Boiler fires Intermittently

brind

I have an apprxly 25 year old weil-mcclain boiler. HE4 Series 3

It has a Fenwal ignition module (05-212226-103)

I've been having more and more issues with it not completing ignition sequence successfully.

The thermostat calls for heat and HSI glows every time for the allotted time of 40 seconds. If it works properly the gas valve clicks and then full gas fires. When unit fires there's 24vac on the gas valve, if not reads 0.

It's becoming more regular now that it glows for 40 and then there's no click. In this case the boiler continues with the pumps, fans..etc running but no fire in the box.

Tuned about 10 days ago and has been running ok until the last day now with probably more misfires than ignitions. Before had run for a week or 2 with maybe 1 or 2 occurrences.

The board is set with 1 try and then lockout. Older board that doesn't have any flashing lights for diagnostics.

JUGHNE

Simple things first; remove/pull off and reinstall/push back on all crimp connections on the control module, gas valve etc.
This cuts into any corrosion that might make intermittent operation.

Clean the flame sensor if separate from the HSI glow igniter.
A volt meter on the gas valve would tell you if 24 volts gets to it at the right time. You know and can feel the click of the gas valve.

I might change the HSI, they have a limited life, not to be cleaned, and then probably the module.

HVACNUT

Once the call for heat is initiated, the Fenwal gets 24v powered. From there it's a countdown.

The HSI is 120v so we're not concerned about that side of the circuit.

Like @JUGHNE wrote, check the wire connections.
Particularly starting at the N.O. contact on the pressure switch. Then go down the line. Spill switch. Power, Valve, and Ground terminals on the Fenwal control. Connections at the gas valve. And all ground connections.

If the HSI goes through its cycle, and there IS 24v between Power and Ground on the Fenwal, but NO 24v between Valve and Ground during trial for ignition, then it looks like an intermittent problem within the Fenwal control.


If you do NOT have 24v between Power and Ground, then trace it back from there.

unclejohn

On the other hand if you have 24v at valve then bad valve. At 25 years old I would replace valve and fenwall and the HSI anyway. Then 25 years from now you can get a shiny new boiler.