You want the fire to be about an inch wide when running on the timer. You really shouldn't be adjusting the idle with the feed screw. That screw is to set the high fire rate. When you have a demand for heat and the unit is continously stoking the red coals should be covering all but the last 1" of the grate. You then adjust you idle fire by adjusting your timer and the feeder rheostat.
I have mine LL set @ 165 and it never goes up past 180. Like I said you really need to use the feed screw to set the high fire rate and ajust your timer to get a 1" wide band @ idle. As long as you are keeping it lit and maintaining draft that is all the fire you need at idle. After the initial temp surge after a heat cycle the boiler should not gain any heat what so ever. You should be losing a degree an hour or so. By chance are you running this boiler on a power vent?
klim1972, you should have our numbers on the manual and instruction sheets (if not send me a PM and I'll send you my cell number), give me a call on my cell or call the shop tomorrow, we can figure this out!
i'm with you on this one Markiii, Set your high fire withe feed screw, and use the timer @ rheostats to set the idle. I think you had you dump zone set @ 210 but what was the differential set for. Also back your HL down to 10* above the LL.
differentials sound fine. Try setting your low limit to 165 and your high limit to 180. Let your dump zone set to 205. That will give you some head room for temp gain after shutting down from a high fire cycle.