I am writing because I can't find a hvac guy who is willing to figure this out.
I have an oil furnace and wood boiler both tied into a hot water baseboard system. The wood boiler is properly installed with its own expansion tank, relief valve, "normally open" valve (for power outages), thermostat to trigger water circulation at a certain temperature, and manual valves to isolate it from the system.
Both systems operate perfectly on their own -- however, I am more interested in being able to have BOTH running than running one or the other exclusively. In other words, I would like to be able to burn the wood boiler, have it provide heat, and have the oil furnace kick in when the water temperature in the wood boiler drops below a certain temperature.
The equipment is all present for this to happen...and it does work, but the problem is that the water in the wood furnace can never drop below that of the oil furnace due to gravity feed/backflow. When the wood boiler cools down, hot water flows backward into the hot water output on the wood boiler. I'm assuming this is due to a temperature difference between the hot water coming out of the oil furnace and the relatively cooler water in the wood boiler.
At any rate the oil furnace has to do the unnecessary work of heating the wood boiler -- which totally defeats the purpose of running both for efficiency.
To make a long story short (TOO LATE!)...I was wondering if anyone has had this problem with an oil burner/wood boiler installation or might have a solution.
My first thought was to add a circulator on the return into the wood boiler that allowed circulation only when temps were reached. But would that stop the backflow? Can't water flow backward through a circulator?
Then I considered a backflow preventer on the wood supply line before it enters the supply coming out of the oil furnace. That might work...but I'm sure there are other ideas out there.
Anyhow, sorry for the long post. I'm not getting any help from the local HVAC guys, nor the original designer of the wood boiler. I know it can be done because I had an almost identical system in another house. I just can't recall what was different about it to prevent the backflow.
Thanks!
I have an oil furnace and wood boiler both tied into a hot water baseboard system. The wood boiler is properly installed with its own expansion tank, relief valve, "normally open" valve (for power outages), thermostat to trigger water circulation at a certain temperature, and manual valves to isolate it from the system.
Both systems operate perfectly on their own -- however, I am more interested in being able to have BOTH running than running one or the other exclusively. In other words, I would like to be able to burn the wood boiler, have it provide heat, and have the oil furnace kick in when the water temperature in the wood boiler drops below a certain temperature.
The equipment is all present for this to happen...and it does work, but the problem is that the water in the wood furnace can never drop below that of the oil furnace due to gravity feed/backflow. When the wood boiler cools down, hot water flows backward into the hot water output on the wood boiler. I'm assuming this is due to a temperature difference between the hot water coming out of the oil furnace and the relatively cooler water in the wood boiler.
At any rate the oil furnace has to do the unnecessary work of heating the wood boiler -- which totally defeats the purpose of running both for efficiency.
To make a long story short (TOO LATE!)...I was wondering if anyone has had this problem with an oil burner/wood boiler installation or might have a solution.
My first thought was to add a circulator on the return into the wood boiler that allowed circulation only when temps were reached. But would that stop the backflow? Can't water flow backward through a circulator?
Then I considered a backflow preventer on the wood supply line before it enters the supply coming out of the oil furnace. That might work...but I'm sure there are other ideas out there.
Anyhow, sorry for the long post. I'm not getting any help from the local HVAC guys, nor the original designer of the wood boiler. I know it can be done because I had an almost identical system in another house. I just can't recall what was different about it to prevent the backflow.
Thanks!