Old Weil-Mclain Boiler No response.

Daboosa

I think i know what's going on now.

This is how the bi-metal switch looks when power off. With power on, the brown heating element heat up and the bi-metal arm gradually bend inwards.

5 minutes later it looks like this, side view, touching and pushing the white safety switch arm. However even after 15 minutes, it still doesn't bend enough to make the switch click. If i push it 2mm more, the boiler fire up.

I'm thinking the possible reasons are:

1. Basement got too cold, right now about 50F, and the heating element is not powerful enough to raise the temperature to the needed point.

2. The heating element got weaker over the years. Not sure what the green rust is, on the connector between the wires and the heating element. Is there some kind of capacitor or anything there?

3. The bimetal strip got weaker or something. Unlikely though.

Whatever the reason, I'll bend the bi-metal strip 2mm more so it will make the switch click when heated up.

I tested the resistance of the heating unit an and it's 5000 ohm, with 138v on it when the electricity goes through probe to water, it's about 3.8W

The warning light is labeled 125v, 1/3w, and i calculated that is 47000 ohm. But with power off, the multimeter does not show it's resistance. Maybe it only works when electricity flow through with higher voltage?

When the wire is off the wingnut on the probe, and power on, 6-7 is 150v, 6-8 is 10v, 8-7 is 140v. This make sense that the probe in water can short the light route. When probe is dry, electricity must to go through the heating element then the light. The light has much higher resistance than the heating element so it's taking the majority of the voltage and light up, while the heating element cools down due to the big drop of the voltage applied on it

Any thoughts or advice on my plan to bend the bi-metal strip a little bit?

Any idea what's the green yellow buildup on the heating element connecting points?

mattmia2

oh, that's a little carborundum resistor with the screw through it on the left that just looks like a post?

don't move the bimetal strip, move the microswitch but make sure the connections to the power resistor are low resistance first

i think the green fuzzy thing is just a copper or brass crimp splice. it could have too much resistance and is keeping the power resistor from getting enough voltage because of its voltage drop. i doubt the value of the resistor drifted much. the corrosion is either just from moisture or possible from some flux that wasn't removed when it was manufactured combined with moisture. some wire insulation degrades and causes that too

there is or at least was a timer the manufacturer could order to their specification instead of rub goldburging their own.

the neon lamp will not conduct until the voltage is high enough to strike it which is usually in the 70-100v range or so

109A_5

@Daboosa Thanks for the pictures. The green stuff is corrosion, not good.

mattmia2

if you push the microswitch manyally does it kick over in to the has water mode? with the box missing over the power resistor and thermostat it isn't going to get nearly as hot as it does with the box holding the heating.

i will repeat again, that safgard has earned its retirement, replace it, you don't want to dry fire the boiler.