Float level controls are sleepin' on the job

AKDISTILLER

SYSTEM DETAILS:
I have a two-steam-boiler (450K BTU) system with duplex condensate pumps activated by McDowell Miller ISOSHD Float level controls. I have a spirits distillery and heat a 125 gallon still + a 250 gallon still with the boilers. They operate as they have been for ten years heating the 125 gallon still, but the 250 gallon still heating-up cycle is not operating correctly any longer.

PROBLEM:
When heating the large still, the floats won't drop with the boiler water level to turn on the condensate pumps. When the steam valve is tuned off at the still, the pumps turn on immediately and fill the boilers back to the correct level. But when the valve is opened on the still again, the problem continues to occurs until the still is heated. At the point the still is up to temperature and not requiring as much steam pressure, the float operates the pumps normally again. I've tested the float by operating them manually and they move freely when I do that. I've also manually opened the drain valve below the floats and the floats drop and turn on pumps, but only to turn back off immediately after closing the drain valve.

QUESTION:
What could be causing the floats to float up under these conditions while the boiler is low enough on water that it should be activating the pumps on its own?

Jamie Hall

Are the floats really reading boiler level, or level in the condensate return tank? And, if they are reading boiler level, are they in a separate chamber with connections to the boiler, or are they in the boiler? And if they are in a separate chamber, how is that connected (top and bottom) to the boiler?

AKDISTILLER

The floats read the boiler level as they are piped into a riser on the side of the boiler that is piped into a larger riser that pipes into the bottom of the boiler and and up to the header pipe coming off the tops of the boilers. the feed water and high water spill traps for the boilers are also piped into this larger riser. Sure seems like there is a vaccum holding the float up. The trap on the still is new and the vaccum breaks break when the still steam is closed off. I attached a couple photos to my original post.

Jamie Hall

I see a copper pipe with a valve on it from the bottom of the float chamber which goes down and then over to near the wet return are the front of the boiler. How does it connect to that wet return?

AKDISTILLER

The copper pipe and valve are used to blow down the float bowl and piping of accumulated sediment, rust, etc. Its also used to test the low water cutoff switch activated by the float. The copper pipe runs to a floor drain, not to the return.

Steamhead

I bet the wiring is messed up.