Ive burned about a cord of wood through my new eko 40 boiler system and I am happy with the way it works. I have 500 gallons of pressurized storage in my basement. The Eko is in an outbuilding 150' away. Since the outside temperature has been up and down lately sometimes my storage and boiler cools off to around 100 degrees when its nice enough outside to skip a fire or two. When I fire the eko up and the primary pump kicks on at 170 degrees the spirovent on the outlet of the boiler purges a little air. This only happens the first time the pump kicks on after the boiler is started. I have an oversized extrol tank hooked up to my storage tank in the basement. I never see pressures over 18 psi. I am concerned that this air is being introduced to the system when the water contracts due to cooling off. I don't think I still have air in my system because its been a month or so since I started burning on and off. I have an automatic full valve hooked to the top of the storage tank also. I know the spirovents can suck air in because when I was draining my boiler outside I could hear the spirovent sucking air in. Do I need to add a small expansions tank outside plumbed off the spirovent? Maybe my expansion tank being so far away is causing me problems.