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42 JuLY 2014 | FuEL OIL NEWS | www.fueloilnews.com By GeorGe Lanthier* Steam Flooding HVAC/ HYDRONICS O ne of the most difficult service calls for many is the flooded boiler and the results. It's not unusual for this problem to require more than one visit to the customer, so let them know up front that you may not get it right the first or second time, but you will get it right! Nobody likes surprises and if you take the 'surprise factor' out of the equation it sometimes may just make your day go a lot better. Many oil boilers still use tankless heaters, most conventional gas and electric boilers do not, so let's start with that and then we can look at all boilers regardless of fuel. Let's look at the traditional boiler driven tankless heater, not the mini hangs-on-the-wall gas job. When a tankless, internal or external, has failed it will leak into the boiler caus- ing the relief valve on the boiler to discharge. As this happens the tankless is merely taking the boiler to the incoming service water pressure. To test a tankless for internal leakage, isolate the tankless through the shut-off valves shown in Figure 1. With the valves closed tight and no air or water leaks present, install a test pressure gauge as shown in Figure 2 onto the tan- kless heater drain valve. Then, with the shut-off valves closed, open the drain valve. The test gauge should show the service water pressure and remain constant. If the pressure drops at all, you have a leak. After making sure the leak is not being caused by a leaking valve, gasket, seal or valve stem you can be pretty sure that you have a leaking coil. We sell those gauges on our website and also have a special low range gauge too! In most cases, and without a tankless, the best place to start is the feed valve and determine if the feeder is at fault. Lanthier's Second Law is 'assume nothing,' so don't just assume that any manual shut-offs, Figure 3, are in fact working—check them. Although ball-valves tend to be pretty reliable, stop and waste and some gate valves have washers, and if you check any manual feed valve you'll know for sure. Many years ago McDonnell & Miller showed the proper piping of automatic feeders for steam boilers and also how to do a 'broken union test.' In Figure 4 we have the procedure and drawing as it appears in their literature and if you can't add anything, just shut up, so I will! Although we spoke of this in an older article it's important to note, once again, that if you have a steam boiler with a bouncing and surging water level the pH should be checked. A surging water condition may be the cause why the feeder may be going on for no reason. With a properly running steam boiler, the water level should stay fairly constant. When the water level surges up and down by a substantial amount it can trip the feeder and the result is a flooded boiler. When surging occurs each down-surge can trick the automatic water feeder into adding water that's not really needed, eventually flooding the boiler. Although most boiler companies like to see the pH between 7 and 11, Figure 5, if the water is too alkaline, 11 or more, it will foam in the boiler and the foam will leave the boiler along with the steam. This action tricks the automatic feeder into adding unnecessary water. When the condensed foam returns, you get a flooded boiler. Check the water pH Figure 1 Figure 2 Figure 3 Figure 4