Thursday, 17 November 2011

What you need to know when installing an airconditoner in HDB flats in Singapore

Types of airconditoners available
Cassette, Wall-mounted, Floor/Ceiling suspended, Duct-Connected, window unit, casement and portable aircon.
Inverter vs Non-inverter
Inverter airconditioners are running on variable speed compressor thereby reducing energy cost as compared to non-inverter airconditioners which is mono speed (on/off) and runs at full load when the compressor runs.
The compressor of inverter airconditioner will reduce the running speed once the preset temperature of the airconditioner is achieved while non-inverter compressor only switches off when the preset temperature is achieved for a while before turning on again when the room temperature rises. Room temperature remains almost constant for inverter airconditioners as compared to non-inverter airconditioners which has a fluctuation in temperature.
Noise level of inverter condenser is greatly reduced as it is using a DC twin rotary compressor.
R410A refrigerant vs R22
R410A refrigerant is CFC free (environmental friendly) and has a operating gas pressure of 1.6 times higher than R22 refrigerant. R410A also has a higher condensation rate due to its slightly higher cooling of the refrigerant as compared to R22. On average, 30% of energy can be saved by getting an inverter airconditoner as compared to non-inverter airconditioner provided the airconditioner is being serviced regularly and cooling capacity of the fancoil is not undersize. R22 refrigerant is used in Non-inverter aircon and has a lower operating gas pressure

Single split means one condenser connected to one fancoil also known as system 1

System 2 means 2 Fancoils (Indoor units) connected to one condenser (Outdoor Unit)

System 3 means 3 Fancoils (Indoor units) connected to one condenser (Outdoor Unit)

System 4 means 4 Fancoils (Indoor units) connected to one condenser (Outdoor Unit) 
BTU is known as british thermal units and is a unit of measurement of thermal energy
Conversion from Kw to BTU. 1 kW= 3412 BTUs.
HP stands for Horse power. 1 HP is the power input equivalent to 746 W and can produce approximately 9000 BTUs
Typically fancoil units are available in 9000 BTUs (2.5 kW) 1 HP, 12000 BTUs (3.5kW) 1.5 HP, 18000 BTUs (5kW) 2 HP and 24000 BTUs (7kW) 2.5 HP. 1 HP = 746 w, 230 V at 50 Hz
To find out what is the sizing of the aircon required for the area you can take area size in square feet multiply by 65 or area size in square meters multiply by 650.
Example 140 square feet area size will require 140 x 65 =9100 BTUs
In this case you can select 9000 BTUs for the room as there will be furniture like built in cabinet or wardrobe occupying the space.
Rule of thumb for installing fancoil capacity in HDB flats.

Flat Type
Rooms BTUs
Living Room/Hall BTUs
9000 x 2
9000 x 3
12000 for Master bedroom
9000 for the rest of the rooms
Executive Apartment/Maisonette
12000 for Master bedroom
9000 for the rest of the rooms

*Living Room /Hall BTUs exclude kitchen area therefore preferably need to have a sliding door or curtain to block out the area to prevent the cold air from escaping if it is an open concept then you will need to get a higher cooling capacity or install one more fancoil at the kitchen area.
How many condensers can one HDB flat install?
It depends on the electrical loading of the flat.
Flats with 40 Amps main switch and flats upgraded
under Main Upgrading Programme (MUP)
Maximum of 2 split-type air-conditioner condensing
units (max. weight of 110 kg each) are allowed to be
installed externally.
(i) No control on running current of electrical appliances.
But to be restricted by the 20Amps DP isolater or
15Amps power point.
(ii) No restriction on number of casement/window unit air
To check whether your flat has a higher electrical loading please visit the website below.
HDB apartment blocks completed on or after 1 Jan 1994 are provided with a 40 amps main switch. Incoming electrical supply is also upgraded for blocks under the Main Upgrading Programme (MUP). Flat owners need not apply for an HDB permit to install an air-conditioner or other higher capacity equipment/appliances if the flat is provided with higher electrical loading.
For flats which do not have higher electrical loading they are flats provided with 30 Amps main switch . Only one condenser is allowed and the following guidelines are to be followed when installing a new airconditioner.
Flats with 30 Amps main switch
Flat Type
Max. Total
Air-Con Condensing
Unit Max. Weight
Multi Generation
Executive Apartment
(with 4 bedrooms)
Executive Apartment
(with 5 bedrooms in
converted block)
11 Amps

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