Hello.
I have a caravan fitted with a Dometic RML 9930 absorpion refrigerator, which can be powered with mains,12v battery or bottled gas. . The fridge is rated 240V, 170W. We generally stay on fully serviced pitches and therefore power the fridge from the AC mains. When powered from 12v the fridge will only maintain the current temperature, making 12v power unsuitable for anything other than use whilst travelling.
I have an issue resulting from the variability of the AC mains voltage on sites (generally low and variable by as much as +/-20V too) and the resulting poor performance of the fridge. I have already added fans to provide forced airflow over the heat exchanger if the temperature inside the fridge is above the required set point (currently set to +3.9 degrees centigrade), which does help. However when we experienced 25C outside temperatures and a mains voltage of 215V on site, the fridge was not able to provide enough cooling. I find the constant adjustment and monitoring of the fridge to ensure the temperature is not too high (or indeed too low) quite stressful, impacting on my enjoyment of our caravan holidays.
So, I would like to implememt an automatic system to ensure the fridge maintains an acceptable temperature without my constant attention.
The requirement is for stability of the AC voltage to the fridge and to incorporate my additional forced heat exchanger airflow. It must also weigh less than 5kg (as there is limited load weight available in the caravan). The controller I use for the forced airflow could be used to switch the fridge on and off if it is in the required temperature range.
I have some electronics experience, but mainly with programming microprocessors interfaced with relays / Mosfets and digital sensors. I have done mains installations (under the supervision of an experienced electrician) too, so not a complete newbie to electronics.
My research to date has suggested this be implemented with a toroidal transformer with multi-tapped secondaries, using a bunch of triacs and a microprocessor to manage the switching of the secondaries depending on the input voltage, in order to provide the required 240V (the fridge does work best at 240v). I have also read about solid state variacs, but have not been able to find any DIY examples.
I would appreciate any comments on the above or suggestions for any alternative approaches.
Any help and suggestions will be very much appreciated.
Thank you.
I have a caravan fitted with a Dometic RML 9930 absorpion refrigerator, which can be powered with mains,12v battery or bottled gas. . The fridge is rated 240V, 170W. We generally stay on fully serviced pitches and therefore power the fridge from the AC mains. When powered from 12v the fridge will only maintain the current temperature, making 12v power unsuitable for anything other than use whilst travelling.
I have an issue resulting from the variability of the AC mains voltage on sites (generally low and variable by as much as +/-20V too) and the resulting poor performance of the fridge. I have already added fans to provide forced airflow over the heat exchanger if the temperature inside the fridge is above the required set point (currently set to +3.9 degrees centigrade), which does help. However when we experienced 25C outside temperatures and a mains voltage of 215V on site, the fridge was not able to provide enough cooling. I find the constant adjustment and monitoring of the fridge to ensure the temperature is not too high (or indeed too low) quite stressful, impacting on my enjoyment of our caravan holidays.
So, I would like to implememt an automatic system to ensure the fridge maintains an acceptable temperature without my constant attention.
The requirement is for stability of the AC voltage to the fridge and to incorporate my additional forced heat exchanger airflow. It must also weigh less than 5kg (as there is limited load weight available in the caravan). The controller I use for the forced airflow could be used to switch the fridge on and off if it is in the required temperature range.
I have some electronics experience, but mainly with programming microprocessors interfaced with relays / Mosfets and digital sensors. I have done mains installations (under the supervision of an experienced electrician) too, so not a complete newbie to electronics.
My research to date has suggested this be implemented with a toroidal transformer with multi-tapped secondaries, using a bunch of triacs and a microprocessor to manage the switching of the secondaries depending on the input voltage, in order to provide the required 240V (the fridge does work best at 240v). I have also read about solid state variacs, but have not been able to find any DIY examples.
I would appreciate any comments on the above or suggestions for any alternative approaches.
Any help and suggestions will be very much appreciated.
Thank you.