A question of curiosity for Poorboy, have you tried swapping the stats from boiler to boiler?
I'm just wondering if there's a problem with the temperature sensor in one.
I've honestly not been impressed at all by the newer digital/electronic stats. I actually chased down a couple of the old mercury switch wall warts.
Yes, I have actually swapped the two thermostats with each other. I bought thermostats on the same day, off the same hook in the big box store. Both thermostats are on the same wall, about 8'-10' apart. There was originally a wall between them, but it has been gone for many years. We did get a bit of this before I put the new thermostats in service, but it has been really noticeable since. It seems that whichever boiler system kicks in first, it brings the temp up before the other boiler fires up, and it is the only side of the house heating. After two or three heat cycles with the same boiler running, the other side of the house gets a lot colder. Enough so you can feel the temp difference walking through a door way. Its almost like one of the thermostats is running about a 1/2 degree above the other and with both thermostats so close together, I'm thinking we are only getting one boiler running. The cold side has cold registers, like that boiler is turned off, until it get real cold, then both will run.
