Added "on demand" water heater

I also have a big interest in this.. following another thread where the same idea was done. Would be great to receive periodic updates how things are going and where potential tweaks to the system for better operation.

For me, I do not want to replace my water heater with a instant-on for boondocking reasons... but have the capability of additional heated water when at a full-hook up RV park. This solution is a good solution for what I would like to accomplish.