Not even the best hydronic sleuthing solves every problem the first time. That was the case here. Some venting changes that I had recommended to a contractor hadn't solved the uneven heat problem on a two-pipe steam system. The radiators furthest away from the boiler were still cold.
Inadequate venting of the steam mains and returns is a common cause of this problem, so the venting changes I had recommended were the logical first step. Unfortunately, it wasn't the final one. The contractor understood that this happens sometimes.
We set up a time that afternoon to revisit the job. Huddled in the boiler room were the homeowner, the contractor, and his partner.
Everything about the venting upgrade was just how I'd proposed. I even complimented the pair on a job well done, but that didn't change the frowns on their faces. Everyone was looking at me for the answer.
I usually stall at this point by looking around the house some more. It gives me time to think and consider the possibilities. As I hadn't been upstairs yet, I decided to check out the radiator valves and traps, which can tell you a lot about the system — if you pay attention.
I was surprised to find a different brand of trap installed. It had the word "vapor" cast in the center of the cap, with the manufacturer's name, "Conners," arched above. Another jolt was the abbreviation for Cincinnati below — I didn't know there was a hometown steam specialty manufacturer. While this was curious, the real clue was the word vapor.
The Troubleshoot
Most vapor systems use a special radiator valve on the supply side. I looked at a few of the radiators and found no originals, just replacements, circa 1950.
I suspected the original valves were similar to other vapor system valves, which have an internal adjustable feature or an orifice that allows only a fixed amount of steam to enter the radiator.
The purpose is two-fold: to proportion the flow to the radiator's rating to keep steam out of the return lines, and to establish a steam "condition" in the system piping for even distribution.
With the valve wide open, only the required amount of steam is admitted into the radiator. By design, all the steam condenses before leaving the radiator, keeping it from causing problems in the returns. This is why some vapor systems don't have to use traditional radiator traps.
The steam condition is used for balance. The steam leaving the boiler at startup is restricted at each valve, forcing the steam to fill all the distribution piping behind the supply valves. The steam then squeezes through each valve at the rate required for that size of radiator.
The result is even distribution. All radiators get steam at the same time and in proportion to their size. Some modern hot water systems do the same thing with flow balancing valves at each baseboard, radiator, or coil.
I checked the rest of the valves in the house; all were replacements and all were wide open. I thought I might have the solution. That also happens sometimes.
I returned to the crowd in the boiler room and explained the idea of steam balance — or, in this case, imbalance. With the replacement valves wide open, the steam was going to the radiators closest to the boiler and not to the radiators at the end. I suggested testing the theory by almost closing off the valves on all the radiators that were heating. The other valves could be left open for now.
The Follow-up
We cranked up the thermostat to get some steam moving, and then walked around to check the trouble-some radiators. We now found each one heating up. The contractor was all smiles. The homeowner was relieved. I reminded them that some fine-tuning of the existing valves would be required to get a proper condition.
I suggested that a permanent fix could be achieved by replacing all the valves with ones that have the internal adjustment feature, or to use orifices.
The homeowner, however, still reeling from high heating bills because of the unbalanced system, balked at any more expense. He said he would make sure the valves would get their needed final adjustments and then stay that way.
The contractor, now satisfied that the customer was satisfied, gave me a wink and a slap on the back. He and his partner had their tools packed and were out the door before I had finished my small talk with the customer.
Later, my curiosity got the best of me, so I did some research on the "Conners" brand in the archives at the Cincinnati Historical Society. The only thing I found was a listing in the business directories for the years 1928 and 1929, during the golden age of steam heating. I guess their version of vapor heating didn't sell too well. That happens sometimes, too.
Patrick Linhardt is the sales manager at Aramac Supply in Cincinnati, OH. He often lends his sleuthing skills and technical expertise to local contractors in need. His newly released book is Linhardt's Field Guide to Steam Heating. To order, visit steamupairoutwaterback.com or call 513/703-5347.
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