Hmm, then it should only fire when there is a call for heat.
If you truly wanted to only use your oil boiler as backup (ie freeze protection) use something some sort of thermostatic switch (again, similar to an A419) and put that inline on the wire that fires the boiler and set it to 50 degrees or something like that.
If the air gets below 50 then it would allow your oil boiler to fire. Your thermostats and the boiler would be out of sync BUT it would keep your house from freezing.
I don't know if that's a great idea but it's an idea...
Maybe there's something you could tie a relay into on your pellet boiler?
Yes it will only come on if ther is a call for heat. since i have cast iron radiators my temp can go to 125 + - and they still will warm house ..unlike base board. It just seems like a waste to fire my boiler (oil) when the pellet will catch up on its own. As you know the PB 105 can take a few min to get its self "ripping" and any residual heat in it will start heating the zone that is calling for heat. GEEZ this is getting frustrating looking for an answer
. I'm sure someone has solved this. I was thinking maybe a snap switch on the pellet boilers vent pipe but that seems like a "cob job"
Still seems (to me) like there would be something on the boiler but I've never played with one so I can't say for sure.
K