We spoke a few months ago about steam boilers flooding, remember? We talked about the low water cut off telling (sending the electrical current to) the automatic water feeder and possibly overfeeding the boiler. That is one way the boiler can flood, but there are more. One thing that I failed to mention (and was brought to my attention via e-mail) is that the automatic water feeder is there to maintain the minimum water level, not the operating level. I love hearing from the readers, really.
It is still customary to have a tankless domestic water coil in the steam boiler. Why not, you get “free” hot water anytime the boiler is running for heat. However, you pay for it dearly when the boiler is running to make hot water. The copper coil in the boiler is subjected to some pretty adverse conditions and after a time it says, “I give up” and may start to leak water into the boiler. This will also cause a flooding condition. As technicians we want to be able to discover the cause of the problem, not just drain the water out of the boiler and tell the customer to “keep an eye on it;” so we need to investigate.
If the coil is to be tested, in my opinion, there is only one way to test it without removing it from the boiler. You need to be able to positively isolate the coil from the system. This means that you have to have good valves on the cold water side leading to the coil and a good valve on the hot water side leading to the house. These valves MUST be before and after any mixing valve or other take off where water can escape unnoticed. You also need to install a 300 psi gauge between these valves. This is a must and everything must be in good working order.
Now go to a sink and open the hot water faucet a little, just enough to allow some hot water to run. Now go back to the boiler and shut off the valve on the hot water pipe to the house. This will leave the coil full of water at street pressure. Notice the reading on the pressure gauge you installed. Now, while watching the pressure gauge, start to close the valve on the cold water pipe that feeds the coil. If the pressure goes up and stays higher than the street pressure you observed earlier, that coil is not the problem. If however, the pressure rises and then starts to drop, keep watching the gauge, if it drops to “0 psi,” the coil is leaking water into the boiler. You may not be able to make the repair (i.e. replace the coil) at this time, but you have found the problem. FYI, this testing procedure is also good to use on a hydronic boiler where the system pressure rises without explanation.
There are, of course, other possibilities. I once came across a customer who called because the steam boiler was overfilled and coming out the radiator on the second floor of the house. I went through all of my diagnostics to find nothing wrong mechanically. As a last resort I asked her to add some water to the boiler (this boiler had a manual feed valve and no automatic water feeder) and after a few moments I had her shut the valve. She asked me which way to turn the valve! I asked how she shuts it off when she fills it. “I turn it until it stops,” she said. I told her to do whatever you would do if I were not here. Of course, she opened the valve until it stopped. Did this cause the problem? I don’t know, but I never had a flooding call again from her.
There was also a time when the customer had a new washroom added on the second floor. Can you guess what pipe the “plumber” hooked up the waste pipe from the sink to? Yep, you guessed it, the 2” steam riser.
Steam is a very good way to heat our homes and it is a lost art. If you are going to work on these old systems you need to learn as much about the different types of steam systems around. If you want to learn this stuff, you might as well learn from the best. A good friend of mine has one of the best collection of steam books I have ever seen for sale. Dan Holohan has been around the same block as I have and has put his knowledge out there for you. Visit him at www.heatinghelp.com and check out his online library. If you read no other book, read “The Lost Art of Steam Heat” for some very interesting reading and a good understanding of steam heat. P.S., tell Dan I say hello!
Enough of my chit-chat, we need to get back to work! But in the meantime don’t forget to send me your war stories, I enjoy reading them. You can send them to firstname.lastname@example.org.