Well haven't seen it get hotter than a needle or two past 230*.
IMO that is sweet spot. Did an empty whole house today.
Outside temp was -10 F . Heat off TM was great. Again my cargo area stays really warm with boxheater plus mount heat.
Once the TM is running for 10-15 mins the waterbox supply water gets pretty warm and that's when the heat is there.
When I prespray... I keep the vac underload too!
Do you have fresh water tank? No way with our cold temps could you run a garden hose feed. I'm assuming if you do tap feed to waterbox , that water is coming into waterbox quite cold.
I keep my fresh tank full when not in use. Fresh water tank water gets up to 70 degrees as I heat my cargo area when boxtruck sits.
I have the underbelly 85 gallon poly fresh water tank