I have a hand fired coal boiler that we are really happy with for the most part. Shake it down, coal in twice a day and ashes out once a week or so and it's rock solid, house is 72 degrees (a little warm, but we have small children) even when its 15 below outside.
This weekend has been a rough one thought with a power outage that started around 2am. By 5am, without the circulator pumps, my boiler was in Chernobyl mode, >240 degrees and hovering around 30 psi, just below the release valve's threshold. We have a private well, so no power, no water service to cool the boiler down. So I dumped the fire and opened the boiler drain to release the steam to avoid damaging anything. Normally it sits around 180 degrees and 18 psi. We sat around the gas fireplace until the power came back on around noon, at which point I drained and recharged the expansion tank (old style bladder-less), refilled the boiler and built a fire. An hour later, the power goes out again. In preparation, I closed off all the air to the fire, and monitored the temps closely. It didn't take long for it to creep up again and I decided to dump the fire again at 220 degrees.
This all was a huge messy pain. First question is does it sound like I'm over firing? I try to target around 180 degrees, and on milder days it might creep up and activate the dump zone, and that keeps it from going over 190. How long should a hand fed coal fired boiler be able to keep itself under control with a power loss to the circulator pumps?
Second question is dependent on the first one I guess, if I'm not over firing and if the system is dependent on circulator pumps to keep it from overheating, I'm thinking about setting up a battery backup by wiring my circulator pumps, and possibly my well pump through an inverter/charger that is backed by a few deep cycle marine batteries. Is this a common thing to do, or is it completely unnecessary because I'm over firing?