most a/c normally tries to hold the relative humidity at the level when the mode was selected. It will not try and reduce the level to something lower.

[Obi Wan]

Hello mchild,

Welcome to RE.

Daikin have been in the US for quite some time or at least had an office in New York. However the US marker has been and still is protected by the US government. For example, I am told that every unit imported has to be checked physically and a certificate obtained. It is not enough to simply check each model type, but to check each and every unit imported. This of course drives up the cost of the units compared to US manufactures.

In the last 2/3 years Daikin Industries have made a major investment to develop the US market. The head office is in Dallas. A lot of the equipment has had to be modified for the US market. Controls have to display Fahrenheit instead of Celsius.
All equipment is rated in BTUs rather then kW, different mains voltage and so on.

Also energy conservation has not been as important in the US compared to the rest of the world (China and India excluded).

As to the “Keep Dry” function, I am not aware of the setting from the factory that can not be changed. What is the model number you are looking at?
The “Keep Dry” function is a form of dehumidification. It does not actually measure the RH as there is no humidity sensor on the indoor units. It works by operating the thermostat in short bursts in cooling mode (6 mins ON 6 mins Off). The idea is to remove the humidity without lowering the room temp too much. A less humid room feels more comfortable then a more humid room. This is also an energy conservation function. It can be selected at will by the end user.

Hope the above helps.

Obi Wan

[l'robot]

When I was in the US four years ago there was interest by the Goverment bodies, but the contractor was not interested as was frightened away with the electronics in the indoor and outdoor. The contractor just wanted simple systems.

[mchild]

Hello mchild,

Welcome to RE.

Daikin have been in the US for quite some time or at least had an office in New York. However the US marker has been and still is protected by the US government. For example, I am told that every unit imported has to be checked physically and a certificate obtained. It is not enough to simply check each model type, but to check each and every unit imported. This of course drives up the cost of the units compared to US manufactures.

In the last 2/3 years Daikin Industries have made a major investment to develop the US market. The head office is in Dallas. A lot of the equipment has had to be modified for the US market. Controls have to display Fahrenheit instead of Celsius.
All equipment is rated in BTUs rather then kW, different mains voltage and so on.

Also energy conservation has not been as important in the US compared to the rest of the world (China and India excluded).

As to the “Keep Dry” function, I am not aware of the setting from the factory that can not be changed. What is the model number you are looking at?
The “Keep Dry” function is a form of dehumidification. It does not actually measure the RH as there is no humidity sensor on the indoor units. It works by operating the thermostat in short bursts in cooling mode (6 mins ON 6 mins Off). The idea is to remove the humidity without lowering the room temp too much. A less humid room feels more comfortable then a more humid room. This is also an energy conservation function. It can be selected at will by the end user.

Hope the above helps.

Obi Wan

Thank you Obi Wan and others for your responses.

I agree the manufacturers that are here in the US market have been here for a while, but the usage seems to be focused more on the mini-split system as compared to the whole building. I do not know yet about costs as I am still in the early stages of investigating these systems. But, the cost may be an issue here.

I also agree with l'robot as there are fewer well qualified technicians here than those that have limited training. Often those techs respond to problems by adding more refrigerant. Too much is just right!! Being afraid of the electronics is common.

As the cost of energy in the US climbs these systems and similar designs by US manufacturers will become more in demand.

If the controls of the unit can not operate in an "On Demand" call for de-humidification then let me make sure I understand how the indoor units operate.

During periods of moderate demand will the indoor units (concealed duct style air handler) flow reduced refrigerant and lower the fan speed? If so, then the longer run times in cooling mode will greatly help with keeping humidity at reasonable levels.

[l'robot]

When I was over there, the concern by the government officials were about energy loading/consumption rather than costs. They were going to “field” try VRF systems in California. To check if the claimed efficiencies were correct. I lost contact when back in the UK so I am not sure if it went ahead.

[mchild]

As to the “Keep Dry” function, I am not aware of the setting from the factory that can not be changed. What is the model number you are looking at?

The “Keep Dry” function is a form of dehumidification. It does not actually measure the RH as there is no humidity sensor on the indoor units. It works by operating the thermostat in short bursts in cooling mode (6 mins ON 6 mins Off). The idea is to remove the humidity without lowering the room temp too much. A less humid room feels more comfortable then a more humid room. This is also an energy conservation function. It can be selected at will by the end user.

Hope the above helps.

Obi Wan


Obi Wan,

The statement as to the humidity level is from the control manual for operation and installation. The model number here in the US are different but I am looking at the Daikin VRV 230 volt single phase outdoor unit in the 5HP size range capable of having multiple indoor units. The indoor units (2) will be duct type of either medium static pressure or high static pressure.

I have also been looking at the Sanyo Mini ECO units (quite similar to the Daikin) and the controls for that read similar. Essentially, there is very little information given on the dry function only that if you want to lower humidity then press the dry button.

I have looked through the setup instructions for the controls and can not find any setup for this feature so I assumed there is not any changeable parameters. In one of the operating instructions (I think Sanyo) it stated that during the dry function the fan would slow down, but noting more than that.

Thank you again.

[Obi Wan]

Hi, Mchild,

I think you are looking at a Daikin VRV Mini system (RXYSQ5M or P). 5 means 5HP. You may have something different for the capacity size.
I looked in my extensive library and could not find any proper explanation for the “Keep Dry” function on the recent VRV systems.
I did however find the attached explanation on a much older VRV G series system and on an older split system. Both work in a similar way. The new VRV systems work along the same lines.
To select the “Keep Dry” mode, you need to put the cool/heat master unit (this could be a heat / cool switch for the system ) into cooling mode and then press the mode button on the remote controller repeatedly until you see the “Keep Dry” symbol (two dew drops). Now switch on the unit and it will do the rest.

Hope it helps.

Regards

Obi Wan

[mchild]

Hi, Mchild,

I think you are looking at a Daikin VRV Mini system (RXYSQ5M or P). 5 means 5HP. You may have something different for the capacity size.
I looked in my extensive library and could not find any proper explanation for the “Keep Dry” function on the recent VRV systems.
I did however find the attached explanation on a much older VRV G series system and on an older split system. Both work in a similar way. The new VRV systems work along the same lines.
To select the “Keep Dry” mode, you need to put the cool/heat master unit (this could be a heat / cool switch for the system ) into cooling mode and then press the mode button on the remote controller repeatedly until you see the “Keep Dry” symbol (two dew drops). Now switch on the unit and it will do the rest.

Hope it helps.

Regards

Obi Wan


Obi Wan,

Thank for that information. It does help.

In the Daikin line I am researching the model you referenced in the 48K BTU (5HP) range as that is the only capacity available here in the US. The Sanyo equivalent models has both a 4 and 6HP size. In the Mitsu line, also only the 5HP. Unfortunately, we don't get all the products here. The model numbers differ also as they are designed for our 60Hz electrical current.

I guess I am a little surprised that there is not an "On Demand" dehumidify setting that is automatically maintained by the controller. Set the maximum humidity level once and the controller would then call for the unit to turn on with low or very low fan speed and not allow more than a degree or two of over cooling.

Here in the US we have many days where it is not hot enough for a call for cooling, but humid enough that dehumidification is surely needed. Having the controller manage it only seems proper and not require the occupants to go through the selection process to turn it on and off.

Having said all that it may be a moot point. If the indoor units reduce the refrigerant flow and lower the fan speed during times of moderate temps then the ongoing operation under that condition would greatly help to maintain comfortable humidity. Is that the way the indoor units operate?

I guess I am still not fully understanding how the indoor ducted units function. I understand that the outdoor units vary the refrigerant volume, but is it only to the extent that the indoor units cycle on and off or do the indoor units also vary the refrigerant volume and fan speed depending on the actual load at the indoor unit?

Thank you.