I have had a catalytic BK “King” for decades.
There’s a variable speed fan knob at the right rear bottom.
The fan is a bit noisy even at low speed setting.
For years on cold nights (Anchorage Alaska) I’d bend over, turn it on after loading with birch for the night (bedrooms upstairs), only to be greeted by the noise in the am with a stove still putting out heat, but needing daytime refueling with spruce.
As I’ve gotten older I got even more tired of bending over and turned the switch on and off.
About 2 years ago I got smart!!
I purchased an Inkbird thermostatic switch from Amazon (maybe $30??). I used metallic heat resistant tape (NOT duct tape), the kind for taping exhaust pipe connections, to tape the thermocouple to the back of the air plenum for the fan near its top.
FWIW, setting the switching temperature at 123F, with a “gap” of 3 F so it stays on for a bit, works the best for me.
With the new Peltier fans, the big (noisy) fan stays off unless I really call for serious heat.
It only runs continuously if I turn the BK air inlet temperature past “2”.
Big improvement,
should have done it a long time ago.