I have an EKO 60 w/ 800 gallons of water storage. The system is open and when we did the final install we had a very difficult time getting it to prime to get the water flowing properly. It is a simple system w/ one pump going into the EKO and another in my basement to push the return water. There are no heat exchangers within the tank. The pumps run at a slow setting 24/7 and it hasn’t stopped with the exception of two short power outages, I believe they were very short because prime was not lost. The system works wonderfully. I have left the house unattended for two and three days and both times have returned to a house that is in the mid 60’s w/out back up heat. Most days I burn from 5-6 hours to fully charge the tank and then I’m done. This is my problem. I have a heat exchanger where the EKO supply meets the house boiler. I have been told that if the fire is out and the water storage has cooled, the gas boiler will heat the 800 gallons of water as well as the house, thru the heat exchanger. This would not be a good situation as my gas boiler is relatively small and it would have a difficult time doing double duty, where the EKO handles this w/ ease. I think I could put simply re-plumb a section that would bypass the heat exchanger and I could manually make the switch. The down side is that it would be all gas or all wood. Or better yet, could something be installed within the line that would electronically switch the system over? This way I could leave for extended periods with the wood being utilized and when the hot water produced by the EKO ran out, the gas boiler would take over. The final install was done by a licensed plumber and I was very pleased with his work, but I’m afraid it was just too simplistic of a system.