The company I work for moved to new premises last autumn that have been flagged by the local press as being “green” and have received an “excellent” rating from Breeam. The office space of 580m² on the first floor has 8 independently controlled zones heated/cooled by a Mitsibishi “City-Multi” twin air source heat pump with a 16Kw input. Generally the system works well, except when the outside air temperature drops close to, or below 0°C.
This week with sub zero temperatures all day, the system has been hopeless. It came on at midnight on Sunday as usual and after 8 hours, the offices were only 15°C. It took 12 hours in total to reach 21°C. Because of this we left the system running all night. The following morning the temperature had actually fallen to 19°C, and it took another 4 hours to get back to 21°C.
In the mornings, for 25 minutes of every hour the system is “defrosting” or on “stand-by” Today it has warmed up and the outside air temperature is 6°C the system came on at 3:00am and it was 21°C when we arrived at 8:00am.
The exception to this is the conference room which has a ceiling mounted Mitsubishi cassette and separate heat pump with its own controls. This worked fine.
There have been a lot of issues with the system since we moved in and the engineers call in every now and again and fix one of them. So before I hit them with another one I want to be sure of my facts.
Any suggestions as to what the problem may be and how to rectify it?
This week with sub zero temperatures all day, the system has been hopeless. It came on at midnight on Sunday as usual and after 8 hours, the offices were only 15°C. It took 12 hours in total to reach 21°C. Because of this we left the system running all night. The following morning the temperature had actually fallen to 19°C, and it took another 4 hours to get back to 21°C.
In the mornings, for 25 minutes of every hour the system is “defrosting” or on “stand-by” Today it has warmed up and the outside air temperature is 6°C the system came on at 3:00am and it was 21°C when we arrived at 8:00am.
The exception to this is the conference room which has a ceiling mounted Mitsubishi cassette and separate heat pump with its own controls. This worked fine.
There have been a lot of issues with the system since we moved in and the engineers call in every now and again and fix one of them. So before I hit them with another one I want to be sure of my facts.
Any suggestions as to what the problem may be and how to rectify it?
