LWCO trip and flooded boiler

ch4man

evening gents,
thought i had this solved last year, but today a fellow tech was there draining the boiler and had to reset the secondary LWCO.

ok the system is a one pipe 650 CFH WM LGB6 in a 6 condo building, 3 gorton#2 on one main and 2 gorton #2 on the other. it also has one hoffman, model unknown vent in the condensate return in the boiler room just before a mepco 1 1/4" 715 F&T that we rebuilt last year. this drains into a sterling feed tank. installed 2 years ago.

as i said, thought i found the issue when we found 2 or 3 radiators on the 3rd floor badly tipped and sagged. ( we weren't the contractor that fixed those but the owner said they were reinstalled.

to be fair i have been in 4 of the 6 condo's so there may be more rads tilting.

what i cant wrap my head around is the system works most of the year but a few times last year and this year on the first firing runs and refills over and over untill both LWCO open all the while no condensate has returned untill it lets loose and floods the feed tank and boiler. i saw it happen once last year but couldnt recreate it. .

when this happens irraticaly how can i find the offending issue? it sounds to me like a vent or two that close but stuck closed? maybe? and whats more likely the main vents or radiator vents.
i'm more of a scorch air/ ac service tech, good with water boilers but i still can not see the steam inside the pipes

sorry for rambling but i know i'll be called in on this very soon and i need a plan.

TIA.. John

Abracadabra

clogged wet returns?

ch4man

theres only one so that i would think rear its uglyhead more often

ch4man

oh and there is a strainer just before the F&T that flows cleanly

Fred

What type LWCO's are on the system? Probe type or float type? If float, when is the last time they were opened up and cleaned? Why is there a feed tank on this system? Slow returns? When was the last time the wet returns were flushed out?
You can forget about the vents (at least on this issue). Stuck vents won't cause flooding.
Are you sure the auto water feed is working properly? It may have an intermittent problem causing it to stick open and feed more water than needed. Does the water supply go to the feed tank or into the wet return near the boiler?
Some pictures of the set up would be helpful.

ch4man

boiler and trim are just 2 years old. its been a year since i was there but i remember a MM 150 and either a MM 67 or a hydrostat LWCO.

city water goes to the feed tank. tank pump is controlled by the 150.
it is a slow condensate return issue when this acts up, then 150 calls so often the feed tank empties, but then the system condensate thats held back suddenly lets loose and floods the boiler. i saw this happen once last year. but then may work just fine for months

i guess thats my question. what failure can cause this

oh and if i can figure out how to get some pix off my iphone loaded here ill try

ch4man

*

JUGHNE

TRV's without vacuum breakers can hold back condensate inside the rad and piping.
Had this happen for 2nd & 3rd floor 1 pipe rads. When the water let go it sounded like toilets draining thru the piping. Held back more water than I imagined possible.

ch4man

thx, if i get back in, ill look for any TRVs

Grey_Hair

I also have one boiler that floods (once a year, and only near at the beginning of the heating season) because of the LWCO MM 67 which was wired directly to the condensate pump.
In my opinion, if a MM67 is used to directly start a cond pump, even once. Flooding may happen, as the micro switch has been heated and compromised. This will only happen with 110v power and a cond. pump which has a little more summertime scale, which breaks down, and it never happens again that heating season.
But if you are running 24v through the LWCO then my guess is your problem is at your 24/110 pump relay and/or scaled up pump. (Possibly go over/trace the wiring). A cond pump will take more amperage to start in the fall depending on your water quality.
This is my first post, many thanks to everyone for the help, and the education, it has been amazing, yet it never ends. Thank God for steam problems and THE WALL

ch4man

found my notes, primary lwco is a 150s, which also controls the feed tank pump. secondary manual reset lwco is a MM 63

if that helps

all NBP is correct and new except for the header (old but correct) and a section between the feed tank and boiler that looks poor. i wonder how much mud and crap is in that line and check valve

Fred

Check valve certainly could be sticking. It would be good if that section of pipe could be flushed and the check valve cleaned.

ch4man

that answers why the boiler runs dry and trips the manual lwco, but not why the system floods. if the feed tank cant feed the boiler it will be full and the internal float will not allow city water in.

i'm still confused.

this is why i condemned the F&T. thinking it was sticking. its now new last year with no improvement.

last question for tonight. one odd thing was the feed tank vent is piped to the ceiling over and down as usual, but then it was extended back down the floor, then 90's and a short pipe to floor drain.

can that be enough to "un vent" the tank? i understand feed tanks must be vented and unpressurized

EBEBRATT-Ed

I don't understand the boiler flooding if the 150 controls the pump and the city water feed is to the feed tank. Is someone inadvertently shutting off power to the feed tank? Maybe the city water feeder is leaking by.

ch4man

i dont understand either.......

keep in mind, this was last year when i saw this happen.

started steaming, water level drops until 150 calls for water. boiler keeps steaming, 150 calls for water...... this goes on and on with NO condensate reaching the ? (feed tank or boiler) yet.

the strainer just before the F&T has a ball valve. the longer it steams and runs i can see by opening the ball valve condensate is backing up. at this point the SYSTEM has to much water. i just dont understand if its blockage (mud or pressure) down stream or vacuum upstream that holding the condensate back.

(sorry, the more i talk, the more i remember)

of course just as i step outside for a minute. when i come bake in the room is steamed from the feed tank and water is spurting from the last air vent thats before the F&T.

i'm really questioning that odd tank vent piping. everything else in the boiler room is textbook

Fred

Was the boiler ever skimmed after the piping work and new boiler were done? If there is oil on the surface of the boiler water, it could be causing the water to back into the wet returns, causing the LWCO to call for water and then, it is over filled and floods. I would skim it well and also check to see if the pigtail that the Pressuretrol is mounted on is open. They can and do get plugged with gunk and the pressuretrol can't see the pressure and it goes way up adding to the pressure necessary to push the water out of the boiler and preventing the condensate from returning.