Delta 252RL heater exhaust fan runs when heat and A/C turned off

[Ninja Panda]

Good morning all... got a bit of weirdness going on. Trailer is plugged into shore power while we do some work on it, but both thermostats are in off / off mode. I noticed while walking by the trailer a couple of times where the fan for the heater kicks on and blow air out of its exterior exhaust port for a minute or two. I have not gotten inside quick enough to see if air is blowing out of the vents.

Why would this be turning on when the environmentals are turned off?

 

[BryanValRox]

Good morning all... got a bit of weirdness going on. Trailer is plugged into shore power while we do some work on it, but both thermostats are in off / off mode. I noticed while walking by the trailer a couple of times where the fan for the heater kicks on and blow air out of its exterior exhaust port for a minute or two. I have not gotten inside quick enough to see if air is blowing out of the vents.

Why would this be turning on when the environmentals are turned off?

Hello, are you sure it is your heater and not your water heater?
The instant hot constant water heaters have a anti freeze strategy built into their logic. They will cycle on below certain temperatures to prevent the water inside from freezing.

 

[Ninja Panda]

Hello, are you sure it is your heater and not your water heater?
The instant hot constant water heaters have a anti freeze strategy built into their logic. They will cycle on below certain temperatures to prevent the water inside from freezing.

As it turns out, it was indeed the hot water heater 😳 - and while the hot water control inside was turned off, I had not turned off the outside switch.

 

[Lantley]

I was thinking that a tankless heater was the source of the fan.
Just another flaw with tankless hot water heaters. The pros of tankless heaters in RV's do not outweigh the cons.