If there is anything to promote about a steam heating system is its absolute simplicity, reliability and durability. How many 50 to 100 year old boilers have we pulled that looked half that age and indeed much less? Can’t remember ever replacing a radiator. Fix a cracked fitting once in a great while (usually from someone banging into a radiator), pack a valve stem that is hissing. Usually it is replacing radiator vents that were hit, breaking the mounting stem or that have become stuck over years and the radiator doesn’t operate properly.

Otherwise it is problems arising from bad water supplies and longer-term neglect that ultimately are the Achilles Heel of “Steamers”. Sludge and sedimentation accumulates untreated and then plugs particularly the return lines and obstructs boiler controls, and in particular affecting water level control.

By definition, a “Steamer” consumes some water in making steam that must be both incrementally replaced and regulated in doing so. This can be done manually or automatically. The “old timers”, both residential and commercial steamers were replenished manually, hence the occupation “boiler tender” or “fireman”. Fortunately few manual examples remain, but there is yet an issue of reliability that must be addressed with “automatic” water feeders. Specifically the Float Style vs. the Electronic Immersion Sensor Style.

An undetected and unregulated low water condition under a heat demand condition is the death knell of a steam boiler. Every failed steam boiler we have replaced, some as low as five years old has been “cooked” in heating jargon. The burner kept firing with low water until the top of the boiler castings glow red, then warp, seals fail and finally the unmistakable acrid smell of hot cast iron. This is always catastrophic and the first thing we look for is the reddish, rust orange color and dusting on the top castings. More importantly is why does this always occur with a supposedly “automatic” water feeder, specifically a “float style” feeder?

The “float style” feeder is easy to recognize, typically an external, black casting extending from the boiler near the water sight glass that indicates boiler water level. Note also that there is also a handle on or very near the device with an open pipe or port used to move water through the float chamber, flushing out sediment and residue. This is a much overlooked feature and maintenance requirement of a steam boiler. READ THE MANUAL — IT MUST BE DONE PERIODICALLY AS STATED! Unfortunately if the feeder is ultimately flushed, even then regularly, the damage may have already been done by the prior negligence. The sure test is to shut off the boiler water feed, drain down the boiler using the boiler drain at the bottom of the boiler until the low water switch cuts off the burner circuit. Refill the boiler “automatically” and verify its functionality. Then repeat the test.

Alternatively speaking, an Immersion Probe Type Low Water Cutoff is a “no-contest” option. Not only does it note low water, interrupting burner operation but can provide additional features, depending upon the individual model such as accurate foaming compensation, “settled down” water level delay measurement before and during operation, water feeder control and control external alarms. On the minus side the immersion probe should be periodically cleaned per the manufacturer’s recommendation. This can be readily done on your service cycle when the technician checks boiler water condition. Note: Many manufacturers now provide the Float vs. Electronic Low Water Cutoff Option in new boiler offerings. There are two (2) major cutoff suppliers, Honeywell and Hydrolevel, the latter being our personal preference. They can and should be upgraded to minimize boiler damage potential.

Along with this must be considered an external “Automatic Water Feeder”. There are again several functional variations offered, ranging from a “dumb” turn-on-turn-off valve to more sophisticated programmable devices that can adapt to any system water usage, condensate return patterns and elimination of the resulting potential boiler “flooding” conditions. We obviously prefer the latter type. It compensates for all conditions during installation and eliminates any unnecessary future service calls. Our personal preference again are the Hydrolevel VTX Series Water Feeders.

In conclusion:

  1. If you’re upgrading by simply replacing a steam boiler, specify an Electronic Low Water Cutoff System.
  2. If your existing boiler has a “float style” cutoff — retrofit it to an Electronic Low Water Cutoff System.
  3. In either case, also consider a Programmable Automatic Water Feeder.

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About the Author

Paul Mercier

A Semi-Retired Manufacturing Process Development and Hydronics Engineer.
Following a stellar career in Computer Hardware & Software, Miniature Ball Bearing, Avionics & Panel Meters, Magnetics, Plasma, IC & Discrete Component and Product Manufacturing throughout New England, have re-focused on a second, parallel skill set in Hydronic Heating.
Received U.S. Patent 10,690,356 on an "ENHANCED CONVECTION, DIFFERENTIAL TEMPERATURE MANAGED, HYDRONIC HEATING APPLIANCE". It is America's first, true Hydronic Heating Appliance, enabled by Taco Delta-T ECM Hydronic Circulation coupled with our proprietary near-boiler piping system. The resultant is a simple, durable and efficient hydronic heating appliance that surpasses all contemporary built-on-site systems both in value and performance.

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