flooded boiler

Rusty Powers

Some Guy Named Dan wrote about this once, and the day after I read it, I ran into it. Spooky.
Check the nipple and tee feeding the boiler and condensate tank for a restriction. Probably mineral build-up where the cold water meets the hot. Somehow this restriction can cause the float in the feeder to drop enough to slowly add water. Good Luck!

ross_5

flooded boiler

My mom's place has a boiler that always looks flooded to me (sight glass always full). It is for a multi-unit residence (like brownstones) built in 1917 with low pressure 1-pipe steam and gravity return. It originally had a coal fired boiler, but now has a cast iron boiler with condensate tank and pump. The pump is controlled by a MM on the boiler, so the boiler should only get feedwater when the level calls for it.

What are possible causes for boiler being flooded? First thing that comes to mind is a leaky stop valve on the fill line. I was just wondering what other things might be worth having checked?

Steamhead

Does the system

have zone valves? Have you checked the brass fittings holding the sight glass to see that the valves are open and they're not plugged?

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EBEBRATT-Ed

Also does it hav a tankless coil that could be leaking city water into the boiler??

ED

Mark Hunt_2

The new


MM mercury free LWCO's need to have an isolation relay installed between the pump and the switch. Otherwise the contacts get pulled in and stay pulled in thus the boiler over-fills.

Mark H





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Unknown

Ross

If this boiler has a Boiler Feed Tank which is controlled by a MM Pump Controller on the boiler, the feed or makeup water should be piped to the Boiler Feed Tank. There is normally a float valve in the tank that controls the level of tank water and this should have no effect on the boiler water level.

What can have an effect on the boiler water level, however, is the rate that the pump is sending the tank water to the boiler. Some of these pumps can pump a whole lot of water when they turn on. Most manufacturers advise to either throttle down on the amount of water being sent to the boiler with a valve. A Plug Valve or Globe valve is very effective in controlling this flow.

Also as Mark has already stated, there are three different types of McDonnell-Miller 150 pump controls out there right now. The older ones were activated by mercury bulbs, the next generation had snap-action switches which required an isolation relay and the third and latest models utilize electronic probes. If you could let us know the model number of the boiler level control it would help. Hope this helps.

Glenn Stanton

Manager of Training

Burnham Hydronics

www.burnham.com

ross_5

thanks!

Thanks for your thoughts on this. First, no zone valves. I will check the sight glass valves. No tankless coil. I'll check the MM model. I'll check if there is a throttle valve on the feed from the pump (I'll bet not). The make-up water is feeds into the condensate tank and comes on with the float, but I think there is also a fill line tied directly to the boiler. I was thinking maybe the fill line shutoff valve wasn't holding, but all of these are good things to check out.

I'll post back once I know some more answers.