Weil McLain GV-6 Series 4 - Exhaust Vent Gas Explosion Issue

CarlWillms

I finally found information on my mystery vent pipe explosion in the Weil McLain GV-6 Series 4 - Exhaust pressure issues post from November 2017. I also have a Weil McLain GV-6 Series 4. The vent pipe explosion happened only once about a year ago (that I know of); the vent gas explosion separated one pipe section and blew off the outside vent cap. I called a local boiler service company, and the boiler technician had no clue, and the condition could not be duplicated.

Recently, I have noticed an occasional strong natural gas smell outside in the discharge vent area. After the boiler automatically purges the gas, it refires correctly (no explosion). I have not been able to get to the boiler and check the control module LEDs, and since it only happens occasionally, the chance of the situation repeating during a service call is quite unlikely.

The ignitor replacement that appears to have solved the TwinLabs13 explosion issue in 2017 may not be a cure for me, as I replaced the ignitor last December, a month or so after the service call. I plan to check the condensate drain and replace the ignitor again, but I wanted to check if anyone has any other ideas. Having a service tech charge me for not finding any problems and billing for a service call for no problem found is a waste of money.

Big Ed_4

Best to call a local tech to go over your unit..

Bob Harper

From the time an ignition system sparks, pilot lit or HSI hot enough to where the main operator in the gas control valve opens you have 4 seconds for all the burners to fully ignite or else it is considered a 'delayed ignition'. This is a serious issue that must be resolved before anyone or anything gets hurt. Having suffered a hard ignition (typically not a true explosion), your equipment may have been damaged from the overpressure. You need a qualified technician to inspect it, document any damage, any tests done, and confirm proper operation or presence of the continued defect. A true delayed ignition is a serious liability issue for the mfr., wholesaler, installer and last tech in.

FYI, a 'detonation' or 'explosion' occurs faster than the speed of sound and produces a significant damaging shockwave from the overpressure. By contrast, a 'conflagration' is a rapid, hard ignition at less than the speed of sound so minimal overpressure and damage.

CarlWillms

Thank you for the time to share your expertise and suggestions. I was able to video the diagnostic LEDs and ignition sequence timing. I identified that the ignition fails intermittently on the 1st HSI cycle when the unit has been off for a while. The ignition is OK during the 2nd HSI cycle. Although the HSI is functional and less than a year old, I replaced it anyway. At this point, the ignition occurs consistently about 22 seconds after the ignitor is energized. You may have identified the issue as being that the HSI is not hot enough during its 1st cycle. I will keep an eye on it and check to ensure that the new HSI has solved the delayed ignition. I am still debating if having a 2nd technician recheck the system as the hard ignition only happened once over a year ago (that I am aware of) and at the time he could not identify any issues.