Would like a perspective on cycling of an oil boiler.
So I replaced a spent Burnham RSA110 steel boiler with a Peerless WBV
cast iron boiler. Everything else remained the same -- still three
zones, configured essentially the same way, and the same size / model
I was expecting, due to the increased water capacity and thermal mass of
the Peerless (new) boiler, plus a smaller nozzle, that there would be
less frequent cycling. However, the new boiler, when all three zones
are cranked open, cycles approximately like this:
- 2 minutes on
- 4 minutes off.
That strikes me as excessive, and as more frequent than the previous RSA
boiler which is counter-intuitive to me for the reasons above.
Does this rate of cycling seem excessive and/or inefficient for a new
cast-iron boiler ?
A couple more data points:
The Aquastat is different, a newer digital model, but the settings are
confirmed the same: 180F high limit, with a (fixed) 10F differential. I
made sure the new digital temp sensor bulb was well seated in the well.
Judging both by the digital readout on the 'stat and the temp guage,
the new Aquastat seems to be doing the job "OK".
The old boiler had a nozzle that flowed 1.00 GPH. I put in the smaller
of the nozzles available on the new boiler -- it flows 0.85 GPH. Now I
know that the cast-iron model will be a tad more efficient, but I would
not expect shorter on-cycle times with the lower flow rate!
I had the burner adjusted by the oil company guy -- seems to have the
right flame -- but he has no idea about the cycle times.
I'm pretty sure the system is substantially evacuated of air, and the
zones seem to be flowing well. And in the correct direction of flow :).
The old boiler was about 150 lbs of steel and 8 gallons of water. The
new one is about 400 lbs of iron and 17 gallons of water.
Everything tells me the cycle should be longer -- but it's not. What
else could I be missing.