Aqua-Therm Wood Boiler Installation

[M1687]

I'm replacing an Aqua-Therm Model 270 outdoor wood boiler with a newer used model (275SS).
The boiler that is being replaced developed a leak in the firebox where the liner expanded inward towards the area where the logs are placed.
Looking at other installations online, I noticed that who ever installed the boiler I'm replacing did not have an expansion tank directly near the boiler as compared to what I have seen with other installations.
This boiler is piped into my house and there is an Amtrol Expansion Tank located near my regular oil boiler and is on the same system when I have the wood boiler carrying the load for the house (dual systems).

My question is do I need an expansion tank near the outdoor wood boiler? Did the absence of this expansion tank cause the original firebox liner to implode/fail?
If the expansion tank is needed near the outdoor wood boiler does this get installed on the pipe coming in (cold) or leaving the boiler (hot)?

 

[Dana]

Most wood boilers are operate at atmospheric pressure, and the buffer tank becomes the expansion tank. Most oil fired boilers need at least 10psi pressure to operate correctly. Sounds like you need to sort out the original system design in a bit more detail, and dig up the installation manual for the new boiler.

According to this Aqua Therm manual:

The system is an open system. A fill cap will relieve pressure if it exceeds 18 psi. An expansion tank allows the water to expand or contract as it changes temperature while maintaining a fairly constant pressure. A pressure relief valve is installed on the appliance to safely reduce system pressure if it ever exceeds 30 psi. The appliance is hydrostatically tested at the factory to 60 psi.

...and...

Some State Codes require that the unit be continuously vented to the atmosphere. In these cases, an Open System Tank is plumbed in place of the Fill Cap. The Tank has a sight glass for level indication and an open vent at the top. The Tank allows for water volume expansion as the system heats up, eliminating the need for the Expansion Tank, Air Scoop and Air Vent.

The location of an expansion tank on the system doesn't usually matter, as long as it is sized correctly and charged correctly, and not isolated from the boiler with check valves or zone valves.