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fenwal 05-21 HSI ignition flame sense
Tim-Was on a call on one of these boilers, ended up being a bad pressure switch as the boiler got hot, but at first I thought it was a flame sense issue. The way the flame sensor is hooked into the wiring with a T tap connector threw me a bit and I'm wondering how this particular control senses the flame since the flame sensor is tied into the neutral of the ignitor leads. Does the control send voltage back through the neutral somehow, or does the ignitor itself do anything in the process? I know there are some that sense through the ignitor. thanks again.