Weil McLain CG 5 PIDN boiler stopped working-I messed up-burning smell

[Alucard]

Hi, it is cold here in Pittsburgh and our second floor wasn't getting heat. I bled the radiators first because there is so much noise when the heat kicks on, gurging, bubling, running water etc. I was getting no water when I tried to bleed valves upstairs. So, I thought system needed water as the automatic fill valve was closed going to boiler-not sure how that happened. Anyway, I made a BIG mistake by not letting the boiler cool enough and when I opened the valave to add water, it was okay for a minute but then the boiler just stopped dead and I smelled burnt electronics which eventually went away. And , I thought I hear a very small "pop" sound when boiler shut off. No leaks on boiler, took front cover off, looked at electronics and nothing appeared burnt but I could still sense a residule odor. I checked breaker but that;s fine. I tuned the on/off switch on an off and I called a couple of HVAC people but they are way too busy. I included a couple of pics. Thanks very much in advance for any help.

 

[Dana]

Before bleeding the radiators or adding water to the system it's ALWAYS important to check the system pressure first. For the water to rise all the way to the top of the system and not suck air when the pump is running the system needs to be pressurized to 3psi + 0.433 psi per foot of vertical distance between the top of the highest radiator and the location of where the pressure is being measured (typically at the boiler), or 12psi at a minimum. In most newer 2-story homes over a basement boiler-room 12psi is enough: 12psi- 3psi leaves 9 psi, divided by 0.433 is enough for 20' 8" of distance between the pressure gauge and baseboard radiator, but ~15psi is more likely. Older houses with taller ceilings and taller radiators would require a bit more- measure it.

Before pressurizing/filling the system the expansion tank needs to be pre-charged to the target pressure plus 1-2 psi.

It's OK to go ahead and make those adjustments and bleed the radiators before the boiler's controls get fixed. But whatever went wrong with the controls may be difficult to debug via web forum, and would require a lot more information that given in the initial post. It's also not clear how a cold-fill would cause the controls to fail.

A "pop" followed by burnt electronics smell could be a capacitor on a control board or some arbitrary wiring fault arcing over. Does the circulation pump run, or is this strictly a burner control issue? Are you competent with a voltmeter, and working with 120VAC power?

 

[Sponsor]

 

[Alucard]

Thanks, nothing turns on, pilot is out, no circulation pump, etc. Something fried and I don't know which componennt. I'm confident working with 120 and semi with a volt metter.

 

[Dana]

Is there a schematic for the controls available (on line, or in your house) that appear to be correct to that vintage?

Is there a manufacturing date encoded in the serial number or elsewhere on the nameplate that shows the input & output BTU rates and other data?

 

[Alucard]

Called an HVAC and they came in and detrmined that the tansformer blew out which makes sense in that the smell when it shut off was definitely a burnt electrical smell. Anyway, they put a new one in and it worked fine for a few days and then this morning, I smell this burnt odor again coming from the basement, and it's the boiler again and of course it doesn't work now. Anyway, I called the HVAC folks and they will be here tomorrow morning. Apparently this is a bit of a head scratcher. What I originally did(added cold water to the boiler when it was still too hot) shouldn't really have caused an electrical component to burn out, so say the experts. Something is causing things to go bad. Anyway, I'm going to poke around to see if I can find any burnt wires or anything out of place. I attached the schematics.

 

[Alucard]

Figured it out, with the HVAC people, of course. When I added water to the not yet cooled down boiler, I waited until the pressure came up. I should have waited until the boiler had cooled down some more although, the HVAC people I spoke to said it's rare that you damage a boiler by adding water to it when it's hot. Anyway, I waited and slightly lifted ceiling mounted expansion tank to make sure it wasn't filling with water. Anyway, about that time, I heard a small pop and the boiler shut down. It also smelled of burnt electrical component. Anyway, I couldn't fix it but figured it was one of basically three electrical components on the boiler. The HVAC people figured it was the transformer and replaced it. The boiler worked fine.....for two days then, electrical smell and boiler stops again. So, we figured there has to be a short somewhere. I know that I only turned the thermostat up and didn't mess with any wires. I retraced my steps and remembered I lifted, actually nudged the expansion tank so I gave it a quick look and wouldn't you know it, the thermostat wire was wedged between that and the rafter and guess what, the wire was partially bare where it ran against the tank. Replaced section of wire, installed new transformer, everything works, so far anyway. Keeping my fingers crossed.

Thanks again for everyone's help, I really appreciate the advice and effort.