MrMackster
New Member
I ran into an issue with my new boiler(Navien NCB-240E) was intermittently not firing even though my Taco Zone controller was lit up and zone pumps were on. About ~25 days after install, woke up to a 45 degree house and my eco bee was saying the boiler wasn't working because the temp had dropped. Zone pumps were on and zone light were lit up, but boiler wasn't on. Tech comes out and right before he gets here, everything starts working. We had emergency gas work on the street during the middle of the night, and he thought maybe an air bubble had caused an issue. He bled the gas lines anywhere just in case. No errors on the Navien.
Later that day, same issue, different tech comes back but again, it starts heating up right before he gets here. We call navien, on hold for over and hour and we get disconnected. Boiler has been running for over an hour perfectly fine. He says to call back if it happens again.
Next day, wake up same issue. Tech comes, boiler turns on magically before he gets here, we call navien and get through, we got through all the navien stuff, and everything checks off. Output Temp good, good enough delta on return temp (25 degrees?), pressure good, all the dip switches are correct, etc. They tell us to short circuit TT and if it runs ok after that, issue probably a bad Zone Controller.
Everything works great for 4 days, so they replaced the zone controller. Well, same thing happened again last night after working for 3 days as we hit another really cold night, Ecobee sent me an email saying it was calling heat for a few hours and the temp had dropped a 5 degrees. I go to the boiler, Zone controller lit up, pumps on, heat and fire icon on the boiler not lit up, no errors.
Since the last time this happened, I picked up a multimeter and did some testing. I removed the TT wires from the boiler and noticed there was no continuity. If I understand how TT is supposed to work, the boiler should be running 24v over the wire to the zone controller, and zone controller should be completing the circuit right? If Zone's aren't calling, TT circuit won't complete, boiler won't fire. I tested 24V over the TT terminals on the Boiler itself.
Well, when I noticed TT had no continuity, I started tracing wires back to the Zone controller, and I discovered that the TT on the Zone controller was actually connected to the Outdoor Reset Temp sensor connection on the furnace control board, and the actual outdoor temperature sensor wire was connected to the TT on the boiler. At some point someone must have crossed wires during the install. I am 99% sure this wiring setup has always been like this since this unit got installed a month ago but I have had working heat except for 3 instances where I got into this state. I was there watching every time they were here checking on this issue and when they replaced the Zone controller, and the outdoor reset wires were never touched.
So my question is, how would my boiler have been working to correctly heat my house to the right temp if TT wasn't connected to the right thing? The only thing I can think of is that the Navien somehow detects the flow from the Zone pumps and turns it self on. I called Navien to try and find out if that is plausible, but they are getting the slammed with calls, and the tech agent wanted nothing to do with diagnosing this issue since everything works fine when I short circuit TT. He claimed TT was the only way and Boiler wasn't at fault.
I guess its also plausible that the outdoor temp sensor was completing TT except in these really cold nights, and on other nights with the zone pumps off, my the house wouldn't be getting over temp and boiler might have been short cycling off because of no change to the water in out water temp?
So anyone have any ideas why my heat would have ever worked?
Side Note: When they came to diagnose this issue the first time, the boiler started firing right before they got here and we had some gas construction on the street that night so the guy figured it as a gas supply issue and bled the gas line, but I did note that the Navien was showing -98 on the outdoor temp sensor to the tech, who thought that maybe it wasn't showing the right temp because I had the outdoor reset curve turned off. I wonder if its -98 because its not actually connected to anything!
Later that day, same issue, different tech comes back but again, it starts heating up right before he gets here. We call navien, on hold for over and hour and we get disconnected. Boiler has been running for over an hour perfectly fine. He says to call back if it happens again.
Next day, wake up same issue. Tech comes, boiler turns on magically before he gets here, we call navien and get through, we got through all the navien stuff, and everything checks off. Output Temp good, good enough delta on return temp (25 degrees?), pressure good, all the dip switches are correct, etc. They tell us to short circuit TT and if it runs ok after that, issue probably a bad Zone Controller.
Everything works great for 4 days, so they replaced the zone controller. Well, same thing happened again last night after working for 3 days as we hit another really cold night, Ecobee sent me an email saying it was calling heat for a few hours and the temp had dropped a 5 degrees. I go to the boiler, Zone controller lit up, pumps on, heat and fire icon on the boiler not lit up, no errors.
Since the last time this happened, I picked up a multimeter and did some testing. I removed the TT wires from the boiler and noticed there was no continuity. If I understand how TT is supposed to work, the boiler should be running 24v over the wire to the zone controller, and zone controller should be completing the circuit right? If Zone's aren't calling, TT circuit won't complete, boiler won't fire. I tested 24V over the TT terminals on the Boiler itself.
Well, when I noticed TT had no continuity, I started tracing wires back to the Zone controller, and I discovered that the TT on the Zone controller was actually connected to the Outdoor Reset Temp sensor connection on the furnace control board, and the actual outdoor temperature sensor wire was connected to the TT on the boiler. At some point someone must have crossed wires during the install. I am 99% sure this wiring setup has always been like this since this unit got installed a month ago but I have had working heat except for 3 instances where I got into this state. I was there watching every time they were here checking on this issue and when they replaced the Zone controller, and the outdoor reset wires were never touched.
So my question is, how would my boiler have been working to correctly heat my house to the right temp if TT wasn't connected to the right thing? The only thing I can think of is that the Navien somehow detects the flow from the Zone pumps and turns it self on. I called Navien to try and find out if that is plausible, but they are getting the slammed with calls, and the tech agent wanted nothing to do with diagnosing this issue since everything works fine when I short circuit TT. He claimed TT was the only way and Boiler wasn't at fault.
I guess its also plausible that the outdoor temp sensor was completing TT except in these really cold nights, and on other nights with the zone pumps off, my the house wouldn't be getting over temp and boiler might have been short cycling off because of no change to the water in out water temp?
So anyone have any ideas why my heat would have ever worked?
Side Note: When they came to diagnose this issue the first time, the boiler started firing right before they got here and we had some gas construction on the street that night so the guy figured it as a gas supply issue and bled the gas line, but I did note that the Navien was showing -98 on the outdoor temp sensor to the tech, who thought that maybe it wasn't showing the right temp because I had the outdoor reset curve turned off. I wonder if its -98 because its not actually connected to anything!
