Mitsubishi Responses to Daikin Heat Recovery VRV Claims
Daikin Claim #1: Daikin uses approx. 27% less refrigerant than its competitors.
Mitsubishi Response to Claim #1: This may be true for the factory charge of the outdoor unit only,
but most likely not when considering a complete system. The amount of total refrigerant will be
dependent on sizes and lengths of refrigerant piping, as well as the size and quantity of branch
selector boxes and fan-coils.
Daikin Claim #2: Advanced Defrost Cycle Operation in Heating. Continuous heating during
defrost cycle.
Mitsubishi Response to Claim #2: City Multi defrost cycle time is minimal, especially in most of
Southern California. This has not been an issue. This is a significant shortcoming for Daikin, as it
has at most 30% of heating capacity available during this time, resulting in uncomfortable supply air
temperatures. Second, it therefore extends the amount of time for the defrost cycle, so more time
with restricted comfort levels. Third, it reduces the total heating capacity available in a 24hour
period, which is why Mitsubishi chose not to do this.
Daikin Claim #3: Continuous heating during oil return.
Mitsubishi Response to Claim #3: This is hardly an issue for Mitsubishi, since oil return is
dynamic, only done if necessary, which is seldom for most applications, whereas Daikin’s is timed
for 2hrs after startup, and every 8 hours after that. This is possible because Mitsubishi has a much
better oil separator, over 99% removal vs. ~80% for Daikin.
Daikin Claim #4: Dedicated Hot Gas line (3rd pipe) for higher off coil temperatures even at lower
ambient conditions.
Mitsubishi Response to Claim #4: Higher than? Are leaving air temperatures across Daikin’s
ambient temperature operating range quantified in any Daikin documentation? This is a Red
Herring, this difference only occurs during simultaneous heat/cool, so normally the mild shoulder
seasons. It has no effect on heating though, because the system compensates by increasing mass
flow of saturated refrigerant. The bottom line is that there is negligible effect on the supply air temp.
and comfort levels.
Daikin Claim #5: Less overall copper piping requirements, saving material costs.
Mitsubishi Response to Claim #5: Does not consider the size of 3-pipe main trunk piping off which
each branch selector box is piped. The cost of copper for the 3-pipe trunk can still be more even
when total pipe lengths are less, due to the higher cost of hard-drawn copper vs. smaller linesets
offered by Mitsubishi. And those are pre-insulated, negating the labor cost of insulating the trunk
line as well. Nothing is said of the additional number of connections with 3-pipe, the required, and
more costly Refnet fittings for all three lines that need to be installed at a specific angle, the number
and expense of branch selector boxes, their placement, mounting, piping, line voltage and control
wiring.
Daikin Claim #6: Back up redundancy in compressors. Gives customer 24hrs of partial capacity on
second compressor while problem is being solved.
Mitsubishi Responses to Daikin Heat Recovery VRV Claims
Mitsubishi Response to Claim #6: May not be best to continue running a unit if one compressor is
down, especially in the case of a burnout where the compressor motor windings have burnt and
contaminated the refrigerant system. Daikin uses one single-speed, On/Off (cheaper) compressor
and one variable speed compressor in their units. Starting current of the single-speed compressor is
much greater than a VFD compressor. Mitsubishi units are 100% variable speed for more precise
capacity control over a wider range. All units sizes 144,000 (high-efficiency version) and above
have two VFD compressors, and can run while the other is valved & shut off, eliminating the risk of
spreading any contaminants throughout the system.
Daikin Claim #7: Automatic Charge Function.
Mitsubishi Response to Claim #7: Additional charge is easily calculated with Design Tool, and a
weight scale should be used regardless, to account for refrigerant quantity used. Auto-charge is a
nice gimmick, but has numerous restrictions due to the inherent inaccuracy of that approach, which
can leave the customer with an improperly charged system, necessitating call-backs and removing &
re-installing the refrigerant charge. Mitsubishi’s philosophy is to do it once, and do it right the first
time.
Daikin Claim #8: Automatic Test Function.
Mitsubishi Response to Claim #8: Mitsubishi has on-board, as well as full system monitoring and
diagnostics through central controls, or by use of a laptop and maintenance tool interface connected
at any point along the 2-wire MNET communication bus.
Daikin Claim #9: Daikin Branch Selector boxes do not require condensate connections. Mitsubishi's
BC boxes have heat exchangers and thus condensate lines are required for each box.
Mitsubishi Response to Claim #9: One condensate line per BC controller vs. as many branch
selector boxes as number of BC controller ports. This is a very minimal add when compared with
the additional fittings, power & control wiring for installation of many more branch selector boxes
than BC controllers. The BS boxes have far less flexibility as well, with the multi-port models only
capable of having a single spare port, or 2 for the whole system. A Mitsubishi BC controller can
have 15 spare ports and operate just fine. This impairs the Daikin’s ability to operate if a portion is
to be phased in or remodeled later. The foamed in nature of the BS Boxes also hinders
serviceability, and the internal heat exchanger of the BC provides sub-cooling which improves
system performance.
Daikin Claim #10: Daikin's Branch Selector boxes do not have solenoid valves and are thus quieter
than the Mitsubishi BC boxes.
Mitsubishi Response to Claim #10: Solenoid operation produces a faint sound that is typically
imperceptible unless installed in an open area that needs to be extremely quiet. There are usually
many location options to prevent a potential listener from hearing the momentary, low level sounds
emitted from a BC Controller. The sound of the solenoids is almost imperceptible when standing
right below the BC. If there is a ceiling or other barrier they can’t be heard at all.