Not shutting off if the fan is at slowest speed, could be a plus..
A few times I tried to figure out why my burner would not stay light and it was I forgot to turn fan on..

My slowest speed is to fast IMHO but it is what it is..

Deano wrote: When would zero exhaust be needed?

When "0" fast as "60"

slickrock wrote:

• 1. Disconnect the taper resistor so the bias pot and fan pot are still in series alone in the circuit. Doing so will disable the responsiveness of the fan, but that's the least of your problems.
  2. Back out the bias pot to max resistance.
  3. Set fan control to 0, which would be max resistance for the fan pot.
  4. At this point the whole setup should be a about a 1Meg Ohm of resistance with mere micro-amps going the SSR. The fan should be not spinning at this point. If you the fan is still running, then maybe your SSR is faulty.
  5. Slowly trim the bias pot, reducing its resistance until the fan starts.
  6. Back of the trim pot till it comes to a stop. Now, you at least have a setup where the fan can be controlled to full off.

Finally! Yes, the fan can be stopped.
Many thanks! Slickrock.

slickrock wrote:
7. If you achieved step 6, then I would measure the resistance of bias pot and the fan pot in the off position. Tell me what it is, then I can work out potential taper resistors values that could work for you.

It is 0.243 mΩ. What taper resistors value are better for it? Thank you.

I did the pot mod and added a digital voltmeter. Works great

Sounds good! Could you please share your mod?

Video of it.
https://goo.gl/photos/sgKTcT3fjQ4EPtrK6

johnny4lsu wrote:<image>

Video of it.
https://goo.gl/photos/sgKTcT3fjQ4EPtrK6

I use this one to control the fan- Magrfhelic Differential Pressure Gauge.