Daiken or Mitsubishi Inverter Systems for Residential?

[mchild]

MCHILD, and the other posters thanks for the information. We had the loads recalculated under manual J to take into consideration blown in insulation, closed attic, low e-2 windows etc. and the loads come in at 7 tons, rather than 10-12.

Here are some additional questions:

1. With the 130% capacity of the outdoor units for these companies units, does this mean that 5 or 6 tons of capacity is sufficient and ideal?

2. How much more efficient are the 3 phase units, such as the 6 ton unit offered by Daiken? compared to running 2 3 ton 2 phase residential units?

3. Would you recommend a one compressor configuration for a two story house with 9 zones? It appears that some of the Sanyo units use two compressors, one as a backup.

4. Do any of these systems have occupancy sensors that set back the thermostat in a zone that is vacated?

5. Are their differences in the ability to connect an erv and whole house air filtration and the sophistication of these products from the 3 companies?



Thank you.

Have your engineer look at the building diversity and see if there is enough to reduce the size of your outdoor unit. If not then you will need the full 84K BTUs. Have not heard yet what your heat loss is. How does it compare to your cooling load?

1. The 130% figure does not mean that the outdoor unit can overrun by 30%, although it can produce a little more when 130% is connected as compared to 100%. It means that the total total capacity of the indoor units combined can be as high as 130% of the outdoor. That number on the newest models is moving up to 150% and 200%. This allows you to size the indoor units such that one part of the building may need at or near full capacity as will another part of the building - just not at the same time (diversity).

2. Efficiency is about the same between the larger sizes and the smaller ones.

3. Yes, some manufactures will use two smaller compressors and others one compressor. When there are two, one is an inverter driven compressor and the second a fixed speed compressor. The system determines when one, or the other, or both run.

4. The more sophisticated PC based controls may be able to incorporate that feature.

5. Have not researched the ERV/HRV differences. Most all can incorporate them within the system though.

[MILTON01]

Heat 95k...is that what you wanted to know?

[mchild]

Heat 95k...is that what you wanted to know?

Yes, thanks.

The sizing is generally as follows, but may be a little different depending on the manufacturer:

Cool/Heat (in 000's BTUs)
36/40
48/54
72/81
96/108

Sanyo does not have a 48/54 but rather has a little larger 53/60. Thus, depending on whether you can use a smaller unit because of diversity, you may decide to go with a two smaller single phase systems such as the 36 and 48. The 36 can have six indoor units and the 48 eight. Diversity may be able to bring you down to the 72, otherwise, you may have to go a little oversized (one ton) and use the 96 (it will help when you have those larger summer gatherings and temporarily increase the load). The 72 and 96 are three phase systems.

In any event, you will still be able to have a central control system that will interface with the outdoor unit(s) and all the indoor units.

[mchild]

That will happen only if there's a herd of competent techs to supplant the hack ranks. The manufacturers of these systems would do well to offer training for those who will both sell and install the systems...many of them already do. To me, the only way the higher technology systems will make it is if the OEM is more involved with ensuring contractors and installers are properly trained on the equipment. They can't afford to let untrained Joe Pickup waltz into the parts house and drive off with a VRV system in the bed sitting next to a hacksaw and a beat up gauge manifold manufactured in the sixties.

I think the manufacturers have increased the training and have a minimum tool provision. Hack saw has been replaced with a sawsall (cordless optional), gauges not dating farther back than the mid `70's, and duct tape on the job site is always good to see. ;>) Things are looking up.