how to tell if pressuretrol is good

danoer1

thought I had a clogged pigtail, so took off the pressuretrol and blew through the pigtail and could see the water in the sight glass moving, so I guess the pigtail is fine. How do I determine if the pressuretrol itself is ok? My pressure never moves off of 0, and I know we may be dealing with ounces here, but other than rigging up some finer scale pressure gauge...is there a way to determine if the pressuretrol is working? My boiler never cycles on pressure, and I might have a leak on a dry return...just haven't had the time to crawl into the crawl space and find it...the crawl space really does make me feel like I am in the WWI trenches. Somewhat surprised by the way that the pigtail works by taking steam pressure and allowing the steam to condense in the curve of the pigtail and then I guess trapping air between the condensed water and the pressuretrol...so these things sense pressure by ways of steam to water to air?...interesting



dan

Jamie Hall

There are a number of reasons...

why you might not see the pressure rise on the standard (and code required) 0 - 30 psi gauge, not the least of which is that those gauges are none to accurate at the low pressures residential heating systems operate.  One can add a low pressure gauge, of course.



Among the reasons are:

Boiler very closely matched to radiation; in that case, except for exceptionally long runs, the radiation will condense all the steam the boiler can make, and you'll never see a pressure rise except maybe a few ounces.  This is, by the way, good, assuming that the system is able to heat the house the way you want it!

A vent or vents which are stuck wide open.  They happen.  Not that uncommon.  You may be adding excessive water if this is the case.

A leak above the water line in the boiler.  This will show up in two ways: first, you will have to add excessive amounts of water (your boiler manual will tell you what they think is normal) and a lovely plume of steam out the chimney (note: all boilers make some "steam" out the chimney, particularly on a cold day, but a great big plume is a problem).  This possibility is not good, as there is no good way to fix such a leak, and it won't get better with time.

A leak in one of the pipes -- supply or return.  Again, you'll be adding a good bit of water.  Not as serious (or expensive) as the boiler leak.



I can think of at least two ways to check that pressuretrol is working.  The most obvious is to crank the thermostat way up, and see if the boiler ever gets to cycling on pressure.  The other is to close off some -- or all! -- of the radiation, assuming that the radiator valves work reliably (don't go closing a valve which might not open again properly!) and see if the pressuretrol trips.  Some steam systems are built with "king" valves on the supply main or mains and returns -- which close the steam supply to the radiation and close off the returns, but still allow the near boiler piping to operate the way it should.  If those are closed, the boiler should build pressure quite quickly; stand by to shut it off manually as soon as it shuts itself off on the pressuretrol (or, should the pressure get above 5 pounds or so and the pressuretrol hasn't tripped -- in which case you have pressuretrol problems), and wait a bit for the pressure to drop before you reopen the king valves and turn it back on (note that if the pressure doesn't rise, you definetly have a leak in the boiler! -- shut it off manually and bemoan your fate, although you can run it for heat, of course, until you replace it!).