The
Utica DV150B has an output of 122,000 BTU/hr. At an entering water temp of 180F, average water temp of 170F it takes about 225-250 feet of
typical fin-tube baseboard on the zone to not cycle at all. Is this boiler is LUDICROUSLY oversized for the space heating loads of most houses. It's probably oversized for the radiation even when all zones are calling for heat, and many times oversized for the radiation on your smallest zones.
How many feet of baseboard (or quantify the other radiation) do you have on the system, zone by zone?
The L4080B1212 aquastat was normally used only as a high-limit aquastat. Is that the only adjustable control? Most boilers usually come with other aquastats for setting low limits and differential temperatures. I'm not sure what the inherent differential on that aquastat is, but it's probably not much. It's been obsolete for awhile now, couldn't even find the manual in a quick online search, but it doesn't have an adjustable temperature range (differential) between turn-off and re-fire. Some online information indicates it's a fixed 8F differential, which is credible. During the 5 minute off interval the boiler's temperature drops 8F. Doubling the differential would nearly double the burn times, and would more than double the off interval. In most systems the house could still be heated if the boiler were allowed to swing from 140F to 180F, which would be 5x the burn time.
Installing an aquastat with a big differential like the
L4006B1163, which can adjustable differential range from 5F to 30F, as well as a high limit. Setting the high limit to 170-180F and the differential to 30F would allow the boiler a much bigger differential temperature swing during continuous calls for heat, utilizing the thermal mass of the boiler's water volume & iron to lengthen the burns. Base on the reported current behavior with a 30F differential you'd probably get 5+ minute burns out of it, and close to 20 minutes of off time with the differential set to 30F, which would be fine, with no more than 3 burns per hour during continuous calls for heat, and burn times long enough to hit it's steady-state efficiency. The only reason to ever run it with a smaller differential would be if some zone isn't keeping up with the heating load when it's very cold outside (which would be pretty rare for most systems.)
For not a huge amount more money a heat purging economizer control like the
HydroStat 3250 Plus can even suppress firing on new calls for heat until the boiler's temperature has dropped to the programmed low-limit temperature. This type of controller auto-adjusts the other settings based on recent burn history to limit the total accumulated burn time and run at lower average temperatures, reducing the standby and distribution losses. It's likely to save more than 10% on the fuel use, maybe even more than 20% compared to when short-cycling on the fixed 8F differential aquastat.
