Steam boiler over filling

Weisinger

I have a steam boiler that is over filling the boiler. Every week we pull out 25 gallons to get the water in the sight glass. It has a McDonald and Miller low water float that powers up a solenoid valve to refill the boiler. We don’t have many steam boilers around any more and all of our guys that knew them well have retired so please take it easy on me . Any pointers would be appreciated. 

KC_Jones

Does the boiler have an indirect water heater in it? If so the coil could have a leak adding water to the boiler.

If that's not it, try closing the valve ahead of the auto feeder to isolate the supply from the boiler. If the overfill condition stops, then it's most likely a bad feeder and that either needs replaced or rebuilt.

EBEBRATT-Ed

There are three possibilities:

1. If you have a tankless water heater coil in the boiler or an indirect water heater hooked to the boiler the coil could be leaking and allowing city water into the boiler. Disregard this if you don't have these.

2. a manual shut off valve used to add water to the boiler is leaking by and filling the boiler

3. If you have a automatic feeder that valve could be leaking water into the boiler or the control that operates the feeder could be defective causing the feeder to operate when it shouldn't

Weisinger

No indirect water heater. By the feeder do you mean the solenoid valve? Or the McDonnell Miller? 

KC_Jones

The solenoid valve, it could either be not closing, or have crud on the valve seat allowing the water to keep flowing.

If the LWCO was feeding continuously, it would be reading a low water situation and should be keeping the boiler shut down.

Jamie Hall

Weisinger said:

No indirect water heater. By the feeder do you mean the solenoid valve? Or the McDonnell Miller? 

Well, really both. Is it just a solenoid valve? Or is it a proper automatic feeder with controls for quantity fed and so on? If it's just a solenoid valve, it could very well be stuck partly open. The best test for that is to close the manual valve which should also be on the same line (if there isn't one protecting the valve... makes it difficult). Proper automatic feeders can stick open, too.

However, don't overlook the possibility that the low water cutoff isn't operating properly. If it's the float type, the float can get sticky if it isn't flushed out regularly, and when activated keep the feeder open too long.

Weisinger

It is a cheap plastic solenoid. The kind you normally see on sprinkler lines. 

KC_Jones

Weisinger said:

It is a cheap plastic solenoid. The kind you normally see on sprinkler lines. 

That would be my guess then. I'd strongly recommend something like this, the counter is also a valuable diagnostic tool on steam.

https://hydrolevel.com/vxt-24-and-120-steam/

Weisinger

Thank all for the help! 

BobC

At this time of year water is pretty cold. If you feel the piping on both sides of a valve you can usually tell if there is flow through that valve. If both sdes are cold there is flow through that valve.

Bob

veteransteamhvac

KC_Jones said:

Weisinger said:

That would be my guess then. I'd strongly recommend something like this, the counter is also a valuable diagnostic tool on steam.

Is there a guide somewhere that provides acceptable ranges for refilling 1 pipe systems? I have several VXT installed on client boilers and would like to have a better grip on it.

Jamie Hall

veteransteamhvac said:

KC_Jones said:

Weisinger said:

That would be my guess then. I'd strongly recommend something like this, the counter is also a valuable diagnostic tool on steam.

Is there a guide somewhere that provides acceptable ranges for refilling 1 pipe systems? I have several VXT installed on client boilers and would like to have a better grip on it.

Not really. The boiler manufacturers will sometimes quote as much as a gallon a day, but most of us kind of think that that is wildly excessive for a normal sized steam system. Most of the loss in a good steam system is from the vents, and that should be minimal, and figures we've seen seem to be in the less than a gallon a week to less than a gallon a month as pretty good.

Anything much over a gallon a week and you should start looking for steam leaks, if not water leaks.

KC_Jones

I'm more conservative than @Jamie Hall , I say anything much more than a gallon a month and you should start looking for leaks, steam or water. Steam can be difficult since it's invisible.