Boiler Pressure

[elmer]

I have an Attack FD 42 add-on (psi 12) oil boiler (psi 22). Both are connected to one zone 12 cast iron radiators. Heating is not consistent. Add-on boiler pulls return water through oil boiler on the return. Could the higher pressure in the oil boiler be the cause of heating inconsistency ? Thanks for any advise.

 

[Hydronics]

Elmerd,
Assuming the boilers are connected without a heat exchanger (directly piped), the pressure in the entire system will be equalized not considering minor increases due to system head loss on the circulator discharge. The difference is probably inaccuracy between the two guages (assuming they are directly connected). What do you mean by not consistent? Have you purged all air from the system?
Jeff

 

[elmer]

Jeff
It Is directly piped, air purged. By not consistent I mean, Some days it will almost drive you out of the house other days I wonder where all the heat is going. When I burn coal I get less heat output but it lasts longer. I think the add-on might be to small. I didn't have this problem with my old wood boiler. (Deep Wood) I might bypass the oil boiler on the return.Less water to heat might help. Thanks