Photo 131345933 © Zvonko59 |
Dreamstime S 131345933


May 19, 2022
Every building I walk into reveals to me a new twist, usually in a good way of learning something new, but unfortunately sometimes in a bad way.

You know that sinking feeling that you get in your gut? The one that happens when you consider that you might have given some poor advice or not paid enough attention to detail until it’s too late. That “Oh S**t” moment that you realize could have been avoided. It happens to everybody that works in the field, where every job is different.

I like hydronics because I have been exposed to such a variety of equipment, radiation, piping techniques, etc. Every building I walk into reveals to me a new twist, usually in a good way of learning something new, but unfortunately sometimes in a bad way.

Routine Job

This job seemed routine enough. A nice couple in the neighborhood near Cincinnati’s historic observatory wanted to add a radiator to their enclosed porch/solarium. It’s an old part of town with plenty of big trees shading this room. It wouldn’t be for growing plants, but for enjoying a good book on a winter day, when they weren’t in Florida.

The contractor and I met them at the end of the summer. Their idea was to have the new radiator heating that space by Thanksgiving when their family would be in town. The contractor had done a heat loss of the space, so we knew what output we would need. Our first question was where in the room would they like their new radiator.

You could tell they liked radiator heat. They weren’t interested in anything but a nice chunk of warm cast iron to heat this room, since they were so pleased with the performance of cast iron radiation throughout the rest of the house—except where some previous contractor had tried to use a propeller fan unit heater attached to duct work to heat a kitchen remodel.

That’s one of those bad ideas I run across sometimes. Since that didn’t work, which didn’t surprise me, they had an electric kick space heater installed under one of the cabinets. Their love of cast iron wasn’t as strong as their desire for more cabinet space. I see that all the time, but I’m not here to judge.

The system is two pipe steam, circa 1915. Other than the kitchen, they said everything was toasty and evenly warm. I loved to hear that, but wondered if what we are about to do was going to affect their cast iron nirvana.

Checking the Boiler Room

Once we got the location determined, we went downstairs to look at the piping. On the way we stopped at the boiler room, always a good idea to get as complete a picture as possible. I don’t know how many boiler rooms I’ve been in during my career, from the nasty to the sublime, but never before were there original oil paintings on the walls. Turns out the man of the house has a studio on the third floor and is quite good.

Of course we weren’t there to appreciate art. I’m looking for the end of the steam main(s) and dry return(s). As with a lot of two pipe systems, there was only one vent at the end of the dry return. This is the vent that releases all the air from the radiation and riser piping. I explained that we want that air to pass out of the vent as quickly as possible to allow the steam to distribute quickly along the main to evenly reach the radiator risers.

When I mentioned that, they mentioned that some of the upstairs radiators had automatic vents. That’s one of those twists that keep me haunting basements, trying to figure out what somebody in 1915 thought the present was trying to do. Two pipe radiators aren’t supposed to have vents, except in some very old systems where each radiator return is piped individually to a wet return. This wasn’t one of those systems. 

We moved to the area under the porch, a nice tall garage that now functions as a workout room. There is a branch steam main that runs right through, feeding a few risers on that side of the house. There was also a dry return running parallel to the steam main. And best of all, there were available tapings on both where a radiator had been removed.

Typically, two pipe steam radiators are connected on the supply side with a ¾” radiator valve and on the return side with a ½” trap or vapor device. The sizes were right on the available tapings, so the contractor did some measurements while I went back to discuss the art in the boiler room with the resident artist.

The Call You Hate to Get

The homeowners approved the bid, material was ordered, and the installation complete right before Thanksgiving. That’s when I got the call that it didn’t heat. Well, it heated a little bit, but not much more than the first few sections on a 20 section radiator. We decided to meet the next available day that they could schedule their steam tech.

When we got there, the rest of the house was fine. Steam seemed to be at the riser of our troublesome radiator and through the valve, but not much further. I had the tech break a union on the return riser down in the garage.  Air and black water came flying out. At this point it looked like an air removal problem. My initial theory was that air wasn’t passing quickly enough, so just a little steam could enter, since steam and air can’t be in the same space.

We suspected that downstream of the union, on the dry return there would be a blockage. Since it was old pipe, the homeowner agreed to have it replaced. That had no effect on our problem, so I was back again. I made sure that the valve on the non-functioning unit heater contraption was shut off and there was no steam in the main dry return, since steam in the return can block the removal of air. Check and check.

Light Bulb Moment

So I was standing in the doorway of the garage when the feeling started. In this case, I was glad that something finally made sense. At least it fit my code: “If something is wrong in a system, fix that first.” What I was looking at was the supply riser from the existing steam main. It ran horizontally for at least eight feet, it was only ¾”, and it didn’t have much pitch before it went up through the floor to the new radiator. The light bulb went off as the gut sunk. I was going to have some explaining to do.

If you look at steam pipe sizing charts, like I was supposed to do, it will tell you that the supply riser pipe size for this size radiator is ¾”. But the charts also have an annotation at the bottom. In my Field Guide, it is on page 161 and states “Use one pipe size larger for: counter flow mains and horizontal run outs over 6 feet.” Right there for the world to see (but for me to forget) when we talked about hooking up this radiator.

The length of the horizontal runout, its pipe size, and its pitch determine how much steam is going to pass to the radiator. If you don’t get it right, it comes back to torment you. The contractor ate the cost of re-piping the horizontal supply riser to 1” and increasing the pitch. Works like a charm, now.

The boilers finally came in for the missing expansion tank job. Hopefully next month the mystery will be solved.

Patrick Linhardt is a thirty-seven-year veteran of the wholesale side of the hydronic industry who has been designing and troubleshooting steam and hot water heating systems, pumps and controls on an almost daily basis. An educator and author, he is currently Hydronic Manager at the Corken Steel Products Co.

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