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Water level fills too high - shuts off boiler - HELP!

In February of 2007 we had a new boiler installed, a Weil-Mclain "gold oil", in our house which has steam heat with cast iron radiators.  It has been running smoothly till spring 2011 but we have noticed that the water level now fills up  way beyond the target level and shuts off the boiler. We have had one technician come and do an annual tune up and he flushed the system and "tapped" the water auto feed to loosen up any dirt but today we again found the water level too high and called for emergency service - and this time the tech told us that the boiler was not installed with a "skim valve"  and he used a liquid called "Squick" to clean up any debris/oil in the boiler. It ran OK for 5-6 hours and the water level went way too high again and shut of the boiler again. It did not happen during late spring/summer and early fall but happened now - the heat has been on more as well. 

Another technician arrived 6 hours after the first one left. he took of the cap on the lwco and poked around it with a "stick" and drained the system - many buckets of dirty water coming out. He said that the water from the return looks pretty clean. We drain the system every week and get half a bucket of dirty water. All radiators do get hot, also near the outflow/exit pipe.

Any advice/sguuestions would be appreciated. I posted this again in steam section. Many thanks!





  • BobC
    BobC Member Posts: 5,473
    edited November 2011
    Could be -

    Does your steam boiler have a coil in it to supply domestic hot water? If so there could be a leak in that coil that is feeding water into the boiler. This probably would have occurred in the summer also but might not have been noticed.

    Auto water feeders on a low water cutoff can develop a leak and let water into a boiler when they should be off. The only way to tel is to close the valve feeding the LWCO and watch the boiler closely for a few days to see if the sight glass shows any increased water level.

    The third suspect would be a partially blocked condensate return that is delaying the returning water to the boiler. Because the boiler runs more at this time of year (making steam for heat) this type of problem can become apparent even though it seemed fine all summer. The LWCO adds more water and when the returning water (condensed steam) does find it's way back you end up with too much water in the boiler.

    You said the boiler shuts off when it gets overfilled, do you see any warning lights on the LWCO when this happens?

    Once the overfilling is solved you might want to have a skimming port, with a valve added so the boiler can be cleaned out.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
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