ASHRAE Journal - July 2024 - 14

COLUMN ENGINEER'S NOTEBOOK
Photo 1. Repiped gas line with unions and shut off valves.
The gas company red tagged the meter and shut it
down. We were permitted to turn it on for diagnostic
and testing purposes with a tech on-site, but the campus
(five buildings served from this single meter) was shut
down. It was cold by Southern California standards at
that time; highs in the low 70s (21°C-24°C) and lows in
the mid 40s (6°C -8°C).
My tech found a leak almost immediately. This led
to a problem: the low bid contractor who installed the
system in 1968 had no shutoff valve for the building.
(Had we had one, we could have restored gas to the
other four buildings much more quickly.) There were
also absolutely no unions in the screwed black iron
pipe! Who not only omits a shutoff valve (other than at
the meter, which was at the street, 200 ft [61 m] away),
but also runs threaded pipe with no unions? To top it
off, the leak was at a fitting that was behind the bank of
three furnaces, without access. My tech called in one of
our construction piping foremen, who decided that the
only logical approach was to cut the line after it entered
the room, thread it, add a shutoff valve, then repipe
around the furnaces with a union. Job done (Photo 1).
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The new piping was pressure tested. Victory! Thinking
we'd solved the problem, the gas company was called to
remove the red tag. Well-not so fast.
With five buildings ranging from 35-65 years old on
the campus, the gas company decided to leak check
everything downstream of the meter at the street,
in toto. When shut off at the street meter, the piping
system failed to fully hold pressure (measured at each
end) for about 10 minutes. There was a time when
the gas company would have been of some assistance
in circumstances like this, but we were simply told
something to the effect of, " Gee, that's too bad. You have
a lot of old gas piping here. Better call your plumber. "
Bear in mind that Christmas week was coming-other
than Easter week, the biggest event of the church year.
Cold church. Five cold buildings (sanctuary, office,
fellowship hall, meeting room building, preschool). No
heat.
We had touched 55-year-old threaded pipe to do the
repipe. No matter how careful one is, there will be some
torqueing of the existing piping. My tech found another
(new? preexisting, but we made it worse? who knows?)
leak at an elbow roughly four fittings away from the
work we had done. This time, we had a union back at the
new shutoff valve, so he unthreaded all the new piping
and related existing piping back to the leaking elbow.
Re-doped, rethreaded, back in business. He also then
found a tiny leak at the little shutoff valve feeding one of
the furnaces, presumably because we had operated the
valve, so he replaced all three of the 1968 furnace shutoff
valves. Victory! The gas company came out, checked the
full campus from their meter and blessed our work. The
church and other buildings were warm for the Dec. 17
service. Two furnaces were working; one was waiting on
some parts. Two did the job. Sighs of relief.
But, as the old Ginsu knife TV commercials used to say,
" But wait! There's more! " (a cultural touchstone-check it
out from 1980 on YouTube).
A day or two after the Dec. 17 service, I get another call.
Everything in the church was once again cold.
The same tech (who is becoming a fixture on the
campus) is now on a mission. I did not mention it
earlier, but old furnaces operate with a pilot light. For
those of you too young to know how that works, there is a
flame sensor positioned close enough to the pilot flame
to sense the heat, and that sensor generates a millivolt
current. The millivolt current opens the tiny " normally
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ASHRAE Journal - July 2024

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