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nexsuperne · 03-10-12, 02:16 PM

I have used a 12000btu portable air con unit. The initial problem was the unit was failing to start when the room temp was below 16C. I got around this by putting a 5k resistor in the ambient temperature sensors place. This way, it thought the room temp was 35C, so would always run. Since then I have removed the control board and put in an etc200b controller and put the probe on the evap hx. This is set at -2C and cuts the compressor for 2 minutes. This also has a 2 minute restart, so that the compressor doesnt lock up. The condenser hx is in a large 80 litre container with water in and 100mm insulation. This is then pumped around the solar coil on my 300 litre thermal store. I have set the controller to maintain the temperature at 40-45C. This then runs my domestic hot water and 2 floors of heating. I have low surface temperature radiators, so 40C is enough heat to hold 21C when it is -3C outside.
Ice was the biggest problem,but I have got around this by putting a flap on the blower outlet from the evap hx with a microswitch connected to the etc200b main power. When the evap hx isnt full of ice, plenty of air flows and holds the flap away from the microswitch. Once too much ice builds up on the hx, then the airflow drops until the flap cannot be blown away from the microswitch. The instant the flap hits the microswitch, the compressor stops and goes into its 2 minute defrost cycle. The -2C is ok if where you live doesnt have an ambient temp below about 4C, but the low tech flap/switch gets around hx's not being iced up, but just below -2C - like first thing on a cold morning.

03-10-12, 02:16 PM	#2
nexsuperne Helper EcoRenovator Join Date: Feb 2012 Location: 30 miles east of London, UK Posts: 88 Thanks: 12 Thanked 19 Times in 18 Posts	I have used a 12000btu portable air con unit. The initial problem was the unit was failing to start when the room temp was below 16C. I got around this by putting a 5k resistor in the ambient temperature sensors place. This way, it thought the room temp was 35C, so would always run. Since then I have removed the control board and put in an etc200b controller and put the probe on the evap hx. This is set at -2C and cuts the compressor for 2 minutes. This also has a 2 minute restart, so that the compressor doesnt lock up. The condenser hx is in a large 80 litre container with water in and 100mm insulation. This is then pumped around the solar coil on my 300 litre thermal store. I have set the controller to maintain the temperature at 40-45C. This then runs my domestic hot water and 2 floors of heating. I have low surface temperature radiators, so 40C is enough heat to hold 21C when it is -3C outside. Ice was the biggest problem,but I have got around this by putting a flap on the blower outlet from the evap hx with a microswitch connected to the etc200b main power. When the evap hx isnt full of ice, plenty of air flows and holds the flap away from the microswitch. Once too much ice builds up on the hx, then the airflow drops until the flap cannot be blown away from the microswitch. The instant the flap hits the microswitch, the compressor stops and goes into its 2 minute defrost cycle. The -2C is ok if where you live doesnt have an ambient temp below about 4C, but the low tech flap/switch gets around hx's not being iced up, but just below -2C - like first thing on a cold morning.