Boiler sometimes won't light

petermatheson

Over the past few days the temp in my city (and basement) dropped from 30's to negative temps, and my 2004 'New Yorker' Boiler (Classic CG-A series gas boiler, electric ignition, no zones, 4 hot-water radiators) has started to sometimes not ignite. It typically happens in the middle of the night: the newish Nest thermostat calls for heat, the boiler's water pump starts and the flue vent audibly opens, but nothing ignites.

To get a flame I've been doing an off/on cycle with the Nest, the gas valve, and the boiler power. This usuals works but is getting less reliable. It helps if I poke at the wires on the hydrostat during the process.

Hopefully I just need to clean the flame sensor rod with steel wool (is that right?), otherwise this might be a ignition module issue, hydrostat-thermostat voltage issue, or even a gas valve issue. I have a pro coming next Tues but thought I would try to DIY first during cold spell.

Does anyone have insight into what might cause this, especially giver it started with the colder weather?

I don't know the boiler high-temp limit or the size of the boiler. 1200 sf house.