Pilot sensor corrosion - chronic problem?

neilc

the white "Sense" wire,
both connectors are snug / tight at the flame rod, and on the controller ?

the boiler 120v bx,
are there any junction boxes, service switches, along the way back to the house panel?
all those connections need to be tight,
consider running a dedicated ground wire from the boiler controller and landing at the house panel

JK_Brown

The connection of the GND(burner) to the module screw seems weird. In your photo it is above the plastic, but even so, that looks like a coated surface. So that GND wire is basically connected to the cabinet only via the screw threads. Is the screw tight? Is it tight when the flame sense has failed? It's almost like it isn't used although the ladder diagram shows it tied to the equipment (chassis) ground.

Secondly, the "C" terminal connected to the equipment ground screw as shown in the schematic upper left?

You might want to run a jumper from the BX shield to the equipment ground screw rather than depending on the shield connection only.

prwood

neilc said:

the white "Sense" wire,
both connectors are snug / tight at the flame rod, and on the controller ?

the boiler 120v bx,
are there any junction boxes, service switches, along the way back to the house panel?
all those connections need to be tight,
consider running a dedicated ground wire from the boiler controller and landing at the house panel

The sense wire connection on the controller is tight. The end at the flame rod is hardwired into the ceramic.

I've gone back and looked at the cables again running back to the house panel, and I'll admit that I may not be using the correct names for the cable types. Some of the cables may be Bx but others may not. Here's my narrative description:

Inside the boiler is a metal electrical box which the transformer is mounted on. On the opposite side of the boiler jacket is the metallic box for the electrical shutoff switch. They appear to be clamped together through a punchout. Coming out of this switch box is a short length of fairly new looking ridged metal cable or conduit. It is then clamped to a new looking, smooth metal conduit, which goes to a junction box. This junction box has a hardwired CO2 detector, and has another new looking smooth metal conduit coming out of it. This conduit has a short run and then connects to a fairly old looking junction box, which then has an older looking ridged metal cable or conduit coming out of it. This runs around the perimeter of the basement almost to the electrical panel. Before the electrical panel, it connects to another old junction box, which has two cables coming out of it - one an older, ridged metallic cable that goes off in a different direction, and another which is a plastic sheathed cable that runs into the electrical panel.

Despite the number of connection points along the path back to the panel, my thinking is that the problem is in the vicinity of the boiler, because whenever it's had trouble firing up, only two things have fixed it:
1. The boiler continues attempting ignition on its own, and eventually succeeds after a length of time, possibly due to environmental changes (e.g. increased heat due to repeated pilot firing causing grounding connections to solidify.
2. Removal/replacement of the pilot assembly.

If it were something along the rest of the length of the grounding path, I would think the above two things wouldn't resolve it, but maybe there are holes in my logic.

prwood

JK_Brown said:

The connection of the GND(burner) to the module screw seems weird. In your photo it is above the plastic, but even so, that looks like a coated surface. So that GND wire is basically connected to the cabinet only via the screw threads. Is the screw tight? Is it tight when the flame sense has failed? It's almost like it isn't used although the ladder diagram shows it tied to the equipment (chassis) ground.

Secondly, the "C" terminal connected to the equipment ground screw as shown in the schematic upper left?

You might want to run a jumper from the BX shield to the equipment ground screw rather than depending on the shield connection only.

The module screw connection was pretty tight. I loosened it and tightened it again just now.

The C terminal is connected to the equipment ground screw as indicated in the schematic. Previously, that connection was dangling, but I corrected this last week. That being said, we had a few ignition failures after that, so I don't think that was the issue.

JK_Brown

Just watched a video on Mikey Pipes youtube channel where he had a Williamson gas boiler installed 2017 with the automatic pilot going out. He replaced the control module. Lady said she'd had issues every year since install.