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Steam Piping Don'ts
There are some common mistakes made while installing steam boilers. I want to try to avoid these mistakes in future installations. Below are some drawings which show the mistakes and an explanation of why the installation may work less efficient or create noises.
Let's start with a diagram of a properly piped steam boiler per manufacturer's specs, US Boiler MegaSteam
We will look at a drawing showing proper piping in this style drawing; all the common mistake drawings are done.
Figure 1
Now let's look at some improper steam boiler piping
The old boiler was removed and was located in the center of the home. The old system riser went up into the branch of a tee. The system mains went to the front and rear of the home.
Figure 2
The first mistake is that you never want to send steam into the branch of a tee except in the boiler header. The steam rises up the 2" system riser and into the tee's branch. The system runs left and right with a 2" pipe. When the steam gets into the tee and starts moving in two directions, it can move freely as it is leaving one 2" pipe going to two 2; pipes due to less resistance to flow. The velocity gets too great in the 2" system riser, and it starts sucking some water up the pipe with the steam. This produces wet steam. Wet steam moves more slowly, travels a shorter distance before turning back into condensate, and causes the boiler to run more frequently to produce additional steam to satisfy the thermostat, resulting in slower heating. Excess water buildup in the system mains can cause water hammer and flooding of the boiler.
Proper piping after removing the Tee connecting two system mains.
Figure 3
Break the cast iron fittings or cut the tee out and thread both system mains in place. Add a second tee to the boiler header and pipe up to the two system mains. Allow at least 6" from the last tee in the header to the ell dropping into the equalizer.
Never Pipe the Header into A Tee at the End of the Header
Figure 4
The header should always end in an elbow. If piped as shown in this drawing, the steam and water will flow through the header and collide with the back of the tee at its end. Some of the moisture will re-enter the steam, causing it to become wet again and resulting in noise and higher fuel bills. Must leave 6" residentially or 12" commercially between the last system riser tee and the end of the header.
When the Boiler Has Multiple Boiler Risers
Figure 5
When installing steam boilers, you never want to pipe system risers between boiler risers. The system risers are always installed after all boiler risers are piped into the header. You always want the steam and water to be moving in the same direction in the header. If the boiler is piped as shown in the drawing above, the steam and moving water will collide head-on. The steam increases in velocity as it goes up the system riser, and suck some water with it. This will create the sounds of wet steam and water. The same rules apply as in a single riser. No tee at the end of the header (Figure 6). Stay back a minimum of 6" residentially and 12" commercially.
Figure 6.
The proper way to pipe a single system riser and multiple system risers off a boiler header that has multiple boiler risers, see Figure 1 and Figure 3 above.
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