Daikin VRV-S Specs

[jkish]

I had a Daikin sales engineer out with some contractors today to take a look at my home. They left me with a brochure and the ARI numbers are confusing to me for a system touted as being one of the most efficient.

The 4 ton ducted unit is rated at an EER of 9, SEER of 13.1, and HSPF of 7.85at 47*. Those are low numbers compared to other heat pump makes out there - you can find plenty with EER of >12, SEER > 16, and HSPF > 9 at 47*.

I realize that there efficiencies in the variable nature of the whole system that are not a part of this test. Is it just that these systems are not as efficient when running flat out, but work much better over the full operating range?

[mchild]

I had a Daikin sales engineer out with some contractors today to take a look at my home. They left me with a brochure and the ARI numbers are confusing to me for a system touted as being one of the most efficient.

The 4 ton ducted unit is rated at an EER of 9, SEER of 13.1, and HSPF of 7.85at 47*. Those are low numbers compared to other heat pump makes out there - you can find plenty with EER of >12, SEER > 16, and HSPF > 9 at 47*.

I realize that there efficiencies in the variable nature of the whole system that are not a part of this test. Is it just that these systems are not as efficient when running flat out, but work much better over the full operating range?

I had a similar reaction when I saw the ARI numbers. Daikin states the ARI test procedure does not reveal the true nature of these systems. SEER rating are marketing hype as they do not reveal real world.

Daikin can do some things for you that may help you in making your decision on one of these systems. First, have them provide you with the VRV-Express report that will show you the exact cooling and heating output for each indoor unit at design conditions for your home. You will be surprised how much heat these units can actually produce at low ambient temps. Your need for supplemental heat will be greatly reduced or can even be eliminated with some design changes. For my 3,100 sf home at design temps of 10* and electric cost of .13 cents per Kw, I have calculated that my average annual cost to run electric supplemental heat should be about $30.

Next, they can run their Energy Calculation tool in which the size of your home, the design indoor temps, bin data for outdoor temps along with your all-in electric cost to arrive at the actual operating cost month by month for an entire year (does not include the cost of supplemental heat). This more accurately uses the part load operating efficiencies of the system.

Daikin used this modeling tool on their corporate office building in Texas and the tool was almost dead on. It was off by only $70 for the entire year for the entire building.

If you have reviewed the Daikin performance data in the engineer manual you can see that there is a significant improvement in operating efficiency whether you have 100% or 130% indoor unit capacity to the outdoor unit. I think the ARI rating is based on 100% connection. Also, at part load, the operating efficiency is higher that at full load. Thus, you will see maximum operating efficiency when you have the maximum indoor to outdoor ratio and the amount of time you will have the system run at part load.

In reality, part load is where these systems will run the majority of the time. For my situation the cooling load will always be less than full cooling capacity and the heat load will max the unit out a few hours per year.

[jkish]

I had a similar reaction when I saw the ARI numbers. Daikin states the ARI test procedure does not reveal the true nature of these systems. SEER rating are marketing hype as they do not reveal real world.

Daikin can do some things for you that may help you in making your decision on one of these systems. First, have them provide you with the VRV-Express report that will show you the exact cooling and heating output for each indoor unit at design conditions for your home. You will be surprised how much heat these units can actually produce at low ambient temps. Your need for supplemental heat will be greatly reduced or can even be eliminated with some design changes. For my 3,100 sf home at design temps of 10* and electric cost of .13 cents per Kw, I have calculated that my average annual cost to run electric supplemental heat should be about $30.

Next, they can run their Energy Calculation tool in which the size of your home, the design indoor temps, bin data for outdoor temps along with your all-in electric cost to arrive at the actual operating cost month by month for an entire year (does not include the cost of supplemental heat). This more accurately uses the part load operating efficiencies of the system.

Daikin used this modeling tool on their corporate office building in Texas and the tool was almost dead on. It was off by only $70 for the entire year for the entire building.

If you have reviewed the Daikin performance data in the engineer manual you can see that there is a significant improvement in operating efficiency whether you have 100% or 130% indoor unit capacity to the outdoor unit. I think the ARI rating is based on 100% connection. Also, at part load, the operating efficiency is higher that at full load. Thus, you will see maximum operating efficiency when you have the maximum indoor to outdoor ratio and the amount of time you will have the system run at part load.

In reality, part load is where these systems will run the majority of the time. For my situation the cooling load will always be less than full cooling capacity and the heat load will max the unit out a few hours per year.

The Daikin rep mentioned the VRV-Express report and I think he said he was going to email me a copy based on the rough design he put together. I'm a little worried that he just took the existing capacities of the units that are already installed and divided it up into a few different indoor units based on how I thought it would make sense to split it up. For now, I'm just going to assume that this was just to get a rough idea about what it might cost to put together such a system. Hopefully, when it came time to really do it, they would come back and do a full load analysis.

I've used HVAC-Calc to get a rough idea of what my heat gain/loss is in the house and I know that the systems are somewhat oversized.

It will be interesting to see what they come back with and I'll follow up with them on the tools you mentioned.

[mchild]

The Daikin rep mentioned the VRV-Express report and I think he said he was going to email me a copy based on the rough design he put together. I'm a little worried that he just took the existing capacities of the units that are already installed and divided it up into a few different indoor units based on how I thought it would make sense to split it up. For now, I'm just going to assume that this was just to get a rough idea about what it might cost to put together such a system. Hopefully, when it came time to really do it, they would come back and do a full load analysis.

I've used HVAC-Calc to get a rough idea of what my heat gain/loss is in the house and I know that the systems are somewhat oversized.

It will be interesting to see what they come back with and I'll follow up with them on the tools you mentioned.

Daikin will help with the design of the system based on load calcs, but those calcs will either be your responsibility or the contractor's. if you are not absolutely comfortable with the calcs you did then have the contractor run their own set of numbers. What are the gain and loss figures you came up with?

Of course each person is different, but ever person I have dealt with Daikin has bent over backward to help and then make sure I am satisfied. So, hopefully your situation will be the same.

[jkish]

Daikin will help with the design of the system based on load calcs, but those calcs will either be your responsibility or the contractor's. if you are not absolutely comfortable with the calcs you did then have the contractor run their own set of numbers. What are the gain and loss figures you came up with?

Of course each person is different, but ever person I have dealt with Daikin has bent over backward to help and then make sure I am satisfied. So, hopefully your situation will be the same.

The house has systems on 3 levels and I did the calcs for the top 2 which is about 4000 sq ft. The middle level is about 2800 sq ft and had a heat gain of 39K (34K sensible) and a heat loss of 55K. The top level had a gain of 18K (16.5K sensible) and a loss of 21K. Currently, the middle level has a 5 ton 10 SEER straight AC system and a 120K 80% gas furnace. The top level has a 4 ton 10 SEER straight AC system and a 60K 80% furnace.

The Daikin guy seemed like he would be willing to help quite a bit.

[mchild]

The house has systems on 3 levels and I did the calcs for the top 2 which is about 4000 sq ft. The middle level is about 2800 sq ft and had a heat gain of 39K (34K sensible) and a heat loss of 55K. The top level had a gain of 18K (16.5K sensible) and a loss of 21K. Currently, the middle level has a 5 ton 10 SEER straight AC system and a 120K 80% gas furnace. The top level has a 4 ton 10 SEER straight AC system and a 60K 80% furnace.

The Daikin guy seemed like he would be willing to help quite a bit.

What are you doing about the bottom level?

What are your outdoor design temps?

Probably going to need two outdoor units 3 and 4 ton - maybe two 4 ton units to get the heat you need. The systems can have lots of indoor units (about 14) probably more than you will want or need to have. If you have areas that do not get used much you may want to have those areas on separate zones and only bring them to a comfort setting when the area is being used. That will help in your operating costs.

The smallest listed ducted unit in the FXSQ model line is 12K BTU. But, that unit can be reduced down to 9K BTU with a simple change of a unit capacity plug on the circuit board. I just mention it in case you were not aware of it and if you need to have zones that small.

[jkish]

What are you doing about the bottom level?

What are your outdoor design temps?

Probably going to need two outdoor units 3 and 4 ton - maybe two 4 ton units to get the heat you need. The systems can have lots of indoor units (about 14) probably more than you will want or need to have. If you have areas that do not get used much you may want to have those areas on separate zones and only bring them to a comfort setting when the area is being used. That will help in your operating costs.

The smallest listed ducted unit in the FXSQ model line is 12K BTU. But, that unit can be reduced down to 9K BTU with a simple change of a unit capacity plug on the circuit board. I just mention it in case you were not aware of it and if you need to have zones that small.

I'm in Atlanta and used 22* and 92* outdoor with 99 grains of moisture. Indoor temps were 72 winter, 75 summer, 50% humidity.

They were talking about two 4 ton units and letting the bottom level have excess capacity off of the 2nd unit. The load is probably minimal there and it is not used as much as the rest of the house. That area is about 2000 sq ft, but much is below grade with a walk out terrace.

I might have a zone that could use 9K BTU, so that is good info about being able to shrink the capacity of the indoor unit.

[mchild]

I'm in Atlanta and used 22* and 92* outdoor with 99 grains of moisture. Indoor temps were 72 winter, 75 summer, 50% humidity.

They were talking about two 4 ton units and letting the bottom level have excess capacity off of the 2nd unit. The load is probably minimal there and it is not used as much as the rest of the house. That area is about 2000 sq ft, but much is below grade with a walk out terrace.

I might have a zone that could use 9K BTU, so that is good info about being able to shrink the capacity of the indoor unit.

Check your outdoor design temps and grains. Temps for summer seem about right, but I think winter would be closer to 17 - 18. Also, I think your grain number is closer to 130. Heat loss for as far south as you are seems high. Check your infiltration amount and also ceilings to make sure you do not have some listed as having an attic area that is unconditioned when they are under conditioned space.

Something to keep in mind. You do not have to have the indoor units on one floor all assigned to the same outdoor unit. You can mix it all up any way that works. The goal is to size the indoor units to the larger load at design conditions. Heat and cool outpoint will not be the nominal amount. At design conditions an 18K indoor may have heat output of 11-12K BTU. That is where the VRV Express comes in real handy.

[jkish]

Check your outdoor design temps and grains. Temps for summer seem about right, but I think winter would be closer to 17 - 18. Also, I think your grain number is closer to 130. Heat loss for as far south as you are seems high. Check your infiltration amount and also ceilings to make sure you do not have some listed as having an attic area that is unconditioned when they are under conditioned space.

Something to keep in mind. You do not have to have the indoor units on one floor all assigned to the same outdoor unit. You can mix it all up any way that works. The goal is to size the indoor units to the larger load at design conditions. Heat and cool outpoint will not be the nominal amount. At design conditions an 18K indoor may have heat output of 11-12K BTU. That is where the VRV Express comes in real handy.

The design conditions came directly from HVAC-Calc. I checked around a bit and found several references to Atlanta outdoor conditions that all were either 22*-92* or 23*-91* so I think those are probably correct. The moisture was hard to find - the only other number I could come up with was 107 grains for Atlanta.

There are two fireplaces that contribute a total of 15K BTUs to the heat loss and nothing to the heat gain. Other than that, I didn't notice any other big mistakes. I'll probably relicense HVAC-Calc to rerun some stuff where I know there are some minor problems.

One reason they may have bunched a single floor together was because I asked if it could be done in stages so I could test drive the system on one floor before doing the rest. That may or may not be a good idea.

[mchild]

The design conditions came directly from HVAC-Calc. I checked around a bit and found several references to Atlanta outdoor conditions that all were either 22*-92* or 23*-91* so I think those are probably correct. The moisture was hard to find - the only other number I could come up with was 107 grains for Atlanta.

There are two fireplaces that contribute a total of 15K BTUs to the heat loss and nothing to the heat gain. Other than that, I didn't notice any other big mistakes. I'll probably relicense HVAC-Calc to rerun some stuff where I know there are some minor problems.

One reason they may have bunched a single floor together was because I asked if it could be done in stages so I could test drive the system on one floor before doing the rest. That may or may not be a good idea.

If you haven't already you might post a question here to confirm the design parameters. The moisture is the one that jumps out at me.

What is the total heat loss for infiltration?

[jkish]

If you haven't already you might post a question here to confirm the design parameters. The moisture is the one that jumps out at me.

What is the total heat loss for infiltration?

When I get ready to run it again, I'll ask for some guidance.

The total infiltration loss is 8100 first level and 3400 second level.

We currently have electronic air cleaners and steam humidifiers.

If you break things into zones, I guess you then have to put separate filtration and humidification on each?

[mchild]

When I get ready to run it again, I'll ask for some guidance.

The total infiltration loss is 8100 first level and 3400 second level.

We currently have electronic air cleaners and steam humidifiers.

If you break things into zones, I guess you then have to put separate filtration and humidification on each?

You are correct that each unit will have separate filtration.

Switching to a heat pump may eliminate the need for humidifiers. Low indoor humidity in the winter is an indication of excessive infiltration. This is partially contributed to by fossil fuel furnaces that draw air from the conditioned space. This puts the home under negative pressure and that increases infiltration. If the home is still too dry then you may want to investigate and correct the air leakage.

[jkish]

You are correct that each unit will have separate filtration.

Switching to a heat pump may eliminate the need for humidifiers. Low indoor humidity in the winter is an indication of excessive infiltration. This is partially contributed to by fossil fuel furnaces that draw air from the conditioned space. This puts the home under negative pressure and that increases infiltration. If the home is still too dry then you may want to investigate and correct the air leakage.

We installed the humidifiers before I made a bunch of improvements to the infiltration. Last winter, we didn't have much need for the humidifiers and so it may not be needed at all once we switch to the HP.