Boiler E18 error (Supply Temperature exceeds 212F)
Hello,
We recently moved into a new house that has 2 Triangle Tube Prestige Solo 175 boilers. One of them has been giving me an error recently, and I was hoping someone here might have some advice for me. I'm not experienced with HVAC or plumbing work, so I apologize if I use the wrong terminology or ask dumb questions.
One of my boilers is connected to a Smart 80 indirect water heater. I believe the problem is related to the DHW. When the boiler goes through its normal startup procedure, heating of the CH water, then shutdown procedure, everything works fine. When the boiler's display shows "4XXX" (where the XXX are the currently supply water temp) which means there is a call for DHW, the heat goes up to 186F and then sometimes keeps going up until it shows b18 and then eventually 318. When it is on for CH, it only goes to 140-150. Also, the 2nd boiler is not connected to the DHW, and never shows an error.
I was finally able to catch it in the act. Here is a video showing the sequence: I watched it repeat this loop multiples times where it would drop in temp, turn on, heat up to 204F and then error out before doing it again. Has anyone seen anything like this before?
To add more info, i found that while it is doing this "rapid increase in supply water temp, error out, repeat" cycle, if I turn down the aquastat slightly, the boiler stops the call for DHW. If i then turn the aquastat back to where it was, the call for DHW is shown again, the supply water temp quickly drops before slowly climbing to 186. It never goes above 186 until the call for DHW stops, then the boiler returns to normal CH operation. It seems like this "turn down the aquastat, turn up the aquastat" breaks the cycle. I don't know why, but hopefully it is helpful info to someone who knows more than me.
I've attached some pictures as well. When it is in the error cycle, the pipe directly to the left of the flow control valve is warm to the touch but NOT hot. Once I do the aquastat down, aquastat up routine, the pipe becomes HOT and everything works as expected.
I really appreciate any insights or advice anyone can provide. Thank you!
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