Mitsubishi Heavy Industries Technical Review Vol. 51 No. 2 (June 2014)32

Energy-saving Proposals and Maintenance Services
through 24-hour Remote Monitoring System of
CO2 Heat Pump Water Heater
S a l e s D e pa r t m e n t
Air-Conditioning & Refrigeration
Division
Air-Conditioning & Refrigeration
Q u a l i t y A s s u r a n c e D e pa r t m e n t
Quality Management Division
M a c h i n e r y, E q u i p m e n t & I n f r a s t r u c t u r e

In recent years as part of global warming prevention, heat pump hot water supply systems,
which are highly efficient and emit less CO2, are attracting attention as an alternative to boiler
systems in which natural gas, heavy oils or kerosene is used. The ESA30-25 CO2 refrigerant heatpump water heater of Mitsubishi Heavy Industries, Ltd (MHI) has achieved the industry’s highest
COP of 4.3 and maintains 30 kW output at ambient temperatures of up to -7°C. Even in extremely
cold regions where the ambient temperature may reach -25°C, it can discharge hot water of 90°C,
thus exhibiting performance superior to the products of our competitors. However, because the CO2
refrigerant heat pump water heater involves a large high/low pressure difference and contains awater circuit, etc., regular maintenance inspections (e.g., regarding blockages or leaks in the circuit
or a decline in performance) are required. The 24-hour remote monitoring system, which isintroduced in this report, enables the accurate, prompt and timely provision of these maintenanceservices to our customers, as well as proposals for more economical ways of using the waterheaters (energy-saving operation). It therefore assists customers with the long and stable use of ourwater heater products.

|1. Service outline(1)

Provision of support services for energy-saving operation
In our monitoring system, suggestions based on the monitored data analyses will be maderegarding the optimum schedule of filling the hot water tank to cause no excesses/shortages ofhot water. The energy consumption by the water heater and the amount saved due to theenergy-saving effect, etc., are also reported regularly.
Figure 1 shows an example of eliminating the unnecessary operation of a water heater,
based on the suggested filling schedule of the hot water tank.
Before improvement

After improvement: 1.5-hour reduction of unnecessary
heater operating time

Problems
・ The unused hot water level at the end of a day is ashigh as 40%.
・ In spite of excessive hot water left after the day, thestored hot water level setting is 100% at night andadditional fillings are conducted in the morning andafternoon.

Improvement
・ The unused hot water level has been reduced to 28%.
・ The stored hot water level is set at 80% at night and isalso decreased by 20% in the morning and afternoon,
resulting in a 1.5-hour reduction of unnecessary
operating time.

Figure 1 Energy-saving effect induced by the suggested filling schedule of the hot water tank(an example of improvement)

Mitsubishi Heavy Industries Technical Review Vol. 51 No. 2 (June 2014)33

Figures 2 to 4 are examples of the visualized energy consumption and cost-reduction
effect based on the regular reports.

Figure 2 Electricity usage comparison (a comparison of energy consumption)

Figure 3 Cost comparison with the alternative
energy sources of electricity (an example oftotal cost comparison)

Figure 4 Cost comparison withalternative energy sources ofelectricity (an example of costdifference comparison)(2)

Provision of preventive maintenance services for the device
The monitoring system allows the detection of abnormal device conditions based on theanalyses of monitored data on hot water discharge temperature, water heat exchanger
performance, pressure sensors readings, operation modes, presence/absence of protection
control, compressor operating conditions, etc. It therefore enables the provision of preventive
maintenance services before precarious conditions can cause real damage to the device. With
this service, we can assure our customers of the long and stable use of our water heater
products.
By making suggestions through monitoring data-based preventive maintenance services
and making use of such activities, retailers and customer service centers can also enhance thequality of aftercare services, establish a connection with customers and utilize opportunities for
obtaining new orders(3) Provision of prompt service in response to malfunctions
In the case of damage to a device, our monitoring system is capable of making a warning
on malfunction by email with the operational data obtained immediately before the occurrenceof a malfunction (Figures 5 and 6). Through this email, the service personnel in charge will be
informed of the relevant property name, address, contact number and type of malfunction. The
likely cause can also be identified by comparing past operational data with the latest data before
the malfunction occurred. Consequently, prompt repair/recovery service can be provided,

Mitsubishi Heavy Industries Technical Review Vol. 51 No. 2 (June 2014)34

minimizing the interruption of the continuous use of our water heaters. We thereby can assure
our customers that they can benefit as much as possible from the economic advantages resulting
from the use of our products.

Figure 5 Example of released operationaldata

Figure 6 Malfunction warning email (anexample)|2. Outline of the remote monitoring system
Our remote monitoring system consists of the master unit (RM-FGW) and the remoteterminal board (RM-PWB) and uses a customer’s LAN to send monitored data to the MHI server
via the Internet (Figure 7). Therefore, the speed of communications in our system is faster than thetelephone line systems which our competitors have adopted for remotely monitoring airconditioners. No special communication fees (payment for phone calls) are charged.
A single master unit (RM-FGW) can handle the monitoring of the operational data of 32 CO2water heaters (Q-ton) and the data monitoring interval can be set as short as 10 seconds, which is 6times more detailed than other companies (shortest interval of 1 minute).
Because the data is transmitted in such a way that the data for a day (i.e., 24-hour operationaldata) is compressed and collectively sent to the MHI server once a day, the load on the customer’s
LAN can be decreased compared with the method in which operational data is constantly reported
to the server. For example, when reporting the monitored data of a single water heater (Q-ton),approximately 5 seconds are required to complete data transmission with a communication speed of
1 Mbps.
On the other hand, the collected operational data, which has been compressed and encoded toprevent third parties from browsing it, is decompressed and decoded before being converted into a
data format that can be browsed from retailers or customer service centers (special software isnecessary for data browsing). Through the disclosure server, the data becomes available for login
users. Based on this data, retailers and customer service centers can make suggestions forpreventive maintenance services to customers, enhancing the quality of aftercare services.

Figure 7 Schematic diagram of the remote monitoring system