mwcasale
07-27-2012, 12:23 PM
Before you get too far along on this project let me suggest you investigate the technology used by the rest of the world. Look at the VRV/VRF systems from Daikin, Mitsubishi and Sanyo. These systems have inverter driven compressors which allow for an extremely wide range of operation and load adjustment while being highly efficient in operation. They really shine in part load operation where most systems operate most of the time.
VRV/VRF (Variable Refrigerant Volume/Flow) uses a fully variable compressor in the outdoor unit with up to nine fully variable indoor units connected to it. Indoor units can be as small as 6,000 BTUs and over sizing is not an issue as they modulate to the load and can operate as low as 10% of the rated capacity. You could have the bathrooms on their own zone and heated and cooled without issue as to the other rooms. Having multiple indoor units allows for the system to more closely meet the diversity of the building as each zone's load changes. If only a couple of zones are calling for a little heat or cooling then the compressor slows down and only those zones operate.
This will resolve your zoning issues without the elaborate duct work required and the space to install it.
As I'm sure you know, with a conventional system having small zones is difficult as the system capacity (even in low stage) is so much greater than the load of a small zone. Bypass ducting and a dump zone are often required. So, you pay to condition air that is then dumped. With a VRV system you can even turn zones off that are not being used and controls can be tucked away in a closet with small (size of a match book) temp sensors all that is required in each zone.
VRV is the perfect solution for zoning and broad diversity within a structure.
There seems to be relatively little information which explains system design of this type. While it is agreed that multiple indoor units per outdoor units provide a zoning solution, there is what seems to me a huge economic cost for a system of this type.
Let us say for instance that we want to have 4 zones, with each individual zone carrying a 1 ton load. In such an instance we would have a 4 ton outdoor unit paired with four 1 ton air handler (indoor) units. The cost of the four 1 ton indoor units is going to vastly exceed the cost of using zone dampers and a bypass duct, as may be found in a conventional system.
So, let us say for the sake of argument that a “Inverter-type ducted split system” is still deemed desirable for the reason that they are quiet and energy efficient, but that instead of 4 indoor units (costly), we want to use the technology with only 1 indoor unit (less costly). In such a case we may want to use the technology, but with a more traditional zoning arrangement. Using the example above, we would have the “Inverter-type ducted split system” arranged so that a 4 ton outdoor unit is paired with a 4 ton indoor unit. However, the ductwork in this case will require some complexities in order to meet the zoning requirements, and this is where there seems to be a lack of information available.
In the case of a Daikin system, let us say for instance, Outdoor Unit RXS50KVMA is paired with Indoor Unit FDYQ50DV1. Now, the Daikin website http://www.daikin.com.au/product.asp?pid=330&tab=3 says that this pair of units combines to allow for ESP (External Static Pressure) with 15 settings, or Automated.
What I find to be interesting is the Automated setting, which would seem to eliminate the need for Bypass ductwork altogether…
The reason for Bypass ductwork is to allow excess pressure, which mounts when one of the zones is not calling for air, to be routed to the Return side ductwork.
So my question is, is this correct? With an Automated ESP setting is the need for a Bypass duct eliminated? And if so, it seems that these type of systems are not only more efficient for the widely stated reason that they allow for multiple indoor units per outdoor unit, but in the case of the Daikin Automated ESP setting, the same advantages are brought about with much less cost.
Please let me know if you see any flaw in this logic, and if you have any information about how exactly the Daikin Automated ESP setting works, please share.
Also, with the Mitsubishi City Multi systems, (similar to Daikin), they do NOT state that there is Automated ESP setting, only multiple ESP settings. In such a case, would a Bypass duct still be needed? It seems like it would still be needed, but if anyone has experience designing with these type of systems please share some of your techniques.
VRV/VRF (Variable Refrigerant Volume/Flow) uses a fully variable compressor in the outdoor unit with up to nine fully variable indoor units connected to it. Indoor units can be as small as 6,000 BTUs and over sizing is not an issue as they modulate to the load and can operate as low as 10% of the rated capacity. You could have the bathrooms on their own zone and heated and cooled without issue as to the other rooms. Having multiple indoor units allows for the system to more closely meet the diversity of the building as each zone's load changes. If only a couple of zones are calling for a little heat or cooling then the compressor slows down and only those zones operate.
This will resolve your zoning issues without the elaborate duct work required and the space to install it.
As I'm sure you know, with a conventional system having small zones is difficult as the system capacity (even in low stage) is so much greater than the load of a small zone. Bypass ducting and a dump zone are often required. So, you pay to condition air that is then dumped. With a VRV system you can even turn zones off that are not being used and controls can be tucked away in a closet with small (size of a match book) temp sensors all that is required in each zone.
VRV is the perfect solution for zoning and broad diversity within a structure.
There seems to be relatively little information which explains system design of this type. While it is agreed that multiple indoor units per outdoor units provide a zoning solution, there is what seems to me a huge economic cost for a system of this type.
Let us say for instance that we want to have 4 zones, with each individual zone carrying a 1 ton load. In such an instance we would have a 4 ton outdoor unit paired with four 1 ton air handler (indoor) units. The cost of the four 1 ton indoor units is going to vastly exceed the cost of using zone dampers and a bypass duct, as may be found in a conventional system.
So, let us say for the sake of argument that a “Inverter-type ducted split system” is still deemed desirable for the reason that they are quiet and energy efficient, but that instead of 4 indoor units (costly), we want to use the technology with only 1 indoor unit (less costly). In such a case we may want to use the technology, but with a more traditional zoning arrangement. Using the example above, we would have the “Inverter-type ducted split system” arranged so that a 4 ton outdoor unit is paired with a 4 ton indoor unit. However, the ductwork in this case will require some complexities in order to meet the zoning requirements, and this is where there seems to be a lack of information available.
In the case of a Daikin system, let us say for instance, Outdoor Unit RXS50KVMA is paired with Indoor Unit FDYQ50DV1. Now, the Daikin website http://www.daikin.com.au/product.asp?pid=330&tab=3 says that this pair of units combines to allow for ESP (External Static Pressure) with 15 settings, or Automated.
What I find to be interesting is the Automated setting, which would seem to eliminate the need for Bypass ductwork altogether…
The reason for Bypass ductwork is to allow excess pressure, which mounts when one of the zones is not calling for air, to be routed to the Return side ductwork.
So my question is, is this correct? With an Automated ESP setting is the need for a Bypass duct eliminated? And if so, it seems that these type of systems are not only more efficient for the widely stated reason that they allow for multiple indoor units per outdoor unit, but in the case of the Daikin Automated ESP setting, the same advantages are brought about with much less cost.
Please let me know if you see any flaw in this logic, and if you have any information about how exactly the Daikin Automated ESP setting works, please share.
Also, with the Mitsubishi City Multi systems, (similar to Daikin), they do NOT state that there is Automated ESP setting, only multiple ESP settings. In such a case, would a Bypass duct still be needed? It seems like it would still be needed, but if anyone has experience designing with these type of systems please share some of your techniques.