I have seen several posts reguarding this fitting and haven't heard anyone who actually found one, bought, and installed it. I ran into all sorts of trouble just finding it. I had to drive an hour to a Harman dealer deep into Amish country to get my hands on one. There is next to no info on this and it doesn't even appear in some of the duravent catalogs. I spoke on the phone with duravent and there are plenty available in the warehouses and they have no idea why nobody can find them. They actually thanked me for making them aware of the stocking issue because apparently to be a duravent distributor you must have this peice on the shelf. Leaman Brothers stoves (my new favorite Harmon dealer) also confirmed this to me. Here are the specs on a regular appliance adapter, the Harman appliance adapter and the exhaust outlet measurements of my P61a.
OD of regular appliance adapter inside liner. 3.050 inches
ID of Harman appliance adapter. 3.519 inches
Harman exhaust ID. 3.145 inches
Harman exhaust OD. 3.504 inches
So the difference here is that the Harman adapter fits on the outside of the exhaust and you seal the remaining 0.015 inches with silicon or you use the regular appliance adapter and put it inside the exhaust and seal the 0.095 gap between the outside of the inner pipe and inside of the Harmans exhaust.
Basically this harman adapter completely eliminates the possibility that hot exhaust gets leaked between the inner and outer layer of the vent pipe. As you can see in the picture the regular appliance adapter did not leak exhaust into the room but it was definantly leaking between the layers of pipe. The harman adapter is a bastard to fit on the exhaust because it is a very snug fit but on the positive side that's less chance for leakage. You still must use silicon but now there is much less space to fill and it is impossible for the exhaust to get between the layers of pipe. This fitting cost me about 23.00 so it's comparable in price to the regular adapter. They are also both the same length so if your replacing the regular adapter for the one meant for a Harman stove it won't be difficult.
OD of regular appliance adapter inside liner. 3.050 inches
ID of Harman appliance adapter. 3.519 inches
Harman exhaust ID. 3.145 inches
Harman exhaust OD. 3.504 inches
So the difference here is that the Harman adapter fits on the outside of the exhaust and you seal the remaining 0.015 inches with silicon or you use the regular appliance adapter and put it inside the exhaust and seal the 0.095 gap between the outside of the inner pipe and inside of the Harmans exhaust.
Basically this harman adapter completely eliminates the possibility that hot exhaust gets leaked between the inner and outer layer of the vent pipe. As you can see in the picture the regular appliance adapter did not leak exhaust into the room but it was definantly leaking between the layers of pipe. The harman adapter is a bastard to fit on the exhaust because it is a very snug fit but on the positive side that's less chance for leakage. You still must use silicon but now there is much less space to fill and it is impossible for the exhaust to get between the layers of pipe. This fitting cost me about 23.00 so it's comparable in price to the regular adapter. They are also both the same length so if your replacing the regular adapter for the one meant for a Harman stove it won't be difficult.
