It has been quite a journey since when I decided to tackle the Honda EU2000i generator's inability to reliably power the 9200 BTU Coleman Mach 8 Polar Cub roof top air conditioner. My determination and self-reliance paid off and I can now declare victory.
Not just that I managed to get to the bottom of the all the causes I also learnt a lot about this kind of RV air conditioner. Most of the US RV AC are crap, including this one. Only very recently there are few newer designs, which are originally for commercial tractor trailer cabs, and designed in Europe. The only good thing about US RV ACs are low price points.
I now resolved the generator problem due to high elevation, compressor's high starting current, and high head pressure. I also solved the limited temperature range and poor cycling behaviors. Before declaring victory with the digital thermostat, I conducted more tests to ensure the behaviors are satisfactory.
more grueling torture tests for the generator in 90s F
today ambient was 96F full sun and clear sky; the AC cycles reliably to maintain around 25C cabin temperature
alcohol thermometer does not lie if installed at a right location
Now even with 96F ambient in full sun of July, I can set the cabin temperature to be comfortable rather than too cold. The mechanical thermostat simple cannot. With the digital temperature controller I have so much more control over the parameters. While the actual dead band can be a few degrees it is nice to be able to set target temperature in fraction of a degree Celsius, which is a few factors better than 1 degree F.
all buttoned up with the air grills back and all the Westfalia screw head caps re-installed; I set the variable blower speed control a wide range from very low speed to full speed
As I set out to accomplish with the digital temperature controller acting as the thermostat, I didn't want to having to switch on the air conditioner's master power and have to switch on the controller separately.
I didn't talk about the thoughts went into the design for usability in the digital thermostat of this project. The first item came to mind if having the controller mounted on the ceiling make it difficult to use, especially changing the parameters as well as viewing the display. An in situ check showed it should not post a problem. I just need to orient the controller such that it is comfortable to use when standing in the kitchen under it.
this is from the user's vantage point
even in the glare of the galley lights it is very readable
on very hot or cold weather I put up this simple thermal barrier
The remaining project for the Coleman is to tame the obnoxious noise level. I have a plan I developed but just need to find time to get up to the roof to implement it.
I purchase a 12Vdc version of the same temperature controller. It is so cheap just to have one around when a project arises. I may want to install it as a provision for Brunnhilde's DC refrigerator/freezer. The benefit is able to monitor the actual temperature at a chose location inside. My tentative location is the defunct black water level monitor panel over the gas hobs.
strangely while basically identical to the 120Vac version, the algorithm is a little different
this is the ideal location for the refrigerator's digital thermostat; as I would not want a glaringly bright red LED display at night I would add a display disable switch hack
Just for a bit of fun, I decide to explore the feasibility of mounting the digital controller for the fridge at our now defunct black water level monitor panel. It is a perfect size there, and I can even repurpose the faceplate to make it looks like it came from Westfalia factory.
the size of the aperture - checked
the size of the faceplate - checked
of course all the guts will be discarded
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