True as others have said DeLonghi oil filled is good, but check your
wiring, Elec heat Pulls the MAX......
I drain my system 1-2-3 when i leave even for a day at 20` or less.
1- Ball valve main shutoff,
2- Open drain next to main.
3- Open valves upstairs,
simple and effective.
For you, drain at night , no worry.