Any Thoughts?

A little background, my system has been running since January 2008. It has been trouble free and the only one happier then me with the system is my wife . I have a Eko 25 with 500 gal. of pressurized storage. I am running Primary / Secondary system. My backup boiler is a direct vent propane boiler. I have made no changes to the system this year.

This past weekend we had to head south for the weekend to do Christmas with the in-laws. When I left storage was at 180*, with a boiler 3/4 full of wood. We get home Sunday night the system had switched to Propane as designed. I get the Eko going to heat storage, when I get up in the AM storage is at 180, there is a call for heat, to my surprise the temp on the propane boiler is at 136*, boiler isn't running. Seems that when the CIRC on the Primary loop is running water is flowing into the Propane loop and running through the boiler back to the Primary loop. In six years this has NEVER happened. I thought maybe because the Propane boiler had been running that the water in the loop was hot so thermal siphon started up. So I closed the ball valve's to isolate the loop and let the water cool. This AM I opened the valves and when I got home form work it thermal siphon is going again.

Any ideas? System is running normal between 15-20 PSI.

Humm, the CIRC on the propane boiler has a check valve. The flow through the loop is in the normal direction based on temp readings on the Supply & Return pipes. I did bleed out 5 gal. of water from both loops and no air. I have 3 speed Grundfos circ's, I increased the speed on the storage circ and the sounded like there was an increase in flow. It is supposed to warm this weekend I may take storage circ out and inspect it and replace (I have a spare). I agree it seems like there is a pressure difference that resulted it the new flow. I hope figure this out, there is a 20* temp drop in the water flowing through the propane boiler.

Yah I was going to check that out also. That is the easy one since I am running n storage. I was looking at thing last night and I put a "Y"strainer down stream of storage (seemed like a good idea at the time) so I am going remove the strainer see if that is clogged.

Supposed to be 45-50 tomorrow and rain so perfect time for this.

Problem solved, the flow check in the propane boiler circulator (Grundfos 3 spd) wasn't seating. I had one circulator as a spare so I removed the check valve from the spare and put the old circulator back in. The good news I could by a replacement check valve, the bad news it is $24, a new circulator is $85; what a racket!

I just have to look at the bright side, I didn't have to make a service call .

On the flip side, took advantage of the warming weather a did a full cleaning of the EKO including the turbulators. Just need to get some wood in tomorrow and I will be already for the next Polar Vortex.