I recently turned on the steam boilers in 2 buildings I manage. Both are Weil McLain steam boilers (EGH-85 and EGH-95). They've been pretty reliable, but I was just curious. What is the duty cycle for a steam boiler? Anotherwords, are these boilers designed to run for long periods of time? Like on an average cold day, is it common for the boiler to be running lets say 20 minutes on, 30 minutes off?
Absolutely.
Sure, depending on size, temperature, etc, they can run 100% on. Built to handle it.
Well thats good to know. Assuming the pressure switch, low-water cut- off,and safety valve are all functioning fine, I guess the boilers are designed to run a long time all day if need be.
"Mikepier" wrote
The low water cut off should be tested. It is the most important part on a steam boiler.
That's the thing. Even if you test the LWCO, and it works, it could fail anytime after that. Not good especially since I'm usually at the buildings only a couple of times a month. There should be somekind of second backup.
They are pretty reliable. Some boiler setups have two. One will automatic reset, the other, at a lower level, requires a manual reset.
Not seeing your setup I don't know what you have. The boilers I'm familiar with have two LWCO and we test them frequently. The high pressure boilers are tested every shift, by law. You just want to keep sludge from building up over time, but for heating boilers, that is not a big concern. Process boilers, much more so.
Mine only has 1 LWCO.However it does have 2 high pressure cutoffs. The first is set to about 2 lbs and it simply opens the T-stat circuit. The second cutoff set to about 5lbs and turns out the pilot if tripped, and must be manually reset and relit.
Whats a process boiler? When I google it, not much info.
"Mikepier" wrote
A boiler that makes steam to be used for a manufacturing process or generation of electricity. Usually larger and higher pressure. In steam terminology, a boiler that puts out 15 psi or more is considered high pressure and is subject to regulations on controls and operations.
In the state where I work (MA), there must be an engineer in charge (me) and a fireman present any time the boiler is running. All of my supervisors and maintenance people are qualified. We use steam to mold foam plastic. One an average day, we turn 300 to 400 gallons of water per hour into steam. Since it is used and vented there has to be a lot of water pumped into the boilers and the evaporated water leaves behind any solids left in it. We operate at 100 psi. Power plants can run 300 psi.
For sure, and the way you know that a boiler was improperly sized is if it has a low duty cycle during the coldest possible weather.
That is why some jurisdictions require two and I don't know the exact requirement but it becomes mandatory after you reach a certain input rating.
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