on watch tool what is it

We don't use ours often but it can be very helpful. It records oil line vacuum, pump pressure, safety control output, stack temp, and cad cell activity. It also monitors voltage to a power venter motor if the system is so equipped. When the burner locks out, you have a pretty good idea why. Even on an intermittent problem, it makes you look like less of a goof if you can't pinpoint it on the second call. That's when we usually will install it.