steam system overfilling

Brian Myers

I am working at a church that has 2 weil mclain boilers. they sit beside each others. steam supply is piped into a header that goes to different parts of church with steam valves. all condensate returns to condensate tank. makeup goes directly into tank. there is one pump for each boiler.the one boiler overfills now and then. i shut it off for a day including pump it still overefills so that eliminates a pump/contactor/float issue. there is a line that drains condensate from header the trap on that line appears to be pok. any ideas

bmyers

In addition I have drained down boiler several times and it always fills right up to thew middle of sight glass. this is a two pipe system mostly with radiators.

Timco

I just had a problem similar to this. It sounds like the float valve in the condensate tank. The fill valve lets it just flood. Isolate the makeup water and see if it still floods. It likely will not.

Tim

bmyers

I do not think it is a tank issue because there are 2 boilers I am only having issues with the one. like I said I shut off the boiler and the pump that has the issue and let the other one run.the water level in the sight glass without it running went from middle of sight glass to above the top in 1 day????????.

ttekushan_3

electrically actuated valve if present

What you are describing is an arrangement where a particular boiler feed pump operates based on the water level demand of its assigned boiler.

I say "if present" because I don't know the water level of the recovery tank versus the boilers. If the recovery tank is high and the boilers (which may have replaced a boiler with a much higher water line) are low, then there's sometimes a zone valve of sorts that opens when the feed pump operates. I just looked at one like that where the valve was not operating and was open. The boiler then floods over time.

Obviously this can't happen if the recovery tank is below the water line. In this case, I'd look at that trap on the header again. If the boiler outlets are fed into the side of the header, then that trap is responsible for draining off any condensate that would otherwise find itself downstream, including the furthest boiler output downstream.

If this is a new problem, something like that trap failure could be at issue, but also any changes in the boiler sequence. Say both boilers always fire in tandem. Then its likely that they will steam at the same rate. No problem. Now introduce new controls that shut off the same boiler every time while the other still fires. The "off" boiler water becomes a condenser and will overfill.

A few photos of the boiler piping would help.

-Terry

bmyers

the condensate feed tank is on the floor so lower than the water line. the general piping arrangement is this boiler is on the left the header appears to be pitched toward the other boiler. this is where the line where the condensate is being removed from the header. i checked the temp difference across the trap on this line it was 30 so i figured that was working. now that i think about i think when this happens i have to hit primary control to reset.and the day i shut the pump and boiler off and the water level rose. these boilers shoul fire all the time based off pressurecontrols which should be the same since they are tied together. so if that boiler is whether on saftey or i shut it off will the water level rise on that boiler. maybe its an intermident problem with a lockout and not a real water level issue.????.

Timco

If there is a slow 'leak' from the float in the tank, water would slowly fill the fill line and would drop off into the closest boiler first. A slow leak would not overfill both boilers at the same time. Once the closest boiler was flooded, then it would move on to the second boiler, I would imagine. Can you isolate the fill line and see if this happens? Does your box have a sight glass? Is it flooded as well? Maybe remove a top cover or plug and check?

Tim

bmyers

yeah i can isolate the fill the boiler with the problem is the farthest from the tank. the one directly beside the tank is fine