A week and a half ago, during the nice, crisp cold snap, I woke up in the morning and felt like something wasn’t right. Still half asleep, I touched the bedroom radiator, which was barely warm. I found my way from room to room touching radiators – all barely warm.
Some kind of subconscious decision making process led me to the thermostat, which showed that the heat was on.
That woke me right up, plus I broke a cold sweat! Something wrong with the heating system in this weather is bad news – well insulated building or not. I skipped the first cup of coffee and instead found my way into the utility room.
I heard a couple of pumps humming, but the boiler (Trinity LX 150) was dead silent. The temperature gauge at the buffer tank that feeds the hydronic heating system (the radiators) registered a mere 90 degrees Fahrenheit, whereas it should have been close to 140. That explained the barely warm radiators.
The small touch screen on the boiler had a message for me: “174 Lockout safety relay feedback incorrect.” Great! If I only knew what that was supposed to mean – other than that something in the pre-ignition testing went wrong.
I don’t know why, but “The IT Crowd” came to mind. So, before making any panicked phone calls, I decided to turn the boiler off and on again. Et voila – once it booted all the way back up, it also fired up and I again had hot water running through our radiators.
That is where the story usually ends – but not so in the world of nerds. Why did I have a safety lockout with a code # 174? What could have failed in the pre-ignition test? Now was the time for phone calls.
My installer pointed me to the two items that usually cause the boiler to shut down. The flame sensor rod and the electrical spark ignition. Both of these components need regular cleaning and he recommended that I check the oxidation levels on the rods and polish them with fine sandpaper.
There wasn’t much oxidation on either the flame sensor nor the electrical spark ignition. I have the nagging feeling that something else may have caused the lockout.
I have a munchkin 140M in my home, and have had a similar fault. In my case, the problem was that the condensate drain plugged up, causing water to back up inside the unit, saturating the refractory material, and causing it to present a lower resistance path to ground for the spark igniter. Clearing the blockage, and some very judicious trimming of the refractory material around the igniter terminals fixed it.
Periodic cleaning of the HX is necessary in these boilers to keep crud from building up and causing problems (clogged drains, corrosion, etc.)
Josh, thank you for your comment. And yes, the condensate drain is another maintenance item that has to be checked. My installer asked me to check it too, along with the flame sensor and spark ignition, but I failed to mention it in the blog post. Thank you for bringing this up.