Need Help with Gas Boiler Vent Problem!

Hello, We bought a house and just moved in and noticed that the propaine gas fired Boiler is vented horizontally out from basement to the outside with pipe and terminating on the outside a few feet from the ground level. The house is a 1 story ranch and the pipe terminates on the side of the house where the eaves are. The problem is that it is causing condensation up under the eaves and frost is forming on the rafters in crawlspace above house. The system is 7 years old. Obviously this was vented wrong needs to be vented elsewhere or some other solution. The previous owners did not use the boiler that often and used wood. There is exsisting chimney that is close to the boiler that was used by the previous owner for a wood boiler that is no longer there. The chimney is not in use now and and we have no plans for using it. The chimney is centrally located in the building The flue is tile. Can the boiler be vented into this exsisting chimney? Do we need to add a galvanized pipe inside chimney or do the following directions mean that if the chimney is insiet the building that the boiler may be vented into it with out the galvanized pipe in chimney? I understand the second part of the instructions for the chimney on the outside wall but not the par for the chimney on the inside. The Boiler is a Weil-McLain High- Efficiency Gas Boiler. (HE II 5) Here is a quote from the Venting directions, they are confusing. "The HE II boiler may be vented directly through an outside wall or through the roof using standard 3-inch galvanized vent pipe. In addition, the boiler may be vented into a chimney inside the building with or without other gas appliances, using single-wall galvaized vent pipe. For extended runs through cold area-or when venting into a chimney on an outside wall- Type 304 or 316 stainlss steel vent pipe must be used. When venting into an outside chimney, the stainless vent pipe must run through the ntire length of the chimney." Any thouhgts and/or advice will be appreciated Thank you.
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