Most residential steam boilers have an automatic water feeder that adds water to the boiler in the event that the boiler’s low water cutoff device says it needs some water. This is not as much a safety item as it is a convenience item. As a matter of fact, there is no requirement by code for an automatic water feeder on a residential steam boiler. It can be said that perhaps it is better to force homeowners to look at their boiler by forcing them to put water into it manually by not installing an automatic water feeder.
The problem with automatic water feeders is that they will turn on anytime they are asked to by the low water cutoff device. This presents a problem since it is the low water cutoff device that tends to fail or be influenced by external factors more than any other device on the boiler. If it gets stuck calling for water and doesn’t release the function, guess what. You get a flooded system and potentially a lot of water damage upstairs as water squirts out of all the radiator air vents, loose valve packing nuts, weak joints in radiators etc. This type of situation happens often.
Water feeders do what they are designed to do. That being feed water to the boiler system. They will do this any time they are asked to do so. What happens if you have the old fashioned style mechanical low water cutoff like the #67 Mcdonnell Miller unit and some dirt gets into the ripples of the float mechanism and causes it to get stuck in the position that its calling for water? Well, what happens is you get a flooded system and potentially some serious damage due to flooding upstairs. I’ve seen this happen more with the mechanical devices than with the electronic devices. I’ve seen 30,000 dollars damage to hardwood flooring because of this. What if you weren’t home when this happens? How safe does that automatic water feeder make you feel now?
Think your safe with an electronic low water cutoff and an electronic water feeder? Think again. There is a situation that seems to come up periodically with these devices. It happens during an electrical ‘’brown out’’ that usually occurs during a rain storm. When the power tries to come back on but doesn’t quite come on at full strength, the low water cutoff somehow tells the feeder to feed water. So during the time that the light bulbs are on, but dim in the house, the boiler is feeding water. This doesn’t happen anywhere near as much as the problem of the mechanical control failing, but I’ve seen it more than a couple times. It doesn’t damage the controls and by the time the plumber arrives the boiler seems to be working just fine. Except for the fact its flooded, and the homes occupants are cleaning the floors. Then when the plumber can’t find anything wrong the homeowner usually tells of how the lights were really dim in the house and it was as if the power was having trouble coming back up to full strength. Bingo. There really wasn’t anything wrong with the boiler but it got influenced by external factors, that being the brown out event.
Okay, now that you realize that your automatic water feeders convenience just came with peril attached to it, what can be done to lessen the peril some.
We can install an interrupter switch into the wire that sends the signal to the feeder. We can do this regardless if your controls are electronic or mechanical. It works by sensing the fact that water is stacking up in the piping and exerting downward pressure. Once enough downward pressure is exerted to cause the switch to ‘’open’’ then the feeder is physically disconnected from its power source. The boiler still gets flooded and will generate a ‘’no heat’’ call to the plumber, but the flooding of the system will be kept to the piping in the basement and the whole idea is to stop the flooding of the system by the feeder before the water gets high enough to cause damage upstairs. We highly recommend that if you have an automatic water feeder on your steam boiler that you install an interrupter switch in the feeder circuit to help prevent costly damage to your house by a ‘’stuck feeder’’. To see a diagram of this set up click here to open a PDF drawing.