@DougH and @Denny16 thanks for the help. Your argument makes sense about the multitude of phones to check. I’m both amazed at technology and annoyed when it doesn’t work (until I hear why it doesn’t... then I feel ashamedly entitled). Humans are amazing. Tech is amazing. The T-Mobile guy tried to talk me into trading in for a Samsung... I always resist upgrading hardware to compensate for advancing software. Yet, I love using the software and get grumpy when my old stuff isn’t relevant any more. Times, they are a changing. Well, the other good news is that we still have our trailer brakes based on our last setting. Thanks for the reminder and test, Denny. i appreciate you guys.
What year trailer is your "new" trailer? Most 400's would have at least 200 amp hours of battery available. And, in your trailer, you should have a Victron solar controller, and along with that, you have access to the Victron App, which will show you information about the status of your battery.
If you have not done it...open up the complete battery area and see exactly what you have: take pictures if you want. Tell us if you have the Victron app. Or, a multimeter.
Depending upon what you actually mean by your question...
Your Alde should have a set of valves that allows the domestic water supply to bypass the boiler. If you drain the HW tank it will stay empty. Cold water will flow from both hot and cold taps.
Draining the glycol is a bit more difficult, and probably not advisable.
You can disconnect the power supply by unplugging the unit and pulling the 12V fuse, but there's no real reason to do this if the unit is totally off.
If you'd like to double your under-bed storage area, you can drain and disconnect everything, remove the entire unit and all the convectors, and ship them to me! :-)