Low Water Level In Steam Boiler

Bwal

New Weil McLain LGB5 steam boiler with a new McDonnel Miller 150SMD LWCO and boiler feed pump controller.  I took great care to install the 150 at precisely the height spec'ed in the Weil McLain installation guide.  The pump controller consistently maintains the boiler water level 1 1/4"  below the spec'ed waterline when the boiler is not firing. ( Yes, I've triple checked my math and the instructions.)



2 Questions:

Assuming I can read a tape measure and do basic math, is there something that could cause this other than inaccurate instructions or a faulty, factory setting on the 150?

Since this new boiler has a relatively small water capacity, is it advisable to pipe the 150  1 1/4" higher to increase the amount of water in the boiler?

nicholas bonham-carter

missing water?

if you can fill the boiler manually to the correct waterline height [  and mark it on the sight-glass with a bull-dog clip ], and then turn off the water to the auto feed; then you can fire the boiler, and see if the waterline drops. further, you can then see if after a few minutes, all of the water comes back to the marked level. if it all comes back, then you may just have slow returns, or water "hiding" in the returns due to over-pressure in the boiler. another cause of "hiding" water is a horizontal pipe in the returns that is slightly higher than the waterline.

more serious is water that doesn't all return because of a leak somewhere in the system. if the W-M instructions were followed and you feel the M-M is still installed  too low, then call W-M tech support about it.

i view the auto-fill as an over-fill and think it should be there only for use during periods of extended absence; and really should be kept off while the owner is able to make weekly inspections.--nbc