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Posted by Curious George on October 13, 2005 at 01:48:16:
Hello:
I have an L7224U digital aquastat on my boiler. The low temp setting is at 170F. I've noticed the following behavior:
On a call for heat, the circulator turns on and the burner comes on. The temperature drops below the low limit (170F) presumably because cold water from the heating pipes enters. When the temp. drops below the low limit and the low differential, the circulator turns off, and the burner stays on. When the temp starts rising and reaches the low limit again, the burner turns off, a couple of seconds pass, and then the circulator and burner turn on again. At this point there is enought heat mass so that the temp continues to rise to the high limit.
Shouldn't the burner continually stay on during this process, and only the circulator switch on an off as needed? It seems to me the burner is needlessly turning off for 2 seconds and then on again as the temp rises thru the low limit setting on a call for heat. Is this considered normal or should something be adjusted?
I've noticed in the L7224U instructions it says that "setting the low limit less than the high diffential below the high limit is not allowd as imporoper circulator and zone control function could result". I'm not sure I understand this statement- shouldnt' the low limit be below the hi limit minus the high diffential?
Current settings are 190F(Hi), 20F(hi diff.), 170F (low) and 10F (low diff.)
Any advice would be appreciated. Thanks.