OK, here is the "always" current draw on propane. 800ma or 0.8 amps 24/7.
When the gas solenoid valve is open (calling for cold) the total draw is 1.5 amps DC.
normal appliance amp draws
0.8 amps x 24 = 19 amp hours without the gas valve opening.
If it calls for cold 6 hours total per day it will consume an additional 4.5 amp hours. or an average of 23.5 amp hours per day.
The propane detector is 50 milliamps (not 500 sorry
) so it is about 1.5 amp hours per day. Safe T Alert RV Propane Detector and LP Detector
The real issue is with the solar panel.
I also question where you got the 21 AH per day production out of a 40 watt panel.
Is this full sun? Clouds reduce production considerably.
Does the panel rotate with the sun's progression across the sky?
The rated output is based on 90 degree solar ray impact on the cell.
The "standard" for solar panels is 0.3 times the wattage rating for amp hour production per standard day. You may get less if cloudy.
0.3 times 40 = 12 amp hour produced on an average day.
how many amp hours from a solar panel or wind generator - Cruisers & Sailing Forums
Using the above requirement of 25 amp hours you will need a minimum or 85 watts solar and unless you have a solar drive you will most likely need a 100 watt panel to keep up with the other parasite draws (like the battery's internal resistance and the radio's instant on feature).