weil mclain cga4 standing pilot boiler intermittent firing

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Old 01-25-14, 07:50 AM
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weil mclain cga4 standing pilot boiler intermittent firing

A couple of nights ago, I noticed that my boiler didnt seem to be working properly. After looking things over and having the power to it shut down for a few minutes, upon power up there were some observations made.

1. Zone valves opened as they normally do.
2. On initial power up, the main relay clicked, (more of a chatter) but the pump didnt start running.
3. Damper vent opened up, reached full open position, then immediately closed.
4. Main burners would not fire.

When this happened, I shut down power to the unit once agian and pulled the troubleshooting sheet from the manual for the unit. After looking things over agian, and following through the flow chart to see if a single issue could be isolated, I powered up the unit to begin testing. (power had been off for 10 minutes)

this time, the unit turned on, and the main burners fired as they should. Any ideas as to the cause of this issue?

does the main relay initiate the pump motor to begin running?
Does the pump have a startup cap that could be going bad? (pump is the standard b&g unit that came with the boiler)

Any help is greatly appreciated.
 
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Old 01-25-14, 08:03 AM
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I would start by powering down the system at the breaker box, verify power is off using a voltmeter, them check every wire connection. It does sound like something is intermittent, so checking terminal connections would be a good starting point.
 
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Old 01-25-14, 02:24 PM
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upon further investigation, (didnt think about this before) the system is a 2 zone system. the main floor (zone 1) thermostat is powered by the furnace that is used for the central a/c system. Then, in order to engage the boiler, a buffer relay is used.

When this thought occurred, I began by going to the thermostat on second floor and engaging it. The boiler powered up and fired just fine. The only thing that is intermittent is the first floor thermostat.

This leads me to believe a couple of things..

1. The buffer relay is faulty .. ( this doesnt seem to be the case, as I tried a different relay)

2. 24VAC supply from furnace is lower than expected. It will trigger the buffer relay and zone valve, but the main boiler relay will chatter and boiler wont fire.

3. Faulty wiring (maybe?....)

The reason that I believe that voltage is an issue is because after shutting down power to the boiler for 5-10 minutes, and turn it back on, it will fire up when the main floor thermostat calls for heat. This would be due to the "in rush" voltage which is a slight voltage spike, but high enough to trigger everything and get it running.

Thoughts?....
 
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Old 01-25-14, 08:14 PM
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After looking into this in further detail, I would consider this issue "resolved". What appears to be happening is that the main floor zone valve (honeywell 4-wire) not sure of the part number, seems to be malfunctioning. This valve is the unit that has 2 yellow wires and 2 red wires.

according to the wiring diagrams for this particular valve, the yellow wires go to power and the thermostat leads. The red wires run to the boiler to trigger the unit on/off. The red wires, or aux switch appear to be the issue.

for testing, I temp jumpered the red wires together. The boiler started and fired as expected. Then, I ran the thermostat up and down to trigger the boiler also. Again, the zone valve would open, but the unit would not fire, engage pump, etc.

So, with that being said, I installed 2 jumpers to the existing buffer relay. So, now when the thermostat triggers and engages the relay, it will in turn open the zone valve, and engage the boiler as well.
 
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Old 01-26-14, 09:02 AM
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I suppose you could try replacing the endswitch in the valve?

272744B - Honeywell 272744B - End Switch for Valves

It must be only recently that Honey is offering the endswitch as a replacement part... but as I recall the older valves had the switches 'riveted' into the head... so check first... even if riveted, it's probably easy enough to get the rivets out and use nut and screw to install new switch.

 
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Old 01-29-14, 04:55 AM
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hey, thanks for the advice. I will have to take a closer look at the zone valve and see if the switch can be removed and replaced.
 
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