Settings: Natural Gas Boiler vs EFM 520

This morning my EFM 520 boiler stopped working. The cotter pin broke. Thus the auger stopped pulling coal into the boiler. I have a dual fuel setup in my house. I switched over to the natural gas boiler so that I can have some heat for the family until I could run to Lowe's and get a new cotter pin. The radiators were searing hot using the NG boiler. I never use the NG boiler because its expensive to operate. But why is the hot water hotter with the NG boiler?

I have the boiler set at 4 teeth, 4 air, 160 low 200 high and the diff is at 10. I do not know how the NG boiler is setup. I think the aquastat is set at 180. What is the diff anyway?

Thanks!
Leo

What was the temperature on the gauge of the gas boiler?

The NG boiler aquastat is set at 185 degrees. The input is 210K btu, the output is 175K btu. I bumped up the low setting on the coal boiler to 170 seeing if that might do it. But it did not. My uneducated guess is that the NG boiler is very powerful and his heating the water in minutes, then sending it back up into the house.

Yesterday with the outside temps around 15 degrees, the NG boiler got the house temp up from 62 to 67 in a couple of hours. After I repaired the coal boiler, I turned off the NG boiler and fired up the coal. By the time the coal recovered the house temp was 64 degrees. The coal boiler could not get the house temp back up to 67. Its warmer today and my house temp is at 67 with the coal burning.

Any thoughts?

With settings at 4 and 4, you aren't making 175K net, and the lower water temp in the EFM will out of necessity require longer to play catch up with a cooled down thermal mass like a house. Remember that you can fire the EFM up much higher if you desire, but is it required? Probably not, but your raising the lower limit setting will cause the temp to increase and over the night, you can determine if that is an acceptable setting for your comfort. Keep everything in perspective, frequently slow and steady will win the race over fast and flashy.

Thanks for your response. I'm still a little confused. If I bump up the lower setting from 160 to 170, doesn't that mean the auger will turn on when the water temp in the boiler is hotter, thus burn less coal to recover? And to just confirm what the "diff" does. The diff controls the circulator. If the low setting is 170 and the diff is 10, does that mean that the circulator will turn off when the water in the boiler hits 160. Right?

The differential causes the circulator to start a certain number of degrees ABOVE the low limit. The circulator will ALWAYS shut off 10 degrees below the low limit regardless of its setting.

Setting your aquastat at 170 will cause your burner to come on (or off) at 170 and nothing more. At 4 teeth, you'll have a hard time getting anywhere near 170 in a cooled down large house with the circulator running. If I was heating up a cold house, I'd run it at 9/9 until the house was warm and then cut back to your normal 4/4 to maintain.